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FORUMS Canon Cameras, Lenses & Accessories Canon EOS Digital Cameras 
Thread started 18 Apr 2013 (Thursday) 15:02
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Front focus on a body?

 
mikeinctown
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Apr 18, 2013 15:02 |  #1

I've been having an issue with a new Sigma 35mm I bought. The first time I sent it to Sigma they did an AF update and it is much more consistant between indoors and out, however it was missing focus quite a bit. So i sent it back to sigma and requested calibration. (on my 5D2)

So I get a phone call from Sigma support and had a nice 10 minute conversation with the tech who is testing the lens. He mentioned that my camera body may be front focusing. (I need between -10MA and -14MA depending on subject distance) What I don't understand is that other lenses I have require no MA and seem very sharp, however they are 2.8 or slower lenses.

Do cameras front or back focus? I was under the impression that the lenses front and back focused. is this something that I would want to have Canon look into the next time I send it in for a clean and check?

On the positive, I have to say that Sigma may be on to something with their new USB dock. He explained how it worked for me. Apparently there are 6 different settings you can change vs just one in camera. So you can set the lens to front focus one amount from say 5' away, set it to front focus a different amount from 15' away, and so on. If a new setting makes it worse, you can just go back to a previous setting. This would also be a godsend for those who sell their used lens. lens plus dock so you can pretty much guarantee it will work and be calibrated with any body.




  
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*Jayrou
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Apr 18, 2013 15:32 |  #2

I think the following link can explain a whole lot better than I ever could.

http://www.lensrentals​.com …s-is-soft-and-other-myths (external link)

I have lenses that have had all different amounts of MA on different bodies , they can both be to blame, My Sigma 50 needed a lot on my 5DII but I couldn't get it to play at all with the 1DIII I owned


James
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John ­ from ­ PA
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Apr 18, 2013 19:09 |  #3

A lens plus a body combination can exhibit either front or back focus. That combo may for instance yield a front focus for you, but that same lens on someone else's body could rear focus. The problem is created because both devices have tolerances which can differ unit to unit.




  
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Front focus on a body?
FORUMS Canon Cameras, Lenses & Accessories Canon EOS Digital Cameras 
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