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05-20-2008, 05:14 PM   #1
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Location: Portland, Oregon
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AF test chart

I cant get enough....

so would an accurate test chart be one that had a single black on white target in the same plane as the sensor, with a distance scale configured at the sides perhaps at a 45 degree angle so the depth of field would be apparent and measureable from the picture?

It seems the 2 cent version of that other thread is that if you put the AF target at an angle, you have no way of knowing what it actually focused on?

hopefully a civil discussion will follow that can help out those of us who dont have the fortitude to wade through all the AF test chart threads.

Is there a nice way of describing a useful test chart instead of pointing out the shortcomings of those that are proposed?

I learned a lot with a piece of paper and a single black line. I had no idea the camera would focus lock where it would. this is still a useful exercise to learn about our cameras in my opinion.

05-20-2008, 05:42 PM   #2
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Location: Belgrade
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Here is how I test: set camera on tripod; pick a box with some pattern on it and put it on a table or desk; set ruler next to the box; AF and when locked switch to MF; move the box 2 inches away from the camera; take a picture; one inch closer; take a picture; one inch closer (you are back at where you started); take a picture; one inch closer; take a picture; one inch closer; take a picture.

You will get a +2", +1", 0, -1" and -2" sequence. Examine the series and find the sharpest result. If 0 offset is the sharpest you are OK. If one of the positive offsets are sharpest you have back focusing issue, one of the negative ones and you have front focusing issue.

Recommended distance for this test is 2-3 meters. You can do more steps, say, +/-5" if you wish (for the series of nine). I recommend +/-3" (for the series of five), that should be enough. Auto focus from infinity then repeat the test with AF from minimal focusing distance and compare the results. Results may be different! And do not expect AF system to work more accurate than 1/4".

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