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1.6 crop IQ tests don't look as sharp compared to full frame, why?

Started Feb 1, 2017 | Questions thread
mordor_74 Contributing Member • Posts: 622
Re: 1.6 crop IQ tests don't look as sharp compared to full frame, why?

I am a newcomer here, but based on my reading:

1) generally speaking not all FF lenses permorm well on a crop sensor. the crop sensor uses only the central part of the lens, so the FF lens must have a very good center resolution to perform well on a crop. On the other side corner to corner the performance tends to be consistent. A good example is my 40mm STM (i know, not in the focal range we are speaking), not extremely sharp but very consistent across the frame already at f2.8

2) after we pass 250mm and a certain distance, we do not have only the sensor noise, but also light noise become evident (there is a dpreview article that talks about that kind of noise)

So i think that the performance of a lens on different sensor size should not be compared at the same focal lenght but at the same equivalent focal lenght.

We should compare the performance of 300mm in FF with 187mm on crop (same distance etc) or compare the long end 300mm of the lens on a crop with a 480mm on a FF (again, a more similar effort) and there evaluate if the difference of performance (i'd expect that the crop to be less good) and price (i expect the 480mm FF lens to be a lot more pricy) and make your mind if can live with the cropped result or you need the better solution.

This is how understand this matter so far...

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