How can I measure lens vignetting without special equipment?
Asked 2/11/2014
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2 answers
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I want to measure the light falloff (vignetting) of a custom lens, but I don’t have access to a light box or other studio gear. Is there a simple DIY way to create an evenly lit target using things like office lighting or outdoor light so I can test the lens accurately?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
12y ago
2 Answers
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Use an overcast sky + put a semi-transparent textile or paper on the lens, covering the front completely. Basically the latter will be so off focus, it will work as a low pass filter, blurring everything, including the textile or paper texture.
Just make sure what you use to cover the lens is pure white. Tissue-paper is a very good candidate.
Use RAW for taking the photo, ISO 100, use largest aperture, do not post-process the image in any way (in camera or later, in Camera Raw/Lightroom, etc.)
You can verify the quality of this approach by picking colors the same distance from the optical center, and comparing them. Unless your lens has errors in the optical assembly, those colors should match pretty well.
Originally by user24785. Source · Licensed CC BY-SA 4.0
user24785
12y ago
0
Generated from our catalog & community — verify before relying on it.
Yes. A simple DIY method is to photograph a bright overcast sky while covering the front of the lens completely with a pure white semi-transparent material such as tissue paper or thin white fabric. Because the material is extremely out of focus, it acts like a diffuser and smooths out detail, giving you a nearly uniform field.
For best results:
- Shoot RAW
- Use ISO 100
- Use the lens at its widest aperture if that’s the condition you want to test
- Avoid any in-camera or software corrections or post-processing
Then inspect the image brightness from center to corners to see the falloff. A good check is to compare areas at the same distance from the optical center; they should be similar in brightness if the setup is even and the lens is well aligned.
This won’t be a lab-grade measurement, but it’s a practical way to evaluate vignetting without special equipment.
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