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Author Topic: LensAlign + Chuck Westfall's December 2008 tips ??  (Read 2175 times)

robackja

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LensAlign + Chuck Westfall's December 2008 tips ??
« on: December 12, 2008, 03:16:21 pm »

The LensAlign system, just reviewed here, has an angled focus chart (on the right hand side)

In Chuck Westfall's December Tips, he states:

Quote
Do not attempt to autofocus on an angled chart, because doing so will degrade the consistency of the camera's focusing measurement. Keep in mind that the camera's AF sensor is comprised of multiple pairs of linear pixel arrays. If you attempt to autofocus on a single line in an angled focusing chart, only a few pixels from each active pixel array will "see" the target. Ideally, the contrast in the reference target should cover the entire area of the camera's center focusing point, and the reference target should be perfectly parallel to the camera's focal plane.

What does this mean for LensAlign? Does LensAlign solve this issue with the "Sighting" step? Having both the parallel plane chart and the angled chart?

DarkPenguin

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LensAlign + Chuck Westfall's December 2008 tips ??
« Reply #1 on: December 12, 2008, 05:48:38 pm »

You don't focus on the angled ruler.  You use that to determine how far out of whack your focus is after focusing on the target.
« Last Edit: December 12, 2008, 05:50:57 pm by DarkPenguin »
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michael

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LensAlign + Chuck Westfall's December 2008 tips ??
« Reply #2 on: December 12, 2008, 05:52:34 pm »

Exactly!

Michael

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GiorgioNiro

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LensAlign + Chuck Westfall's December 2008 tips ??
« Reply #3 on: December 12, 2008, 06:01:10 pm »


Additionally tweaking the adjustment a point or two after using the camera/lens combo in the field is something that I have found to be beneficial in achieving hard focus where I want it. Especially with a telephoto lens.
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David Anderson

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LensAlign + Chuck Westfall's December 2008 tips ??
« Reply #4 on: December 12, 2008, 11:13:16 pm »

Very interesting and thanks for the video demo..

The angled chart I've been using has been giving mixed results and frankly was a pain with the fast wide lenses, this thing looks a lot more sensible..

Is the unit portable ?


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ErikKaffehr

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LensAlign + Chuck Westfall's December 2008 tips ??
« Reply #5 on: December 15, 2008, 03:53:36 pm »

Hi,

First I felt the LensAlign was an overpriced gimmick, but after having read Chuck Westfalls's recommendations and having some thought I don't any longer think so. Being able to mount the thing on a tripod is a good thing, especially if you need to calibrate a long telephoto lens. On the other hand, shooting a tripod mounted device with a tripod mounted telephoto lens in a public place may got you arrested as a terrorist suspect. ;-)

One question:

Shouldn't we first calibrate the camera, that is adjust for lens flange to sensor and AF-detector mismatch and first that calibration has been done try to calibrate each lens? The problem is I don't know how tell one problem from the other.

Best regards
Erik


Quote from: robackja
The LensAlign system, just reviewed here, has an angled focus chart (on the right hand side)

In Chuck Westfall's December Tips, he states:



What does this mean for LensAlign? Does LensAlign solve this issue with the "Sighting" step? Having both the parallel plane chart and the angled chart?
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Erik Kaffehr
 
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