Fuji GFX 50S Review: Autofocus Performance
Just like the Hasselblad X1D-50c, the Fuji GFX 50S has a relatively simple contrast-detect only autofocus system. This means that if one were to compare the GFX 50S with any modern mirrorless camera with a smaller sensor (say with something like the Fuji X-T2), it is noticeably slow and lenses tend to hunt when there is not enough contrast – all normal behavior for contrast-detect AF systems.
Still, based on my experience with the GFX 50XS and comparisons to the X1D-50c, I can confidently say that Fuji did everything it can to get the best out of the AF system. While the X1D-50c has a very limited and simple AF system with a total of 35 focus points that are painful to pick, and no implementation of continuous AF whatsoever, the GFX 50S has a much more robust AF system with a total of 425 focus points covering the whole image frame and both single servo and continuous-servo modes.
When shooting with the X1D-50c and GFX 50S side by side, one can easily see the big difference between the two cameras in terms of autofocus features and capabilities. The GFX 50S has all kinds of focusing options available, including Single Point, Zone AF and Wide / Tracking in both single servo (AF-S) and continuous-servo (AF-C) modes. The camera also has face and eye recognition built-in (which work reasonably well), and one can customize and fine-tune the focusing behavior of the camera. Fuji has far more experience than Hasselblad in making a functional autofocus system and it really shows – the AF options we see on the GFX 50S closely match those of existing Fuji X-series cameras. So if you compare the two, the GFX 50S comes out on top by a huge margin, there is simply no comparison.
With the latest firmware update, Fuji solidified the GFX 50S as a very accurate camera that is capable of producing consistent and sharp results, something it certainly struggled with before. I have been testing the GFX 50S with all three lenses and the difference is very obvious, especially with the GF 120mm f/4 Macro OIS lens. I can no longer see focus drifting away from subjects when the shutter release is triggered and the camera seems to be doing a much better job when dealing with focus shift. Fuji silently implemented a new feature on the v1.1 firmware that makes the camera stop the lens down to the chosen aperture when shooting, which pretty much eliminates the focus shift behavior.
And while some might be concerned that the camera’s AF system might struggle when shooting at very small apertures in dark environments, Fuji came up with a great solution to deal with this issue – the camera opens up the lens aperture enough for the AF system to get enough light, then it stops the lens down.
In addition, the GFX 50S now remembers where focus was set to, so if you turn the camera on and off, you will no longer need to reacquire focus. These improvements to the GFX 50S are very significant, to the point where I would love to see the same fixes applied to all other X-series cameras. All these fixes played a key role when I resumed testing of the GF lenses via Imatest. Prior to the fixes, it was nearly impossible to properly test lenses, because they would yield very inconsistent results and focus would constantly drift away from the subject, as stated above. After updating the firmware, I was able to properly test all three GF lenses, the results of which will be posted soon in separate reviews.
Overall, Fuji has done a great job with the focus system on the GFX 50S and I applaud its engineers for addressing the above-mentioned critical focus issues. Prior to the latest firmware, the AF system accuracy was going to be my biggest criticism of the GFX 50S, but now that the issues have been taken care of, I am happy to recommend the camera for serious fieldwork where critical sharpness is important.
Fujinon GF Lenses
As of early 2020, I have been able to test pretty much every lens Fuji has released for its medium format system. Although G mount lenses are quite bulky and heavy (which is expected, given that they cover such a large image circle), I found their performance to be excellent for a high-resolution medium format camera. Fuji says that its goal is to focus on high-quality primes that can deliver enough resolution to be able to cover at least 100 MP sensors, and we have already seen that most Fuji GF lenses perform exceptionally well, even on the 100 MP Fuji GFX 100 body. Below is a quick summary of the lenses that I tested for this review.
The Fuji 63mm f/2.8 is an excellent lens that I highly recommend to anyone considering the GFX 50S. That’s the lens I ended up using the most when traveling, since it is small and very lightweight, which works perfectly for street and travel photography. It is insanely sharp in the center of the frame and the mid-frame, but it does have some pronounced field curvature at close distances, so if you focus at the subject in the center, the edges of the frame might look a bit blurry. The good news is, the field curvature issue goes away when focusing at longer distances, which makes the lens a good candidate for landscape and architecture photography.
The Fuji GF 32-64mm f/4 is a very useful and versatile lens for landscape and architecture photography since its full-frame equivalent field of view is roughly 25-50mm. It is not great at its maximum aperture, but when stopped down to f/5.6 and smaller, it produces very good results all the way to the edges of the frame at shorter focal lengths. Its performance goes down when zoomed at 44mm to 50mm range at the edges of the frame, but the sharpness picks up again a little at 64mm. It has practically unnoticeable barrel distortion at the wide end, which switches to very slight pincushion distortion when zoomed in. In short, unless you shoot very straight lines, you will never notice distortion on this lens. Chromatic aberration levels are controlled very well, with lateral CA being around 1 pixel at 32mm and even less than that when zoomed in. The lens is also optimized to yield very little vignetting – even at 32mm, the extreme edges never get darker beyond 1.5 stops and stopping down the lens to just f/5.6 reduces it significantly.
The Fuji GF 120mm f/4 Macro is without the doubt the best of the three optically – it shows superb sharpness from the center all the way to the edges of the frame at every aperture, even when shooting wide open! It has no distortion, no signs of lateral chromatic aberration, very little longitudinal chromatic aberration and practically no vignetting either. It is a large and heavy lens, but don’t let its size and weight intimidate you – it is a lens that always delivers. The only slight concern of mine is the loose focusing element inside the lens – when the camera is turned off or the lens is detached from the camera, the loose element in the lens moves freely, making a rattling sound. This can scare some people into thinking that there is something wrong with the lens, but in reality there is nothing wrong. According to Fuji, the lens is designed that way and it is not going to break over time, even if you transport the lens a lot.
I have no doubt that Fuji will work hard in making sure that all the lenses they release for the GF system are going to perform at a high level. So far, I am impressed by what I see and I cannot wait to test all the future-generation Fujinon GF lenses.
Focal Plane Shutter and Adapter Options
One of the biggest advantages of the Fuji GFX 50S when compared to the X1D-50c, is the fact that it uses a focal plane shutter instead of a leaf shutter. This gives additional versatility to the GFX 50S, because one can use all kinds of adapters to adapt third party lenses. Ideally, one should only try to adapt lenses with large enough image circles that can cover the whole sensor, which limits lens choices to medium and large format lenses only.
However, some lenses designed for smaller full-frame cameras might have large enough image circles to be able to cover the whole sensor, so you might want to look into those lenses, particularly if they offer some advantages the GFX 50S cannot provide. For example, I tried out a few Nikon F mount lenses with a third party FotodioX Nikon F to Fuji GFX 50S adapter and I found out that some lenses performed adequately well with the GFX 50S without showing significant vignetting issues at the edges of the frame. For example, the Nikon 85mm f/1.8G turned out pretty well when mounted on the GFX 50S, producing excellent detail and very smooth bokeh:
And if one were to use something like the Nikon 85mm f/1.4G, it would be possible to get even shallower depth of field with a wider f/1.4 aperture.
Being able to adapt third party or older lenses is a huge benefit for those with existing glass collection, so keep this in mind when comparing the GFX 50S to the Hasselblad X1D-50c or the Pentax 645Z.
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