Image Sensor and Autofocus Performance
At the heart of the X-M1 sits the same superb X-Trans CMOS sensor used on the X-E1 and X-Pro1 cameras. While traditional sensors with a repeating Bayer-pattern color filter array exhibit moire problems and hence need an anti-aliasing filter to reduce moire by essentially blurring the image, the X-Trans CMOS sensor has a new color filter array that has a more random pattern, which does not cause moire to occur in the first place. Hence, an anti-aliasing filter is not necessary, which in turn translates to sharper, more detailed images.
Here is an illustration of a traditional bayer pattern color filter array compared to the new Fuji color filter array:
Top image: 1) Lens, 2) Sensor, 3) Optical low-pass filter.
Bottom image: 1) Lens, 2) Sensor, 3) Natural random arrangement of the fine grains of silver halide in film.
As you can see, the difference between the two is quite big.
Fuji says that their sensor not only delivers sharper images due to the lack of an anti-aliasing filter but also has better color reproduction. Does the new X-Trans CMOS sensor work as advertised? It certainly does, in my opinion. The amount of detail from the camera when using Fujinon and Zeiss Touit lenses is very impressive, especially when looking at images at 100% view. As a long time digital Nikon shooter, I am very impressed by what the X-M1 does with the colors. Not only does the camera produce beautiful colors, but Fuji clearly knows how to process skin tones – something Nikon is historically not very good at. This is quite evident even when looking at JPEG images straight out of the camera.
The X-Trans CMOS sensor with a new color filter is a great innovation. Sadly, most digital camera manufacturers today, including Nikon and Canon, still rely on the Bayer pattern that was invented back in 1976 in Kodak labs. With all the new ultra-high-resolution sensors coming out, I believe manufacturers need to start adopting such innovations to get rid of the outdated anti-aliasing/blur filter. Nikon has started removing the AA filter from its cameras to get as much resolution as possible from lenses but at the expense of introducing moire.
The only problem with the X-Trans sensor is rendering issues of RAW files when using Camera RAW and Lightroom. I am not sure why Adobe has still not worked this out with Fuji, but the RAW processing engine in Adobe’s products introduces artifacts to images and weird patterns in different color channels. I really hope that these issues will soon be ironed out since I am not very keen on introducing another RAW rendering software package to my workflow process.
Autofocus Performance and Accuracy
Thankfully, the X-M1 came pretty much free of all the nasty autofocus issues that plagued the X-Pro1 and X-E1 cameras. My copy of the X-M1 came with the original 1.0 version of the firmware and I have yet to see any serious AF problems. The camera autofocuses as fast as my X-E1 and its autofocus accuracy feels to be the same as well. Lola and I have shot a few weddings with the X-series cameras (including the X-M1) and the cameras did not experience any issues with autofocus performance, even in challenging low-light conditions indoors.
In fact, where my Nikon D800E with the Nikkor 85mm f/1.8G suffered in AF accuracy, the Fuji cameras did not! Now I am not here to say that the AF system on Fuji mirrorless cameras is better than on DSLRs because it is clearly not. Autofocus speed is still pretty slow in comparison. However, seems like contrast-detect has its own advantages in low-light situations. Here is an image that was shot with the X-M1 in a very dark environment outdoors:
When compared to the AF speed champ, the Olympus OM-D E-M5, the Fuji X-M1 definitely performs slower and feels a little less responsive when quickly changing from one subject to another – there is a noticeable lag on the X-M1. However, autofocus is not as bad as it used to be on the X-Pro1 when it first came out and it is certainly adequate for most photography needs. I personally would not shoot a sporting event with the X-M1, but as I have already pointed out earlier, the X-M1 is not meant to be for photographing sports and wildlife. The AF-C mode is extremely slow and practically unusable for serious subject tracking. In addition, Fuji does not even have a fast telephoto lens in its arsenal yet (neither the 55-200mm, nor the 50-230mm lenses are suitable for that) and we might not see anything until AF gets faster and lags/blackouts are completely eliminated. I hope that Fuji will incorporate the phase detection system into its future X series cameras and make sports / wildlife photographers happy. For everything else though, the X-M1 performs admirably.
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