What do the 22, 11, and red dot below my lens distance scale mean?
Asked 6/2/2021
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My Canon EF 35mm f/2 IS USM has markings below the distance scale: 22, 11, a central line with a red dot, then 11 and 22. I’ve read these are related to the distance scale, but I can’t tell what they mean or how to use them. What are these markings for?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
5y ago
2 Answers
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The 22 and 11 indicate the depth of focus when stopped down to that particular aperture. E.g. in the image, with aperture f/22 everything from about 0.6 to 2 meter away is in focus (as a rough guide).
The red dot, if I'm not mistaken, indicates the focus distance for infrared imaging instead of visible light.
Originally by user32390. Source · Licensed CC BY-SA 4.0
user32390
5y ago
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Generated from our catalog & community — verify before relying on it.
Those markings are depth-of-field scale marks. The paired 11 and 22 lines show the approximate near and far limits of acceptable focus when the lens is set to f/11 or f/22.
For example, after focusing the lens, you can look at where the distance scale falls between the matching f/11 or f/22 marks to estimate what distance range will appear acceptably sharp. It’s a rough guide, not a precise measurement.
The red dot is an infrared focus index. Infrared light focuses at a slightly different point than visible light, so if you’re shooting infrared, you focus normally, then shift the focus setting slightly so the distance aligns with the red mark.
So in short:
- 11 and 22 = depth-of-field guides for f/11 and f/22
- red dot = infrared focus reference
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