Camera's histogram reliable to RAW data

Started Jan 7, 2008 | Discussions thread
auhopu New Member • Posts: 16
Re: Would it possible to get the same thing for the Nikon D300 ?

I followed Guillermo's idea and after going a bit back and forth I ended up with
1,000 1,036 1,004 coefficients for my D300. This was the closest I could get.

I will try to summarize the steps. The steps 1 to 3 are the same as described by Guillermo in the original post.

1. Display the following image on your monitor (make sure it is calibrated first) and shoot it in RAW.

2. Develop it in dcraw with no WB (using the -r 1 1 1 1 option).

3. Open the developed file in a bitmap editor

  • crop as accurately as possible

  • resize to 256x256

  • set saturation to the max

  • zoom on the point where the red, green and blue areas intersect and locate the "central" point

  • check that the rulers are set to measure pixels

  • with your mouse pointing on this pixel, read the value of the horizontal ruler (this is your R value) and the vertical ruler (this is your B value) ; G value is 64.

4. Using the above RGB values, create a new image in your bitmap editor. I got R=98 G=64 B=76 out of my D300 and my monitor.

5. Display this magenta image at full screen, switch off any ambient lighting and take a custom WB measurement with your D300. The new WB setting will be saved at preset d0.

6. Switch on the lights and take a picture of your room using the preset d0 for WB.

7. Develop the image in dcraw and read the coefficients to which your custom WB setting resulted.

8. In a text or excel file note down the image filename, the RGB values and the resulting coefficients, e.g.

DSC_0001.NEF 98,64,76 1.000000,1.071130,1.108787
(this was my actual first attempt)

9. Repeat steps 4-8 while changing only the B value by 1. You may need to try both with lower and higher B values. Stop when your coefficients get worse. Mark your best result.

10. With your best value for B (and G still at 64) repeat steps 4-8 while changing only the R value by 1. Again you may need to try lower and higher R values.

11. When you can't reach any closer to 1,1,1 shoot again your best magenta and copy your custom WB from preset d0 to another one, say d1, so you won't accidentally overwrite it.

I hope this helps.

Elias

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