Blotchy Gradient problem again..need help

Any of the 1600x1200 PNG images from Digital Blasphemy's web site (you have to be a member to get those) will show the problem on the 16" SXGA display. Tell them to compare it with the 16.1" UXGA display which shows no problem at all.

Try this PNG image of all 16M colours. I see it as a completely smooth (I don't get the banding on my SXGA) colour transition within each box.

This whole banding issue is a real mystery at the moment. Short of actually seeing in real life the effect, it is so hard to work out what might be causing it.

I can display 1600 x 1200 images (jpegs, pngs etc etc) rendered or otherwise without any gradient. I sometimes do see artifacts ("I see dead people" .... ) in jpegs but those show up on three different systems (Samsung CRT, Toshiba and Sager SXGA LCD) so those artifacts are not an LCD issue.

That is why the best tests are png or bmp images of original renders as artifacts don't get introduced. BTW most images I have seen on digital-blasphemy are jpegs btw that do have artifacts in them that can be seen on any good quality CRT monitor as well as the LCD.

I know Dennis had a lot of problems with his LCD whereas mine did not, so something is causing it on some SXGA LCD's. Maybe it is a manufacturing defect after all. Who knows.

smooth as a baby's arse on mine. only thing is...now i get the flickering everyone is talking about. i only got this after i upgraded to the 7.93 whql drivers on sager's website.

This link seems to be working better for me. This is also totally smooth on my machine when viewed in either IE or Mozilla (latest versions).

Hmmm.. this makes me think that the problem with gradients in certain applications, like the menu background of IE and in photoshop, under certain circumstances, MUST be driver related.

Wierd stuff!

Thanks for finding that link again eludwig . I had lost it and could only find the long one.

If you use eludwig's version you should see 16 x 16 boxes of smoothly graduating colour within each box. If you have a screen that does not display all 16M colours you will see colour banding within each box because the dsiplay has to step between colour gradients. You will need to expand the image in order to see it properly.

16M colours is about the extent of what the human eye can distinguish between differing colours. It should also be pointed out that the human eye is not linear either. It has better colour resolution near the green part of the spectrum than red or blue ends (consider our evolutionary path - green is important for camouflage/survival - and don't ask me why Martians are green. Maybe it is the only colour that goes with red ).

Jebus - interesting observation about the 7.93 WHQL drivers. Since I did not run any games before I upgraded I can't tell . Maybe reverting back might be an idea.

What do you mean by "the lappy makes me feel bad"?

I assume that the 16 x 16 boxes image as displayed on your laptop SXGA screen is not a smooth gradient within each box? But that it is a smooth colour gradient on your external LCD and CRT?

The 16x16 boxes image should display on your 8890 SXGA screen as colours within each of the 64 boxes as having a smooth colour gradient with no colour steps.

If not, double check you are running 32 bit mode not 16 bit. If you are in 32bit mode and the LCD display is not smooth then you have a problem. Thing is we still don't know if it is a driver issue or a manufacturing fault.

Good luck.

BTW if you save the 16M png image to your harddisk, you can then open it using the XP image viewer and use its zoom in function to enlarge just one of the colour boxes to fill your entire screen.

One more thing - don't look at the boxes for too long - your eyes will start to play tricks with you (and for the skeptics amoungst us this is not an indication that the LCD has a problem - you get the same effect if you look at the image on any display).

confused again..

Ok, just had a closer look at the picture the I linked to above. This image seems to be made up of 256x256 shaped squares, with each pixel in each square being a different color. If I am down at the bottom of the image, where the colors do not get as dark, all seems smooth. If I scroll the image to the top, It looks like each 256x256 square is made up of a smaller matrix of say about 5 pixel by 5 pixel squares. This is very visible in the upper left most 256x256 square. There is definite banding. I looked at this same image on my Hitachi 21 inch monitor & matrox G400 card and there is none of that. So the bottom line is that I am definitely seeing some quantization, but it is hard to put a finger on it. If the LCD bit depth was like 6 or 7 bit rather than 8 bit, that would definitely explain it.

Anyway, more grist for the mill, as it were.

one more time..

Just to add to my own post, I just tried looking at the image on my 15" iMac, which has a 1024x768 LCD screen. NO BANDING. Absolutely smooth. Hmmmm.. So I wonder.. is the 8890 16" SXGA LCD not capable of showing 24 bit color? or is it a driver thing? To be honest, I dont really care that much myself. This LCD is so sweet I can live with it as it is.

I think you will find eludwig that the iMacs support 8 bit colour depth. The screen resolution has little bearing on colour depth. It is one of Apples selling points as they target the graphics industry and have always had a better grasp of colour space issues. On my Toshiba which has a 6 bit LCD, the banding is really noticable.

That being said I can only see the colour banding if and only if I change from 32 bit mode to 16 bit mode. Then I can see that each box is made up of smaller squares.

I do take your point eludwig about the top left hand square. If I zoom in so it fills my screen I can see very subtle colour banding on the LCD. This is what you would expect. The smaller squares at that resolution (your "5x5 pixel squares" as you call them) represent one level of colour (256 boxes x 256 x 256 colours in each box = 16.7M). Your eye should be able to just distinguish the boxes if you are zoomed in. I assume your Hitachi is a CRT - then it probably will not show the banding as well (if at all) because it is analog and the transitions are not as sharp. I can just make out the banding on my Samsung 17GLsi CRT but I have to look really really hard. The LCD on the other hand is digital and the transitions at that zoom level are much sharper.

Just remember you will get funny optical effects from your eyes if you do look at one spot on the image for too long. The effect is colour banding that appears to move . What you start to see is lines of colour that appear then disappear or move as you move your eyes. This occurs irrespective of the type of display used. What you eye is picking up is indeed the edge of each colour and due to your eye's small movements, the rods and cones in your retina then pickup the subtle differences present. Normal colour banding does not move as you move your eyes.

Some of this issues of colour banding on the SXGA being visible at high zoom levels in the top left of that image is because of the specs of the LCD. You get the same effect if you view something under bright "white" light. The contrast goes up and the image is sharper. Use a "softer" light and the sharp edges of the image begin to blur. This is why surgeons use specially designed lamps when they operate - they need exacting detail, where as a photographer will use a soft low colour temperature lighting when photographing people's faces to reduce wrinkles.

If you understand anything about sampling theory and spectral analysis and how that impacts a signal then you will understand what I am talking about. (If you don't well ignore all this and just realise that the SXGA screen in the 8890 uses a high colour temperature backlight and has a high dynamic range - and if you didn't understand that then just realise the SXGA screen is bloody good at displaying sharp images ).

aussie,

All points well taken. Color theory is a very complex issue, indeed. That said, do we know whether or not the 8890 SXGA LCD is 6bit or 8bit? My guess is that it is 6bit based on the level of banding visible. I, as I said, really dont care either way.. I took the machine on spec, as it was listed, i.e. 16" SXGA LCD. The number of color levels didn't even occur to me at all when I ordered. If I wanted a laptop for photographic work or imaging, I would have made damn sure it would do what I needed it to do. As it stands, I only use the machine for software development and games and general purpose stuff. Nothing so exacting. I have other machines here for higher quality visual work.

I love the LCD I have and would be *extremely* hesitant about trading it for an unkown, at this point.

It is definitely 8 bit. That is direct from the Sharp LCD datasheet.

If you want to prove to yourself it is 8 bit just change the video settings from 32 high colour to 16 bit colour. You will then notice the banding.

Unfortunately no Nullboy. I did post some of the specs here but because I had to sign a non-disclosure agreement to get the specs (don't ask me, my friend just works there) I could only scan the front cover of the datasheet which unfortunately does not give you much .

Coming back to the problem at hand you said that when you switched to 16 bit mode you could really see the gradients. Ok so we have a reference point - good. Now when you go back to 32 bit mode you still see the gradients is that correct?

If you do, I would suggest their is something not quite right with your laptop. When I switch to 32 bit mode the gradient is smooth(that is within each of the 16 x 16 boxes of course and excepting zooming in at very high magnifications at which you *should* be able to see the gradients - I would worry if I couldn't).

We don't know if its hardware or software unfortunately .

When you tested your 1850X (LCD? CRT? brand?) did you set its colour depth to 16 bit. The reason I ask is that I am not sure if the DVI output also goes to 16 bit colour depth simultaneously with the main display. How I make sure is to set the monitor to "Extend desktop" then I can control the colour depth of the LCD and external monitor independently as well as being able to move the image between the two for comparison.