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DP1M v Panasonic DMC-GH1 (Siemens Star Target)

Started Oct 18, 2018 | Discussions thread
xpatUSA
OP xpatUSA Forum Pro • Posts: 23,016
Different Test Method (Siemens Star Target)
1

xpatUSA wrote:

I tried to compare micro-contrast using a 144-cycle sinusoidal Siemens Star target created by the well-respected Bart van der Wolf. The test failed, mainly because the GH1 shot had low global contrast, no idea why.

One way to analyze micro-contrast is look at the difference between high and low brightness values in a region of an image. ImageJ has several ways to do that. One way is to draw a line through a region and then display the gray-scale values along that line:

Here, the superior micro-contrast of the DP1M (top plot) in this test is obvious. However, the Siemens Star target is less amenable to this type of analysis - a bar chart would have been better, preferably sinusoidal like those published by Imatest.

Since we are now talking about contrast, we are edging towards MTF (contrast ratio) being just as good for comparative purposes e.g. MTF curve near Nyquist or just below. Like many things photographic, there are several ways to skin a cat, eh?

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Ted

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