Sony 20mm F/2.8 only gives 30mm in APS-C camera?

Started 4 months ago | Discussions thread
Martin_99 Senior Member • Posts: 1,664
Re: Sony 20mm F/2.8 only gives 30mm in APS-C camera?

Invanovich22 wrote:

idsurfer wrote:

Invanovich22 wrote:

I know on APS-C sensors there you have to multiply actual focal range by crop factor which is 1.5 so 20mm optics really is 30mm?

In specs they say same thing "35mm equivalent focal-length (APS-C)30mm" https://www.sony.ee/electronics/camera-lenses/sel20f28/specifications

Yes, 20mm on aps-c will be 30mm FF equiv.

I am confused why they label it 20mm then?!

Martin_99 wrote:

Invanovich22 wrote:

I know on APS-C sensors there you have to multiply actual focal range by crop factor which is 1.5 so 20mm optics really is 30mm?

In specs they say same thing "35mm equivalent focal-length (APS-C)30mm" https://www.sony.ee/electronics/camera-lenses/sel20f28/specifications

Yes, correct. But if you have only apsc camera, no need to bother with FF equivalents. Just need to know, that 20mm will give you wide field of view, slightly more narrow in comparison of most smartphone main lenses which are mostly in range 16-18mm.

Good lens by the way, recommended. Probably the most compact lens with AF for Sony apsc.

My question is why full-frame 20mm lens SEL20F18G has field of view 90 degrees and APS-C 20mm lens SEL20F28 has field of view 70 degrees?

This is not accurate. SEL20F18G have field of view 94° only on FF, when attached on apsc camera, it have also 70°. So as I said, don't bother with equivalents, just follow the numbers on the lens. On your camera it means allways the same.

See official Sony specs:

I get it crop factor in APS-C vs full-frame sensor, i am more confused why its labeled 20mm for APS-C it would make more sense to label it 30mm...

Technically not make sense, see my note above.

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