RF 16 mm f/2.8 or 35 mm f/1.8 for EOS RP user ?

ggasquecc wrote:

Is the quality gap between 24-105 STM and 35 mm really worth it ?

The gap is significant, but whether it's 'worth it' is entirely subjective and I don't offer an opinion on that. Fortunately you have the 50/1.8 to help you decide. Do you like what it allows you to do, and do you think you would use it more and to better effect if it was a 35 mm?

The 35 mm angle of view is about 40% more than the 50 mm, which is very useful but not night and day. Think of it this way - it's much less than the difference in width between one person and two. Back in the days before zoom lenses were commonplace and most people had a selection of primes, 35 mm was the smallest step up in width from a 50 mm standard lens. If you wanted wide, a 28 mm gave you a lot more - that was a proper wide angle. You can see all this by experimenting with your 24-105 of course.

On the other side, although it is not a portrait lens, the RF 16 mm will open up new possibilities to me (I've never used such a wide angle), such as landscape or astrophotography.

Others have been quick to favour this lens because it offers you something completely new and this is of course true. On the other hand this is firmly in the ultrawide bracket and compositionally much more difficult to use than an ordinary wide angle. At 16 mm everything more than a few feet away is tiny in the frame. You might love it, or you might just find it frustrating as dramatic landscapes become a vast expanse of sky.

Personally I have always had zooms for very wide angle - the EF-S 10-22 on crop (which is equivalent to 16-35 on full frame), and now the EF 16-35/4L IS which is phenomenal on the R5 with an adapter. This way I have the full ultrawide experience when I want it, but I can ease off to a more modest ultrawide when I need to, which can be quite often depending where I am.

I've seen the RF 16 mm described as a 'no brainer' in at least one review, because it's cheap and decent, but 'the poor man pays twice'... as you will if you end up deciding that what you really needed was an ultrawide zoom.

Once again no opinions offered, just thoughts to provoke.