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| p.8 #14 · LensAlign: Get the most out of your lenses! |
Michael, thank you for the detailed response. I agree with the criteria that you listed.
As you see in my ruler shot, there is NO need for the target being perfectly parallel to the camera sensor frame. Only requirement is that the tape runs reasonably along the line of the lens axis, which is extremely easy to achieve just by locating the camera right above the stretched tape measure. The angle between the ruler axis and the lens axis won't matter either. We rely on the simple fact that the tick mark spacing is even ( which most rulers guarantee )....Show more →
Thanks for your reply to my reply. The problem with your setup (IMO and from a commercial product point of view, which means all the criteria I listed), is that:
1: The focus target is not parallel to the film (image) plane of the camera. Again, Canon will not allow this as documentation, so that, while it may be useful to you as an individual, it will not work as a product that I want to be used in conjunction with people documenting their "problems" based on LA images.
2: The placement of your "focus cross" in addition to not being perpendicular to the line of sight of the camera, leave much too much "room" for the AF to latch onto the ruler itself, negating the repeatability and accuracy of the test.
3: Obviously if the 2 issues are carefully controlled for you use, this would he hard to be used to compare results across people and equipment except in a loose manner.
Having said that, if one is careful and controlled, each time that it is set up. surely it can be used to set AFMF, although with some degree of risk of incorrect data. I think your setup is better than the 45 degree charts like Tim Jackson, but still leaves open areas of doubt, at least for me.
The best document that I found discussing all these issues is by Jeffrey Friedl on his Blog. He developed the best of an printed test charts, and acknowledged the pitfalls in the others, and even in his. He wrote about the development and use of his chart, and later about LA.
Regarding DIY and LA, each person has to make up their own mind as to how they value their time, expendable cash, the benefits of LA (if they perceive them <g>, etc. As always the choice is in the hands of the buyer. No one need to diss a BMW 7 series because it is priced too high. Simply say it is priced too high, or it is priced too high for my budget and emotional and transportation needs.
Thanks and happy holidays..