5DII Bad Noise Red Channel - Dark Blue Skies

Started Feb 23, 2009 | Discussions thread
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Hondo Lane Junior Member • Posts: 26
5DII Bad Noise Red Channel - Dark Blue Skies

I've been recently testing converting color 5dII files to B&W using CS4. I've noticed that red channel tends to be very mottled in large areas of medium grey to black, e.g. dark blue skies. The only digital camera I have ever used extensively was the Sony R1 and it produced a very smooth dark tones in the red channel when photographing blue skies. My 5DII mottling of the red channel is very distressing for me! I primarily shoot B&W landscapes and many in very glaciated areas with BIG BLUE SKIES. Do I have a bad sensor??

I shoot just raw and I have set everything to neutral or off to get the cleanest raw file possible. I tired DPP, Lightroom 2.3 and ACR 5.2. They all produce mottled skies. I have now taken a few dozen photos of blue sky scenes and I always get noise in the red channel. If you look at the color image it looks fine. Look and the green and blue channel and things look smooth. Look at the red channel and it all falls apart!

I print up to 16x20 using Baryta paper and this type of mottling will show.

This is really disappointing. Below are some samples, my first attempt at posting files so hopefully it works. Jpegs were produced from raw files using very high quality. Color file first to show that things look normal and then the red channel were all hell breaks loose. I won't even post the higher ISO shots because things get very ugly, very quick.

I need this camera to work! (other than this issue the camera works very well for me).

Images below are 100% crops, ISO 100. Color first, red channel follows.

Ideas?

Thanks,
Peter

P.S. I am primarily a 4x5 B&W (film) photographer so there is a really good chance I am doing something wrong.

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