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Weird Gradient Banding Issues When Saved As .jpeg


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#21 Guest_vreb_*

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Posted 21 July 2009 - 07:39 AM

Hi Wilson, yes at first I thought maybe it could be my calibration but then this wouldn't explain the weird patterns of compression and gradient banding I am seeing when viewing .jpegs only. It must be a colour or compression issue but finding out is really hard.

Thanks again though and yes I am using a pc.

Cheers,

Jay

#22 baramdo

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Posted 21 July 2009 - 07:40 AM

Part of the problem is that you are only getting red pixels involved. A jpeg does have the possibility for millions of colors 255 X 255 X 255 = 16,581,375. Unfortunately when you save from tiff to jpg the compression squeezes all those red channel pixels.

To fix your problem I recommened putting a 1% noise filter over your entire image in Photoshop. Do not use monochromatic. You want to introduce blue and green into that red area. Then save as jpg and you will see a big difference. Your gradient shading will be much smoother.

#23 Guest_vreb_*

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Posted 21 July 2009 - 07:50 AM

Hi baramdo,

Thanks so much for the info here, it is really appreciated and I will go try it now. Can I just check that you can also see problem too please, as so far nobody else has said they can even see the problem and I am going crazy here checking it on both monitors and from diferent angles etc.

Thanks again,

vreb

#24 doubledope

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Posted 21 July 2009 - 07:58 AM

To make you feel a bit better: I can see a little stroke from a certain angle on the text in the .jpeg you posted. If I look straight at my monitor it isn't visible at all.
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#25 baramdo

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Posted 21 July 2009 - 08:03 AM

I didn't see anything on the image of the text. On the vein I did notice a flattening of the shadows and highlights. It was small but noticable. You only have 0 - 255 colors of each channel. The compression was just part of the jpg algorythm (sp?). That is why I suggested adding the noise. This adds information to the color channels in the areas that were all red.

My monitor is a Dell 2005FPW. PC based.

#26 Guest_vreb_*

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Posted 21 July 2009 - 08:07 AM

Thanks guys, this is weird. I will try the solution baramdo suggested and get back to you. Has anyone else experienced such issues bofor though? Thanks again guys, it's really appreciated.

Jay

#27 Rantin Al

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Posted 21 July 2009 - 08:30 AM

Any particular reason for the 13000x11000 render size? This gives almost a square metre @300 dpi which is just about enough for a banner image for the side of a truck.

Rendering out to a psd file is fine, converting to jpg through PhotoShop is fine with no banding. Render took 1hr 50.

Are you by any chance resizing (downsampling) this in PhotoShop?

Still to check the text file but a single omni light is not up to illuminating this properly. An Area light plus fill lights is needed.
The material with a fake specular is not going to help either. Use material reflection and environment panels with a white luminance channel.

Cheers, Alan.

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#28 Guest_vreb_*

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Posted 21 July 2009 - 08:56 AM

Hi Alan, I am really grateful for the time you have taken looking at this for me, so thanks. I am sorry it took so long to render too. I am rendering out at that size as it is being used on a stock image web site (currently my only source of income as I was made redundant a few weeks back) and it needs to be as big as possible. I am not downsampling or changing the file size at all in most situations either. I will take note of the other suggestions you made too, so thanks again as I am sure it will all help lots.

All the best,

Jay

#29 Guest_vreb_*

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Posted 22 July 2009 - 01:15 AM

Hi baramdo, I tried the solution you suggested and it appeared to make a huge difference as you said it would. Thanks for the advise and hopefully this has solved my original problem with the gradient banding. Alan, your solutions have also helped solve my red issues and I will also look at rendering out to a .psd file and then saving to a .jpeg.

I have now calibrated my monitor at last too, wasn't easy though. I had to trawl all over the HP web site for the best software and configuring both correctly took some time. Hopefully this will make a difference though, but even calibrated it doesn't look far from how I had it set up anyway!

Anyway, thanks for all the time and effort put into this and I really appreciated it. Your all a credit to the C4D Cafe.

Jay

Edited by vreb, 22 July 2009 - 01:55 AM.


#30 Rantin Al

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Posted 22 July 2009 - 05:37 AM

No problems about the render time, I had to go out for a while and just left it rendering. I only mentioned it in case you were going to animate it. [img]http://www.c4dcafe.com/ipb/public/style_emoticons/default/laugh.gif[/img]

If you are creating these as stock images keep in mind a few points.

The RGB PSD file comes straight in at 256MB and the jpg comes down to 4.5MB. More if you convert to CMYK.
Offer the option of smaller native PSD image files. Repeating the jpg compression will eventually create more compression artifacts.
The RGB images will need corrected for conversion to CMYK. Not all RGB colours (monitor colours) can be reproduced in CMYK printing. Use the Proof Preview and Gamut Warning options in PhotoShop.

Adding grainy noise is a common trick used with vector gradient banding in Illustrator.
Add the minimum amount of noise and follow with a low pixel setting of Gaussian Blur. But do it in stages, don't do it in one fell swoop or you will end up with mud.
(It might even work using the Material Layer Shader in C4D instead of adding it in PhotoShop.)

Check if there is a standard range of sizes for the Stock Images. It could save you rendering time.

Good luck anyway, Alan.

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#31 Guest_vreb_*

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Posted 22 July 2009 - 07:28 AM

Hi Alan, thanks again for your time on this issue. Luckily, I don't have to worry about converting files to CMYK as they company I sell the images to only require them in RGB. With all the info provided here I should hopefully be able to avoid such issues in the future and its good to know what the possible issues were as well. There is nothing worse than coming up against such problems and not knowing how to solve them or what could have caused them.

Once again, thanks for everyone's help and time here and all the best,

Jay




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