Photo cropping

[Wilson]

Is there a difference in photo image quality if I crop my 42 megapixel photo taken at 70mm focal length to look like 200mm focal length when compared to photo taken with 200mm lens besides the reduction in megapixels? 

[chardinej]

Depends on what you intend to do with the image. At 100% side by side, you would see a difference of course. The one taken with the 200mm lens would have a lot more detail. Printed small, or put up on the web, you would probably not see much if any difference. 

[BlackRockArt]

A lot of difference, the details will be vary a great deal.

[GhostWalker]

On 10/30/2018 at 4:39 AM, BlackRockArt said:

A lot of difference, the details will be vary a great deal.

I agree that there's likely to be a lot of difference, in part depending on the lenses used and their respective resolving power.

Even with a particularly sharp 70mm lens, a crop (as in this example) that represents about a third of the image area is unlikely to rival the detail offered up by a 200mm lens (unless the 70mm lens is about "three times sharper" than the 200mm lens) - and that's before the reduction in px resolution is taken into account...