Choosing between EF 35mm f/2 IS USM and EF-S 35mm f/2.8 IS STM

Sittatunga wrote:

Canon_Guy wrote:

Torschlusspanik wrote:

Andy01 wrote:

Torschlusspanik wrote:

I’m looking to get my first fast prime lens, as I really want to have better quality low light photos and video. My current EF-S lenses only go to f/4 (kit 18-55mm IS STM and 55-250mm IS STM), and I’m not very comfortable using my T7i any higher than 800 or 1600 ISO. I‘ve lately been mostly, but not exclusively, shooting events and live music, and I’m finding that my setup’s low light capabilities are the weakest point right now (a new camera is way out of my budget at the moment).

Image stabilization is a hard requirement as I shoot almost exclusively handheld or with a gimbal, and so I’ve narrowed my choices down to the EF-S 35mm f/2.8 IS STM and the EF 35mm f/2 IS USM. They’re the only IS lenses I’ve been able to find within my price range (about $300 refurbished from MPB or KEH), and are in the range of focal lengths that would be most useful and flexible to me.

I’ve mostly set my mind on the EF lens (the longer focal length

The focal length will be identical on your camera - 35mm is 35mm, period. ANY 35mm lens fitted to your APS-C body will have an effective FF FoV of a 35 x 1.6 = 56mm lens. So both of these 35mm lenses will have identical (at least theoretically) focal lengths and FoV on your camera.

Really? I must have horribly misunderstood how crop sensor focal lengths work.

Probably you have.

I had thought that lenses for APS-C cameras, for example, EF-S, were modified or calculated differently so that, for example, an EF-S lens listed as 35mm when used on an APS-C camera would have the same field of view as a 35mm EF lens on a full frame camera.

No no no... The focal length number on a lens is always a full frame equivalent. All manufacturers do so.

No, for interchangeable lenses it's always the actual focal length in mm or inches, never a full frame equivalent. My RX100 uses full frame equivalent when it describes its 10.4-27.1mm lens as 28-100mm but every interchangeable lens that I've ever used gave its actual focal length. That's very important when the same lens mount supports different sensor formats as it means that, for the same sensor size, you can compare focal lengths and fields of view directly no matter what sensor size the lens was originally designed for (as long as it wasn't smaller than the sensor you're using)..

I should have written "FL on FF" instead of "equivalent". But I suppose my point is clear.

I thought that full frame lenses didn't have this adjustment, so if you used a 35mm full frame lens on an APS-C camera it would have a field of view equivalent to that focal length times whatever the sensor's crop factor is (such as 1.5 or 1.6).

Correct.

If this isn't the case, then, aside from market segmentation, what is the point of having a dedicated lineup of APS-C lenses if they have the same field of view as the lenses designed for full frame cameras?

Smaller image circle. That gives the space for APS-C lenses to be smaller, lighter, cheaper.