Canon crop factor?

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jrf23

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James
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Basic question. Crop factor on a canon 450D is 1.6 right? So, if I have this right, if I use a 200mm focal point lens, it will actually be 320mm? Unless, I'm using an EF-S lens in which case its as stated and 250 is 250. Is that right?
 
No, focal length never changes, but it gives a field of view that is multiplied by 1.6

EF and EF-S lenses are affected exactly the same
 
jrf23 said:
Basic question. Crop factor on a canon 450D is 1.6 right? So, if I have this right, if I use a 200mm focal point lens, it will actually be 320mm? Unless, I'm using an EF-S lens in which case its as stated and 250 is 250. Is that right?
Click to expand...

Not quite.

The focal length of the lens does not change all that changes is the Field of View.

What that means is that the 200mm lens covers the same field of view as a 320mm lens on a full frame camera such as the 5Dmk2.

The EF-S is simply a mount and the same rules apply as above.

.
 
55-250mm f4 EFS lens is equivalent focal length to a 88-400mm (info taken from Canon 2009 Lens Guide)

Al'
 
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The hint is in the name, it gives the same view as cropping a full frame image by the crop factor.
 
petersmart said:
Not quite.

The focal length of the lens does not change all that changes is the Field of View.

What that means is that the 200mm lens covers the same field of view as a 320mm lens on a full frame camera such as the 5Dmk2.

The EF-S is simply a mount and the same rules apply as above.

.
Click to expand...

Right, i think i get that. So, basically, with a full frame camera you get what looks like less 'zoom' but it actually is the same level of detail. If you were to crop this image by the right factor, the images would be the same as on the rebels?

That makes more sense about the EF-S mounts.
 
The only difference with the EFS lenses is that they have an element that sticks out the rear of the lens, bringing it closer to the shutter and focal plane. This isn't a problem for the APS-C cameras as the smaller sensor has a smaller mirror in front of it. There is enough room for this mirror to flip up behind the lens.
If you ry to use one of these lenses on a full frame camera, the bigger mirror will hit the back of the lens. Definitely NOT a good thing!
 
chameleon said:
The only difference with the EFS lenses is that they have an element that sticks out the rear of the lens, bringing it closer to the shutter and focal plane. This isn't a problem for the APS-C cameras as the smaller sensor has a smaller mirror in front of it. There is enough room for this mirror to flip up behind the lens.
If you ry to use one of these lenses on a full frame camera, the bigger mirror will hit the back of the lens. Definitely NOT a good thing!
Click to expand...

That's not the only difference. The main difference is that EF-S lenses (and Nikon DX) project a smaller image circle that is only big enough to cover the smaller 'cropped' sensor. So even if you could fit the lens on to a full frame camera the image would not fill the frame and the edges/corners would be black. You can actually do this with Nikon.
 
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