7artisans 12mm/f2.8 image quality
Sharpness through the f-stops
There is a little shift in position from the first image to the rest, but I did refocus all the pictures. Here is the full picture @f5.6:
Centre and top right corner crops
7Artisans 12/2.8 @ f2.8, centre and top right corner
7Artisans 12/2.8 @ f4, centre and top right corner
7Artisans 12/2.8 @ f5.6, centre and top right corner
7Artisans 12/2.8 @ f8, centre and top right corner
7Artisans 12/2.8 @ f16, centre and top right corner
The centre is already good at f2.8, improves a bit till at f8 diffraction starts to soften the image a bit. The corners only sharpen up at f5.6.
Comparison with the M.Zuiko 12-45/4
Here picture with the 7Artisans @ f8:
Conclusion: overall the M.Zuiko wins but the 7Artisans does not drag far behind. At f4, the maximum both have in common, the centres are close and the outer field (the tower) clearly is better in the M.Zuiko — here one can see that the M.Zuiko is more expensive as it has an evenly sharp image field, both borders and centre. At f8, the winner is less clear in my opinion — the centre is similar and the borders are now also quite similar. I am not saying or implying that the M.Zuiko is not worth its much higher price; what I mean is that having the fun of a completely manual lens that is very affordable does not mean one has to sacrifice image quality.