Black level checker M9

[t024484]

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I wrote a small program to check, in how far the black level written by Leica in the M9 DNG file is really the value it should be.

To use the program, you will first need to produce Image files with the lenscap on, at 1/4000 exposure time from ISO 160 to ISO 2500.

 

The program only works for DNG Images right from the camera, and uncompressed.

 

Calculated are resp:

The average value of all the pixel values from the first two lines represented in block 1 (10432 pixels)

The pixel values of the last two lines of the image are averaged in block 2. (10432 pixels)

Four lines exactly in the middle are averaged in block 3. (20864 pixels)

 

"Black Level Value" is the value that Leica writes in the DNG, and that is used in the raw processor like LR or C1. "Overall Average" is the calculated average of block 1, 2 and 3.

Here you can see if there is a large spread between block 1 to block 3, and if the overall average differs substantially from the "Leica" value.

 

To start the program, select the button "Open Raw" and select a file.

 

The Image files that I have, do not have a significant difference up to ISO 640.

As from ISO 640, the differences is becoming greater, with ISO 2500 on top.

One thing that stroke me was that the top two lines always gave the highest average, close to the Leica Value. and that the average of the bottom two lines always had the lowest average, and the 4 lines in the middle were always in between the other two.

If this has to do with a sensor temp. effect because of the processing of the Image, I have no idea.

 

Hans

 

http://dl.getdropbox.com/u/2008358/RawData.exe

[sandymc]

Cool!

 

Sandy