50mm or 35mm on APS-C

[ahab1372]

For portraits you tend to want a slight telephoto to compress facial features (nobody is happy with their nose). Typically you want 85-135mm (or more).

While the 50mm "acts" like an 80mm on your crop body, that's only in terms of framing. In terms of compression it's still a 50mm. We love our 85mm f/1.8 for portraits, and people like it for indoor sports, but it's a bit long for indoor general purpose. If you're solely doing portraits, I'd recommend it over the 35 or 50. If you're hoping for multiple uses out of the lens, you'll have to figure out what those uses are and which are most important.

The compression is actually determined by the distance from your subject, so a 50mm on APS-C would require the same shooting distance as a 80mm on a FF, and thus have the same compression. Depth of field will be different IIRC, because on FF you have a longer lens but are closer to the subject (also the Circle of confusion eehm contusion also plays into this equation).

Back to the original question:
50mm on APS-C is okayish for portraits, and also okayish as a low-light general purpose, but IMO not great for either one. For portraits is should be longer, for general purpose in low light it might be a little too long. I would also recommend the 85mm f/1.8 for portrait and low- light short telephoto, and something in the 30mm range for general purpose. The Sigma 30mm has many happy owners, maybe the old 28mm f/1.8 used is another option, or the 35mm f/2.

If it can be only one lens to cover both use cases, then the 50mm 1.8. 30mm is not a recommended portrait focal length.

I personally started with the 50mm 1.8, added the 85mm 1.8, and have not yet added a 30mm low-light. I might in the future, but I don't miss it desperately yet. Really depends on personally preferences. So far I make due with the 50mm 1.8
If you find a good deal or buy refurbished or used, you might get the 85mm and the 50mm within or slightly above your budget. You can then add a 30ish mm lens later if you miss that focal length