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Old Mar 27, 2009, 12:09 PM   #1
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I have seen the "framing" difference between what a full frame sensor (24x36 = 864) gives me vs what a cropped sensor {14.8 x 22.2= 328} sensor gives me. This means that I have a 1.6 magnification factor built into my system. (864/328=2.6. 2.6 less 1 leaves me with the 1.6 magnification)

For the discussion, I'll use my 18mm -55mm lens using the shortest focal length of 18mm.

The 18mm setting x 1.6 means I actually shooting at a 29 focal length.

Okay, with all that in mind, here's my question.

If I use a full frame Canon 5d and shoot at a 29 focal length lens, and then shoot the exact shame shot using a Canon XSi (with the 1.6 factor) at 18 focal length, then print both photos, will the framing be the same? Will the photos be virtually identical? (forget the mexapix difference). But will the framing be the same? If they're different, then what in my feeble brain is missing?

Thank you my photo guru buddies.






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Old Mar 27, 2009, 12:34 PM   #2
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Quote:
The 18mm setting x 1.6 means I actually shooting at a 29 focal length.
Actually you are still shooting at 18mm focal length, but the apparent field of view it gives you equals to the field of view of a 29mm lens on a FF camera. The image quality will be different, but you will get the same framing in your exercise with a 18mm on APS-C and 29mm on FF.
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Old Mar 27, 2009, 12:35 PM   #3
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Basically yes they will be very close to the same field of view. What won't be identical is the dof if you use the same aperture settings.
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Old Mar 27, 2009, 12:38 PM   #4
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Is there a 10mm EF (not efs) equivalent lens made to fit a canon? I've seen a canon 10mm efs, but efs won't fit the 5D markII (my camera of the future).

So I wondering if sigma, tamron or one of the other 3rd party lens manufacturers makes a 10mm lens. Any ideas?


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Old Mar 27, 2009, 12:44 PM   #5
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You have the Sigma 8mm or Sigma 12-24mm Zoom to start with. I use a 12-24 on my 5D, it does a pretty good job.
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Old Mar 27, 2009, 3:47 PM   #6
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The Tokina 10-17 too (fisheye):
http://forums.dpreview.com/forums/re...ssage=21110821
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Old Mar 28, 2009, 11:12 AM   #7
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Canon also have a 17-40L f4 and a 16-35L f2.8.
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Old Apr 1, 2010, 12:05 AM   #8
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Quote:
Originally Posted by algold View Post
Actually you are still shooting at 18mm focal length, but the apparent field of view it gives you equals to the field of view of a 29mm lens on a FF camera. The image quality will be different, but you will get the same framing in your exercise with a 18mm on APS-C and 29mm on FF.
So if I have a 7d crop sensor body with a Canon EF-S 17-55mm f/2.8 IS USM then the actual focal range will remain the same...at 17-55mm? And not jump to 27-88mm?
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Old Apr 1, 2010, 3:17 AM   #9
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Quote:
Originally Posted by William Richard View Post
So if I have a 7d crop sensor body with a Canon EF-S 17-55mm f/2.8 IS USM then the actual focal range will remain the same...at 17-55mm? And not jump to 27-88mm?
Focal length is a physical property of the lens, it never changes. However the field of view is affected by the size of the recording device (film, sensor) that captures the image. This is then where we start hearing the 35mm equivalent, it is just a standardisation so comparisons can be made.

I'm on my iPhone so can't show you the link but if you check out either the general questions or newbe help sections there is a sticky thread at the top which explains in more detail.
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Old Apr 2, 2010, 11:20 AM   #10
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Quote:
Originally Posted by William Richard View Post
So if I have a 7d crop sensor body with a Canon EF-S 17-55mm f/2.8 IS USM then the actual focal range will remain the same...at 17-55mm? And not jump to 27-88mm?
Without getting technical.... on that body, using that lens, you basically have a 27-88 mm lens. The fact that its an EF-S does not change that.
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