Fisheye lenses compared

I like fisheye lenses: They can cram an impressively wide field of view into the image frame, and create perspectives that you would not be able to see with the human eye. Another aspect of fisheye lenses is that they create a lot of barrel distortion (rounded images), which you can remove through a defish process, or retain in the final image.

Here is a collection of fisheye lenses for Micro Four Thirds and other systems:

From the left: Samyang 7.5mm f/3.5 (my review), Lumix G 8mm f/3.5 (my review), Yasuhara Madoka 180 7.3mm f/4 (my review), Olympus 9mm f/8 (white) (my review), Lensbaby 5.8mm f/3.5 (the biggest) (my review)

There are basically two types of fisheye lenses: A circular fisheye lens renders a circle in the centre of the image frame, which usually extends to 180° all around. A full frame/diagonal fisheye, on the other hand, renders the full imaging sensors, and usually extends to 180° from corner to corner.

GH3 has less rolling shutter artefacts than GH2!

Rolling shutter denotes a type of shutter mechanism, and can refer to both a mechanical shutter, and an electronic shutter. It also refers to the type of tilting artefacts you get when panning quickly during video recording. Some refer to these artefacts as "jello video".

This is not strictly related only to digital cameras. Older film based cameras often feature a focal plane curtain shutter, which "rolls" across the film plane and exposes the film horizontally or vertically. A very famous example of this is the racing car picture taken in 1913 by Jacques Henri Lartigue using a 4x5 Speed Graphic camera.



The shutter moves relatively slowly on this camera, when compared with modern SLRs, which gives the distortion of the racing car. The distortion is especially visible in the wheels, which appear to be leaning forward. This effect was later copied by cartoonists when they wanted to give the impression of speed.

Lumix G 100-300mm f/4-5.6

The Panasonic Lumix G 100-300mm f/4-5.6 Mega O.I.S. is a long tele zoom. This kind of lens would normally be used by people who are interested in photographing birds, wildlife, spectator sports, safaris, and so on.

More mature DSLR camera systems are, generally speaking, better suited for these applications. This is due to a better continuous autofocus, which is possible with the PDAF system used in DSLR cameras. Hence, people with these interests, are probably using Canon and Nikon cameras, rather than Micro Four Thirds. However, with the introduction of the Lumix G 100-300mm, M4/3 users have a possibility to check this out.

GH2, built-in flash for macro use

Lightning is critical for macro photography. To illustrate this, I will present a scene I tried to photograph. I used the Panasonic Leica Lumix DG Macro-Elmarit 45mm f/2.8 1:1 Macro lens. To make sure I used the maximum magnification, I selected manual focus (MF), and moved the focus ring until I reached the closest focus distance. Then I placed the camera so that the subject came in focus. This way, I was sure that I used 1:1 macro, which means that the subject is the same size as the sensor area, 17.3mm x 13.0mm.

As a test subject, I originally intended to use a bee. However, I found that chasing a bee around while it was visiting flowers, was much too difficult. Therefore, I found a bee that had been killed by a spider's web. With the bee being suspended, it was much easier to photograph in a controlled fashion.

First, let's consider what aperture to use. The PL45 lens has a maximum aperture of f/2.8, which has been criticized as being too small. Many would have preferred it to be f/2, to make the lens more useful for portraits. In this case, I want to have some depth of field, so I try to set it to f/5.6, a point at which many Micro Four Thirds lenses reach their optimum performance.

Here is the image at f/5.6, 1/60s, ISO 3200:

As you can see, the image is in fact not very good. One wing is in focus, the other is not. The rear part of the bee is in focus, but not the front. We can easily conclude that the depth of focus is too thin: Only parts of the insect is in focus.

To get a better depth of field, let's set the aperture to f/13. Some may worry that f/13 is too small, and will give some dullness due to diffraction. That is true, but as long as you don't make a big magnification of the print, that should not be a problem. For web use, f/13 is no problem at all, and you could even try to use f/16 if needed. I have studied the diffraction effects here.

I took ten images at f/13, 1/15s, ISO 3200, and this one is the most successful:

There are some problems here. First, you can see that the image is not framed very well. I was handholding the camera, which makes framing hard. Also, while the image has much better depth of focus than the previous, it now has some motion blur effects. The shutter speed, 1/15s, is much too slow to handhold the camera, even with Optical Image Stabilization (OIS). Finally, the high ISO at 3200 makes the image a bit noisy.

There is an easy way to solve all these problems: Just use the built-in flash. It turns out that the small built-in flash does cover the entire frame when using the PL45 lens at the closest focus range. The illustration below explains why.

In the illustration, a LEGO figure is placed at the minimum focus distance of the lens. At 1:1 magnification, the distance from the front lens element is 7cm. The built-in flash covers the focal length of 14mm, which corresponds to 75° diagonal field of view.

The resulting image is this:

As you can see, the entire image frame is illuminated by the built-in flash, even at maximum magnification.

A note about the lens hood: I don't like the supplied hood. It is much too wide, and does not do a good job at keeping out stray light. So I made my own hood, composed out of three elements: A 46mm stand off ring (glassless filter), a 46mm-37mm step down ring, and finally a 37mm-28mm step down ring. This gives the ultimate protection against stray light (in my opinion), and also good protection against objects touching the front lens element accidentally.

If you use the original hood, the light from the flash will be blocked by the hood, and you cannot use the built-in flash with macro images.

Back to our bee example. Here is the same image taken with the on-board flash, at f/13, 1/60s, ISO 160:

Using the flash allows for base ISO (160), and there is no problem with camera shake. The flash light is very quick, and freezes the image instantly. We clearly see that this image is much more sharp.

On the other hand, this method is not perfect for macro images: We see that the background has become very dark. This is because the flash light spreads out, and becomes less powerful for the background at a larger distance. Also, the flash light coming from a single light source does give a "flatness" to the image, which is not optimal. The nature of the image changes completely when using the flash.

Using the built-in flash for macro is a quick and easy way to get usable macro images.

Third party battery for the GH2

Having a spare battery is convenient. Without it, you cannot photograph anymore without going home and recharging the battery, should you run out of power.

Original spare batteries from Panasonic tend to be somewhat expensive. For the GH2, spare batteries have even been hard to find in certain markets.

One option is to buy a third party spare battery. They can be bought inexpensively from various auction sites. I decided to try one. It cost around US$20 including shipment from China.

The battery arrived very swiftly. It was packed well in a padded envelope, but beyond some bubble wrap, it did not come with any box for storing. Here is the original battery (on the left), and the third party battery (on the right):

The original battery comes with the official name, DMW-BLC12E.

On the reverse side, the third party battery, to the right, somewhat cryptically says: "For Pan.DMW-BLC12".

In use

The third party battery charges just like the original one. When inserted in the camera, though, there is one major difference which is easily spotted: You have no battery bars in the display anymore (using the third party battery on the right):

If you're going to use the battery for emergencies only, then this is no problem. But for normal use, it is a nuisance not to know how much power is left in the battery.

There is another consequence to this as well. When using the normal battery, the camera knows when the battery is almost depleted, and will not allow the user to take any more pictures. If recording a video, the camera will stop the recording, to allow for safely saving the footage already recorded.

The third party battery, however, does not allow the camera to see how much power is left. Hence, the power might go out during video recording, which could damage the whole recorded file, so that all your most recently filmed footage is lost. The same goes for images taken when the camera is almost out of power.

When the camera notes that there is not enough battery left, it leaves a message saying that the battery power is out, please recharge. With the third party battery, however, the camera simply uses up all the power until it is completely out, leaving the camera completely dead when having used up all the power. This is not a real problem, but can be confusing for some users.

Another side effect of using the non-original battery is that the camera loses the power save mode. So you must make sure to turn off the camera when not using it, otherwise the battery power will be drained too soon.

How much juice in the batteries?

I tried to compare how much video footage I could record with the two batteries. My camera is the European version, and can only record 30 minutes in one go. With the original batteries, I could start the video recording five times, with the last video being cut off after 24 minutes, due to too low battery. So the total recording time was 144 minutes, with the LCD display on all the time.

With the third party battery, I could only start three recordings. After that, the camera was completely dead, and did not respond until I replaced the battery with one that had some charge. The total recording time was 90 minutes.

This difference could be due to the new, third party battery not being worn in properly yet. Some say that batteries need to be used and recharged some times before reaching their optimal performance. I don't know.

Conclusion

The third party battery is good for emergency use. If your main battery goes empty, it would be good to have it in the camera bag to be able to continue using the camera until you can recharge the main battery.

But for critical use, it is not good. The battery could go empty while you are photographing or recording video, so that your most recent work is lost.

Bad aperture diaphragm in Lumix G 14-42mm f/3.5-5.6

When investigating the bokeh of some Panasonic Lumix lenses, it came to my attention that out of focus highlights using the Lumix G 14-42mm f/3.5-5.6 kit lens was irregularly shaped when stopped down. I decided to take a closer look, to see what the problem is.

First, I took a picture in which I set the lens to tele (42mm), focused as close as possible, and placed a flashlight in the background. The flashlight renders out of focus. Here is the full image at f/5.6, the maximum aperture. The flashlight is placed in the centre of the image:

To see how the roundness changes when stopping down, I have made 100% crops from the centre at various apertures:

This verifies the problems I saw when studying the bokeh. The out of focus highlights are definitively not circular. It looks like the aperture diaphragm blades are misaligned.

Micro Four Thirds lenses are always wide open when powering the camera down. This means that normally, you cannot look at the diaphragm blades from the inside, since the aperture is wide open.

However, a trick is to stop down the lens, and then remove the camera battery. That way, you can remove the lens while stopped down. This procedure is not exactly recommended by the manual, so use with caution.

Using this trick, I could photograph the back side of the lens when stopped down:

Here it is clear that some of the blades are misaligned. Thus, the resulting image has non-round out of focus rendering.

I've made a video showing the stopping down of the aperture blades. The apertures goes from f/3.5 down to a full close in 1/3 stops.



I filmed it using the Panasonic Lumix GH2 and the Leica Lumix DG 45mm f/2.8 macro lens. To get the needed magnification, I used the new Extra Tele Converter (ETC) mode.

Here's a photo of the setup for capturing the video:

Conclusion

My lens most certainly has a bad aperture mechanism. Whether this is a one-off bad copy, or a systematic problem with the lens line is hard to say. I would guess it's an example of poor quality checking, and that most lenses are ok.

This problem annoys me a bit. I've previously found the basic kit lens to be a good one, despite the mixed reception it generally gets online.

Now, this is not really a big issue. Generally, you don't get much bokeh with kit zoom lenses anyway. So the problem is not very likely to show in images. If using the camera at full auto, it generally chooses the maximum aperture anyway, in which case the aperture opening is round.

This problem might affect the exposure correctness. The defective aperture blades could cause slight exposure irregularities. But again, this is not likely to be a big problem

Epilogue

If found the aperture to be so bad, that I took the lens back to the shop where I bought it in the first place.

The store keeper has some problem verifying that his off the shelf lens did not exhibit the same non-round aperture. I helped him by taking a photo with the lens mounted to the Panasonic GF2 camera at f/9, 2 seconds, and removed the lens during the exposure. Looking towards the light through the lens showed that his copy had a round aperture.

So he accepted my lens as defective, and sent it for repair.

After one month, I started enquiring about the lens. I always got the same answer: "The lens is just around the corner, should be in our store the beginning of the next week."

It was not until after three months that the lens finally did arrive in the store. When I went to pick it up, I was told that they simply replaced the lens with a new one. Why let me wait for three months when they would just give me a new copy?

Coming home, I once again checked if the aperture was rounded. I found that my new lens had exactly the same problem, the aperture blades are misaligned. I did check that the new lens has a different serial number, so it is not the same lens that I returned.

Letting me wait three months for a new lens is bad. But giving me a new lens which has the same problem as the one I returned is simply appalling.

GH2, does ETC affect the video quality?

ETC, or Extended Tele Converter, is an interesting feature with the Panasonic GH2. I've previously looked at how it can be used to get closer video recording of the moon using the Lumix G 45-200mm lens.

Essentially, ETC is a digital zoom for video. During normal video recording, the entire sensor area is scaled down to 1920x1080 pixels. When enabling ETC, the camera crops the 1920x1080 pixels from the centre of the sensor. This achieves full HD resolution, as well as a digital zoom. See the illustration:

Since 2800/1080 = 2.6, the ETC mode gives a tele conversion effect of 2.6x. If you use the 720p video mode, the conversion effect becomes larger still, 2800/720 = 3.9.

A question that remains is to see if the video quality is still good using the crop mode. In theory, it could be somewhat worse, since the camera doesn't have the option of scaling down from a larger number of pixels.

On the other hand, we know that the camera doesn't actually sample all the 16MP of sensor pixels for each frame in the video.  That would require too much bandwidth and processing power.  Just how many are sampled is unknown, but given that the electronic shutter 40fps continous mode has 4MP, one can guess that about that many are sampled during video recording.  This is, of course, just speculation.

To study this, I have used the kit zoom lens, Lumix G 14-42mm f/3.5-5.6. Since it has a zoom ratio of 3x, using ETC in the short end should give the same field of view as the longer end without ETC. This is a good basis for comparing the video with and without ETC.

I used 40mm without ETC, and 15mm with ETC. Since 15mm times 2.6 is approximately 40mm, these two modes give about the same field of view. I recorded video using ISO 160, 640 and 2500. Here are the recordings in sequence:



To better evaluate the quality differences, I have compared still images from the video streams (click for a larger version):

It appears that the video stream recorded using ETC has worse image quality than the normal stream, at all ISO values. There is some lack of sharpness and contrast, and more noise in the ETC video streams.

The reasons for these differences could be the sampling from a higher number of pixels when not using the ETC mode, as discussed above. Or it could also be related to the lens sharpness, see the discussion in the Appendix, below.

This does not mean the the ETC videos are useless, far from it. But it is fair to say that there is some image degradation when using ETC. As a rule of thumb, I think you should avoid using ISO higher than 640 when using ETC.

ETC is still a very good tool to use when you need extra reach during video recording. If you don't have any longer lenses, ETC is the only way to get quality videos at longer reach.

Appendix, some technical aspects

I used the new 1080p, 24fps cinema mode. This is the video mode on the Panasonic GH2 which gives the highest bitrate. It is generally recommended to use this 24ftp progressive mode, except when you have significant movement in the picture frame. When there is movement, people generally recommend to use the 60fps (NTSC) or 50fps (PAL) modes.

When the lens was set to 15mm, I stopped down the aperture to f/4. In ETC mode, the camera only uses the centre of the image, where lenses are generally very sharp. I've previously looked at the sharpness of the Lumix G 14-42mm kit lens, and found it to be good wide open at 14mm. So I don't think the centre sharpness at 15mm f/4 is a significant limiting factor when using the ETC mode.

But there is probably some impact on the sharpness due to the lens performance when using ETC. Remember that the ETC mode is more demanding on the lens sharpness, since there is no downscaling. When video recording without ETC, the image is downscaled from a larger sensor area, and the lens doesn't need to be tack sharp. It is like putting the lens designed for a 16MP sensor on a 2MP sensor camera.  It's not very likely that you can identify a lack of sharpness with a 2MP sensor.

In real life use, it is of course silly to use ETC in the short end of the Lumix G 14-42mm f/3.5-5.6 kit zoom. It is better to just zoom in. But I did this to get comparable images with and without ETC.

It is much more relevant to use ETC with the longer end of the Lumix G 45-200mm tele zoom lens. However, many have concluded that it is not very sharp in the longer end, so it may not be sharp enough to get a good video quality with ETC. You may want to stop down the aperture to f/6.3 or f/7.1 for the best result.

Bokeh comparison @ 14mm

The Lumix G 14mm f/2.5 pancake and Lumix G 14-42mm f/3.5-5.6 are both rather new lenses. What they also have in common, is that they have received a mixed reception online.

The pancake lens has some disappointed over lack of sharpness, and not being as fast as the Lumix G 20mm f/1.7. While the comment about not being as fast is correct, I have found the 14mm to be very good optically.

The new kit zoom lens is said to be worse than the lens it replaces, the Lumix G 14-45mm f/3.5-5.6. While it is probably true that the old kit lens was better, I have found the new one to be good, too.

In this article, I have taken a look at how the lenses render out of focus parts of the image, the bokeh. I did this by taking the same image with both lenses. The lenses were focused on the checkered pattern in the lower right part of the image, which is about 30cm from the camera. (click for larger images):

Lumix G 14mm @ f/2.5	Lumix G 14-42mm @ 14mm f/3.5

The pictures were taken with ISO160, base ISO for the Panasonic GH2.

To better evaluate the images, here are 100% crops from the left, centre and top parts of the images, respectively. The images were taken with apertures ranging from f/2.5 to f/8:

(Click for larger images.)

Due to diffraction, one should avoid using apertures smaller than f/8, i.e., avoid larger aperture numbers. This is especially true if you are going to be studying enlargements from the images. If you plan on publishing the images in web size only, go ahead and use apertures as small as f/22. The diffraction will not be a problem if you are going to downscale the images that much.

Conclusion

I think this test does not reveal any bokeh problems with any of the lenses. Perhaps the test could have been made more challenging by having some strong highlights in the background.

The patterned textile in the first compilation image is in focus. We can see that it very sharp already from the smallest aperture. This appears to verify my initial claim that both lenses are in fact quite good, despite their rather bland reception.

The Lumix G 14mm f/2.5 pancake lens appears to be sharpest. This was to be expected, I think, since it is not a zoom, and hence has fewer optical compromises. Further, it also lacks an OIS lens group, and has a simpler construction with only six lens elements. The 14-42mm zoom lens has twice as many lens elements. Generally, more lens elements can lead to worse optical performance, for example reduced contrast. However, modern quality zoom lenses can retain superior optical performance with 15-20 lens elements.

TTL flash metering and flash delay

Flash metering has come a long way the recent decades. TTL flash metering for SLR cameras was first introduced by Olympus in the mid 1970's. TTL refers to Through The Lens. The camera measures the amount of light coming onto the film through the lens during the exposure, and cuts off the flash as the exposure is sufficient.

Film based SLR cameras

For film based SLR cameras, this is usually implemented by having a flash light meter in front of the film plane. The amount of light reflected off the film from the flash is metered, and the flash is turned off when there has been a sufficient amount of light for the desired exposure. See the illustration below.

Film based SLR camera with lens

In this illustration, the mirror is raised for exposing the film.

This generally worked well, at least as long as the subject was not too dark or too light, in which case you needed to manually adjust the flash exposure.

Digital SLR cameras (DSLR)

With digital cameras, this does not work well, since the imaging sensor, replacing the film, is not reflective enough. To overcome this problem, most DSLR cameras fire a pre-flash before raising the mirror, and then fire the main flash after exposing the sensor.

The pre-flash is used to determine the amount of flash needed for the exposure. With this method, the TTL flash meter is no longer needed, the camera's ordinary light meter is used. See the illustration.

DLR camera with lens

There are some DSLRs that still measure the amount of light reflected off the sensor chip, and avoid the pre-flash. The Fujifilm S1 and S3 does this.

Mirrorless cameras

As you know, Micro Four Thirds is a mirrorless camera system. The camera has no light sensor anymore. The imaging sensor is the light sensor. So to find the correct flash exposure, a pre-flash is triggered while the sensor is exposed. Then the camera must make the sensor ready for a second exposure, and fire off the flash with the correct amount of light. This typically takes a bit more time than with a DSLR. The DSLR used the separate light meter for the pre-flash, and could expose the main imaging sensor only once.

Here's a basic illustration of a mirrorless camera with lens. It is much simpler, since there is no mirror, pentaprism, or light meter.

Mirrorless camera with lens

Flash and pre-flash timings

To examine the pre-flash and main flash timings, I have video recorded operating the Panasonic Lumix GH1 and GH2 cameras. I also measured the Pentax K10D, which is an older DSLR from 2006. I turned off autofocus, to measure the flash delay only, and not also the autofocus delay.

I used 50fps when recording, which gives an accuracy of approximately 0.02s.

	GH1	GH2	K10D
Time to pre-flash	0.16s	0.12s	0.08s
Time to main-flash	0.12s	0.14s	0.12s
Total flash delay	0.28s	0.26s	0.20s

The first timing is the delay from pressing the shutter until the pre-flash is fired. The second is the delay from the pre-flash until the main-flash. The third figure is the sum of the two first: The total delay from pressing the shutter until the main flash is fired.

You can see the recordings here. I uploaded them as 25p videos, so they are not as good for verifying the actual timings.



Conclusion

One could say that the GH2 improves slightly on the GH1 in terms of flash delay. However, the difference, 0.02s is not significant with my way of measuring. So we can only say that they are comparable.

When comparing with the older Pentax K10D, we see that the GH1 and GH2 perform almost as good. The difference between 0.20s and 0.26s is not very large. Probably, the autofocus speed is more important to the average user, and we have seen that both the GH1 and GH2 perform very well in terms of autofocus.

One way to avoid the TTL pre-flash, is to use a flash in Auto mode.

Now, we should not conclude that the extra flash delay with Micro Four Thirds cameras is exclusively a bad thing.  As opposed to DSLRs, which have a limited number of light metering sensors, the Micro Four Thirds cameras essentially take one full picture to determine the correct exposure.  This means that the camera has at least 12 megapixels of information available.  It probably doesn't use all of this information.  But what it can potentially do, is to use the information about where in the frame faces are, to enhance the exposure.  Also, the camera knows which areas are in focus, and can make sure that these areas are properly exposed.  The extra information the camera has can be put to good use to give you a better exposure.

Chromatic Aberration and lens correction

Chromatic Aberration (CA) is a type of lens distortion. It is caused by light of different colours being refracted differently by the glass lens elements.

This is one reason why lenses often consist of pairs of lenses grouped together: The two lens elements in the pair are made of different glass types, and have different optical properties. The aim of the construction is to neutralize the effect of chromatic aberrations, so that all visible colours focus in the same place.

Here is an example image illustrating CA. The image was taken with a Panasonic GH1, using the Olympus Zuiko 9-18mm f/4-5.6 wide angle zoom lens at 9mm f/4:

An enlargement of the lower left corner reveals the CA artifacts:

You'll see that there is red and green fringing off the high contrast areas, where the white and black paint meet. These artifacts are typically seen in the corner of the frame, while the centre of the image is generally free from them.

In the extreme corner, the artifacts take up about 2-3 pixels, which is a moderate effect.

CA artifacts are generally found in the corner, especially when using wide angle lenses.  The lack of CA artifacts indicate a high quality lens design.

Automatic lens correction

Panasonic Lumix G lenses are automatically corrected for CA artifacts by the camera. In the JPEG output files, the camera has adjusted the images with the intention to remove these distortions.

When using Panasonic Micro Four Thirds lenses on Olympus cameras, the CA corrections are not done with current camera models. Future cameras from Olympus may employ the same technology as Panasonic uses, and adjust for these effects.

We can still see the original exposures by opening the RAW image files in a converter which allows for not implementing the CA adjustments. One such RAW converter is UFRAW. By using this converter, we can compare the original exposure with the out of camera JPEG output, to see what kind of adjustments were done.

I am fully aware that there are RAW converters which will do the CA corrections as well.  So this is not a test of the RAW converter, but rather a look at the image before the CA correction, to see what kind of CA artifacts the lenses generate.

I have done these comparisons for three lenses. The images were taken with the Panasonic GH1 at ISO 100:

Lumix G 8mm f/3.5 fisheye

Here is the full image, take with a wide open aperture at f/3.5:

And the upper right corner at f/3.5 and f/5.6:

In this example, we can see that the fisheye lens is very sharp in the corner, even wide open at f/3.5.

In the extreme corner, there is some red and green fringing where white meets black.  Perhaps around 2-3 pixels of colour artifacts.  They are corrected well in the JPEG output, though.

Lumix G 14mm f/2.5 pancake

Here is the full image, take with a wide open aperture at f/2.5:

And the lower right corner at f/2.5 and f/5.6:

We see here that when using the lens wide open, there is some vignetting in the corner, and also, the sharpness is not optimal. This is quite common for any lens, really, and I wouldn't say it is a problem.

Looking at the CAs, it looks like there is about 1-2 pixels of red and green fringing in high contrast areas in the original RAW image. In the adjusted JPEG image, there is still some purple fringing.

Lumix G 20mm f/1.7 pancake

Here is the full image, wide open at f/1.7:

And the lower right corner at f/1.7 and f/5.6:

My comments here are mostly the same as for the Lumix G 14mm lens: There is vignetting, and there is dullness in the corner at f/1.7. Again, this is not uncommon, and especially so for a low light lens with a large aperture.

Before conversion to JPEG, there is some small amount of green and red fringing. In the converted JPEG image, the green fringing is gone, but there is still some purple fringing.

Olympus Zuiko Digital 50mm f/2 1:2 macro (Four Thirds lens)

This lens is rather well known for it's CA artifacts. Here is a video showing the lens being used on a Panasonic GH1 camera (with an adapter). When focusing manually close to the minimum focus distance, you can see clearly black text on white background is black only when in perfect focus. Focusing a bit longer gives a green outline. And focusing closer gives a red outline. Doubleclick on the video to get a larger view, up to 720p is possible.



Here is a 100% view of a photo taken using the Olympus 50mm f/2 macro at 1:2 magnification, and f/2 aperture. As you see, text which is beyond the focus point has green fringing, while text nearer has red fringing.

The Panasonic-Leica 45mm f/2.8 macro lens for Micro Four Thirds does not exhibit these kinds of artifacts.

Conclusions

When using Panasonic lenses on Panasonic cameras, some CA artifacts are corrected automatically. However, there are still some purple fringing left in the corners.  It is generally restricted to around one pixel width, which is not much.

Even before the CA correction, the CA artifacts are very moderate on the Lumix G 20mm f/1.7 and the Lumix G 14mm f/2.5 pancake lenses. The Lumix G 8mm f/3.5 fisheye lens has somewhat more CA effects in the extreme corner, but it is well corrected by software.

All in all, I think that CA artifacts are nothing to worry about with these lenses. Even when using the lenses on Olympus cameras, without in camera CA correction, this should not bother you much.

Comparison: Lumix 14mm vs Lumix 20mm pancake lenses

The Lumix G 14mm f/2.5 and Lumix G 20mm f/1.7 pancake lenses are similar, yet still very different. They are of course similar since they share a pancake characteristic: They are both very compact. They are shown below, with "home made" lens hoods:

(From the left: 20mm and 14mm.)

Still, there are many issues which make them different. The Lumix G 14mm f/2.5 has internal focusing, which makes the autofocus very fast and silent.

The Lumix G 20mm f/1.7, on the other hand, has a more traditional focus assembly, which moves all the lens elements back and forth. This is not as fast, and does generate some noise. This is not an issue in daylight, since both are very fast in sufficient light. But in low light, the 20mm lens can take in excess of one second to focus, which can be annoying.

And low light brings us to another area where the lenses are different: The 20mm lens is a true low light lens, with a maximum aperture of f/1.7. The 14mm, still gains about one stop of light gathering compared with the kit lens, but it is not at all a low light lens.

And, of course, the field of view is quite different: The Lumix G 14mm f/2.5 is a wide angle lens, and the Lumix G 20mm f/1.7 is more of a "normal" lens, which can be used for, e.g., environmental portraits in low light without a flash.

It is an interesting fact that you have exactly the same field of view with the pair of inexpensive pancake lenses from the Nikon Z system: Nikon Z 40mm f/2 and Nikon Z 28mm f/2.8. As these are full frame lenses, there is no crop factor, so the M4/3 20mm lens corresponds exactly to the Nikon Z 40mm lens. And the same goes with M4/3 14mm versus 28mm on full frame.

In terms of pricing, they tend to sell for approximately the same amount. The 14mm lens was included as a kit lens for the Panasonix GF3 camera, and these kits did not sell well. They were often split, and the lens sold separately off auction sites, which lowered the perceived value of the lens for some time.

Sharpness

What about the sharpness? The general opinion is that the 20mm lens is very sharp in the centre, even wide open at f/1.7. It does require stopping down to at least f/2.8 to get sharp corners, thought. When it comes to the 14mm lens, people generally say that it is not as sharp as the 20mm lens.

I prefer to find out for myself, so I made a field study. I put the Panasonic Lumix GH2 camera on a tripod, set it at base ISO (160), and used 2 second shutter delay to avoid camera shake.

I took the same picture using both lenses, at different apertures. I used the out of camera JPEG images. The shutter speed was always 1/100 second or faster. Below are the full images, scaled down and resharpened. Both images were taken at max aperture.

Lumix G 14mm f/2.5	Lumix G 20mm f/1.7

To better compare the sharpness, I have cut out 100% crops from the images. These crops were not sharpened. Here are some comparisons. These are from the centre of the images:



And here are crops from the top left corner:



Click to see larger versions of the images.

Sharpness Conclusion

First of all, we can conclude that the centre images are boring: They are virtually the same from max aperture down to f/5.6. They show that there is little to gain by stopping down the aperture when it comes to the centre resolution. Perhaps we can say that the Lumix 20mm lens is a tad bit softer at f/1.7 than f/2. But the difference is very subtle.

In the corner, though, there are more issues to comment. The Lumix 14mm lens does sharpen up a bit when stopping down, and appears to reach an optimal aperture around f/4. Stopping down further to f/5.6 does not appear to give better performance.

The Lumix 20mm lens appears to sharpen up quicker when stopping down. f/2.8 appears to give a sufficient sharpness, bit there is a tad bit of improvement also when going to f/4.

What about comparing between the two lenses? In the centre, I would say they are equally sharp. There is little to complain about in terms of sharpness at any of the aperture values.

In the corner, though, it seems that the 20mm lens is a bit sharper overall. Also, the 14mm lens has some purple fringing artifacts around the branches, which cannot be found in the 20mm corner images.

When it comes to vignetting, the 14mm lens again appears to have somewhat more vignetting wide open. You must close down to around f/3.5 to lose the vignetting, but it is not a huge problem even at larger apertures.

Optically, it seems that the 20mm lens still has an edge over the 14mm lens, especially in the corners. However, unless you are very critical, and make huge enlargements, I don't think any of the lenses will disappoint in terms of optical performance.

Chromatic aberrations

When using these lenses on Panasonic Lumix G cameras, the JPEG output images are automatically corrected for some Chromatic Aberration artifacts, like red/green fringing around high contrast areas, especially in the corners of the frame.

As at the current date, Olympus cameras do not employ this CA adjustment.

Based on my examination of the CA artifacts, these lenses do not generate a significant amount of them anyway. So even without the in camera CA correction, CA artifacts are not a significant problem.

Some purple fringing are left after the in camera processing, as we can see in these images as well.

Geometric distortion correction

Perfect rectilinear projection is one of the traditional quality indicators of lenses. If the lens gives a pincushion or barrel distortion, then that is commonly interpreted as a sign that the lens design is bad.

Both of these lenses give a significant barrel distortion without any post processing. Bear in mind, though, that this processing is done automatically in the camera, so that the JPEG images come out looking rectilinear. And when using RAW, most RAW converters will apply the geometric distortion correction seamlessly. So the user might very well never notice that the lenses feature significant distortion.

Using some third party RAW converters, it is possible to look at the images prior to the distortion correction. This reveals the true nature of the distortion properties of the lens. Below are images of a tiled wall. The black lines show how the image looked after the automatic in camera correction, while the red lines illustrate how the camera sensor actually saw the scene:

Lumix G 14mm f/2.5	Lumix G 20mm f/1.7

Read more about this study here. The 14mm lens has somewhat more barrel distortion. To get a rectilinear image, the 14mm lens requires a correction of -16% in the "Lens Distortion" filter in The Gimp, while the 20mm lens requires -11%.

What this means, is that the 20mm lens wastes less pixels in the corners of the image frame, and, potentially, can give slightly better corner sharpness. On the other hand, this effect is rather subtle, and for any real life application, I'd say you can basically ignore it.

Further, the 14mm lens does not correct enough for distortion at close focus distances. Hence, while you get good, rectilinear images at moderate to far focus, you'll get some small amount of barrel distortion at close focus. Again, this is not a problem for most real life usages, but it may be worth to note that this is not a lens for close focus reproduction of art, for example. The 20mm lens, on the other hand, is well corrected for all focus distances. I would guess that this difference is due to the internal focus of the 14mm lens, which is known to produce different geometric distortion properties at different focus lengths.

The lenses are designed to require post processing for a reason: Lens design is a matter of balancing various optical properties against each others. With this choice, the lens designers can focus improving the artifact that cannot be corrected in post processing, while leaving the geometric distortion to be adjusted in post. This can, potentially, lead to smaller lenses with better quality.

Bokeh

I have made a comparison of the out of focus highlights rendering for both lenses. The study shows that neither lens has a "perfect" bokeh. They exhibit various problems, for example non-circular out of focus highlight discs, ringing, dirty and uneven bokeh. See another bokeh comparison here, which has the same conclusion.

However, you must focus quite close in order for these problems to show. When photographing people, you will normally want to keep a distance of one meter or more to avoid perspective distortion, and the bokeh should not be a problem with this distance.

Field of view

Obviously, the 14mm lens has a wider field of view than the 20mm lens. The 14mm lens is a wide angle lens, while the 20mm lens is what people would normally call a "normal" lens. Normal lenses have a focal length which correspond roughly to the diameter of the sensor. The Four Thirds sensor diagonal measures 21.6mm, so the 20mm lens is in fact a slightly wide normal lens.

Based on the field of view difference, which is quite significant, which lens would you want to buy? Experienced photographers will probably not ponder long about this. They are already well aware of the concepts "wide angle" and "normal lens", and know their preferences. What about the rest of us?

If you have used the kit zoom lens for some time, you could take a look at your favourite photos and see what focal length they were taken with. Did you typically use the wide end of the zoom lens? Or the longer end? The answer here might determine your focal length preference.

There is a philosophy which goes like this: You can always get closer to an object, but you cannot always get further away from it. So to be able to photograph what you want, choose the widest lens. In this case, this philosophy dictates that you choose the Lumix G 14mm f/2.5 lens over the Lumix G 20mm f/1.7 lens, since the former is wider.

However, it doesn't take much thinking to see that the premises are not always right. Let's say you want to photograph people. Then, you should not get closer to them than around 1 meter. Going closer will give you perspective distortion, which can make the photo unflattering.

Hence, if you intend to photograph a person, and want to have their face as the main part of the image, you will want to choose the longer lens. At a 1 meter distance, their face will be just a small spot in the frame with the 14mm wide angle lens. Even the 20mm lens is not long enough to be a portrait lens, but it is still the better choice. For a portrait headshot, you will generally want a focal length of around 40mm or higher. But the 20mm lens can be used to take an environmental portrait.

On the other hand, if you intend to photograph a group of people, you will want to choose the wide angle lens. You cannot always back up more, so the widest lens is best to cover a group of people.

Aperture range

We have already discussed the different maximum apeture. The 20mm f/1.7 lens has the larger maximum aperture, obviously. However, the 20mm lens also has the larger minimum aperture. Here are the ranges.

14mm: f/2.5 - f/22
20mm: f/1.7 - f/16

The smaller possible minimum aperture for the 14mm lens is an advantage when shooting video. Generally, one would not want to have too fast shutter speed when recording a video.

For motion pictures, a 180° shutter is commonly used. This means that the shutter is open half the time. If you have 30 frames per second, this means that the shutter speed should be 1/60 second.

When recording a video outdoors on a sunny day, you may need to close down the aperture a lot to achieve 1/60 second shutter speed. In that case, the f/22 option comes handy with the 14mm lens. Otherwise, you may need to use an ND filter to get the right shutter speed.

Common knowledge says that you should avoid using small apertures, due to diffraction. Diffraction is known to blur the image at pixel level when using very small apertures. However, when shooting video, the resolution used is smaller, so I don't think diffraction is any problem. In fact, one could say that diffraction acts as an extra anti aliasing filter, which could actually improve the image quality during video capture.

Video use

Both lenses work perfectly fine with video. However, the quick and virtually noiseless autofocus of the Lumix G 14mm f/2.5 pancake lens makes it preferable for general video use.

In low light situations, you could find that when using the Lumix G 20mm f/1.7 you can lose focus for some seconds when there is movement in the scene. This is not so likely to happen with the 14mm lens, in my experience.

Apart from the autofocus differences, the choice between the two lenses largely comes down to the same issues whether you intend to use them for video or photo: The field of view and the maximum aperture. So the considerations in the rest of the article apply just as well for video use.

Here are some example videos.

Low light video with some action using the Lumix G 14mm f/2.5 pancake lens on a GH2:

More information about the video parameters used in the movie above. You'll notice that the audio quality is poor in the video. However, this is due to the sound system, which clips the sound at high levels.


This video showing the ice breaking up in Stockholm was recorded using a Lumix G 14mm f/2.5 pancake lens on a GH2, at 1080p, 24fps:

A low light concert movie using the Lumix G 20mm f/1.7 pancake lens on a GH2:

More information about the video parameters used.

The following video was recorded outdoors using the Lumix 20mm f/1.7 lens on a GH1. You'll see that the camera loses focus now and then, which is a bit annoying. Both the lens and the camera have had firmware updates since this video was recorded, and the autofocus performance during video has improved.

More information about the video parameters used.

Compared with the Sigma 19mm f/2.8 EX DN

In 2012, Sigma released their first Micro Four Thirds lenses, the Sigma 19mm f/2.8 EX DN and the Sigma 30mm f/2.8 EX DN. The 19mm lens is quite similar with the Lumix G 20mm f/1.7 pancake lens, so it makes sense to compare them.

See my main comparison article here. A brief summary: The Sigma lens focuses much quicker, and more silently. It also has a short startup delay, just like the Sigma 30mm lens, and it rattles when not in use. The rattle is no problem, it can just be a bit annoying.

The Sigma 19mm lens has the most pleasing bokeh. It is also cheaper.

In terms of image quality, I think it is clear that the Lumix G 20mm f/1.7 lens is the better. The 20mm lens also has a larger maximum aperture, and a smaller size.

I think that reasons for buying the Sigma 19mm lens over the Lumix G 20mm lens could be to save money, and to get better autofocus performance, especially during video recording.

After just a year, Sigma discontinued the Sigma 19mm f/2.8 EX DN lens, but introduced a new version at the same time. The new version has a different exterior design, but other than that employs the same optical layout, and, hence, the same image quality. The new lens retails for a bit more than the old one did before being discontinued. I guess that Sigma thinks the new metal exterior appears more desirable, and allows them to charge a premium price:



New version of the 20mm lens

In the summer 2013, this lens was discontinued, and a new version of the lens, Lumix G 20mm f/1.7 II (H-HS020A) was released. The new version has the same basic specifications, and has the same optical design. The exterior design is new, though, with a black or silver metal finish.

As the new lens has the same optical design, it still has the old style focus assembly which moves all the lenses back and forth. Reports indicate that the focus speed is the same as the first one, i.e., not very impressive. Even with the new design of the lens, the autofocus is still the slowest among the Micro Four Thirds lenses.

So the only reason to buy the new version of the lens would be if you prefer the new design to the old one.

The new designs of the Panasonic Lumix G 20mm f/1.7 II:


Conclusion

It seems to me that the Lumix G 20mm f/1.7 is valuable as a sharp, low light lens, while the main benefits of the Lumix G 14mm f/2.5 are the very compact size and the fast autofocus. Both lenses are optically very good, but the 14mm lens, lacking the true low light capability, is not as interesting. From my perspective, anyway.

This note is written six months later: After using the Lumix G 14mm f/2.5 lens a lot, I have come to like it more and more. Now, I use it more than the Lumix G 20mm f/1.7 lens.

The reasons for liking it more are the same as I have written above: Fast and silent autofocus, small size, very good optical qualities. It's also very good for video, due to the AF performance and silence. Besides, the field of view is generally quite useful when photographing and videographing people.

Appendix

To make the comparison of the images easier, I have applied auto levels to each row. That way, the exposures are more comparable.

The centre of the images:



The corner of the images: