new photo blog

i started this blog in 2006, and it's shifted along with my interests through the years. it's been witness to a lot of learning for me...

still, i feel that i need a home for my photography -- so from now on, i'll be posting my pictures on the journal on my reworked website. if you like my photos, you might decide to follow me there!

my first post is here -- check it out!

as for this blog, i'm not sure what will happen. i don't think i'm willing to let it go, and certainly i'll keep it as an archive, but i need some time to figure it out.

for those of you that pop in from time to time, thanks for the visits and encouragement.

Friday, November 11, 2011

perspective, distortion, distance and sensor size

yesterday on google+ i posted a link to a nifty page which illustrates the effect that lens length has on the distortion of a portrait.

a friend then asked me this:  what happens if you use a DSLR which has a cropped sensor instead of a full-frame sensor?  here, i make an attempt to answer -- as i understand it.  in other words, i'm no authority, so i'd appreciate corrections from anyone who's more knowledgeable.

in this illustration, i compare a full-frame sensor (36x24mm) with a APS-C sensor (23x15mm):

perspective distortion distance and sensor size in photography
click to enlarge

the first column depicts a wide-angle lens from a short distance, the second, a standard lens from slightly further away, and the third, a mild telephoto lens from even further away. notice that the combination of lens length and distance allows you to fill the frame to a roughly similar extent.

the first row compares what both sensors are able to see if you keep the same lens and switch camera bodies -- obviously, a cropped sensor can see a smaller area than a full-frame can.

the second and third rows compare what the picture will look like, when printed to equal sizes or fully projected onto the same monitor.

notice that the degree of perspective distortion is the same for both sensor sizes, but the subject fills a larger portion of the image on a cropped sensor.

feedback, please!

©2011 helen sotiriadis

1 comment:

  1. The logic seems fine to me. The effect of using a cropped sensor should be the same as simply cropping a picture in the editing process. That may be the simplest way of explaining it to someone.