color banding in gray background???

[Holaday]

Anyone know what caused the color banding in the gray background on this image? I use Varitone gradated smooth paper, three strong tungsten lights (500+250+250), a pure white tent for diffusion, no other light source. This is not a "low light situation" . ISO 100, 1/20 @ f/22. Camera is on tripod, lens has a lens shade, no filters on lens. This is an expensive Canon lens, so I sure hope it is not the fault of the lens but perhaps something else I don't understand about digital photography.

The color banding and "grain" is mildly annoying (barely visible) online, but really obvious in the slides made from large TIFF files. Everything I read about "noise" points to high ISO, low light situation, but that is not the case here IMO.

Thanks for any input.
Carol

www.carolholaday.com

[pipyr]

How far away is the background? I'm wondering if the light that is reaching to the background is making the camera record the banding...does the background have any banding on it at all? Try moving the background farther away, maybe. How much after-shot editing did you do? Any? That could be part of the problem too. Your shutter speed isn't very slow, so I can't imagine that is the problem, as long as the picture looked pretty darn close to this coming out of the camera. It's really hard to say, especially because in the on-line version it's a beautiful, band-free shot ;)

[Holaday]

Pipyr,
Thank you for your reply.

I am still trying to figure this out as most of my photography customers want the images for jury slides and submission to publications. Since most of my photography is of jewelry I am hoping someone in this forum can help.

The background is a smooth Varitone paper (no bands, no texture) and is about 10" behind the pendant. Saved from RAW to TIFF, black and white levels adjusted just a little. Small bit of contrast added. The image attached is cropped to show the color banding. This area should be black at top, lighter gray at bottom, no color anywhere. On my monitor, it is obviously a bit cyan near middle area, a bit red pink at bottom. No way to make it totally neutral. I also see "texture" which shouldn't be there. All of this is admittedly subtle viewed online, but in the slide it is really obvious. I am still trouble shooting and testing the variables, but I get the same color shifting and artifacts with a different lens, a different set-up entirely (on dark glass, drop shadow, etc.); always most noticeable in the areas between the darkest and lightest areas. Not on the same place in the image.

On a photography forum it was suggested that it could be the fault of the sensor. Oh no! This is not a lower end DSLR camera, and of course it is slightly past warrenty. Repairs could be very expensive if indeed that is the problem. I spoke with a Canon tech and he was very helpful, but bottom line was "send it in and wait for an estimate".

73920
Thanks again for your help Pipyr.
Carol

[topher wren]

try taking photo in to a photo edit program hilight the bottom portion and diffuse or un sharpen it will probably clear it up . just be sure its only the back ground you deffues. it actually looks like pixeling. If you try de fusing the back ground try changin the back ground to a black and white setting in the program it will most likley kill any of the color showing up.

[Mike Jordan]

You will get this is your images is saved with to low of a resolution. If you are saving it at a low resolution (under 100 dpi) or as a jpeg with a low quality, you have lost a lot of information in the image. If you then save it as a large tif file, you have increased the size of the image, but you are still missing information in the image itself. It's like having a perfect image on a balloon that isn't blown up and then blowing it up to full size. The image stretches but it isn't as good as it was when the balloon was not blown up.

If you aren't doing this, the first thing you should do with the file after you bring it from your camera to the computer, is save a copy as a tif file. Do this before you do any edits, crops, tweaks, etc. Then don't touch the original. That way you will always have the orginal to make another tif file if you need too. Now with the tif file you just created, do your sizing, cropping, color correctons, etc and save it for your large tif file for the slides. Now you can make another copy of your work tif or work on it to create your web image and save that as a jpg. Do not use the web jpg image to create a larger image again. It just won't have enough image information to do a good job.

Mike

[sislonski]

My photos were doing this at one point as well and I don't have an SLR. Just a basic camera. I'm not sure what exactly I did to get rid of it, but I did make some changes and it went away.

But it's not a camera problem, just a camera setting change or lighting change.

[Dale M.]

I think Mike has got it correct..... When compressing photos using compression algorithms as JPG or other formats, it changes the color depth of a image....

Simple proof will be to print a "raw" image (cameras highest resolution) from camera and then print same picture saved as JPG or some other compression format and you will see where the compression utility has reduces color depth and banding becomes apparent.... While digital is very good for lots of things.. There are some draw backs to it also....

This is also very apparent is music..... Digital music as good as it is, kind of distorts the original sounds and smooth them out....

Any time you take a color or a tone (sound) and convert it to a number you are going to get some abbreviation when that color or tone is reproduced...

If a raw picture is sized at 253k, and the saved compressed version is only 38k, where do you think all the extra "picture data" when.... It was tossed out by a averaging method.... Hence banding in pictures.

As a side note always save and "Lock" (protect) original picture. Always work with a COPY of origional picture.

Dale

[Dale M.]

My photos were doing this at one point as well and I don't have an SLR. Just a basic camera. I'm not sure what exactly I did to get rid of it, but I did make some changes and it went away.

But it's not a camera problem, just a camera setting change or lighting change.


You probably changed the resolution at which camera originally saves picture at... That would be only feature to effect how color definition could be altered in camera. Providing "white balance" is set correctly.

Dale

[Holaday]

Mike and Dale,
Thank you for your input. However, I don't think you read my posts carefully. I specifically mentioned that this is happening on large tiff files that have minimal processing. It is not a jpeg/compression issue. It might be something with the lights, although since I always use the same ones and it doesn't happen every time, I am still at a loss to pinpoint the cause.

I have switched cameras, lenses, set-ups, tents.... still getting some color banding on some images and not on others. Next I am going to try daylight balanced fluorescents (not the hardware store variety) and after that I might even try an off camera flash... although I prefer working with continuous lighting.

Sislonski,
Yes, it could well be a lighting issue... although with same lights and tent it only happens some of the times. I'll go back and look at the RAW files that have no processing and see if I can spot the problem.

Carol

[Mike Jordan]

Carol, yes, I read that you said a large tif file, but you didn't say how you got that tif file. Was it straight out of the camera? If it was straight out of the camera, as Dale pointed out, what quality are you shooting in? There are several different levels that most cameras save in, usually referred to as small, medium, large for how much data it saves. The other question is, how are you bringing it into you photo editor? With Photoshop, you can bring an image in in several different ways and resolutions as the default. I always shoot in raw format and convert to a 16 bit tif file. Then in Photoshop I have it automatically open that file as a 300dpi AdobeRGB file. If you are bringing yours in as a sRGB, then you have already lost information. If you are saving as a AdobeRGB, rather than sRGB for screen display, you are losing information and quality. Same thing with printing... if you don't save convert the color space to what your printer wants, it will not be able to print as well as it could if the color space was correct when it received the file.

So even though you are working with a large tif file, banding like this still points back to resolution, color space or quality setting or a combination. Lack of enough digital information will show up in the shadows more than highlights in digital images because shadows are under exposed and under exposed areas already have very little information in the pixels.

If you would like, I'd be happy to look at one of your out of camera images and see what the file information tells me in Photoshop CS2. Sometimes, even when we do read carefully, not all the information is there that someone needs to pin point the problem. Kind of like digital files. :D But if you get enough suggestions and guesses, one of them is bound to be the right one. But looking at an actual file would help a lot.

Mike

[Holaday]

Hi Mike,
Now that is good information and a very helpful offer. I will search for a particularly bad image with obvious problems and I will send untouched files to you as well as the tiff that I worked on. Are you able to receive large files?
RAW are 10MB and TIFFS are larger still.

I have a Canon 40D that shoots large raw and large jpegs (used for easy viewing without touching the RAW files but not used for any final purpose) simultaneously. I follow a work flow recommended by Scott Kelby. I don't do much editing (if any) in RAW, save to TIFF for editing, save to jpeg, resize for purpose, including optimizing for web. I am using CS3.

What you wrote regarding 16 bit, dpi 300 and Adobe RGB is also very interesting. And now I am really getting out of my depth. I have recently started preparing images for the ZAPP application and that process has strict rules. I sometimes submit images for Lark Books and they also have specialized criteria.

I may not get the images to you today as I am in the midst of preparing Easter dinner, but I wanted to respond to your offer immediately and say that I really appreciate it. Thank you for any help you can give me on this vexing technical matter.

Carol

[Mike Jordan]

Yes, I can take large files, although you might not want to send them all at once. I'm on a fiber link, so it won't take long to download them.

I first got in to digital with a D30, went to a 10D and now shoot with a 1DMKII. I've almost always shot raw because of the type of photography I do and raw gives me the most flexibility. It takes up a lot more disk space though. :D

My e-mail address is mjordan@europa.com and I'll see how the images look.

Mike

[Dale M.]

Any update?

Dale