How many bits per color channel in rendered pictures?

I often get ugly transitions in my rendered pictures. It looks like rings or a rainbow without colors. The falloff of brightness is not smooth, but looks like in a gif picture with only 256 colors. But I use jpg, and jpg should as far I know support 24 bit (8 bit per channel). And bmp format actually doesn’t look better.
How can I get better quality, means smooth transitions?

Which quality do you use for your Jpeg? Assumed it’s not a comrpession issue, you certainly suffer from a banding issue. In the render buttons, Output pannel, increase the Dither value (actually it’s 0.000, try 1.000 and see if it’s better; if it’s noisy, then decrease the value until achieving a good compromise between noise and banding)

Cheers,

Caravaggio, are you sure that your computer’s DESKTOP colour depth is set to 32-bit true colour at all?

If you render from Blender as JPG and/or BMP and you get this banding and lack of decent colour, it sounds more like a problem with your Windows colour depth settings to me.

1.) Render an image in Blender. Save it as a JPG.
2.) Screengrab your desktop with the Blender render window open.

Post the two images here.

If it’s Windows at fault, the Rendered JPG will look 100% fine here in Elysiun and the screengrab will look wrong.

Just an idea :wink:

hi olivS!

I used 100% jpg quality and dither 0.000. Now I tried a simple rendering of a plane with one lamp shining on it. Especially lower lamp energy provides horrible banding, which is even with dither 2.000 noticeable. Is this a problem of the Blender internal render engine?

Thanks,
caravaggio

Hi PolygonUK!
No this isn’t the problem. I am using Mac OS and of course have set the colour depth to the highest value. And in other programs there was never a problem with noticable banding. Even in jpg photos of higher compression I have smooth transitions.
But thanks for your advice!
caravaggio

Could you post one of these troublesome renders then so that we can see if the same occurs with us? :wink:

I have no webspace where I could upload the file. But the effect is very easy to reconstruct (and occurs quite often). Just use a plane and a normal lamp with rather low energy. let the camera look down to the plan in an angle of 45 degrees (I think, it doesn’t really matter). Use jpg 100% and at least PAL resolution and render. Then you should see noticable rings with distinct brightness areas.

Does this problem occur when you open the rendered image inside a photo program such as GIMP or Photoshop? Also, if you need a host for images, use www.imageshack.us . (Free host, and you still remain the copyright holder for the images that you upload.:))

DwarvenFury

The blender render window is not the best place to view rendered images. Try opening it up in another image editor.

If there is still noticable banding, play around with the dithering options in the Render options. It should go away with dithering.

Thanks for this URL, it’s perfect for my purpose!
Of course I tried to open the file in various programs (like photoshop), but the effect doesn’t change.
Here ist the test rendering:

On first impression the gradient smoothness of the light falling off looks okay. Seems smooth enough to my eyes.

Only when I really move closer to my monitor, say 10" from it, I can start to see very, very faint ‘rings’ which could be counted as ‘banding’.

But compared to some renders I’ve seen, and some I’ve done in the past, there’s nothing I’d be worried about.

Anyone else seeing anything? %|

In my opinion it looks really bad. It looks like Blender doesn’t use the full color depth of jpg, because this example looks like a gif image with 256 colors.

Without being able to actually see what’s on your monitor, I can’t help much more.

Looking at your last image on my machine, I’d say it’s definitely not 256 colours, and certainly not GIF quality.

It is JPG quality and there are some very faint, and I mean faint signs of possible banding, but here on my 19" monitor it looks pretty decent. %|

Can you upload the .blend file or something so others like myself can render the exact same scene you are?

Well, in your example (all gray) you won’t be using 16+ million colors as you’re limited to one hue. 24 bit color is 8 bit red, 8 bit blue, 8 bit green. If you make an image all in red (for example), it only has 256 colors to deal with.

The answer has been given in the above responses. By default the dither setting is 0.000 (no dithering) which results in color banding on a uniformly colored surface. Increase that number to 1.000 or so and you’ll see the banding go away.

This problem isn’t as apparent when dealing with textures, as you don’t normally have a big field of uniform color anywhere where it would be apparent.

Change the Bias value of your shadow lamp.

%<

Do a simple radial blend (white to black) in Photoshop or Gimp to the same size and resolution and see how it compares. I did a render and a PS blend and both pretty much match what I see in your sample above - which looks fine.

Maybe we’re not seeing what you’re seeing.

I’d agree with everyone above. The suggestion that grey is only one colour channel so therefore is only 8 bit is worth noting but technically your image is 24 bit RGB with equal values throughout. So I suspect the noticeable banding (such as it is) is due more to the low value of the shades (you’re not using the full spectrum of values from 0-255 for each channel) and the fact that the RGB values are equivalent throughout the blend suggests each one bands to the same extent.

Having said that - the banding is barely noticeable (on my screen) until you look for it. I tried changing my monitor (Apple LCD) to 256 colours and believe me - that’s REALLY bad (almost no blend at all).

Ok, then we have the same or a similar monitor. I switched my monitor to 256 colors, just to see, how it looks: you were right, it’s really bad.
But the blender rendering is bad too. Now I tried different versions: brighter, only red, only blue and only green. The brighter and the only blue version have only very little banding. Really bad it looks in the green and in the above posted grey version. Maybe it is a internal limitation of the Blender render engine.

Do you have a blend you can post, because it really looks like your renders are with dither set to zero.

I inserted a plane, set a low energy spotlight on it and rendered with dither set to 0 and again with the value set to 1.something (I just slid the value, but didn’t bother to set it at 1.000 exactly)

Afterward, I took the renders and adjusted the levels so as to amplify the banding effect to make it more visible. As you can see (image below), the dithered version is much smoother because it mixes pixels of different values to simulate ones that it doesn’t have the full range to make. The banding is very apparent in the non-dithered version (which is the default of 0.000). There is still an ever-so-slight appearance of the banding in the dithered version, but prior to doing the level adjust, it was invisible.

Just to see how it is handled elsewhere, I did roughly the same thing in C4D CE+. Cinema4D’s version looks smooth, as it seems to do dithering by default (and no option I can find in that version to change the amount). So while the Blender default value of 0 has banding, it is easily changed to get the same smooth appearace I got from C4D.

I’ve had a similar problem before when I try to render things in one solid color. I’m glad to see that dithering will fix this. What exactly does dithering do? I’m sure there’s a trade off for the better blending.

In low resolution images dithering produces more fluent color transitions. Dithering mixes pixel of different colors to produce the optical illusion of a transition, like pointilist artists in 19th century have intended in their paintings.
See also http://de.wikipedia.org/wiki/Dithering_(Bildbearbeitung)
(it’s german, but with interesting images, which are not shown in the Englisch wikipedia).