Banding with integrated GPU (Intel HD 3000)

[butteredpopcorn]

Hi,

When viewing this test image ( http://www.lagom.nl/lcd-test/gradient.php ) with the integrated (Intel HD 3000) GPU running I see banding, whereas there is no banding at all if the discrete (AMD Radeon HD 6750M) GPU is rendering. This is the same in both Safari and Chrome.

Why is it that the integrated GPU cannot/does not render the image without banding?

(2011 MBP 15" 2.2 HR AG)

Thanks,

T

 

[mape2k]

All I can think of is changed color depth. But I would assume both the HD3000 and the 6750M support 32-bit.

Conclusion: For graphic editing, use dedicated graphic unit (usually switches automatically). For everything else: Don't worry, be happy

 

[Detrius]

They shouldn't look any different. If you take a screenshot, does it show up in the screenshot? I suspect it will based on the premise. If it does, post it here (and it'll likely be either software or logic board). If it doesn't, then it's intermittent, it will likely do it under discrete graphics too, and you have either a bad LCD or LVDS cable.

 

[LurkinTuff]

re

If I take a screenshot of the gradient while the discrete is running, and then I switch over to integrated, the banding appears in the screenshot taken with the discrete running. And vice-versa... The banding disappears if i take a screenshot with integrated and switch over to discrete.


Thats what I thought: they shouldn't look any different. But they do.

BTW, this is the OP, butteredpopcorn.... I had to make a diff account bc i lost a pasword then couldnt activate blah blah

 

[LurkinTuff]

RE: Banding with integrated GPU (Intel HD 3000

Im guessing that the display is not 8 bits but rather 6 bit+dithering/FRC (a technique used to produce the illusion of millions of colors on a display thats only capable of producing hundreds of thousands of colors) and the integrated chip doesnt implement the dithering algorithm very well. Sound reasonable?

To anyone with knowledge on this subject: Your input is greatly appreciated.

Thanks

 

[Detrius]

I guess the dithering option is plausible, but I'd really like to see what it actually looks like. We've established that it's not in the actual screenshots, so whatever it is, it happens after it leaves the video memory.

Is the machine still under warranty?

 

[mape2k]

How bad is the banding really? Could you provide a photo of you screen? If I look at my screen from 5cm distance I clearly see a difference between 6490M and the HD3000 (also on the HR AG 15"). There is also a tiny bit of banding visible with the HD3000, but I really have to be close to actually see it.

The OP's MBP is a 2011 model, so it still must have warranty.

 

[LurkinTuff]

OK, so here are photos of each....

The difference may seem insignificant, but I can definitely make it out at a distance of 1.5 feet. The photo's dont render the fine gradation in the highlights so well. In other words, its worse in person.

Yes its under warranty. I wasnt necessarily looking for a replacement or whatever, I just thought they should look the same, and I wanted to find out why they dont.

Thanks

Oh, discrete is on the left, integrated on the right, and be sure to look at them at 100%

 

[mape2k]

Looks almost identical to what I get when I switch between discrete and integrated.

 

[Detrius]

From what I can tell, they both have banding, but one is horizontal, whereas the other is vertical.

It doesn't look like the kinds of things I see with faulty graphics cards. Maybe the dithering explanation is right.