APS-C "zoom"

Rokdktr

So I understand the "zoom" crop factor of using an APSC sensor camera (40D, etc). My question lies in comparing the new Canon 5D Mk2.

A sale person told me the other day to stick with my 40D if I was taking telephoto pictures more often than not. My thoughts were that with the pixel density of the new 5D MK2 sensor, can I not just get the same "zoom" by cropping the center out of a picture taken with the 5D?

Would a 10mp 1.6X sensor take the same quality pic as the center crop from a 21mp FF? Examples? I could be wrong, but I'm trying to make sense of keeping the 40D in lieu of a 5D.:scratch

Candid Arts

Read this. Should answer your question.

mercphoto

Rokdktr wrote:

So I understand the "zoom" crop factor of using an APSC sensor camera (40D, etc). My question lies in comparing the new Canon 5D Mk2.

A sale person told me the other day to stick with my 40D if I was taking telephoto pictures more often than not. My thoughts were that with the pixel density of the new 5D MK2 sensor, can I not just get the same "zoom" by cropping the center out of a picture taken with the 5D?

Would a 10mp 1.6X sensor take the same quality pic as the center crop from a 21mp FF? Examples? I could be wrong, but I'm trying to make sense of keeping the 40D in lieu of a 5D.

Its not a "zoom" factor. "Zoom" refers to a lens that has a variable focal length. For example, a 24-70 lens is a zoom lens, where as a 50mm is not. Notice that a wide-angle 17-40 is still a zoom, as is a 75-300. In other words, zoom has nothing to do with telephoto or magnification, as you seem to be implying. Since the crop factor is constant and not variable its not a "zoom" factor.

You probably can get good results by cropping pictures from a 5D. However there are other reasons to consider getting a 40D versus a 5D. Full-frame sensors provide for less depth-of-field than crop sensor cameras. Whether this is good or bad depends on the type of photography you do. Also, there are going to be significant differences in auto-focus speed and performance between the two bodies, the 40D should be faster than the 5D. Lastly, there is the inconvenience factor of doing all that cropping. On the plus-side, a full-frame sensor camera usually has a larger, brighter viewfinder.

It all depends on the type of photography you do. Personally I don't sweat sensor size all that much. I really don't think its the big deal many seem to think it is.

Rokdktr

Thank you Candid Arts. That thread had the exact numbers I was after. So I will probably pick up a Mk2 now, then maybe do my own comparisons after the fact.

And I guess I should have used the word 'telephoto" instead of "zoom"??? or "higher focal length"?

ziggy53

Rokdktr wrote:

... And I guess I should have used the word 'telephoto" instead of "zoom"??? or "higher focal length"?

Please just call it a "crop factor" as that is the current industry standard nomenclature. Trying to call it "telephoto" or "higher/longer focal length" is incorrect and will cause a misunderstanding in a conversation.

Taking a "crop" of an image is the correct way of understanding both the process and the results. If you don't understand about what that means then I encourage you to explore the process of "cropping an image":

http://en.wikipedia.org/wiki/Cropping_(image)
http://www.unisa.edu.au/help-webimage/crop.asp
http://www.dgrin.com/showthread.php?t=5482