Crop calculator

Started Oct 18, 2009 | Discussions thread
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vvume Regular Member • Posts: 400
Crop calculator

The 18MP from a 7D has a huge crop potential. Is it mathematically possible or is there an online calculator that will help me determine crop equivalency? For example:

Inputs:

Body (FF or 1.6x)
Input MP
Lens focal length
Aperture
Desired Crop focal length (to get cropped FOV)

Result:

Crop MP
Crop aperture (assuming crop is centered)

What the above calculation should give me is the size in mega pixels I would get if I cropped an image taken with a certain focal length lens/body to mimic the field of view of another focal length lens. Obviously the "perceived" aperture would also change.

So if I took a 18MP image with a 300mm f/4 lens, how many MP/f would i get if I were to crop it to get a 800mm FOV. Maybe 6MP f/11?

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