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05-15-2009, 11:44 AM   #1
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rpriedhorsky's Avatar

Join Date: Dec 2008
Location: Minneapolis
Posts: 210
Advice on vignetting test setup

All,

My personal bugaboo is vignetting. I would like to set up some tests to teach myself how my lenses behave in this regard, so I can learn how to avoid it and/or get rid of lenses which don't make me happy.

For each lens, I'll make a matrix of f-stop and focal length; for each cell in the matrix, I'll image a target. Then I can organize the images into some way that lets me compare.

Now, the question is: what kind of target? I read that vignetting is most severe at infinity focus, and that's the condition where it bugs me the most (landscapes with a big blue sky), so I'd like a target at infinity focus.

I don't have a softbox or any fancy equipment to make a target. I can think of two possibilities:

1. Blue sky.

Pros:
- Exact match for when vignetting bugs me the most

Cons:
- Illumination not even, especially at wide angles???
- Have to wait for a clear day

2. Tape a big sheet of paper to the side of my house. Image at infinity focus even though target will not be at infinity.

Pros:
- Can do it any day
- Illumination more even???

Cons:
- Not as good match for when I encounter the problem in the real world
- Out-of-focus target may cause problems???

Thoughts?

Reid

05-15-2009, 12:24 PM   #2
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Lowell Goudge's Avatar

Join Date: Jan 2007
Location: Toronto
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Posts: 15,400
use the side of a big building

what you forget to discuss is how to measure it.

most photo editors have the ability to measure greyscale within a selection.

so do a small selection at each corner, and compare to the middle. with neutral contrast 45 greyscale is about 1 f stop.
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