High ISO performance of the GH series cameras

When new camera generations get launched, everybody expect the high ISO image quality to improve over the previous generations. While we would use a low ISO as possible at all times some years ago, it is generally quite safe to use ISO 800 with newer generation cameras. Let's take a look at how the Panasonic GH series handles high ISO.

To test this feature, I rigged the Panasonic GH1, GH2 and GH3 on a tripod, using the Sigma 30mm f/2.8. I left the lens wide open, it tends to be quite sharp. To be able to compare the cameras, I set both in the Shutter speed priority mode (S), at 1/10s and auto-ISO. The camera would then select the ISO needed for the exposure to be sufficient. I used Auto White Balance (AWB).

Here are the three images:

GH1, 1/10s, ISO 1250

GH2, 1/10s, ISO 1600

GH3, 1/10s, ISO 1600

These are the out of camera JPEG images, with standard image settings. The histogram below shows that all cameras expose the scene pretty similarly. The GH3 exposes it a bit brighter, though:



Another thing to note is that the GH1 uses the lowest ISO value of the three, 1250. This confirms again that the Panasonic GH1 had a somewhat conservative ISO scale, compared with other Micro Four Thirds cameras.

Looking at the image quality, we can compare 100% crops from all three images. I rescaled the GH1 image, to make it comparable with the 16MP output of the other cameras.



I think we can see that the GH2 images look sharper, but at the expense of shadow details. The GH3 appears to give a higher dynamic range, with more usable details in the dark parts of the image. With the advances of high ISO image quality, I feel quite confident using ISO values of 1600, and even 3200 when needed, with the Panasonic GH3.

GH1, GH2 and GH3 @ ISO 200

Whenever a new camera is launched, there is usually a lot of discussions about what the true ISO values of the camera is. Is the ISO rating conservative, meaning that the true sensitivity of the camera is higher than the rated sensitivity? Or are the manufacturer cheating by stating that the sensitivity is ISO 200, for example, when in fact it is ISO 100?

To try to shed some light on this question regarding the Panasonic GH series, I have taken a picture of the same scene at the same time of day with the three cameras. I used the same lens, the Lumix G 20mm f/1.7, and I set the aperture to f/1.7. The other settings were: ISO 200, 1/250s, sunny white balance. Here are the out of camera JPEGs:

GH1:

GH2:

GH3:

When isolating only the wall part of the image, and looking at the histograms, it reveals that the ISO ratings are probably a tad bit different:

This indicates that at ISO 200, the Panasonic GH1 appears to be a bit more sensitive, while the GH2 and GH3 appear to be fairly comparable. This is consistent with the DXO ratings, which show the GH1 to be more sensitive than the GH2.

Note that the above results are based on the out of camera JPEG images. I have also developed the RAW images using Lightroom 4.3 RC with no exposure compensation, and gotten these histograms:

These results indicate a similar conclusion as the JPEG tests: The GH1 has the higher sensitivity at ISO 200, while the GH2 and GH3 are fairly similar.

Using the RawDigger program, I extracted the average exposure from the wall area of the images, again from the RAW images. The results are here:

Camera	GH1	GH2	GH3	GH3(*)
Red	215	153	267	123
Green	618	427	470	326
Blue	430	287	346	202
Green2	612	422	471	327

The current version of RawDigger does not set any default black level offset for the GH3, since it is a new camera. For the GH1 and GH2, it sets a black level offset of 15. Some say that the Panasonic GH3 should have a black level offset of 144, in which case you get the rightmost values in the table, denoted by "GH3(*)". The other GH3 column is taken without any black level offset.

For comparison, here are the images converted from the RAW files using Lightroom:

GH1:

GH2:

GH3:

2x Fisheye on a bicycle

It so happens that I have both the fisheye lenses available for Micro Four Thirds at this time. I bought the original Lumix G 8mm f/3.5 fisheye when it was available. It is a fine lens, for sure, with good sharpness even in the corners.

The Samyang 7.5mm f/3.5 fisheye lens did interest me, and I decided to pick that one up as well. It is much cheaper, and performs even better optically, in my experience. The Lumix lens can be better when photographing close items, like closer than around 30cm (one foot). Then, autofocus is useful. Otherwise, I generally use the Samyang lens now.

But having both at the same time can also be useful. Since I have both the GH1 and GH2 cameras, I can use both lenses at the same time. Mounting them both to my bicycle using Manfrotto Superclamps and ballheads, I can record the scenery passing by from two angles, which can make some interesting footage:

Here is the footage I ended up with, after editing the video. I'll get back to the details of how I edited it later in this article:



Front camera

Pointing forwards, I have the GH1 camera with the Lumix G 8mm f/3.5 fisheye lens. The camera is set to auto-ISO. With the exposure set to f/3.5, 1/25s, the camera has picked the maximum ISO 1600 for most of the ride, which is still a bit too low, leaving the footage a bit underexposed. I pre-focused at about 1m distance, and left the autofocus off. The camera records at 25fps 1080p.

Rear camera

Pointing backwards, I have the GH2 camera with the Samyang 7.5mm f/3.5 fisheye lens lens. I used the same settings as for the GH1 camera above. However, the auto-ISO goes to 3200 for videos, and hence, the rear camera has a better chance at capturing a more correct exposure.

In my experience, both cameras will consistently underexpose when using the Samyang lens at night, with high contrast. So I dialed in +1 1/3 exposure compensation.

Video editing

First of all, I had to synchronize both video streams, which was quite difficult. In retrospect, I should have clapped my hands in front of both cameras, to have a more clear point of reference.

Here you can see both videos in the Kdenlive video editing software timeline. The GH1 footage is on the top. I'm using the audio from the GH2, pointing backwards.

Then, I wanted to fit both videos into one single frame. This was achieved by cutting off the top and bottom of the original frames, and then compressing the rest by about 20%. To do this, I use the "Scale and Tilt" effect in Kdenlive, with these parameters:

Here is an illustration of an example image frame before and after cropping and scaling:

After halving the vertical size of each stream, I can fit both of them into one 1920x1080 video frame.

Conclusion

One would think that having two lenses that are virtually equal is a waste of money, but it can give you some creative possibility.

After seeing the resulting video, I think I should have cut it much shorter. I doubt that many will want to see the whole thing, as it is too long.

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.

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.

Pixel RW-221 wireless RF remote control

Panasonic Lumix G cameras do not come with any remote receiver. Neither infrared (IR) nor radio frequency (RF). I like to have the possibility to trigger the shutter remotely, and so I have been searching for an appropriate remote shutter release.

Of course, there's always the self timer. But it is more of a hassle to use, and it doesn't give you any control over the autofocus.

I have previously tried the JJC JR series Infrared Controller. While it does do the job, it is awkward to use, somewhat unreliable, and has a poor build quality. Also, since it is an IR controller, you need to point the remote towards the receiver.

So I was not happy with the JJC JR remote.

I decided to try an RF remote from Pixel, called "Pixel RW-221 Wireless Remote Control". It is made for the Panasonic G series, as well as the older Panasonic DSLR cameras.

When unpacking, it is immediately clear that this is a higher quality product than the JJC JR remote. The parts have a better look and feel, and the buttons operate better. Also, the cord is spiraled, and has gold plated contacts. It comes with batteries, two sets of two AAA units. Here are the contents:

Clockwise from top left: Spiral cord with 2.5mm jack connectors, the remote receiver with a power button, and a shutter release button, the wireless remote control, batteries (4xAAA), and the operation manual.

The following picture shows the two units open, with batteries installed. You can see the dip switches, which are used to change the RF frequency. This is useful if you have several units, or if your neighbour has the same product.

If you are practical, like me, you can operate the unit without reading the manual. It is very intuitive. The video shows how to use the remote:



The remote is used on a Panasonic Lumix DMC GH1 in the video above, but should work with all Panasonic G series cameras. I have confirmed that it works with the Lumix GH1, GH2, and GH3. The latter has a separate remote control socket, not combined with the mic. It also works with the Lumix GX1, GX7, G5 and G6. The Lumix GM1 does not have a remote control socket, and cannot use this remote.

The right angle plug goes into the camera, and you must make sure to insert it fully. Some times, this requires pushing it in quite hard.

The remote receiver unit doesn't need to sit in the flash socket. But as long as you don't need to mount a flash, it is a practical place for it to stay. When pressing the power button, the red LED flashes to indicate that it is on.

The remote shutter can be half pressed for focus, and pressed fully for triggering the shutter.

There is an auxiliary shutter button on the receiver unit, which works in the same way.

I could not get the Bulb mode to work. It appears to trigger the shutter quickly over and over again. So if you need the Bulb mode, this remote might not solve your needs.

Conclusion

This product can be bought at a reasonable price from various auction sites. It has a good quality feel, and works in an intuitive way. All in all, it is highly recommended for those who need a remote control.

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.

AF speed, GH1 vs GH2

I have previously checked the AF speed of the Panasonic GH1, and the Panasonic GH2. However, the tests were done at different times, and with different setup, lightning, etc. Also, the GH1 firmware has been updated in the mean time. So I decided to check both cameras again, under exactly the same conditions.

Again, I set a LEGO figure in the centre of the image frame, and found the time from pressing the shutter release button to the camera taking the image. I turned on the camera just before testing the autofocus, which means that the focus is near infinity when first pressing the shutter release button.

I did the test under two different conditions. The first was in dim light, with a black background: There is artificial lights, and rather dim at around EV5. The distance from the camera to the LEGO figure was about 0.6m.

The second was with daylight coming in through the windows, and white background. The lightning was about EV9.

Here are a couple of examples:



Panasonic GH1, Lumix 20mm, dim lights, black background



Panasonic GH2, Lumix 20mm, dim lights, black background



Panasonic GH1, Lumix 14-140mm @ 140mm, daylight, white background



Panasonic GH2, Lumix 14-140mm @ 140mm, daylight, white background


And these are the timings I found:

Lens	GH1, dim	GH2, dim	GH1, daylight	GH2, daylight
Lumix G 14mm f/2.5 pancake	0.43 seconds	0.43 seconds	0.37 seconds	0.20 seconds
Lumix G 20mm f/1.7 pancake	0.57 seconds	0.53 seconds	0.53 seconds	0.40 seconds
Leica Lumix DG 45mm f/2.8 macro	1.07 seconds	0.93 seconds	0.73 seconds	0.43 seconds
Lumix G 14-42 @ 14mm	0.43 seconds	0.33 seconds	0.30 seconds	0.20 seconds
Lumix G 14-42 @ 42mm	0.47 seconds	0.40 seconds	0.37 seconds	0.20 seconds
Lumix G HD 14-140 @ 14mm	0.40 seconds	0.33 seconds	0.27 seconds	0.17 seconds
Lumix G HD 14-140 @ 50mm	0.53 seconds	0.57 seconds	0.40 seconds	0.23 seconds
Lumix G HD 14-140 @ 140mm	0.70 seconds	0.53 seconds	0.50 seconds	0.33 seconds

What we see here, is that the timings are remarkably similar in the tests done with dim lights. The GH2 has a small advantage to the GH1, especially with the fast focusing zoom lenses. But in this test condition, there is little to gain by using the GH2.

On the other hand, when testing the cameras with more light available, the difference is larger. The GH2 really excels in this test condition.

My previous test gave a larger difference between the two cameras. However, the GH1 firmware has been upgraded several times since that test, and so has the lens firmware. It seems that the GH1, with the up to date firmware, is still very capable.

As for the accuracy of the focus, it is very good with both the GH1 and GH2. Both cameras use CDAF (contrast detection autofocus). This means that the image sensor checks the actual image for focus before the camera takes the picture.

In contrast to SLR cameras, which use PDAF (phase detection autofocus). This means that there are separate AF sensors behind the mirror, which check the focus in some spots in the frame. These sensors must be calibrated to the image sensor, a process which is costly and complicated. Users of SLR cameras often worry that the camera/lens combination is back-focusing or front-focusing, i.e., that the AF sensors are noe correctly calibrated. This is something that users of Micro Four Thirds don't need to worry about.

Modern DSLRs can also use CDAF, which is generally refered to as "live view". However, this focus mode is often quite slow on DSRLs, since few lenses are optimized for CDAF. All native Micro Four Thirds lenses, and some Four Thirds lenses, are optimized for CDAF.

GH1 vs GH2: AF during video

When the Panasonic GH1 was launched, it was the only consumer system camera to provide continuous autofocus during video recording. Since this time, several competitors have launched their own systems, with the same capabilities. To regain the throne, Panasonic's most recent GH2 model must improve upon the original GH1. How does it fare?

To test this, I made a LEGO contraption which moves a paper sheet back and forth. The paper sheet has a printout of a sharpness test pattern. Here's how it looks:



But filming this and seeing how well the camera AF can keep up, we can compare the performance of the GH1 versus the GH2.

Lumix G HD 14-140mm

I set the camera up with the Lumix G HD 14-140mm superzoom lens at f=100mm. My experience shows that the lens performs best in terms of AF in the shorter focal lengths, so setting it at f=100mm is extra challenging. Both cameras were left in iA (intelligent auto) mode. Both were filming in 25 fps, 1920x1080 pixels

The camera was mounted to a tripod, not entirely perpendicular to the paper. That way, the test pattern can be seen to move a bit sideways, and not only back and forth.

Here are the results:



Panasonic GH1



Panasonic GH2

Based on these videos, it's easy to see straight away that the GH2 can keep up the focus in a better way. However, I wanted to check more thoroughly. So I studied the frames to see which were reasonably in focus.

What I found, was that the GH1 cannot keep up the focus at all. Rather, only the frames in which the paper is close to the initial position are in focus. The rest are out of focus.

The GH2, on the other hand, manages to follow the sheet's motion. The frames in which the paper moves most quickly are out of focus, but the camera regains focus when coming near the end-points, in which the paper sheet moves more slowly.

Based on my simple study, it is clear that the GH2 continuous autofocus is better than that on the GH1.

Lumix G 45-200mm

Using the Lumix G 45-200mm f/4-5.6 lens at 100mm gave the same result:



Panasonic GH1



Panasonic GH2

It looks like the GH1 with the Lumix G 45-200mm f/4-5.6 keeps up the focus a little bit better than with the Lumix G HD 14-140mm. This is consistent with my previous experience, in which I found that the 14-140mm is a bit slow to focus in the longer part of the zoom range, and that the 45-200mm is very fast except in the very longest end.

Leica Lumix DG 45mm macro

I also did the same experiment with the Leica Lumix 45mm f/2.8 macro lens. However, the lens was not able to keep up the focus with either camera. It is clearly not as fast focusing as the Lumix G HD 14-140mm lens.

Comparison: GH1 and GH2

When I first got the Panasonic GH1, I noted down some improvement areas for the camera. While it was a good camera, there where many areas where I felt it could be improved. Upon getting the GH2, I am happy to note that many the items have been ticked off.

Panasonic GH1 (left) and GH2 (right)

Some of the items I wrote down were very unrealistic, like implementing in body image stabilization. Panasonic have chosen their strategy, to implement image stabilization in some lenses only, not in the camera bodies. So this is not going to happen.

But a lot of other areas have improved. Here are some examples from my list:

• The control wheel has been moved to the rear side, which I prefer.
• The built in flash has become taller (as can be seen in the images below), meaning that the premium kit lens Lumix G HD 14-140mm casts a smaller shadow when using the flash.
• The new camera does feature a simplified focus scale in the display when focusing manually with a Micro Four Thirds lens. This is not an absolute focus scale with measurements, but it tells you if you are moving towards the close or far end of the focus scale, for example.
• The camera can autofocus with more Four Thirds lenses. For example the Olympus Four Thirds 50mm f/2 1:2 macro. However, the focus is slow for some of these lenses.
• When using legacy lenses, you can access the magnified focus assist view by pressing the rear control wheel. On the GH1, you needed to press two keys to get this mode: First the left arrow key, followed by the down arrow key.

There are also some development areas that remain. For example, the buffer clearing speed is very slow when recording both JPEG and RAW images.


Physical appearance

The basic shape remains very similar. The shell has been made from a different plastic material with a "crinkle" appearance. While the majority of the GH1 body was covered with a rubber-like covering, the shell of the GH2 is more slippery.

On the other hand, the GH2 gains a more solid rubber grip. Somehow, I find that the rubber-like surface of the GH1 feels safe to operate: The camera is less likely to slip out of your hands. On the other hand, the GH2 has a better grip area for the right hand.

Some people have reported that early versions of the G1 had the rubber surface peeling off. This caused negative publicity for Panasonic, and may be the reason why they have chosen a plastic surface without the rubber coating for the GH2.

On the rear side, we can note some changes. The GH2 (left) has a more pronounced frame around the LCD, which I suppose is good for protection. The red video record button had to be moved to the top-side, since the space it previously occupied is now taken up by the thumb wheel.

A subtle, but good change, is that the display button has become flatter. On the GH1, it was easily pressed by a mistake, and now this is not a problem anymore.

From the side, we can see that the SD card compartment has been moved a bit inwards into the camera. My speculation is that this was needed to fit the extended processing power in the GH2 camera.

This placement makes the card a bit more awkward to extract: There is little space for your finger between the card and the compartment door.

As a consequence of the new SD card placement, perhaps, the battery needs to be slimmer. The GH2 battery (DMW-BLC12, left) is new, which has angered some fans. This means that you can not reuse your extra GH1 battery (DMW-BLB13) for the GH2.

In this view, we also see that the tripod mount has shifted backwards.

In this side view, we see that the new flash is taller, which is very good news. Ideally, the built in flash should be as far from the lens as possible, when extended.

Video quality

The GH1 was marketed as a hybrid stills and video camera, the first in it's class to have continuous AF during video recording. In the mean time, some competitors have launched their systems. So to regain the throne as the best video enabled system camera, the GH2 must excel in video quality.

My experiments so far indicate that the GH2 does indeed provide better video quality. I devised a simple test to compare the GH1 (hacked) with the GH2 in otherwise identical settings.

What I found was that the white balance and saturation of the GH2 is more pleasing, and also that the sharpness of the video is probably a tad bit better. But in my opinion, there was not a dramatic difference.

The GH2 features a much appreciated ETC (Extended Tele Conversion). This is essentially a digital zoom that works during video recording. So your lenses become 2.6 times longer, and you can still record at full HD 1080 resolution.

I've also checked the rolling shutter properties of the two cameras. I found that they were mostly identical in this respect. The GH2 might be slightly better.

Anyway, rolling shutter artifacts is not a huge problem with the GH1 and GH2 cameras. Unless you deliberately generate the artifacts, you're very unlikely to find this being a problem. This is in contrast to the Samsung NX10, which I found had significant rolling shutter artifacts.

Autofocus speed

While I had no problems with the autofocus speed of the GH1, I am still happy to see that they have further improved with the GH2.

I'm especially happy that the autofocus has improved when using the Lumix 20mm f/1.7 pancake lens, which felt a bit sluggish on the GH1. Here is a summary of my AF speed readings.

The GH2 appears to be better at continuous autofocus too, according to my test.

Taller built in flash

As mentioned above, the GH2 has a taller built in flash. In theory, this should be good for several reasons: Keeping the built in flash as far away from the lens as possible is generally a good idea. It makes the lightning more flattering when photographing people.

Also, it is a known fact that the GH1 built in flash casts shadow when using the premium kit lens Lumix G HD 14-140mm. Here's how the shadow looks using GH2 (left), and GH1, both at 14mm and having the lens hood attached.

GH2	GH1

As you can see, the GH2 flash reduces the shadow cast a tiny bit, but the difference is rather subtle. On the other hand, you would probably not use the flash at 14mm focal length and 1 meter distance very often. And increasing either will reduce this problem. So for real life use, this is not that much of an issue.

Mirrorless cameras, like the GH1 and GH2, typically require a pre-flash to measure the intensity of the flash. This takes some more time than with DSLRs, since mirrorless cameras don't have a light sensor. They use the imaging sensor as a light sensor.


Battery life

Compared with most DSLR cameras, the battery life of the GH2 is not very impressive.  This is due to operating in live-view all the time.  DSLR cameras don't need the LCD for viewing during SLR mode, and save power that way.

With freshly charged battery, I found that I could record 144 minutes of video before needing a recharge.  This was with the LCD display on all the time. Using the EVF rather than the LCD probably gives better battery life.

It is possible to buy third party batteries for around US$20, but they give some reduced functionality.

GH1 vs GH2: Rolling shutter evaluation

Rolling shutter is the name of a type of mechanical or electronical shutter mechanism. In this type of shutter, the whole film or sensor is not exposed exactly at once, but rather, a shutter rolls across the frame and exposes it bit for bit. Rolling shutter is also the name of the distortion associated with this shutter implementation.

You can see this distortion for example when panning heavily during video recording. It looks like the scenery is "leaning" towards one side when panning. I tried the Samsung NX10, and immediately noticed that the viewfinder had much more rolling shutter artifacts than the Panasonic G-series.

This shutter implementation also leads to distortion to rotating elements. To test which camera has the most rolling shutter artifacts out of the Panasonic GH1 and GH2, I made a simple LEGO contraption which rotates a propeller at a constant speed. Then I videofilmed this with both cameras, using the Olympus 50mm f/2 lens.

Here are the two video streams:

GH1, ISO 1600, f/2, 1/500 second, 25p, 1080

GH2, ISO 3200, f/2, 1/1000 second, 24p, 1080

To more easily compare the rolling shutter artifacts, I have made similar framegrabs from both:

What we see here, is that the distortion is slightly smaller in the GH2 video stream. The shorter the distance between the two prongs to the left, the more the distortion.

So my conclusion is that the GH2 handles rolling shutter at least as good as the GH1.

For real life usage, rolling shutter is not a problem with GH1 or GH2 video. You can generate these effects by filming a rotating propeller, like I did here. Or by panning heavily. But most types of video footage will not display any noticeable rolling shutter artifacts.

As a side note, the amount of rolling shutter artifacts depend on the speed of the rolling shutter (in a mechanical implementation), or the speed of the sequential image data readout for a digital shutter. It does not depend on the shutter speed itself. Here is an illustration, where you can see three different shutter speeds generating the same amount of rolling shutter artifacts. But the amount of motion blurring is of course different.

Another term widely used is global shutter. This refers to a system in which the exposure values from the sensor are read all at once. Since the values are not read out sequentially, there are no rolling shutter artifacts with a perfect global shutter.

Before launching the GH2, a Panasonic representative was quoted saying that implementing a global shutter in Micro Four Thirds cameras is not coming soon: At the very earliest with the GH3. In retrospect, the the Panasonic GH3 did not introduce global shutter. And now, it looks like the GH4 (aka GH4K) is going to be more about 4K video than global shutter.