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FORUMS Canon Cameras, Lenses & Accessories Canon EF and EF-S Lenses 
Thread started 21 May 2009 (Thursday) 09:23
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50D using Lensalign Question????????

 
TheFloridaShooter
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May 21, 2009 09:23 |  #1


I'm hoping for a quick answer.
When you calibrate a 50D using a LenAlign at what distance do you set between the LensAlign and a EF-S 10-22mm and a 70-200mm ?
I’d really like the distance in feet.
Thanks


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gasrocks
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May 21, 2009 10:45 |  #2

And LenAlign is ?


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unnerv
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May 21, 2009 11:41 |  #3

I don't have one gasrocks, but you can see what they are here: http://www.rawworkflow​.com/lensalign (external link)




  
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BigBlueDodge
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May 21, 2009 13:38 |  #4

Canon recommends 50x the focal length of the the lens being tested. When calibrating a zoom, you need to decide what focal length you are calibrating against. If you want to calibrate at the 10mm end, the LensAlign target needs to be 500mm away (or 19.58 inches). If you want to calibrate it at the 22mm end, then the target needs to be 1100mm (or 43.3 inches away).

Same thing appies to the 70-200.It's really easy to calculate

Distance In MM = (Focal Length * 50)
Distance In Inches = (Focal Length * 50) / 25.4

Do understand that calibration is really only guaranteed for the focal length tested. If it possible, via manufacturing tolerances, or lens design, that the calibration for the wide portion of the lens is not applicable to the tele portion of the lens.


David (aka BigBlueDodge)
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number ­ six
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May 21, 2009 16:01 |  #5

Bear in mind that the recommended distances are from the sensor, not the front of the lens.

-js


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joove
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May 21, 2009 16:24 as a reply to  @ number six's post |  #6

If you need the numbers again, pick the longest focal length of the zoom and open to the widest aperture. The whole point is to get a DOF thin enough for you to be able to distinguish the OOF regions. Then enter into google search

(200mm * 50) in feet

and you'll get it in feet. I love google for unit translation. Use it for cups in tsps and such esoteric (for me) conversions.


Vamsi
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int2str
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May 21, 2009 16:28 as a reply to  @ joove's post |  #7

This chart was posted on the lens align forum:

IMAGE: http://www.whibalhost.com/_ss/lensalign/lensalign_dof_distance.jpg

Note that Michael from lens align suggests that 25x focal length is fine as well.



  
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50D using Lensalign Question????????
FORUMS Canon Cameras, Lenses & Accessories Canon EF and EF-S Lenses 
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