Trick: correctly pushing D800 to higher (ISO) limits

Started Mar 29, 2012 | Discussions thread
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Dominique Dierick
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Trick: correctly pushing D800 to higher (ISO) limits
Mar 29, 2012

People trying to produce raw images at H2 or pushed H2 with the new Nikon D800 have surely already noticed the blue-magenta cast on the image, with a band running along the longer side of the image, caused by amplifier glow. Fwiw, even the D3s shows traces from it at extreme high ISO values. There is a fairly simple method to get rid of it in post processing and start with a much better image color. The alternative is manually start to tweak the image, rather time consuming.

The only thing you need to do is make a bias frame to correct it. It's an image at approx the same exposure and ISO, but with lens cap on and viewfinder closed. You will obtain an image only containing the glow (and noise). No need to each time make one. Make a library of some different temperatures and exposures.

Open the raw images in a good image editor, with exactly the same settings. If you push the source image by a stop, also do so with the bias frame! Now subtract the bias frame (e.g. PS apply image) from your light frame. Perhaps you need to tweak the percentage of subtraction, but it will be minor. The result will be a much better image to start with. Maybe the de-dusting image in the camera could have the same effect (not tried), but this is far more flexible.

The sample show an H2 image, pushed one stop in post to 51k ISO.

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My equipment: Nikon D3s, D800, EOS 450D
The ladies equipment: Panasonic LX5 and GH2 for video

 Dominique Dierick's gear list:Dominique Dierick's gear list
Fujifilm X100S
Nikon D3S Nikon D800
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