What Lens Specification To Look For Sharpness At Distant Subjects When Cropped??

Started 2 months ago | Discussions thread
rich_cx139 Senior Member • Posts: 1,787
Re: What Lens Specification To Look For Sharpness At Distant Subjects When Cropped??

rpszone wrote:

Take two, different, 200mm lenses, same body and subject at 100 feet. Which one can crop better with sharpness and clarity?

Do I look at "perceived megapixel" rating, "resolving power", what makes one lens better than the other for this task?

I think ZilverHaylide has given a pretty good explanation of the problem.

In addition, a few more thoughts:

If you are talking about a centred DX or other crop from a FF sensor output then life gets marginally easier in that it becomes easier to get some idea of performance from MTF graphs if you spend time understanding what they can and cannot tell you.  Since there aren't many 200mm lenses around then you may be looking at zooms and unless its a 70-200, or a 200-x, you probably will be left trying to guesstimate performance from nearby FL MTF data.

If you are cropping hard then you may need more data than the 10lp/mm and 30 lp/mm that Canon and Nikon typically give you but if its a modern lens produced with high mpx sensors in mind then you should be better off than with an older lens designed over 10 years ago for lower mpxs. There are no hard and fast rules however and some, even, film era 200 ish primes are still very very good.

A problem doing anything other than trying two lenses side by side yourself is that the resolution can vary significantly with the target distance - I have several where this the case. No one publishes data for a lens at different target distances and apertures.

The best guide is to see what people who use the lenses you are interested in actually say is their experience.

Price is usually a good pointer but not necessarily so since there are examples of really cheap lenses outperforming most people's expectation. Not sure about the converse: when prices get up and beyond 2K it would be surprising to find many 'lemons'.

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