hubie said:Lee Jay said:hubie said:privatebydesign said:Yes a Canon APS 50-100mm f1.8 has a Full Frame equivalence of a 80-160mm f2.88. So less range and less dof, factor in the greater than one stop of noise advantage a ff camera has for the apparent EV difference of the aperture to get a faster shutter speed and it seems like a strange lens.
But there are a lot of APS users out there and Canon are not making compelling lenses specifically for them, so good luck to Sigma.
Excuse me, but this lens still has 1.8 aperture. So only because you have to rearrange your framing and therefore lose a bit of DOF because you have to step back, there is still more cd/cm² available on the sensor at f/1.8 than at f/2.8. That's the danger with all this unscientific calculations (as tony northrup is famous for to throw in here and then) in order to make a comparison between FF and APS-C... people get confused. You will have more than a stop of brighter illumination, so the noise performance of a smaller sensor can be compensated quite a bit.
Total light captured is what matters for image quality, not light per unit area. That's why f/2.8 on full-frame is about the same as f/1.8 on 1.6-crop ( 1.8*1.6~=2.8 ).
Overall, this lens will likely produce similar IQ to the 70-200/2.8 on full-frame, but the 70-200+FF combo is wider, longer and has IS.
Well, I would say, the amount of light gathered per pixel (with comparable sensor technology) is what counts.
And you'd be right if you only look at the pixels rather than the image.
So if you get more than twice of the amount of light with one aperture more, your pixels, that are 1/1.6 of the size of a FF sensor should at least deliver comparable SN-performance.
Yeah...that's just all false. For overall image quality, it's the total light captured not the light per pixel that matters. Think of the total light captured as a pizza. How you slice it up doesn't change how much pizza you get. In fact, especially at moderately high ISO, smaller pixels generally beat bigger ones for overall image quality, but only for secondary reasons.
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