thank you very much for the illustrative review of both small format primes! Whereas I don't have any issues with the nifty-fifty, here my impressions and minus points about the 17 mm (translated by< google, pardon for any imprecise wordings therefore...): A short focal length, packed relatively compactly, is a good idea. Although the image quality is very good, except for the strong distortion in RAW (which costs image quality when corrected!), I have two points of criticism - the lens is actually much "too small" - measured against the 20 mm 2.0, its size would have been okay and would have fitted in very well with the series, at least with a speed of 2.8 IMPORTANT: that's why the classic B+W S-Pro filters (clear / UV) don't fit - the tube on which the lens hood is attached using a bayonet lock is narrower than the broader filter. Consequence: the filter protrudes slightly over the edge, the attachable bayonet hood no longer fits in! So I had to buy a new B+W Master Clear Filter for 40 E, which makes the following point even more important: - Measured by the mechanical aspects and the low "speed", I find the price too high, actually it should be at least 100 € cheaper I don't understand why Sigma (like many or actually all photo manufacturers unfortunately) doesn't ask the users beforehand about their wishes. In any case, I would have said that I find so much compactness for so little speed problematic. A bit bigger, but F 3.5 or 2.8 would have been great! I now use it as a second lens next to, for example, the Canon TS - E 17 mm shift lens - at least the focal length and perspective match So, dear company Sigma: set up a customer advisory board, then everything will be better