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Help: Severe Posterization of Sky with 5D RAW

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Michael Friedman

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Has anyone had this experience:

I just got back from a week in the Aspen area, where there'd just been 15 inches of snow. I did a lot of shooting using my 5D and a variety of lenses. Many of the shots of were of snow-covered mountains under a deep blue sky. I shot exclusively RAW+Medium JPG.

When I got home and downloaded my photos, I was dismayed to find that in most of the RAW shots containing the sky, the blue was severely posterized, or had large, blocky areas of color. The jpg versions showed much less of this effect. I am able to reduce the effect somewhat using Noise Ninja, but it still looks pretty bad. (I am not at my home computer right now, but I can post samples later if that will help).

One thing I noticed was that the files in question seemed extremely large-as big as 18 megabytes in some cases, which is nearly half again as large as most of my previous 5D RAW files. Also, I was using a circular polarizer to cut cut glare, and it is a rather cheap filter. These are the only clues I can think of at the moment.

What's really weird is that the jpgs look considerably better than the RAW versions, at least on my monitor. This is something I've never seen before.

Anyone have any ideas?

Thanks,

-Michael

--
-Michael
http://www.novalight-imaging.com

'When you come to a fork in the road, take it!'
-Yogi Berra

 
Michael Friedman said:
What's really weird is that the jpgs look considerably better than
the RAW versions, at least on my monitor. This is something I've
never seen before.
Click to expand...
What program are you using to "view" a raw file? Some programs are not capable of properly rendering a raw file and others merely show you the embedded jpg (not the accompanying jpg.)

Which program did you use to convert the raw before hitting it with any other post processing?

Olga
 
I'm using Photoshop CS2 with Camera RAW, and also Adobe Lightroom beta 3.

These should work fine with the 5D ... and, in fact, they have in the past, until this shoot. The problem seems to be just with this series of photographs.

-Michael
Olga Johnson said:
Michael Friedman said:
What's really weird is that the jpgs look considerably better than
the RAW versions, at least on my monitor. This is something I've
never seen before.
Click to expand...
What program are you using to "view" a raw file? Some programs are
not capable of properly rendering a raw file and others merely show
you the embedded jpg (not the accompanying jpg.)

Which program did you use to convert the raw before hitting it with
any other post processing?

Olga
Click to expand...
--
-Michael
http://www.novalight-imaging.com

'When you come to a fork in the road, take it!'
-Yogi Berra

 
Michael Friedman said:
When I got home and downloaded my photos, I was dismayed to find
that in most of the RAW shots containing the sky, the blue was
severely posterized, or had large, blocky areas of color. The jpg
Click to expand...
Color Space (in camera and application)? Bit depth? Monitor display settings?

I've seen this from time to time, but not when loading the RAWS into the converter (ACR is my preference), just on the previews.
Michael Friedman said:
versions showed much less of this effect. I am able to reduce the
effect somewhat using Noise Ninja, but it still looks pretty bad.
(I am not at my home computer right now, but I can post samples
later if that will help).
Click to expand...
Application?
Michael Friedman said:
One thing I noticed was that the files in question seemed extremely
large-as big as 18 megabytes in some cases, which is nearly half
again as large as most of my previous 5D RAW files. Also, I was
using a circular polarizer to cut cut glare, and it is a rather
cheap filter. These are the only clues I can think of at the moment.
Click to expand...
File size I don't think is inivolved. Some of mine are 17+ mb (high ISOs account for most of that).

I think Olga's right - you should detail what you're viewing with, and what the settings are in that app.

--
...Bob, NYC

http://www.pbase.com/btullis

You'll have to ignore the gallery's collection of bad compositions, improper exposures, and amateurish post processing. ;)

 
Assuming that you ve taken care off things like monitor calibration I wanted to ask if the photographs you took were under extreme cold conditions?

Could e-mail your sample to some of us?
--
Yiannis

'We don't take pictures with our cameras,' Newman once said. 'We take them with our hearts and we take them with our minds, and the camera is nothing more than a tool.'
 
I find that all digital cameras I have used have a "mottle effect" with generated textures in low tones. This happens at different tone ranges for different cameras (Nikon does this a higher tone levels than Canon). I have this textured effect in recent images of "dark blue sky" and "dark shadow tones" taken on my 5D.

I don't know if this is the same effect as your "posterization".
--
tony
http://www.tphoto.ca
 
As I said earlier, I'm using Photoshop CS2 with the latest version of Camera RAW.

I'd have to check some of the settings, but as the light was just coming up, I believe my ISO setting was 640. I know this could be part of why the files seem large.

Cold? Yeah, it was pretty cold. Around 25 degrees F.

I have tried Lightroom, Beta 3, with more or less the same results.

Saturation was at camera's default, as was contrast.

Most of the photographs were slightly underexposed. And, yes, the more under-exposed, the worse the the posterization. But the underexposure did not seem enough to produce such a severe effect. I've worked with under-exposed photographs before, without seeing this.

Perhaps it would help to post some examples.

-Michael
Steven Noyes said:
Also, What ISO, 50, 100, 200? This can make a difference. Any
under exposure? Any PP EC? What about NR? Have you tried C1 Pro,
Bibble or other RAW engine besides Adobe? Have you pushed the
contrast or the Saturation too far?

Steven

--
---
2006 Southern Arizona Monsoon Wildflowers
http://www.pbase.com/snoyes/images_summer_2006_ii

Summer 2006:
http://www.pbase.com/snoyes/gallery/images_summer_2006

Click to expand...
--
-Michael
http://www.novalight-imaging.com

'When you come to a fork in the road, take it!'
-Yogi Berra

 
Michael Friedman said:
As I said earlier, I'm using Photoshop CS2 with the latest version
of Camera RAW.

I'd have to check some of the settings, but as the light was just
coming up, I believe my ISO setting was 640. I know this could be
part of why the files seem large.

Cold? Yeah, it was pretty cold. Around 25 degrees F.

I have tried Lightroom, Beta 3, with more or less the same results.

Saturation was at camera's default, as was contrast.

Most of the photographs were slightly underexposed. And, yes, the
more under-exposed, the worse the the posterization. But the
underexposure did not seem enough to produce such a severe effect.
I've worked with under-exposed photographs before, without seeing
this.

Perhaps it would help to post some examples.
Click to expand...
Post a RAW file. That has the most info for determining cause.
marty
Michael Friedman said:
-Michael
Steven Noyes said:
Also, What ISO, 50, 100, 200? This can make a difference. Any
under exposure? Any PP EC? What about NR? Have you tried C1 Pro,
Bibble or other RAW engine besides Adobe? Have you pushed the
contrast or the Saturation too far?

Steven

--
---
2006 Southern Arizona Monsoon Wildflowers
http://www.pbase.com/snoyes/images_summer_2006_ii

Summer 2006:
http://www.pbase.com/snoyes/gallery/images_summer_2006

Click to expand...
--
-Michael
http://www.novalight-imaging.com

'When you come to a fork in the road, take it!'
-Yogi Berra

Click to expand...
 
Watch out it's not your monitor that is cliping.

Histograms should help you determine if you have a problem that's recoverable or not.
 
I agree with this poster. I've noticed artifacts which could be what you are talking about - slight posterisation. But when you print say at 24"x16", no issue.

Could well be the monitor...
what is it btw ?
 
If tis is suddenly ocurring, sometimes its the monitor set-up. Maybe you inadvertantly changed it from 32 bit true Color to 16 Bit High color. Right click on the desltop, selctt properties, select Settings and look to see if the Color Quality is set to highest (32 bit)
--
EJP
 
I've had the same problem with some of my images where there is a large area of clear blue sky. I've spent hours re-processing various permutations and even with 16 bit TIFFs in Adobe RGB, I still get posterization.

It's not just the monitor, but final prints at 13x19 show the banding of the posterization.
I too would like a solution to this phenomenon.

Stevo.k
 
My monitor at home is a Nuevo flat panel, but the same thing is happening on my View Sonic CRT at work, so I really doubt the problem is monitor- related. My monitor at home is calibrated, by the way.

I'm also seeing the same thing on my Epson P2000 (though it's somewhat harder to see on a 3.8 inch LCD). No, these appear to be actual artifacts in the files.

Someone suggested posting a RAW file. How do you do that on the Internet so that anyone can see it?

I'll create a high-res JPG from the RAW and also post the JPG that came out of the camera. I'm not sure, but I think there will be a clear difference.

-Michael
Stevo K said:
I've had the same problem with some of my images where there is a
large area of clear blue sky. I've spent hours re-processing
various permutations and even with 16 bit TIFFs in Adobe RGB, I
still get posterization.
It's not just the monitor, but final prints at 13x19 show the
banding of the posterization.
I too would like a solution to this phenomenon.

Stevo.k
Click to expand...
--
-Michael
http://www.novalight-imaging.com

'When you come to a fork in the road, take it!'
-Yogi Berra

 
I started using Lee ND grads and lin. polarizer. Until that time my skies were fine. Now I have the same issue. Talked to Lee today and they say its underexposure possibly. Im sending him the raw files to look at.
 
Posterization in the way you described it has also ruined some of my otherwise nice pictures and I have spent a lot of time in finding the reason as well as talking to the people in the labs etc. I also shoot exclusively raws which are converted to 16bit tiffs using Capture One Pro.

Here are my findings:

It's definitely not the monitor as it is shown in the inkjet prints as well as in the posters I got back from online print services. Oftenly the printed result is even worse than the image on the screen - especially if larger outputs are required..

It happens mostly in darker and/or highly saturated areas; a polarizer can amplify the loss of smooth transitions additionally if the image is underexposed more or less.

If you check the histogram of the channels in PS you will probably see a clipping in one or two channels (i.e. the red channel) though this is not necessarily shown in the combined RGB histogram. It might be a caused by the limited dynamic range and only 8-12 bit color depth of the digital images - since it's not shown in identical exposured photos taken with film cameras.

Also, too much postprocessing (compressing or stretching the tonal values) can cause larger gaps in the histogramm and therefore lead to posterization or banding.

Higher ISO additionally introduces some noise which also enforces this effect.

Finally channel clipping can also occur (or be intensified) if the image is converted from a larger color space (i.e. AdobeRGB) into sRGB, especially if there are histogramm is already sitting at the left side in aRGB.

Until now I could not find a general solution but the following steps could help:

Exposure to the right, so that clipping in the shadows is avoided - even if it's only shown in one channel. Try to avoid to much saturation in the darker areas of the captured raw -image. Be cautious with the polarizer that's to say don't darken the sky or other uniform areas too much. Use low ISOs if possible and watch your histogramm when adapting the tonal range in PS or in your raw converter or when converting the image into another color space.
Evidentally reduce the saturation in PS.

Hope this helps

Wolfgang
CPS- member
 
I'll have to work on getting the images posted this weekend, when I have the time to select appropriate examples. It's just gotten too late tonight, and I'm too exhausted.

I was using a graduated ND filter on some of these, and a polarizer on others. The polarizer is cheap, but the ND is a Singh-Ray, which is anything but cheap. I'm suspecting that this is in fact an exposure problem. As you'll see when I post the samples, the sky came out a very dark blue. Still, I would expect the 5D to be handle this better.

-Michael
technoid said:
Michael Friedman said:
Someone suggested posting a RAW file. How do you do that on the
Internet so that anyone can see it?
Click to expand...
Michael,
Email the files to my dropbox at [email protected]
I'l make them publicly available
marty
Click to expand...
--
-Michael
http://www.novalight-imaging.com

'When you come to a fork in the road, take it!'
-Yogi Berra

 
I have seen this a couple of times with my d2x in clear blue skies on screen, but never in prints.

Since the screens are all 8 bits devices, there is a real possibility that posterization on screen is not actually present in the 16 bits TIFF resulting from RAW conversion.

Skies are a challenging subject because you typically can have very slow transitions of color over a large area, meaning a very gentle gradient. I think that it is unavoidable to some extend.

I am in fact not sure than under-exposed skies are the only case where these occur. Over-exposure of the blue channel might also contribute to this. Overall I tend to avoir using pola filters with naturally deep blue skies.

What I did to get rid of the posterization on screen was to add some Gaussian noise to the image. The dithering process of ink jet printers is in fact similar to that, which is why posterizations typically show up less in print than on screen.

Regards,
Bernard
 
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