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Author Topic: My crop factor confusion.  (Read 10799 times)  bookmark this topic!
cropfactorconfusion
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My crop factor confusion.
« on: December 04, 2008, 11:33:42 AM »

Hi everyone I wouldn't mind a bit of help with this question. I read the explanation given about crop factors and the difference between ef and ef-s lenses. I understand that the only difference betwen using an ef and ef-s lens (on APSC) is that the sensor captures the whole image that the ef-s lens projects, whereas it only captures a % of the projected image of the ef lens (hence the 'crop factor').
I've got a 300d and took 2 pics at 35mm focal length, one with ef-s and one with ef. Identical image produced on the camera, but the ef one was cropped. So the image doesn't appear any closer using an ef lens at the same focal length.
This I thought was the end of my confusion. Until I read a comparison review between the 40d and 5d. Two identical images were produced, from exactly the same place. In order to produce the same field of view with the same lens the 40d used a 44mm focal length, and the 5d 70mm. But I thought by doing this the shot with the 40d would appear much further away because you are zoomed out. It doesn't. Why not? (see sample pics found at http://www.cwaynefox.com/Wayne_Fox/5d_vs_40_test.html
A cure to my confusion would be greatly appreciated.
Thanks
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Bob Atkins
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Re: My crop factor confusion.
« Reply #1 on: December 04, 2008, 11:50:36 AM »

Have you read this article:

http://www.bobatkins.com/photography/tutorials/crop_sensor_cameras_and_lenses.html

If not, take a look at it and see if it clears up your confusion!
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cropfactorconfusion
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Re: My crop factor confusion.
« Reply #2 on: December 04, 2008, 12:53:31 PM »

I think I may have answered my confusion caused by the pics in the review I read. Please confirm if correct/incorrect:

The image on the 40d is actually multiplied (blown up) more in order to create an identical image. The image that comes off the 40d is smaller than the 5d, even though the visible image protrayed is identical.
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Bob Atkins
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Re: My crop factor confusion.
« Reply #3 on: December 04, 2008, 09:23:59 PM »

That's correct. The 40D sensor is smaller, so it captures a smaller part of the image produced by the lens.


« Last Edit: July 05, 2009, 01:22:07 PM by Bob Atkins » Logged
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