Crop factor question (PP)

[AESamuel]

Hi,

I'm getting a sony RX100 tomorrow and the focal length is 100mm (35mm equivelant) at the long end with a 20MP image.

If I were to crop this down to a 10MP image, would this give me a 200mm equivalent?

Thanks!

 

[HoppyUK]

Hi,

I'm getting a sony RX100 tomorrow and the focal length is 100mm (35mm equivelant) at the long end with a 20MP image.

If I were to crop this down to a 10MP image, would this give me a 200mm equivalent?

Thanks!

No, cropping down to half, ie 10mp, is 1.4x reduction - area difference is crop factor squared, 1.4x1.4=2. So you'd be looking at 140mm equivalent.

For true equivalence, there are several other changes going on too, such as depth of field that goes up, and lens sharpness that goes down - regardless of pixels.

 

[AESamuel]

No, cropping down to half, ie 10mp, is 1.4x reduction - area difference is crop factor squared, 1.4x1.4=2. So you'd be looking at 140mm equivalent.

For true equivalence, there are several other changes going on too, such as depth of field that goes up, and lens sharpness that goes down - regardless of pixels.

Great! Thanks very much for the info