Lens Sharpness and Contrast
As I have previously stated, the Zeiss Touit 12mm f/2.8 is a pretty sharp lens. Its performance is great wide open in the center frame, and it gets even better when stopped down to f/4. If you want the best overall performance, including the extreme corners, you will need to stop down to f/5.6 – that’s the sweet spot of the lens, as can be seen from the below MTF chart:
So if you want to use the Zeiss Touit 12mm f/2.8 for landscape or architecture photography needs, just remember to stop it down a little, and you will get solid results. Anything past f/5.6 is going to result in softer images due to lens diffraction.
The samples I tested did not seem to show any issues with focus shift, which is good news. There is a little bit of field curvature wide open, but it gets reduced greatly at f/4 and smaller apertures.
Contrast-wise, the Zeiss Touit 12mm f/2.8 is superb, as expected from all Zeiss lenses.
Being a wide-angle lens, the Zeiss Touit 12mm f/2.8 is not designed to yield pleasant bokeh. In addition, the aspherical lens elements do their part in rendering busy, onion-shaped background highlights. You will need to get very close to your subject and shoot wide open in order to get decent subject isolation. Here is a sample fun shot that I captured slightly stopped down, at f/3.2:
As you can see, the out-of-focus background looks fairly busy, and the highlights have distinct outer rings. Obviously, the Zeiss Touit 32mm f/1.8 is going to be a much better candidate for portraiture work, and it has much better bokeh in comparison. My personal favorite for portraits is the Fuji XF 56mm f/1.2 R.
If you shoot JPEG, you will see little to no vignetting, because Fuji does a great job of keeping it under control. The same is true if you use a post-processing tool like Lightroom, which has vignetting corrections enabled by default. However, if you shoot in RAW and you use third-party software for editing your images, then be prepared to see quite a bit of vignetting on this lens. Here is the actual level of vignetting the lens exhibits, which I was able to get by converting the image with Dcraw, then processing it with Imatest:
As you can see, the Zeiss Touit 12mm f/2.8 has close to 2 stops of vignetting wide open. While it is a normal thing to see on a wide-angle lens, vignetting can usually be reduced when stopping down. Except in the case of this lens, it does not happen – even stopping down to f/8 keeps vignetting above 1 EV, which is unfortunate.
Ghosting and Flare
Zeiss coated the Touit 12mm f/2.8 with the same high-quality ZEISS T* multicoating that one can find on high-end lenses. It does a great job at keeping ghosting and flare under control, even when including a relatively large source of light in the frame. Take a look at a pretty extreme example, with the sun in the frame, captured at f/5.6:
You can see a few large ghosts to the right of the frame, and there is a little bit of green cast visible in parts of the image – a common occurrence on T* coated Zeiss lenses.
One thing to keep in mind is that shooting with mirrorless cameras that have very short flange distance can result in red dots appearing around the bright source of light, especially when stopped down. This is not an issue with a lens or a camera – internal reflections between the rear of the lens and the microlenses on the sensor surface cause this issue, which is known as the “Red Dot Flare“. So if you see that in your images, keep this in mind and try to use larger apertures and block parts of the bright light source to avoid the problem.
The Zeiss Touit 12mm f/2.8 shows 2.14% of barrel distortion, which is not bad, considering that it is a wide-angle lens. Don’t confuse it with perspective distortion, which can be pretty extreme if you use this lens to shoot people up-close. If you see distorted figures and faces of your subjects – you are standing too close to them.
Lateral chromatic aberration levels are well under control. Imatest measured less than a pixel of chromatic aberration, as illustrated below:
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