Question about other lenses on the T2i.

[brandonanthony1]

From what I've read with the focal plane, it appears that other brands lenses, when put on the t2i, are not actually what they seem to be.

Is it true that if I were to attach a wide angle Nikkor lens onto the t2i (28mm), that it wouldn't be wide angle anymore?

Thanks.

 

[Barry_Green]

That's not related to the focal plane, it's related to the so-called "crop factor". And it depends on what camera you're used to using the lens on. If you're used to a full-frame 35mm film SLR (or comparable digital), then your lenses will appear to be more telephoto when used on a t2i, since it has a 1.6x crop factor.

Which means that a 20mm lens on a full-frame camera, when put on the t2i, will act more like a 32mm lens when used on a full-frame camera.

 

[PerroneFord]

This information is not correct. Your lens won't magically change when you attach it to a T2i (or any other crop sensor camera for that matter).

Here is what happens:

The lenses you are attaching are designed to project an image onto a piece of film that is a certain height and a certain width. Imagine pointing a projector at the wall so that it takes up the entire wall. The sensor in the crop sensor camreas (T2i, 7D, GH1) are all smaller than a piece of 35mm film. It's like taking a bedsheet and putting it on that wall where the bedsheet is smaller than the wall. Some of the image misses the sheet. This is what is happening in your camera. Some of the image is missing the sensor.

So we say the field of view is smaller. The smaller the sensor, the smaller the field of view. So since we are not seeing everything, only a portion cut out from the middle, it has the effect of making a wide angle lens appear less wide angle.

This confuses a lot of people, and hopefully that explanation makes more sense now.

 

[Timbit]

Now I'm confused as well!

A very good answer PerroneFord, but I was always told to multiply the focal length of the lens by 1.6--also known as the crop factor of the sensor. So a 50mm lens becomes an 80mm lens when used on the crop sensors.

Am I on the right track, or way off?

EDIT:
I actually see what you were saying now. Because a crop sensor only sees a portion of what the full-frame sensor sees, it brings it up to the same size, and therefore the "longer" appearance of the focal length is in reality cropped image blown up to the same dimensions.