JPEG Compression and Gray Background

JB
Posted By
Jani_Bryson
Oct 20, 2007
Views
360
Replies
11
Status
Closed
I have some studio shots using a gray background. I use both Lightroom and Photoshop CS2. Although shot at 100 ISO, the gray areas at times require noise reduction, which I handle with a Nik plug in. Although the final image looks great in the PSD format, when I convert to JPEG, the gray areas develp what looks like a pink rash when viewed at 100%.

Are there special settings and/or procedures that can be done prior to, or during, the JPEG conversion to eliminate this undesirable effect?
Related Tags
background compression gray

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RK
Rob_Keijzer
Oct 20, 2007
Jani,

At what compression rate do you generate the Jpeg? I mean the quality setting.

Also, convert the file to sRGB from whatever it is now (Edit – Convert).

Can you show an example at a 100% crop of the effect?

<http://www.pixentral.com/>

After uploading the image right click in the HTML code below your image, choose "Select All", right click again,choose "Copy".

Then back here paste (Ctl-V) the code in your reply.

Rob
JB
Jani_Bryson
Oct 20, 2007
Thank you for your response!

I am using maximum quality setting of 12 (is that compression rate?), and I am using Prophoto RGB as the color space in Photoshop (is that a problem?).

The JPEG example is here:

< http://www.pixentral.com/show.php?picture=1VHFgIjmityGzwuBTm fvIZH5Ukxb Av>

I’m sorry I can’t include the pre-compression example (PDS format), as I don’t think it will be readable on line.

Your assistance is GREATLY appreciated, as I am tearing my hair out. Also, I have a Canon 1D Mark III, and I cannot figure out why I always have noise in the darker tonal ranges even at ISO 100.
JB
Jani_Bryson
Oct 20, 2007
I
ID._Awe
Oct 20, 2007
Jani:

I do not see the ‘pink rash’ but if you are seeing it then you did not use a pure grey as a background, it is difficult to discern sometimes.

Have you used the eyedropper tool on the background in PS to make sure the background has equal values of RGB?
MD
Michael_D_Sullivan
Oct 21, 2007
I didn’t see the pink rash either. Using the eyedropper in the Firefox Colorzilla extension, your gray background didn’t seem to have higher numbers for red in the pixels I looked at; R and G were usually equal, while B was a bit lower, so it isn’t a completely pure, neutral gray. I’d venture that your monitor needs to be re-profiled.
JB
Jani_Bryson
Oct 21, 2007
Thanks for the help on this. Did you open up the image and look at 100%?

I can’t see it in my laptop, even at 100%, but my desktop has a large monitor and that’s where I see it.

I use the Spyder2 Pro for monitor profiling. I will recalibrate and see if that helps.
MD
Michael_D_Sullivan
Oct 21, 2007
I viewed it in Firefox on a 21" monitor, both full-size (100%) and zoomed up to 400%. Just now I pasted it into Photoshop and viewed it at 100% and many other zoom levels. No redness at all.
JB
Jani_Bryson
Oct 21, 2007
Thank you, thank you, for giving it such thorough scrutiny. It must be my monitor, I will look into it in the next day or so.

On another note, did you find it to be overfiltered? I am really struggling with noise issues in that particular gray background, as well as some darker areas in my images. I am a stock photographer, and noise as well as overfiltering are big no-no’s.
MD
Michael_D_Sullivan
Oct 21, 2007
The background looked a bit like it was over-NR’d, in that there were fairly large swathes of the same RGB, rather than a bit of noise that looks more random. Kind of watercolor-looking. A small bit of noise looks more natural.
BD
Brett_Dalton
Oct 22, 2007
What monitor are you working on, it may be dithering to produce full 24bit colours if it’s a Mac book Pro. Also Jpg compression can cause this sort of colour shift if neutrals but it’s pretty unusual without LOTS of compression.

BRETT
RK
Rob_Keijzer
Oct 22, 2007
Also Jpg compression can cause this sort of colour shift

But then we would see it on the example.

I too think it’s monitor calibration/profiling.

Rob

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