Detector Size vs Print

I read somewhere that the maximum print size obtainable depends not only on the number of MP, but also detector size. Hence, a 10 mg dslr produces a better image than a 10 mp pocket job. There is supposed to be a formula to calculate the maximum print size based on the detector size (length and width in cm), as well as megapixels. Does anyone know the formula? Thanks for any input.

Greg, these formulas are based on diffraction limits but in reality only provide a rough approximation. Whether an image works at a given size also largely depends on the image itself and how it is displayed (viewing distance, lighting etc.)

There's an example of such a calculator on this page:

http://www.cambridgeincolour.com/tutorials/diffraction-photography.htm

Guy

Greg, from experience I can say that one should not get to caught up in the "formula" version on how big an image can be printed with very good results. As Guy pointed out there are other factors that in my opinion play a more substantial role on size/quality of a given print. I have had large prints produced at 150 dpi that actually look better than ones produced at 300 dpi. (I almost never interpolate an image when increasing it's size, native size is should always be maintained). It all depended on what I started out with. An excellent initial capture from a lower mp camera will go much further in size/quality than a ho-hum capture at a higher mp camera.
I believe this equates to master skills on your end and don't rely on the camera to make things right.

Brad