Help with sharpness test.

Started May 8, 2012 | Discussions thread
Jerry-astro
Veteran MemberPosts: 4,375Gear list
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Sorry, can't agree...
In reply to krob78, May 18, 2012

krob78 wrote:

btw, the really good focus tools are set at 45 degree angles, that's the only way you'll get a really, really strong indication if it's front or back focusing... flat papers just don't work as well for that...

I'm really sorry, but I'll have to disagree with that. The problem with angled tools is that the focus points are larger than they appear to be and the camera will often not focus exactly where you think it is. That can throw your adjustment off, at times by a pretty decent amount depending on your aperture and DOF. I know you were successful in using one, and more power to you, but there's a reason why Canon specifically suggests using a flat, high contrast target. That way, there's no doubt as to where the camera is actually focusing. BTW, there are some tools like LensAlign which combine both -- i.e. give you a flat target, but put an angle off to the right to help you see more easily whether you're front or back focusing. That also works well.

If you use a tethered approach as outlined in the following link, it's quite easy to see which direction you need to go to adjust your focus, if needed. I've had great success using this method with all my lenses:

http://forums.dpreview.com/forums/read.asp?forum=1019&message=39900880

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