What does "lines per picture height" mean in MTF and sharpness measurements?
Asked 8/10/2012
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I’m reading about MTF and sharpness measurements and saw this wording: “MTF50 … is given in cycles per pixel (c/p) and line widths per picture height (LW/PH).” What does “picture height” mean here, and how should I interpret a value like lines per picture height?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
14y ago
2 Answers
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The picture height in this context is the height of the image. It is an output-size independent way of specifying the amount of detail contained in an image.
For example saying an image contains 2300 lines per picture height means an image has 2300 lines that fit within the height of the image (in landscape format). Regardless of whether you are looking at that image on your phone, or on a 30" display.
The other way of specifying resolution is lines per millimetre, which will obviously depend on how large you display your image.
Originally by user1375. Source · Licensed CC BY-SA 4.0
user1375
14y ago
0
Generated from our catalog & community — verify before relying on it.
“Picture height” simply means the full height of the image frame. In this context, “lines per picture height” or “line widths per picture height” expresses how much detail fits across the image height, regardless of how large the image is displayed or printed.
So if a result says something like 2300 lines per picture height, it means 2300 lines can fit within the height of the image. This makes it an output-size-independent way to describe image detail and perceived sharpness.
That’s different from a measurement like lines per millimetre, which changes depending on the physical display or print size.
In short: LW/PH is a normalized resolution/sharpness measure based on the image’s height, not the screen or print size.
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