Eye of the eclipse...

by darkhausen

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"The Spatial Frequency Response (MTF), shown to twice the Nyquise frequency. The key result is MTF50, the 50% MTF frequency, which corresponds to perceived image sharpness. It is given in cycles per pixel (c/p) and line widths per picture height (LW/PH). ……" How to understand the “picture height” in these sentences. Can you help me? thanks

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Could you provide some context, and not just a quote? – Guffa Aug 10 '12 at 10:59

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up vote 5 down vote accepted

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.

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line pairs per millimeter should be the most generic, because it's independent from sensor density. OTOH if your sensor isn't dense enough, you won't be able to discern pairs from each other... – Baczek Aug 11 '12 at 20:39
How to i understand the SQF result in the Imatest Documentation? you can see the picture in [link]imatest.com/docs/sqf. i don't understand the x-axis--Picture Height(for short PH), what is it mean?How should i take SQF value for the camera being test.For example,The SQF value is 85 when PH equals to 40centimeter;The SQF value is 92 when PH equals to 20centimeter,and so on.If so,i should choose which value, Why? – petalse Aug 15 '12 at 12:09

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