Posterised shadows w/ raw

[Adey]

Well then, i decided about a month ago to start shooting in Raw. Im obviously very happy with the level of power and flexibility it gives, but the has been an unexpected side effect. Im having greeny/brown, noisy posterisation occurring in the shadows and mid-tones transitions.

Here is an example that i have (though not the worse case)

My workflow is as follows;

-Camera set to sRGB From my jpeg days, i've read that Raw has no colour profile so, this is irrelevant right?

-View photos in bridge and launch into ACR (CS4)

-At the bottom of ACR i see that Adobe RGB is now the workspace (i assume this is assigned after raw editing and when i export into either PS or saved as tiff/jpeg?

-I then open in photoshop for final editing, convert to sRGB, then save as jpeg (quality 12)


I only get this effect once i've exported the file, it never shows up in ACR or PS. Interestingly if i view in PS and take a screenshot, it appears in the capture too. I've tried changing colour spaces, i've tried not doing any editing to the photos at all and it still happens. Its worse at high iso but still noticle at iso 200. Could it be a bit depth issue?

If anyone could help me shed any light on this i'd be eternally grateful, and be happy to spread the word, for any other people caught in the same dilema.

Cheers guys!

Adey

Edit - After previewing this post, i see that it isnt showing up on the web
So colour spaces then?:shrug:

 

[jon ryan]

Running it through cs4 noise reduction & tweaking the levels gives this:

What other edits are you doing? Could it be that you have a somewhat underexposed file and have pushed it to try to get detail in the dark bits?

 

[Chappers]

Have a look at the Histogram. is the image generally underexposed. Lack of exposure reduces the data in the shadows. It's usually a good idea to have the histogram pushed over to the right hand side. This ensures that there is a lot of data in the shadows. Some over exposure is easily tolerated when shooting RAW and the balance can be brought back by using the exposure controls in ACR. Despite reducing exposure in ACR the orriginal data for the shadows is still there, this can be brought back by using the other controls, such as fill light, or by use of curves in ACR.

I don't know what camera you are using, but it seems that Canon when designing there exposure algorithms tend to try and protect the highlights, this can give some degree of underexposure. I've had to give at least 1/2 -1 stop exposure compensation with all my canon cameras

You might find this short tutorial useful

http://www.luminous-landscape.com/tutorials/expose-right.shtml

and a supplementary article with images to show the effect

http://schewephoto.com/ETTR/

 

[Adey]

Guys here's a raw photo (iso200) exported straight out of ACR with no adjustments as an sRGB jpeg. I took a photo of my monitor because its the only way i know that you can see it. On the left is the picture viewed on Flickr, on the right is opened with Windows Photo Gallery.



See all the off colour parts in the shadows around the chin, in the right side version? Im only seeing that in Windows Photo Gallery. I don't see it in Bridge, ACR, PS or as a desktop wallpaper, im pretty sure its not there in explorer when in a folder(with small thumbnails its hard to tell), but when viewing in windows photo gallery, its there:shake:

Vista Home btw.

Any ideas?

Adey

 

[jon ryan]

Guys here's a raw photo (iso200) exported straight out of ACR with no adjustments as an sRGB jpeg. I took a photo of my monitor because its the only way i know that you can see it. On the left is the picture viewed on Flickr, on the right is opened with Windows Photo Gallery.



See all the off colour parts in the shadows around the chin, in the right side version? Im only seeing that in Windows Photo Gallery. I don't see it in Bridge, ACR, PS or as a desktop wallpaper, im pretty sure its not there in explorer when in a folder(with small thumbnails its hard to tell), but when viewing in windows photo gallery, its there:shake:

Vista Home btw.

Any ideas?

Adey

Well, one of those is rendered by flickr, the other in Windows - neither of them is the RAW image as they have both gone through some processing. I guess they're both jpeg images. Also, you have taken a further image at, according to the exif, 1/13th @ f/5.6 & 400 ISO and possibly with some other in-camera adjustments that could include saturation and a camera calibration that may have adjusted the balance. And we know nothing of how your monitor is calibrated. So quite a few variables in there.

Open the original file in the RAW dialogue, set the camera profile to neutral, WB to `as shot`, exposure, vibrance and saturation to zero. That should get you pretty close to what the camera actually saw.

 

[Adey]

Damn this Communication thing is tricky...



Never mind, it doesnt matter, i've now realised all photos from whatever source look bad in WPG. So its MS's problem, i'll try and fix it myself.

Thanks