Multi aspect sensor

After the recent announcement of the Panasonic GH3, much has been said about the missing multi aspect sensor feature, including on this blog, I have to admit. The GH3 was expected to have this feature, since the GH1 and GH2 had it. Also the premium compact cameras Panasonic LX3, LX5 and LX7 have the oversized multi aspect sensors.

But what does the feature actually do?

Put shortly, the multi aspect sensor is an oversized sensor. It covers a larger area than the normal Four Thirds sensor, which is 17.3mm x 13.0mm. The larger sensor allows for a constant diagonal field of view at 4:3, 3:2 and 16:9 aspect ratios, with the latter normally being used for video. It also means that parts of the corners of the sensor are never used in any of the modes.

It can be illustrated with this picture. The green outline shows the normal Four Thirds sensor size, while the oversized sensor is the larger outline. Non-oversized sensor cameras, like the GH3, use the orange box for video recording, while the GH1 and GH2 use the larger red box:

Here is a short video demonstration which illustrates the advantage of the multi aspect sensor. First, it shows the Panasonic GH2, while switching between photo mode (4:3) and video mode (16:9). When switching to video mode, the image grows a bit in horizontal size, while it shrinks a bit vertically.

Later, it shows the same with the Panasonic GF3, which does not have a multi aspect sensor. When switching to video, the top and bottom row disappear, but the horizontal size remains the same. This is because the camera lacks the multi aspect feature:



Ok, so that was the technical stuff. Now again, what are the consequences of losing the multi aspect sensor?

Video

Most zoom lenses start at 14mm. This is not too wide, but it corresponds pretty much the standard wide field of view for kit zoom lenses. For example, APS-C cameras tend to have zoom lenses that start at 18mm, which also correspond to 28mm equivalent field of view.

If you are used to video recording with a GH2 at 14mm, you will be disappointed with the GH3 at 14mm, though. Since it no longer corresponds to 14mm in video mode, but 15mm. This is calculated as 14mm times 5710/5287, with 5710 being the multi aspect sensor diagonal at 16:9, and 5287 being the normal Four Thirds 16:9 sensor diagonal measured in pixels. See this illustration:

Most Micro Four Thirds standard zoom lenses start at 14mm, which is common for the basic kit zooms. But it's not so impressive, and when the non-multi-aspect-sensor of the GH3 makes it into 15mm in video mode, it can be limiting. With a non-multi-aspect-sensor, you may see the need for the Lumix X 12-35mm f/2.8 or the Olympus 12-50mm f/3.5-6.3, which start at a the wider 12mm focal length.

On the other hand, if you don't like to use the wide angle end of the zoom, but care more about tele, then the GH3 is going to be better for you, of course, as the tele effect of the lenses increase slightly in video mode, as compared with the GH2. On the GH3 in video mode, the kit zoom lens corresponds to 45mm in the longest setting, rather than 42mm on the GH2.

Still images

If you like to take photos in the 4:3 aspect ratio, then there is no difference whatsoever between the GH2 and the GH3. The resolution is exactly the same.

However, the GH1 and GH2 had the option of using the 3:2 and 16:9 aspect ratios for photos as well, while still retaining the same diagonal field of view. If you intend to use the images in this format, then you would use the lens image circle more efficiently with these cameras, and the GH2 will give you better resolution to boot. Here is a comparison table:

Photo resolution	GH2	GH3
4:3	4608x3456 (16MP)	4608x3456 (16MP)
3:2	4752x3168 (15MP)	4608x3072 (14MP)
16:9	4976x2800 (14MP)	4608x2592 (11MP)

These differences are not that important, surely, but there is in fact a significant difference.

On the other hand, with a camera like the GH3, it is best to stick with the 4:3 format when photographing, and crop the image later, if needed. And that saves time and hassle while photographing, which is not the worst thing you could do.

Multi aspect sensor

An important feature of the Panasonic GH1 and GH2 was the multi aspect, oversized sensor. They had sensors larger than that of the other Four Thirds sensor cameras. This allowed taking pictures in the aspect ratios 4:3, 3:2 and 16:9 with the same diagonal sensor length, and, hence, using the full image circle. This is in contrast with other Micro Four Thirds cameras, which apply sensor cropping at 3:2 and 16:9 aspect ratios.

When the Panasonic GH3 was launched late 2012, it was a big disappointment that it did not offer the multi aspect sensor feature of the two predecessors. But what does it mean?

The illustration below shows the two sensor sizes. The green rectangle is the standard Four Thirds sensor size, while the black corners outline the GH1 and GH2 sensor size. Since the GH3 has the standard sensor size, it crops to achieve 16:9 video recording (orange box). The GH1 and GH2, on the other hand could use the red rectangle for video recording, using the image circle more efficiently and also achieving a wider field of view given the same lens.

In video

In the illustration above, the GH3 video crop of the sensor (orange box) is 7.4% smaller than that of the GH1 and GH2 (red box), when measured by the diagonal. This means that when using one of the kit zoom lenses at the widest setting, 14mm, the diagonal field of view of the GH3 corresponds to 15mm in video mode. This was calculated as 14×(1+7.4%). So, as compared with the predecessor, the kit lenses will give you less wide angle when video recording.

What you can do, then, is to use a different lens. The Lumix X 12-35mm f/2.8 lens starts at 12mm, and hence, gives you a better wide angle during video. On the other hand, it has a more limited zoom range, stopping at 35mm, well before the typical portrait lens focal length of 42mm. It is an excellent lens, though, probably the best I have ever used.

Another option is the Olympus 12-50mm f/3.5-6.3 power zoom lens. While this lens generally gets mixed reviews, probably because of the limited maximum aperture, I think it is a very interesting lens. It is the only zoom lens to cover both the very wide and portrait lens focal length. On top of this, it also adds a macro mode and power zooming, as well as coming in a weather sealed constant length package. On the downside, though, it does not feature optical image stabilization, so using it for video recording on a Panasonic lens is going to be tough. Without a tripod or a good support, your videos risk being shaky.

It's good to keep in mind that the lack of a multi aspect sensor in the GH3 is nothing extraordinary. In fact, out of all video enabled consumer system cameras, the GH1 and GH2 were the only to feature the oversized multi aspect sensors. All other do not have this feature. On the other hand, most other video enabled system cameras have an APS-C sized 3:2 aspect sensor. When cropping such a sensor to 16:9 for video, this wastes a relatively smaller part of the sensor than when cropping a 4:3 sensor. Hence, the oversized sensor doesn't make that much sense with APS-C sensor. The illustration below shows this:



The Four Thirds sensor wastes 25% of the sensor area when cropping to video mode, and 7.4% of the image circle (diagonally). The APS-C, on the other hand, wastes only 16% of the sensor size, and 4.5% of the image circle. So the oversized sensor feature does not make as much sense with the more common APS-C sensor format.

Here is a side by side video showing the GH2 and GH3 in photo and video mode, both using the Lumix G 14mm f/2.5 pancake lens. It shows that when changing to video mode, the GH3 loses some field of view due to cropping the from the Four Thirds sized sensor:

In photography

If you like to take photos in the 4:3 aspect ratio, then there is no difference whatsoever between the GH2 and the GH3. The resolution is exactly the same.

However, the GH1 and GH2 had the option of using the 3:2 and 16:9 aspect ratios for photos as well, while still retaining the same diagonal field of view. If you intend to use the images in this format, then you would use the lens image circle more efficiently with these cameras, and the GH2 will give you better resolution to boot. Here is a comparison table:

Photo resolution	GH2	GH3
4:3	4608x3456 (16MP)	4608x3456 (16MP)
3:2	4752x3168 (15MP)	4608x3072 (14MP)
16:9	4976x2800 (14MP)	4608x2592 (11MP)

These differences are not that important, surely, but there is in fact a significant difference.

On the other hand, with a camera like the GH3, it is best to stick with the 4:3 format when photographing, and crop the image later, if needed. And that saves time and hassle while photographing, which is not the worst thing you could do. With the GH2, I would often change the aspect ratio when photographing something wide, giving me slightly better resolution. With the GH3, I just skip this part, which is easier anyway.

Conclusion

Losing the multi aspect sensor feature with the GH3 was a setback. However, the consequences are not that severe. You lose the very widest field of view in video mode. If you prefer using longer focal lengths, this might actually be an advantage.

Producing two sensor sizes was probably too costly for Panasonic. So I can understand their desire to standardize the sensor size from an economic point of view. The Panasonic G5 and Panasonic G6 cameras are said to have sensors based on that from the Panasonic GH2. However, they still do not have the multi aspect sensor feature.

In fact, Panasonic has done the same also in the compact camera market. Their LX3 and LX5 premium compact cameras featured a 1/1.63'' (8.07 x 5.56 mm) multi aspect sensor, larger than the typical 1/1.7'' sensor mostly found in these cameras. The newest Panasonic LX7 has a standard 1/1.7'' (7.44 x 5.58 mm) sensor, from Sony, incidentally. It still achieves the multi aspect feature by having a slightly smaller image circle. This also allows for the very impressive aperture rating of this camera, f/1.4-2.3.

I think losing the multi aspect rate sensor opens up the need for more wide zoom lenses. Only two lenses start at 12mm so far, the Lumix X 12-35mm f/2.8 and the Olympus 12-50mm f/3.5-6.3. The first of these is very good, but also very expensive, and a bit short. The second does not have OIS, and is hence not so useful for video on Panasonic cameras. With this in mind, I think that Panasonic should make a lens specified at something like 12-50mm f/2.8-4.5 with power zoom and OIS. That would be great for video use with the GH3.

Micro Four Thirds sensors

The imaging sensor is the heart of the digital camera, and, hence, it is not hard to understand that there is a lot of interest and mystique surrounding the issue of sensors. In this article, I am trying to make a bit of sense of the various generations of sensors used in the Micro Four Thirds cameras so far.

Some of the information here is based on a bit of guesswork. If you think some of this is wrong, then please feel free to comment it.

Panasonic interview re GH3

Imaging Resource recently published an interview with some Panasonic staff, mostly engineers. The interview was centered around the technology of the Panasonic GH3, their long awaited new top camera model.

Here are some of my comments and analysis of the interview:

Dynamic range

It is not unusual that new camera models are advertized as having a better dynamic range than previous models. I think that the dynamic range was a shortcoming of both the GH1 and GH2 models, and so I would be very happy to see a significant improvement to the GH3.

The engineers were quoted to say that the saturation level of the sensor photosites was 45000 (in theory), but that the actual number would be lower. They also compared this with the fill capacity of typical compact cameras, which is 8000.

So, what does this mean? When light hits a pixel, electrons are released, and counted by the sensor. The more electrons released and counted, the lighter tone this photosite will report. When 45000 electrons are released, the pixel is saturated, and cannot report any brighter tone. We have then overexposed the pixel.

For simplicity, let's say now that the theoretical number, 45000, is also the actual number of electrons of fill capacity. Keeping in mind that one stop of light difference represents a doubling of the light amount, i.e., the number of electrons, we can count the number of stops of dynamic range this will give:

Tone segment	Number of electrons
0 (black, underexposed)	0
1	1
2	2-3
3	4-7
4	8-15
5	16-31
...	...
15	16384-32767
16	32768-45000
17 (white, overexposed)	more than 45000

So we see that there is a theoretical maximum of 16 stops of tones in the dynamic range. Actually, the true number would be 15.5 stops, calculated as log₂(45000). However, in practice the number of stops will be much smaller, of course. First of all, the number 45000 was quoted as the theoretical fill capacity. And what the actual fill capacity is was not stated.

Second, noise is going to affect this evaluation. Not only due to technical shortcomings, but also due to the physical nature of the light and electrons.

For example, it is natural to assume that the electron count is Poisson distributed. This means that the standard deviation in the first two groups, 1 and 2, is 1 electron and the square root of 2 electrons, respectively. Hence, categorizing between the groups 0-2 is going to be almost pure chance only, even with some noise reduction techniques. It is perhaps only group 4 that can be categorized correctly with some reasonable significance. And on top of this comes the extra noise added by the sensor equipment.

So how many stops of dynamic range can we expect? It is probably impossible to calculate based on this information only. But if they are correct that 8000 is a figure for point-and-shoot cameras which is comparable to the 45000 figure, then the GH3 can be expected to have 2.5 stops more of dynamic range compared with a point-and-shoot camera, calculated as the difference between log₂(45000) and log₂(8000). And 2.5 stops improvement over a compact camera does not sound very impressive, honestly.

As a side note, the table above explains why some people use the Expose To The Right (ETTR) technique for improved noise performance. This philosophy states that you should expose the subject as much as possible, without losing details in the light parts. The light parts, to the right in a histogram, correspond to the lower part of the table. In this section of the histogram, there are more electrons behind the measurements, hence, it is reasonable to believe that the significance of the tone segment grouping is higher. And this means less noise.

Using ETTR will of course give you too bright images, but you can open them later in a RAW editing program, and reduce the brightness, while retaining the good noise performace.

ETTR only makes sense when you have less dynamic range in the subject than the sensor can handle, which is perhaps not so often.

Autofocus

Many new Micro Four Thirds camera models have been launched stating that they are the quickest in terms of autofocus, and the GH3 is no exception. In the interview, they refer to a 240 frame-per-second mode. This is easily misunderstood.

It does not mean that there is a video mode which records video quickly, suitable for making slow motion videos. Rather, it refers to the sample rate used for the Contrast Detection Auto Focus (CDAF) system.

The CDAF system relies on sampling the contrast of the subject while changing the focus of the lens. The faster it can sample the contrast, the faster it can reach optimal focus.

The GH2 also improved upon the GH1 by having a maximum of 120 fps sample rate, to be compared with 60 fps for the GH1. As I saw in my AF study, this made the GH2 beat the GH1 in bright light. In dim light, however, the GH2 had to revert to a slower sampling rate, and the focus speed of the two was virtually identical.

With the GH3, I expect that the 240 fps option will only work in fairly bright light, and that the focus speed gain due to this feature will be limited in dim light.

They also stated that using the 240 fps option requires that the lens is also capable of reacting very quickly. At this time, they said, only the Lumix X 12-35mm f/2.8 lens is capable of using this mode, and only after a firmware update to be issued later.

Multi aspect sensor

The interview also confirms the rather sad news that the GH3 will not have a multi aspect sensor. Both the GH1 and GH2 had this feature.

The multi aspect sensor feature means that the sensor is over-sized. At any one time, the whole sensor area is never used. But various parts of the sensor area can be used, to enable 4:3, 3:2 and 16:9 aspect ratios, while retaining the same diagonal field of view. This uses the lens imaging circle more efficiently, especially in video mode.

The engineers do not state any reason for dropping this feature, beyond saying that a sensor was not available. With the GH1 and GH2, I guess that they had separate production runs for these camera sensors, even though they were not volume models. This must have been an expensive sensor to make, relative to the volume of the cameras.

The GH3, costing even more than the predecessors, will probably not become a volume model, either. So I am guessing the reason is economics: It will be too expensive to order special production runs for this single camera model, and they think this extra cost is not worth the benefits of the multi aspect sensor.

I would say this is consistent with the LX5 and LX7 premium compact camera models. The LX5, launched in 2010, had a sensor slightly larger than the common 1/1.7'' size, to accomodate the multi aspect feature. The LX7, launched in 2012, on the other hand, reverts to the usual 1/1.7'' sensor size, probably to make the sensor production cheaper. Producing sensors in odd sizes (as with the GH1, GH2 and LX5) is certainly more expensive than common sizes.

On the other hand, the LX7 does retain the multi aspect sensor feature, but now with a smaller total image circle, so that it still fits into the common 1/1.7'' sensor size.

I have written more about the Multi Aspect Sensor here.

Put APS-C sensors in Micro Four Thirds cameras

By far the most common sensor size for system cameras is APS-C. As the name suggests, the size is derived from the Advanced Photo Systems, a still image film format introduced in 1996. Almost all mirrorless camera systems use APS-C, with the exception of Nikon 1, Pentax Q, and Micro Four Thirds. There is also the Sony A7 with a full frame sensor, but it still has a very small volume.

On top of this, all consumer DSLR cameras use the APS-C format. Again, there are some exceptions: Some full frame cameras that sell in smaller volumes.

While never officially confirmed, there is a strong belief that all recent Olympus M4/3 cameras use sensors from Sony. They are: E-M5, E-PM2, E-PL5,E-P5, and E-M1. In addition, the Panasonic GH3 is said to use the same sensor.

The imaging sensor is one of the most expensive items in a digital camera. And the cost is strongly correlated with the sensor size. Hence, some have speculated that the choice to use a sub-APS-C sensor size in Four Thirds and Micro Four Thirds cameras is more related to economy than an evaluation of what the optimal size is: With a sensor that is approx 40% smaller, Micro Four Thirds cameras can be sold at a larger margin, compared with APS-C cameras.

However, there is more to the cost of production: There is also economics of scale. As Sony is producing a massive number of APS-C sensors, I suggest to use this sensor size also in Micro Four Thirds. That would probably cost pretty much the same as a 4/3 size sensor, given that they don't need to support one more sensor size.

GH3 comments

So, the new Panasonic GH3 camera has been announced now, after a long wait. How do I view it?

Of course, by this time, I have no first hand experience of the camera what so ever. My knowledge of the camera is solely based on images, video and text online.

In terms of technical specifications, not so much has changed. We have a higher video FPS rating at 1080p, as expected. And we have a higher video bitrate. Under the hood, there is of course a lot of technical details, for example a higher frame rate used for the contrast detection auto focus system (CDAF), which has the potential for better and faster autofocus. And there is a higher sensitivity, as well as the usual promise of a better dynamic range.

Ergonomics

The really big change is the ergonomics. The GH3 is bigger than the GH2:

	GH2	GH3
Dimensions (w, h, d)	124 x 90 x 76 mm	133 x 93 x 82 mm
Weight	442g	540g

The size accommodates a better grip, more space for buttons, three control wheels (the GH2 had one single only), more connectors. As the camera does not really take up that much more space in the bag, I see this as purely a positive thing. The ergonomics of the GH1 and GH2 left quite a bit to be desired. The layout is rather cluttered, and it is easy to press a button by a mistake. The GH3 is going to be much easier to handle, especially with a large lens.

On the flip side, one could argue that the whole purpose of the Micro Four Thirds system was compactness. So why introduce a larger flagship model?

Sensor

The GH3 deviates from the predecessor GH cameras in a significant way: It no longer offers the oversized, multi aspect sensor.

With the multi aspect sensor, the GH1 and GH2 could take photos at 4:3, 3:2 and 16:9 aspect ratios while retaining the same diagonal field of view. This has the advantage of utilizing the lens imaging circle better. More importantly, it could record videos at the 16:9 aspect ratio while retaining the same field of view as well.

Without this feature, the lenses effectively lose some wide angle feature when switching to video. It means that the wide angle property that you were used to when using the GH2 are going be a bit disappointing when switching to the GH3. The difference is not too significant, but noticeable.

When using a fisheye lens on the GH2, for example, you get a 180° diagonal coverage in both photos and videos. With the GH3, though, you get the 180° diagonal field of view only in the 4:3 still image mode, and less than that in video mode. This applies to the Samyang 7.5mm f/3.5 fisheye lens for example.

Conclusion

The GH3 takes the Micro Four Thirds system into the professional territory: With better ergonomics, splash protection, better video bitrate and connectivity. Sadly, it also comes at a significantly higher price point.

While it doesn't live up to all the expectations people had, I am confident that the GH3 will be loved by the users.

Those who are put off by the size increase could still look to the Panasonic G5. While it does not offer quite the same feature set as the GH3, it is still a quite impressive camera given its size.

Sigma 19mm autofocus comparison

The Sigma 19mm f/2.8 EX DN is perhaps a strange lens. In terms of specifications, it is quite close to the Lumix G 20mm f/1.7 pancake lens, except that it is slower, and less compact. So, why would anyone be interested in it?

Lately, it sells at a reasonable price, and besides, it features the normal internal focus system, while the Lumix G 20mm has an old style focus mechanism which moves all the lens elements, being slow and noisy.

I have found that the Sigma 19mm lens is slightly less sharp than the Lumix 20mm lens, at similar apertures. This is consistent with other people's findings.

With still images

What about the autofocus performance, then? Is it faster, as one could guess? Here is a comparison where I put both lenses on the Panasonic GH2, and focused down to around 0.3m:



The Sigma 19mm lens spends 0.28s focusing down to close to the minimum focus distance, while the Lumix 20mm lens needs 0.64s. So the Sigma lens is indeed faster, as we had expected in advance.

During video recording

Another important aspect is continuous autofocus during video. This is still the achilles' heel of the Micro Four Thirds system, and not even the most recent cameras do this well.

To test it, I mounted the Panasonic GH2 with the Lumix G 20mm f/1.7 lens to a wooden plank, and next to it, mounted the Panasonic GF3 camera with the Sigma 19mm f/2.8 lens. I used Manfrotto Superclamps to mount the cameras, just like when I tested the rolling shutter properties of the GH2 and GH3. I set both lenses to f/2.8 for similar depth of focus properties.

Of course, the 19mm lens has a wider field of view. But on the other hand, the GH2 has the multi aspect sensor, oversized sensor property, which gives relatively wider field of view in video compared with the non-multi aspect sensor GF3 camera. So the field of view is probably quite similar for the two cameras.

Here are the two video footages, combined to one clip. To see the focus performance, it is best to view this in 1080p, click on the youtube icon to access this possibility.



The results are not completely consistent, but I think the Sigma 19mm lens and GF3 combo keeps the focus better during the video. One could speculate that the GH2 probably has the better image processing technology, and hence, should have the advantage in terms of handling continuous autofocus. Despite the handicap of being combined with the basic GF3, the Sigma lens performs better.

It would have been better to mount the lenses to the same camera, of course, but I don't have two of the same camera model. Also, I would normally have used the newer GH3 camera, but my camera is sent back for repair. I hope I get it back soon, and that I don't have to wait for three months, like I had to when sending back the Lumix G 14-42mm lens for misaligned aperture diaphragm blades.

Conclusion

What this shows, is that the Sigma 19mm f/2.8 EX DN lens is better for video use, as long as you can live with the f/2.8 aperture. While it is not as sharp as the Lumix G 20mm lens, it is still very sharp, and certainly more than sharp enough for video use. The autofocus is also less audible.

Even if the Sigma 19mm lens is larger, it is still quite non-obtrusive, with a matte black finish.

The Lumix G 20mm f/1.7 pancake lens is a classic Micro Four Thirds lens, praised for the very good sharpness. However, people also find it annoying for the slow and noisy autofocus performance. People have also reported that the focus mechanism can be clogged with dust, due to the moving front elements. The Sigma lens has no moving lens elements on the outside (only internally), and is probably more solid in that way.

Given the low price the Sigma 19mm f/2.8 EX DN sells at, it can be considered a good value for money, and an interesting alternative to the Lumix G 20mm f/1.7.

I haven't tested the "brother" lens, the Sigma 30mm f/2.8 EX DN in the same way, but I would guess that it, too, performs well in terms of autofocus speed.

GH2 vs GH3 rolling shutter evaluation

The Panasonic GH1 and GH2 had pretty much the same rolling shutter properties. I have previously examined the rolling shutter artefacts of the GH3, compared with the GH2, and found that the GH3 has somewhat less artefacts. But my test was based on a rotating propeller setup, which is not so realistic.

Rolling shutter artefacts are typically identified when panning quickly during video recording. This can lead to "wobbly" effects, square objects can be seen to lean towards one side.

To compare these artefacts again between the GH2 and GH3, I mounted both cameras to a piece of wood:

I used Manfrotto Superclamps with ball heads to fix the cameras to the piece of wood. These are quite useful.

Panasonic GH3 review

The Panasonic GH3 was released in December 2012, two years after the predecessor GH2. While the GH2 was an incremental improvement over the GH1, the GH3 is a completely new camera.

This is for better and for worse, of course. The camera has grown significantly in size over the GH2, but it also adds better ergonomics and more features. Whether this is good news for you, or bad news, depends on what you want from the camera. If you want a camera which has a good grip, and a good layout of buttons and control wheels, then the GH3 is for you.

On the other hand, if you came to the Micro Four Thirds system for the smallest camera with a good photography and video recording performance, then there are other cameras that may fit your needs better, e.g., the Panasonic G5 and G6 (announced April 2013) or the Olympus OM-D E-M5.

Panasonic GH2 (left) and GH3 (right)

Using Micro Four Thirds lenses on Sony NEX cameras

When the first Micro Four Thirds cameras were launched, they became instantly popular for using old, legacy lenses with adapters. Since the register distance is smaller than most other mounts, it is possible to create adapters for mounting lenses from many other systems to Micro Four Thirds cameras. This makes the most sense with lenses that feature a manual, mechanical focus ring and aperture. Even if there exist adapters for mounting Canon EF lenses on Micro Four Thirds, they do not allow for changing the aperture, hence, they are not very useful. This is because the Canon EF mount is an electro-optical system (EOS), which means that there are no manual rings to control the aperture setting.

As the Sony E mount has an even shorter register distance, though, this is one of the few formats that can not be adapted to the Micro Four Thirds system. Sony NEX lenses have a register distance of 18mm, hence, even if a thin adapter was made for using them on M4/3 cameras, you would not be able to focus to infinity with them. This is because the Micro Four Thirds cameras have a register distance of 20mm, too long for the optical formula of the Sony NEX lenses.

But, the other way around is possible: There are adapters for mounting Micro Four Thirds lenses on Sony NEX cameras. As the difference in the register distance is only 2mm, these adapters are very thin. Note that most Micro Four Thirds lenses are electro-optical, just like the Canon EF lenses, so you will not be able to control the focus or aperture from the camera, rendering most M4/3 lenses useless for this purpose.

The most useful M4/3 lenses for adapting on Sony NEX are those that are fully manual, e.g., the Samyang 7.5mm f/3.5 fisheye, the Olympus 15mm f/8 body cap lens, the Cosina Noktor 17.5mm f/0.95, and so on.

Here is what my adapter looks like:



It does not appear to be the best quality, but works ok. You use it as you would expect: The adapter goes on the Sony NEX camera, and then you can mount a Micro Four Thirds lens to it. Note that the adapter has no electrical contacts: Electronic focus operation and aperture operation is impossible, as is the use of the optical image stabilization (OIS), if the lens has this feature.

Using the Wanderlust Pinwide

Here's the Sony NEX-3N with the Micro Four Thirds to Sony NEX adapter, and the Wanderlust Pinwide:



The Wanderlust Pinwide is not a lens, but a pinhole camera body cap. It is recessed into the camera, for a better wide effect. It corresponds to 11mm focal length, hence, behaves like a 22mm lens on a traditional film camera. Which is very wide indeed.

But when used on the 1.5x crop sensor in the Sony NEX-3N, it becomes like a 17mm lens, i.e., extremely wide. See the difference below:

Used on the GH3	Used on the Sony NEX-3N

The problem is the light falloff outside the centre of the image frame. The extra wideness does not help much, as there is a very significant vignetting. The vignetting is caused mostly by the sensor's sensitivity to the angle of the light hitting it: Light coming from a steep angle does not work well, ideally the light should come perpendicular to the sensor. This appears to affect the green channel the most, giving a purple tint outside the image centre.

Using the Samyang 7.5mm f/3.5 fisheye

The Samyang 7.5mm f/3.5 fisheye is a manual focus lens with a manual aperture ring, hence, very well suited for adapting on a non-Micro Four Thirds camera. See the lens mounted below:



One problem with this setup, though, is that the adapter appears to be too thick, placing the lens too far from the sensor surface. This gives problems focusing to infinity. This is still not a fatal problem: You can still stop down the lens to achieve infinity in focus. I had to set around f/8 to get infinity reasonably in focus.

Here are some example images taken on both a Micro Four Thirds camera, and the Sony NEX-3N:

Used on the GH3	Used on the Sony NEX-3N

In the right image, above, you can see that the left and right sides are black. This is due to the built in lens hood: It keeps out light which would fall outside of the Four Thirds sensor surface, hence, giving black sides. Notice also that the black areas are a bit skewed, because the lens adapter mounts the lenses slightly rotated.

In the corners, you can see parts of the image circle ending. The image circle spans 180° field of view, and where this ends, you can see the black bits in the corners. So one advantage of using the fisheye lens on the Sony NEX camera, is that you can crop the image to several different aspect ratios, and still achieve a 180° diagonal field of view. Using a native Four Thirds sensor, you can only achieve this in the 4:3 aspect ratio. Due to the multi aspect sensor, the Panasonic GH1 and GH2 cameras could achieve this also in 3:2 and 16:9 aspect ratios.

Another comparison example:

Used on the GH3	Used on the Sony NEX-3N

Using the Lumix G 14-42mm f/3.5-5.6 kit zoom lens at 14mm

So, the kit zoom lens is of course an electro-optical lens, and you can only adjust the focus and aperture while having the lens mounted to a native Micro Four Thirds camera. However, there is a small trick. You can mount the lens to a Micro Four Thirds camera, turn on the camera, set the focus and aperture you want, take a long exposure, and then remove the lens during the exposure. The lens then has your desired focus and aperture set.

Using this trick, I used the kit zoom lens at 14mm, infinity focus, f/8 aperture:

Used on the GH3	Used on the Sony NEX-3N

Again, we see the vignetting due to the lens hood. This time, though, I could have removed the hood, but I left it on to illustrate that the lens is mounted slightly rotated when using this adapter. We can also see that the image has a bit of barrel-distortion. This is because the lens needs in camera geometric distortion correction to give rectilinear images. And when using the lens this way, there is no such distortion correction done.

Finally, even when pre-focusing at infinity and setting the aperture to f/8, infinity is not really in focus here. Again, this is due to the adapter being slightly too thick, making it impossible to focus on infinity with most lenses.

Conclusion

Using an adapter, it is possible to mount Micro Four Thirds lenses on Sony NEX cameras. However, my adapter was a bit thick, making infinity focus impossible. Also, most electronic lenses cannot be used at all, since there is no way to operate the focus or change the aperture.

This could be a way to reuse your manual focus Micro Four Thirds lenses on Sony NEX, though, like the Cosina Noktor 17.5mm f/0.95, especially if you don't care about infinity focus. That way, you can use the Sony NEX focus peaking as a manual focus assistance.

GH1: Use RAW and gain 1% megapixels

The Panasonic Lumix GH1 has a 14 megapixel multi aspect sensor, with around 12 megapixel output at three different aspect ratios: 4:3, 3:2 and 16:9.

At 4:3, the JPEG image is 4000x3000, which is easily calculated to 12 million pixels. The corresponding RAW file, on the other hand, yields 4018x3016 pixels, or a total of 12.118.288 pixels, which is 1% more megapixels than the JPEG output.

The same goes for the other aspect ratios. At 16:9, the JPEG image is 4352x2448, or 10.65 megapixels. The RAW file has a 4396x2464 resolution, 10.83 megapixels, a difference of 1.7%.

Of course, an increase of 1-2% of the resolution is hardly significant, and no real reason to use RAW alone. But there could be situations where you need a little bit extra details around the edge, and then looking at the RAW file could help you.

Here is an example exposure in two versions, developed from RAW (top) and JPEG (bottom):

From RAW, 4396x2464

From JPG, 4352x2448

It is hardly possible to notice any differences between the two images, when shown scaled down like this. However, when looking at a 100% crop from the right hand border, the differences are obvious:

We are losing a little bit of details in the borders when using JPEG, as opposed to RAW.

Appendix

The lens used here was the Four Thirds Olympus 9-18mm f/4-5.6, with the Panasonic DMW-MA1 adapter. The lens was used at 9mm, f/4, ISO 100. In the image above, you can see a typical example of chromatic aberration (CA). This is noticeable as the purple and green fringing along areas of high contrast, where black and white paint meet.

I have been using UFRaw to convert RAW files in Linux.

What framerate to use in videos?

Excellent video is one of the reasons to use Micro Four Thirds cameras, especially the ones from Panasonic. Some come with different framerate choices, so which to use?

First, here's an overview of the existing alternative framerates. I have outlined the choices for full HD 1920x1080 resolution only. For lower resolutions, there may be more framerate selections available:

Framerate	Panasonic	Olympus
24 fps	GH3, GM1, GX7, G6	None
25 fps	All PAL area cameras	None
30 fps	All NTSC area cameras	All
50 fps	PAL area cameras: GX7, GM1 (only interlaced), GF6 (only interlaced), G6	None
60 fps	NTSC area cameras: GX7, GM1 (only interlaced), GF6 (only interlaced), G6	None

As you can see from the table above, Panasonic gives you much more choice in terms of which framerate to use. All current Olympus cameras only have one single choice: 30 fps.

GH4: The game changer

The big news this week is of course the announcement of the Lumix GH4, the new Micro Four Thirds flagship camera from Panasonic.

While the Lumix GH3 was more about competing with pro DSLR cameras, the upcoming GH4 has the most breaking news in the video area. More about that further down.

Product news

These are exciting times, with a lot of product announcements in relation to the Fotokina trade show. Here is a short summary:

Lumix G 35-100mm f/4-5.6

This lens is designed to match the Lumix GM1 and GM5 camera, both in terms of styling and size.

It is expected to cost US$400. But it will probably be primarily sold in twin lens kits with the new GM5 camera.

AF during video, comparison GH2 vs GH3

Recent Micro Four Thirds cameras have very good autofocus performance for still images. Mostly, the performance is among the best in this class, certainly better than DSLR cameras in live view mode. However, there is one area where mirrorless cameras don't perform well at the moment, and that is continuous autofocus: Both during video recording, and for photographing moving objects, e.g., for photographing sports and birds.

Some camera manufacturers have been trying to solve this by adding phase difference sensors (PDAF) on the imaging chip, like the Nikon 1 and Canon EOS M cameras. However, the real world benefit of that solution is still undecided.

Panasonic have said in interviews that the on-sensor PDAF solution is not going to be used for Micro Four Thirds, at least not anytime soon. Rather, Panasonic expects to achieve better continuous autofocus performance by using faster image readout from the chip, better image processing algorithms, and more processing power. Have they achieved this with the most recent Panasonic GH3?

To compare the autofocus performance during video recording with the GH2, I used a Lego Technic contraption to move a cardboard box back and forth at a steady pace. I then set up both cameras, in turn, with the Lumix X 12-35mm f/2.8 lens at 35mm f/2.8 at close range, and recorded video at 1920x1080, progressive, 25fps. Comparing the resulting footage, it is easy to see which camera better finds the focus during the movement. Here is the video footage, for comparison:



It's easy to see that the GH3 achieves correct focus more often than the GH2, in fact, about twice as often, according to my frame counting. The GH3 also has a better overall sharpness: It is possible to see the offset printing pattern more easily with the GH3. This could be partially due to the multi aspect sensor feature that the GH3 misses: It means that you get slightly narrower field of view when using the GH3, as compared with the GH2, and hence, more enlargement of the subject.

One of the new features of the GH3 is the 240fps contrast detection autofocus (CDAF) sensor readout. The GH2 only does 120fps, maximum. The smaller print in the GH3 specifications state that the 240fps is only possible when using the newest f/2.8 zoom lenses, the Lumix X 12-35mm f/2.8 and the Lumix X 35mm-100 f/2.8.

And can the camera use the 240fps feature during video recording? Probably not, since the sensor is busy reading the image at 25fps for the video stream anyway. I previously compared the GH2 video AF performance during 25fps and 50fps video, and found that it does better at 50fps, indicating that more frequent image readout is better for the AF performance. As long as the shutter speed is faster than the video rate, there is surplus time between the frames for CDAF readout. Perhaps the GH3 camera can utilize this for better AF performance?

Conclusion

The Panasonic GH3 camera appears to be able to focus better during video recording than the GH2, even at the same frames per second (fps) rate.

Overview of Panasonic cameras

It was Panasonic who released the very first Micro Four Thirds camera, the Lumix G1, back in 2008. While it was a very ergonomic camera with photography oriented functions and one of the best kit zoom lenses in its class, it never made much impact. It was not until Olympus released the retro looking E-P1 that the format took off.

Since this time, they have released a number of cameras. Here is an overview of the current models.

Camera	Lumix GH3	Lumix G6	Lumix GX7	Lumix GM1	Lumix GF6
Price	$1000	$600	$900	$750	$500
Announced	Sep 17th, 2012	April 24th, 2013	Aug 1st, 2013	Oct 17th, 2013	April 9th, 2013
Dimensions	133 × 93 × 82mm	122 × 85 × 71mm	123 × 71 v 55mm	99 × 55 × 30mm	111 × 65 × 38mm
Weight	550g	390g	402g	204g	323g
Style	SLR	Compact SLR	Rangefinder	Compact	Compact
EVF	Yes	Yes	Yes, tilting	No	No
Tilt LCD	Articulated	Articulated	Tilting	No	Tilting
Flash hotshoe	Yes	Yes	Yes	No	No
Focus peaking	No	Yes	Yes	Yes	Yes
IBIS	No	No	Yes	No	No
In a nutshell	Weatherproof, pro ergonomics, the best video	Compact, value for money, good on features	Retro rangefinder style	Very compact, retry style	Compact, enthusiast friendly
Body

GH3, quality of ETC video vs non-ETC

Just like the predecessor GH2, the Panasonic GH3 has the ETC (Extended Tele Conversion) mode. This is useful for videos, when you need more tele effect, a longer reach.

Normally, the camera uses the whole imaging sensor during video, and scales the output down to 1920x1080 pixels for the video stream. In ETC mode, though, it only uses the central 1920x1080 pixels of the sensor, giving an effective 2.4× crop factor, while retaining the full resolution, see the image below:



With the Panasonic GH2, the ETC crop factor was 2.6×. The reason for the difference is that the GH2 has an oversized, multi aspect sensor. The GH3 does not.

Let's say that you use the Lumix G 20mm f/1.7 pancake lens. When using ETC during video recording, it effectively becomes 48mm f/1.7, with 48mm = 20mm × 2.4. Which can be useful at times.

The ETC mode can be enabled in the video menu (left below), or by using the Q-menu (right below):


This feature is very good to have when you want to record videos at a long tele, and you don't have a long enough lens. However, since the camera has fewer pixels to use for making the video stream during ETC mode, one can guess that the quality will suffer. Unlike when using the full sensor, there is no possibility to scale down the image for better noise performance.

Comparison: Non-ETC video vs ETC video

To compare the non-ETC output with the ETC output of the GH3 camera, I recorded video sequences using the Lumix X 12-35mm f/2.8 lens at 35mm without ETC, and at 14mm with ETC. Both these two modes give approximately the same field of view, since 14mm multiplied with the ETC crop factor 2.4 gives approximately 35mm.

I used f/5.6 for the best sharpness. In both these modes, I used ISO values from 200 to 6400. I used the 25fps 1080p, ALL-INTRA mode for the best video quality.

Normally, one would of course not use the ETC mode with the Lumix X 12-35mm f/2.8 lens at 14mm. It would be better to just zoom the lens to 35mm. However, using this trick, I was able to compare the non-ETC and ETC modes using the same lens.

Here is a video summary of the comparison:



And here are 100% crops from the videos, for comparison. The normal non-ETC images are on the top, and the ones with ETC on the bottom:



We see that even at ISO6400, the non-ETC video footage holds up pretty well. It is a bit noisy, and the colours are not as good, but the video is still usable. With ETC, though, the quality degradation is much more severe.

Conclusion

The ETC mode is a very useful feature, but it is best used at low ISO. At higher ISO, the video quality will suffer. We also see that even at ISO 6400, the video quality is quite good with the normal, non-ETC mode.

We don't know exactly what algorithm the GH3 uses for scaling down the video stream from the full sensor to the 1920x1080 pixel output. It probably does not use every 11 million pixels of the sensor (in the 16:9 subsection of the sensor area), that would take too much processing power. But it is clear that it does use some averaging technique, to keep the noise down. In ETC mode, there is no scaling down, and hence, no noise reduction from using more pixels.

I've also compared the ETC video quality of the GH3 with the predecessor GH2. They seem to perform quite similarly, although I generally like the colours of the GH3 better.

When using ETC with a long lens, you can get an extreme tele reach. In the example below, I am using the Lumix G 100-300mm f/4-5.6 at 300mm, together with the ETC mode. This gives a very compressed perspective, due to the extreme tele effect.



You'll see the image wobbling. This is due to atmospheric disturbances, since the light travels through a lot of air before it reaches the camera. There is no way to avoid this, beyond, perhaps, getting up early in the morning while the air is cooler.

When using the Lumix G 100-300mm lens at 300mm, and with ETC, the effective equivalent focal length becomes 1500mm, which is a lot. Even when placing the camera on a tripod, I had to remove the first seconds of video footage while waiting for the camera and lens to settle down after pressing the shutter button.