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View Full Version : LCD banding on MB C2D!! WTF!



jubilantjeremy
7th July 2007, 05:34 PM
Hi guys,

In what I hope is to be the last post on 'things that are wrong with my macbook', I present to you :

"The LCD display in my macbook (black) is BANDING"

I just got off the phone with the apple technician, and he couldn't find anything in the KB about it. This is a bit weird because, after I got off the phone, I googled a bit more extensively and found a lot of angry articles talking about how apple has put 256K colour LCDs in Macbook Pros, instead of 16.5 Million colours. There was a class-action lawsuit abou this I think.
However, I'm pretty sure that I have a 'full' 16.7 Million colour display, because this image (from here) (http://www.leppik.net/david/blog/?p=58)..

http://www.visi.com/~leppik/images/bit_test24.png

..Looks 95% OK. As I understant it, if I had one of Apple's 6-bit displays, that image would be completely banded.

The part that DOESN'T look OK is the very right end; the ligther bit. I see a definite band there, that is made of many pixels of two other colours that approximate the colour that is supposed to be represented. I think this is called Dithering.

I get this dithering everywhere else on my Mac too. If I load up iTunes, the green 'display' bit (where track is displayed) shows very clear banding of colours. If I draw a gradient in Photoshop, it's not as obvious - but you can still see it.

I can also tell that the drop shadows on windows are different. They seems sharper, as if there isn't as much of a gradation or fade. It's most clearly visible on a white background.

I'm pretty sure that this is a videocard issue, probably software or at least driver/firmware related.

I'll be taking this to an Apple service center on Monday, but has anyone else heard of this?

Cheers, Jeremy

jubilantjeremy
7th July 2007, 05:59 PM
OK, I've just tried to capture the effect with Grab, but, as expected, it's proving impossible.

If I take a screenshot of an affected area of the screen, and then zoom in (with preview), I can clearly see the 'mixing of pixels' effect. However, It's apparent that this is only within the display, (and not a part of the actual image *sent* to the screen), because it changes as I zoom in.

In other words, say I create a square of a particular colour in photoshop. This looks OK from far away, but as I move physically closer to the screen, and tilt the screen to improve the contrast, I can see that this colour is actually emulated with a pixellated mixture of two or more other colours.

- Jeremy

geektechnu
7th July 2007, 06:18 PM
Any chance we could get a closeup macro photo of the dithering?

As you describe it, the banding is minor - I'd check the colour calibration settings first.
Set it all a little darker (to pull the image back into the panel's range), then brighten back up using the MPB's screen backlight controls.

jubilantjeremy
7th July 2007, 06:40 PM
Any chance we could get a closeup macro photo of the dithering?

As you describe it, the banding is minor - I'd check the colour calibration settings first.
Set it all a little darker (to pull the image back into the panel's range), then brighten back up using the MPB's screen backlight controls.

I've just been trying, mostly unsuccessfully, to get a macro shot..

Good idea about the screen calibration, I'll give that a shot now. The brightness (f2 f3) is set to max now; that's another thing about this mac - i don't feel the LCD is exactly bright.

- Jeremy

jubilantjeremy
8th July 2007, 01:14 AM
OK, took some actual pictures. Took a bit of experimenting with Grab, and I soon realised that this problem isn't reproducible with screenshots.. i.e it's not in what is 'sent' to the video card.

Photos are here :

Here is an example :

http://lh6.google.com/jubilantjeremy/Ro-tOHJSspI/AAAAAAAABX4/X3VkUDfuvFs/P7087586.JPG?imgmax=576
(You can see all five or so of my photos here (http://picasaweb.google.com/jubilantjeremy/NewAlbum707071108PM), and enlarge them if you like)

This is by far the best example (it's a desktop wallpaper actually) of it I have been able to find, probably because the tones in the actual image are mostly a slight variation from white. This is the original image :

http://lh4.google.com/jubilantjeremy/Ro-tWnJSssI/AAAAAAAABYQ/_t_JU-apSe8/99%20Reasons-crop.png


Now, that image will (should!) look normal to you, and for me, viewing head-on at about 1m away, it IS normal - but as soon as I tilt the display or move closer I see that the pixels don't know what's going on.

EDIT : OK, I realise that the image below has quite a dramatic effect on _any_ screen because altering the viewing angle changes the contrast, and so makes it look quite terrible. I'll just point out again, though, that my problem isn't specifically banding - It's that the display seems unable to reproduce subtle tonal differences and so compensates by inserting random pixels nearby, in order to approximate the tone that it is trying to represent..

EDIT AGAIN : Alright, so I just thought of this better analogy.
You know in comic books or newspaper halftone print, where dots of, say, RED are pattered over white space, with quite a distance between them? When viewing from afar, the result is pink - but viewed up close, they are clearly lots of red dots separated by white. That's what I'm getting. If you zoom in on this picture (http://picasaweb.google.com/jubilantjeremy/NewAlbum707071108PM/photo#5084472962272375442) you can kind of see it; the areas of mostly flat tone are made up of sparse pixels like i described as above.


- Jeremy

Edge
8th July 2007, 01:45 AM
You can send your MacBook in to be checked out, but a simple search on 6-bit displays in Macs will reveal that all laptop LCD displays are in fact 6-bit. So feel free to kick and scream, but you're only going to get yourself all worked up.

jubilantjeremy
9th July 2007, 07:01 PM
You can send your MacBook in to be checked out, but a simple search on 6-bit displays in Macs will reveal that all laptop LCD displays are in fact 6-bit. So feel free to kick and scream, but you're only going to get yourself all worked up.

Checked out a 2.16Ghz Blackbook (mine is 2.0Ghz) in Myer today and I reckon the dithering is significantly less visible on them. And a *lot* more noticable on the MBPs.. ahah.. glad I didn't fork $3500 for one.

The MB is in an apple service center at the moment, hope this gets resolved..

- Jeremy