Software correction to the PL45?

One important aspect of the Micro Four Thirds system is the software correction to the images. Traditionally, lenses need to correct the images optically, so that the medium capturing the images sees the correct image. With the advent of digital imaging, though, the camera can do software based corrections to the image, adjusting for aspects that the lens does not correct.

This has the potential of making the lenses smaller and cheaper. Also, by allowing some aspects of the lens output to be adjusted with image processing, other aspects not possible to correct with software can be given more weight in the design process. This has the potential to give a better image quality. I think that software correction of lens output is a good thing, however, it remains a controversial issue.

One aspect which is corrected with a number of Micro Four Thirds lenses is geometrical distortion. I have explored this in a number of articles, here is one summarizing the effect for a number of lenses.

The other aspect corrected with some lenses, is some chromatic abberations. In my study, some chromatic abberations are corrected for lenses like the Lumix 8mm fisheye, the Lumix 20mm pancake and so on. Currently, this correction is only done when using Panasonic Micro Four Thirds cameras. At the time of writing, Olympus cameras do not perform the CA corrections.

Panasonic Leica 45mm f/2.8 macro

There is some rumor on the internet that Leica branded lenses are not corrected using software. This is clearly not true, since a number of Panasonic compact cameras feature Leica branded lenses that are corrected for geometric distortion. Examples include the Lumix LX3, and Lumix LX5, as well as the Leica branded counterparts.

But what about Leica branded interchangeable lenses? The Panasonic Leica 45mm f/2.8 macro lens (PL45) is the first Leica branded Micro Four Thirds lens. Are there any software based adjustments to the image output? Let's try to find out.

Geometric distortion correction

Here is an example image taken with the Panasonic Leica 45mm f/2.8 at f/2.8:

By looking at the uncorrected RAW, and comparing with the out of camera JPEG, we can easily see if there was any geometric distortion correction. Here are 100% crops from the lower left corner:

As we can see, they are identical in terms of geometric distortion. The RAW image contains about eight more pixels along the borders, which is why a bit more detail is visible from the wall and the leaves. I have previously written about this: Using RAW gives you approximately 1% more megapixels.

Corrections of Chromatic Abberations

So we conclude that there is no geometric distortions correction when using the PL45 lens. What about CA corrections? Usually, we see the CA artifacts most easily in the corners of the image frame, and where there is a huge contrast between light and dark elements. A typical place where this is visible, is where foliage meets the sky. So let's try to see in the upper right corner:

The exposure and white balance is not entirely the same in both crops, so it's not straight forward to compare them. But I think it is safe to conclude that there is no more or less CA artifacts in either image, thus indicating that there is no in camera CA correction performed for this lens.

In my previous study of some Panasonic lenses, it was easy to see that there was a correction of some CA artifacts.

Conclusion

Based on my study, I conclude that there is no software correction of the image when using the Panasonic Leica 45mm f/2.8 lens on Panasonic cameras.

This does not necessarily mean that no Leica branded Micro Four Thirds lenses will feature in camera adjustments to the output image. There is a newer Leica branded Panasonic Lumix 25mm f/1.4 lens. I have not tried it, and so I cannot say if it features this kind of image processing or not.

Note that this is in no way a criticism of using RAW images. There are many RAW image converters which will do the distortion correction automatically and seamlessly, and you will never notice that there was any geometric adjustment done at all. I am using the RAW images to visualize the initial image captured by the sensor, as it is the only way to access it.

Sharpness comparison, PL45 vs ZD50

At the moment, there are two medium long prime lenses that can be used on a Micro Four Thirds camera: The Panasonic Leica DG 45mm f/2.8 1:1 macro lens (PL45) and the Olympus Zuiko Digital 50mm f/2 1:2 macro lens (ZD50).

They are somewhat different. As you can see from the specifications, the PL45 has a better close focusing distance, hence, is more suitable as a macro lens. The ZD50, on the other hand, has a larger maximum aperture. For that reason, it could be better to use as a portrait lens.

The lenses are compared below. As you can clearly see, the PL45, to the left, is the smallest lens. The ZD50 requires an adapter for use on a Micro Four Thirds lens.

But what about their performance? Quite obviously, the PL45 is much better in terms of autofocus speed. The ZD50 could not autofocus at all with the first generation of Panasonic G series cameras, and with newer cameras like the GH2, the focus speed is barely usable at all.

I have compared the bokeh of the two lenses. In my experience, the bokeh of the PL45 is more smooth. The ZD50 has somewhat sharper edges around the out of focus rendering of highlights.

Also, I've tried to compare their sharpness. My study, which focused most on closeup focus distances, is probably not the best. But I believe it shows that the sharpness of the PL45 is a bit better. But there is certainly room for interpretation of the results.

It is also a well known fact that the ZD50 has some Chromatic Aberration artifacts. I have explored that here.

I have also compared the PL45 with the Nikon Z 105mm f/2.8 for the Nikon Z system. It very apparent in this review that the Nikon lens is way better. Sharpness comparison

I've tried to do a second test of their sharpness. This time, I focused on a distant object. I put the camera, the Panasonic GH2 on a tripod, used the lowest sensitivity available, ISO 160, turned off image stabilization, and used a two second shutter delay to avoid camera shake.

Here are the full images, taken with maximum aperture with both lenses. The images have been rescaled and sharpened:

PL45, f/2.8	ZD50, f/2

To better compare the sharpness, I have cut out 100% crops from both images at similar apertures.

Here are 100% crops from the centre of the image frame. Click on the image for a larger view:

And these crops are from the lower left corner of the image:

And from the upper right corner:

Conclusion

First of all, we see again that the Olympus 50mm f/2 lens has more chromatic aberration artifacts. The artifacts persist until stopping down to f/5.6. This is three stops smaller than the maximum aperture.

You can see the artifacts as purple fringing around high contrast areas, e.g., around the scaffolding when there is a bright sky in the background.

The CA artifacts only appear when having a large contrast in the image. In a portrait photo, you're not very likely to experience high contrasts, and hence this is not likely to be a big problem.

Vignetting does not appear to be a problem with the ZD50. However, keep in mind that at f/2.8, it is already stopped down one stop from the maximum aperture. The PL45 gives some vignetting at f/2.8. We see this in the corner crops: They are darker at f/2.8 than f/4 and f/5.6.

When it comes to the general sharpness and contrast, I think that the 100% views show the PL45 to be slightly better. I think that the PL45 shows the most pleasing results. But both are certainly very capable. Unless you are going to print the images to very large sizes, I cannot see that any of the two lenses will displease you.

Some users of the Micro Four Thirds system are still waiting for the portrait prime lens. They could be unhappy with the Panasonic 45mm f/2.8 macro, since it does not have the sufficiently large aperture they expect.

According to the Olympus lens roadmap, they are going to release a 50mm macro lens for the m4/3 format soon. If it has a maximum aperture of f/2, like the Four Thirds counterpart, then it may perform better as a portrait lens than the PL45.

Rumors also say that Olympus will release a non-macro lens with a focal length of 40-50mm, and a maximum aperture larger than f/2. This has later been specified as an Olympus 45mm f/1.8 lens. If so, this will be an even better candidate for the portrait prime. We shall see quite soon, as these lenses are announced.

GH2: Buffer flush speed

The Panasonic Lumix GH2 is currently the top Micro Four Thirds camera. Still, it is not a camera with pro features, in my opinion. Of course, there is no firm definition about what constitutes a pro camera. But I would expect to find features like weather sealing, built in remote control receiver, wireless TTL flash control, twin control wheels, all of which are missing on the GH2. Another annoying feature is the slow buffer cleaning speed when using RAW images.

Single exposure

When taking a single exposure and saving both JPEG and RAW images, the delay from taking the image until playback is available is four seconds. I used a SanDisk Extreme Class 10 SD card. See the video below for a demonstration:



As you can see, pressing the PLAY button does not bring up the playback until the buffer has been flushed, which takes four seconds. Without RAW images enabled, this is pretty much instantaneous.

Multiple exposures

Using a fast SD card, the camera can take seven consecutive images in the high speed mode, at 5 FPS, when recording both JPEG and RAW images. But after this, it takes a very long time before you can review the images.

One could speculate that a high quality SD card could be better in this respect than a lesser quality one. I decided to test this, but trying two different cards. Below are two Class 10 SD cards at 8GB each, the premium SanDisk Extreme, and the value Transcend card:

I tested it by putting the GH2 on a tripod, turning off autofocus, and setting the aperture to the max, to avoid any delay caused by changing aperture. I used the Lumix G HD 14-140mm lens.

Here's a video recording of the experiment:



The results speak for themselves. The time from the first picture was taken until the playback was available was: 34.5 seconds (Transcend Class 10), and 24.5 seconds (SanDisk Extreme Class 10).

You can still take more images

While waiting for the buffer to clear, you can still take more images, even if you cannot enable the playback. After the buffer is filled initially, the camera will take one image approximately every third second. So this is not such a huge problem as it may seem like.

Here is a demonstration:



Auto review

Even if you cannot enable playback until some delay, the camera can still show a quick preview after capturing the image. This feature is called "Auto Review". You can find it in the "Setup" menu:

The Auto Review is a simple playback, and does not allow zooming in, for example.

Conclusion

The result surprised me. I was expecting to find that a Class 6 card is sufficient for use with the GH2, and that any faster card is a waste of money. Quite to the contrary, I find that using a more expensive premium Class 10 card actually has some real benefit, when recording RAW images.

Another conclusion is that even with a high end SD card, the buffer flush delay is significant with the GH2. 24 seconds is a long wait. Of course, when taking many exposure one could consider to turn off RAW recording, which would solve the problem.

The Panasonic GH1 has also got a slow buffer clearing speed. I haven't tested them head to head, but they feel pretty similar.

If you only use JPEG images, you don't get these significant buffer clearing times. In that case, you can basically ignore this test.

So do you need to use RAW? I find that if I have a good exposure and the correct white balance, I can use the JPEG image straight from the camera with no problem. But if the exposure is tricky, or the white balance is off, then having the RAW file comes handy for getting the best results. So for low contrast images at daytime, using RAW has little benefits, I'd say.

Home made camera bag

I like the small Panasonic pancake lenses. However, some of the size advantage is lost when putting the camera in a standard sized bag, as most camera bags are too large. I find that camera bags generally come in two categories: For compact cameras, and for system cameras. The former are too small to accommodate the camera with a lens mounted, and the latter are always too large for the camera with a pancake lens.

So what to do? Of course, the solution is to make my own bag. I wanted to make it out of neoprene fabric, a rubber like material commonly found in divers' suits. However, buying neoprene is difficult. So I ended up just buying a laptop case in the desired fabric, and then cannibalizing it for the material:

To get the right shape, I cut a piece of cardboard to fit the camera inside it:

The cardboard template was then used to cut the fabric. The extra flap on the top left side is for a separate, small pocket:

Here I have started sewing together the fabric. I'm testing that the Panasonic GH2 and the Lumix G 20mm lens fit inside:

At this stage, the bag is mostly finished. The zipper is taken from the original laptop bag. There is a smaller pocket in the left side of the bag:

Here, the bag is finished. The strap is stolen from an old backpack:

And here's how it looks when wearing it:

Conclusion

The bag works well, and has room for the camera with a pancake lens. But making it took very long time, and required a lot of sewing.

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.

Bokeh comparison @ 14mm and 20mm

Many people are looking for camera systems that can give a thin depth of focus (DOF). With a thin depth of focus, objects that are beyond the focus distance, or closer, are out of focus.

The Micro Four Thirds system is not ideal for getting thin DOF. To get a thin DOF, you are better off buying a camera with a large sensor, for example full frame DSLR cameras.

However, it is still possible to get a thin DOF with Micro Four Thirds if you use a close focusing distance. I have evaluated the out of focus rendering (bokeh) at close focus using three lenses: The Lumix G 14mm f/2.5 pancake, the Lumix G 20mm f/1.7 pancake and the Lumix G 14-42mm f/3.5-5.6 kit zoom lens.

I took the same picture using the three lenses at various apertures. Here are the full images at maximum aperture:

Lumix G 14mm @ f/2.5	Lumix G 20mm @ f/1.7
Lumix G 14-42mm @ 14mm f/3.5	Lumix G 14-42mm @ 20mm f/4.1

The focus was set on the emblem on the bell in the middle left part of the image. I used the Panasonic GH2 at base ISO, and the shutter speed was around 1-6 seconds. I used a tripod, and also two second shutter delay, to avoid camera shake.

The images above are taken using the maximum aperture available with the given lens. Hence, the DOF is as thin as possible, given the focal length and focus distance.

To better evaluate the bokeh, I have made 100% crops from two parts of the image (click to enlarge):

The first crops are from the focus area. From these images, it could look like the 14mm pancake lens is unsharp. However, these images were taken primarily to evaluate the bokeh, not the sharpness, and the focus point might be slightly different between the lenses. In my experience, the sharpness of the 14mm pancake lens is rather good.

In the seconds image, we see the out of focus highlights. I suppose one could say that neither of the lenses give a very nice bokeh. They have various problems. They all exhibit some ringing, but it seems to be worst at 14mm. Also, the bokeh is uneven, and "dirty", "swirly".

The 20mm pancake lens shows the most non-circular highlights, both wide open and closed down.

The 14-42mm lens shows some strange irregularity at f/5.6, at both 14mm and 20mm. This could look like a construction error of the aperture diaphragm. However, it is not likely to pose much of a problem, since only at very close focus distance would you see much out of focus rendering at f/5.6

In terms of roundness, the 14mm pancake has the most consistent appearance.

GH1 and dead pixels

Back in the day when people started replacing CRT computer monitors with LCD panels, dead pixels was a big deal. When you received the LCD panel you had ordered, you would have to review it to find the number of dead pixels, and consider whether or not to return it. Some claimed that dead pixels could be massaged with your fingertip and revived. After the production process improved, though, dead pixels has ceased to be a problem with computer monitors.

A computer monitor with 1280x1024 pixels has a total of 1280x1024x3 individual dots, one for each primary colour. This makes almost four million individual dots that make up the image you see. Previously, I took a macro closeup picture of a computer monitor to reveal the pattern of red, green and blue dots.

With camera sensors, the number of pixels is counted as the number of individual dots, each capable of seeing only one of the primary colour. Generally, these pixels are arranged in a Bayer-pattern, with two green pixels for each red and blue:

So a camera with 12 megapixels has 12 million individual light measuring cells, three times as many as the dots on a typical computer monitor. So is dead pixels a problem with cameras?

I tested my Panasonic GH1 camera. I took one very underexposed picture (which turned out black) and one very overexposed picture (which became white). The JPEG images are here, straight from the camera:

You don't need to look at them, though. Trust me, they are completely even, with no signs of dead pixels whatsoever.

However, what if the camera corrects the dead pixels in the JPEG files it generates? Perhaps there are "holes" in the image data, which is filled in by the JPEG engine in the camera's algorithm.

To check this, I opened the RAW files in a third party RAW converter program, the UFRAW. This did in fact reveal some dead pixels. I found eight pink dots. The colour pink is due to the green sensor element being dead, I suppose.

In the image below, a pink ring has been put around the dead pink pixels. After scaling the image down to 1000 pixels wide, the dead pixels themselves are of course not easy to spot anymore.

When investigating the black image in the RAW converter, I found no evidence of stuck pixels. So no pixels were generating a "phantom" light even though the exposure was non-existent.

I looked at other exposures, and found the dead, pink pixels in the same spots. So these pixels are definitively permanently dead on my GH1 camera.

Is this a problem? Hardly. As we saw, the JPEG engine is clever enough to mask these dead pixels, so when using JPEG images out of the camera, don't worry.

When using the RAW images, though, the dead pixels might disturb the image when using high resolution prints, for example. I would guess that the supplied RAW conversion program fixes these problems automatically, so this is likely only to be a potential problem with third party converters. And even then, eight dead pixels out of a total of 12 million is not exactly a huge percentage. It is very unlikely that this will cause any unwanted side-effects.

Appendix

Panasonic G series cameras do have a function to map these dead pixels. To do so, use the function "Pixel Refresh", which can be found in the custom menu (on the last page). The custom menu is the one with the "C" and wrench icon.

Self portrait on a bicycle

The Lumix G 8mm f/3.5 fisheye lens is fun to use, due to it's extremely wide perspective. This type of lenses are commonly used in extreme sports videos, like skateboard and BMX. I don't do this type of things myself, but I figured I could use the lens to record myself bicycling anyway.

To do this, I attached the Panasonic GH2 camera to the front fork of the bicycle. I used a Manfrotto Super Clamp, which is essentially a clamp with a tripod head attachment stud. To be able to attach the camera, I also used a tripod ball head, and I chose the Benro BH0, which is pretty compact. After putting it on my bicycle, it looks like this:

Here's the video I recorded:



I prefocused at about 50cm, and set the camera to Manual Focus (MF) before starting the video recording. This was done to avoid focus hunting during the video. The 8mm fisheye lens focuses very quickly, but still, I wanted to avoid short periods of out of focus footage.

I think the colours look a bit dull in this video. It was a somewhat dull day, but still, I think that the next time, I will increase the colour saturation setting before using this lens for videos.

Hacked GH1 vs GH2: Video quality comparison

A matter of some dispute is which camera gives the best video quality: The hacked GH1 or the newer GH2.

The GH1 has earned some popularity due to the possibility to change the firmware. Adjusting the firmware is generally referred to as "hacking" the camera. There are many options, and the most useful ones are the possibility to get native 1080p 25fps (with the PAL version), and to increase the bitrate. I have done both with my GH1.

I've compared them before, and my conclusion back then was that the GH2 had better auto white balance (AWB) for indoor lightning, but other than that, it was hard to find much evidence of better video quality. I was advised that I should try to pan the cameras while recording foliage.

There are two problems with that: One is that there is no foliage in Scandinavia at this time, since spring is not yet here. The other is: How would I know that I have panned at the same speed, giving comparable footage?

For the second problem, Technic LEGO again comes to the rescue. Previously, I made a rotating object using Technic LEGO, and video recorded that. This time, I made a platform for the camera out of Technic LEGO, and used that to pan the cameras at the same speed. Here is how the platform works:



Putting the platform outdoors enabled me to record the same footage using both cameras. I used the same image parameters for both cameras: ISO 200, f/3.2, 1/400s shutter speed, outdoor sunny white balance, manual focus. Due to limitations in the cameras, I could not use the same frame per second count. I used 1080p for both, but 25fps for the GH1 and 24fps for the GH2.

I used the Lumix G 14mm f/2.5 lens, which is more than sharp enough for this test.

In real life use, one would not normally use a shutter speed of 1/400s. The normal speed to use is twice that of the framerate, which is 1/50s in my case. This is called a 180° shutter, since it is open half the time on average.

One reason why a 180° shutter is normally used, is to get motion blurring for objects moving across the frame. Without motion blurring, the movement can look unnatural on film, since the object will appear as if it materializes in different spots at different times. This is confusing for the person watching. I have a discussion about this, and the need for Neutral Density (ND) filters here.

In my case, though, I want to avoid motion blurring. The whole point of the experiment is to see which camera resolves the most details, and then I must make sure that the video stream contains as much details as possible to begin with. Motion blurring typically makes the footage softer.

Due to the hacked GH1 having a higher bitrate, it generated larger video files. The GH1 gave 5.4 MB/s, while the GH2 gave 2.8 MB/s.

Here are the two video recordings:



GH1



GH2

It's somewhat difficult to evaluate the quality of the video by looking at the videos, especially since YouTube compresses them anyway. So to aid in comparing them, I have grabbed single frames from them to compare.

Here are two similar frames (click for larger versions of them):

GH1

GH2

The first thing we can see, is that the GH1 still image is brighter, despite having the same image parameters. I interpret this to mean that the ISO scales of the cameras are not the same: The GH1 ISO scale corresponds to higher ISO values with the GH2. It is a well known and documented fact that the GH1 ISO scale is generous, meaning that a given ISO value gives more sensitivity than the same value for comparable cameras. The GH2 ISO scale is more normalized.

Another thing we can note, is that the trees lean a bit to the right. This is due to panning the camera, and the rolling shutter. I've evaluated the rolling shutter effects of the two cameras before, and found them to be comparable. Rolling shutter can create artifacts when using both the GH1 and GH2, but for normal use, it is not a real problem.

Here are direct comparisons between two areas from the two video streams. They are shown here in 100%, i.e., not rescaled and not sharpened.

Since the exposure is slightly different, I have also done an autolevels on the images, to make them comparable. Here they are:

Conclusion

One could be tempted to think that the GH1 gives better video quality, due to the twice as high video bitrate. But the GH2 has other advances. We don't know for sure just how the GH2 handles the video compared with the GH1, but it is reasonable to guess that it samples more pixels as a basis for the video output, and that the compression algorithm is better.

So, which video stream is better in my test? I think they are quite similar. Perhaps one can conclude that the GH2 gives somewhat better contrast and sharpness. The GH1 has slightly washed out colours, I think. But the difference is small.

My conclusion so far is that the GH2, even with lower bitrate, gives slightly better video quality. But both cameras are very competent.