Crop sensor extends reach of lense?

Started Feb 10, 2013 | Questions thread
(unknown member) Veteran Member • Posts: 3,849
It's the angle

Ruud81 wrote:

I see so "the more reach argument" has everything to do with the amount of pixels inside the "cropped" area.

People say crop sensors are generally better for wildlife photograhy, which turned out to be my favourite subject in past years. I'm considering getting a replacement for my "old" 40D, but not sure if I should go for a 5DIII or 7D.

I still love my 40D, but bit disappointed now with low light performance and AF speed/accuracy and lack of microadjustment. I guess a 5DIII will still achieve an equal or better crop as the cropped 40D (10.1MP)?

Lenses always have a certain angle of vision. A wide angle lens has, as the name implies, a wide angle. The longer a lens gets (the more mm), the smaller the angle becomes. See it like this: Your own view also has an angle (somewhere around 35-50mm equivalent), but using binoculars that angle becomes smaller in favor of seeing something far off much clearer.

A sensor in a crop camera like the 7D is smaller than a FF sensor in a 5DmkIII. If you think back to the geometry lessons in school, you can imagine that using a smaller sensor means you are using only part of the light cone, effectively narrowing your field of vision.

The lens doesn't change, the image doesn't change, it's just that a 7D uses only part of the incoming light cone. The angle used is similar to a 1.6x longer lens on a 5DmkIII.

What is better for wildlife? I'm still not sure myself. The images from the 7D require less cropping, but I'm sure the images from the 5DmkIII allow more cropping and will be of a better quality overall. If I were buying now and money wasn't the main issue, I would be more tempted by the 5DmkIII because of it's amazing AF and image quality. (Although the 1.3x crop 1DmkIV offers the best of both worlds.)

I have also seen some bird photographers favor the 7D because of the high pixel density that is capable of resolving a lot of details when used properly. I don't know if that's true, but I'm not the most experienced bird photographer.

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