Filed under: Hardware, Rumors, iMac
20" iMac LCD color problems?
Okay this one is a little shaky because my French is non-existent. But in this post (Google translation) at the French Mac site MacBidouille, they present evidence that the LCD panel in the new 20" iMacs is not a 24bit color panel as in the previous generation, but an 18bit panel instead. Support for this includes the Kodawarisan take-apart photos which appear to show the panel as a LG PHILIPS LM201WE3. This panel seems to be a TN (twisted nematic) display most of which, according to wikipedia, "...are unable to display the full 16.7 million colors (24-bit truecolor) available from modern graphics cards." Other discussions online seem to support this conclusion.
Of course, we heard complaints before about color reproduction on Apple LCD displays. If true, this is consistent with the reviews (e.g. Macworld magazine) that have complained about the quality of the 20" screen versus that of the 24" iMac. If correct this would be a powerful reason to prefer the 24" iMac, particularly if color accuracy is very important to you (e.g. for working with photos).
Thanks Gabriel!
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Reader Comments (Page 1 of 2)
Phosphor said 8:10AM on 9-12-2007
It's crap like this (and the already hashed over same issue with the Mac Books) that make me STILL covet a good CRT over LCD any dang day of the week.
I love the form factor, low weight, low power consumption, and the general concept of LCDs in general, and of the iMacs in particular, but I'm still not sold on them looking as good as even a mid-line CRT.
And yes. I work on photos.
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Jules said 8:11AM on 9-12-2007
Check the english version of macbidouille on http://www.hardmac.com/ and that specific news on
http://www.hardmac.com/news/2007-09-10/#7165
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JohnPQ said 3:55AM on 9-13-2007
Glossy screens and a crappy panel. I'll pass.
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Eric said 9:14AM on 9-12-2007
http://www.lgphilips-lcd.com/homeContain/jsp/kor/prd/prd201_j_k.jsp
Most panels *UNDER 20"* are 6 bit... the lg site lists this one as a 8 bit panel ( as opposed to others that clearly state 6 bit ).
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Mike said 9:27AM on 9-12-2007
I have lots of issues with colour inconsistency and have posted my comments, photos and a video on my website http://www.silvermac.com/2007/imac-colours-washed-out/
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Gabriel Radic said 9:24AM on 9-12-2007
"This would be a powerful reason to prefer the 24" iMac" you says? I'd say it's a powerful reason to prefer a Mac mini under the HD TV set. From a purely subjective point of view, of course.
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Don MacPherson said 9:38AM on 9-12-2007
If Apple is using 18(6)-bit panels, instead of 24(8)-bit ones, it goes against their specifications. On the site at http://support.apple.com/specs/imac/iMac_Mid_2007.html they list the display as having millions of colors at all resolutions. As mentioned in the earlier post, 24-bit gives you 16.7 million color values, however 18-bit only gives roughly 262,000 potential values. For the book, that's thousands, not millions, Apple. Anyone having this problem should point this out when they contact support.
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Eric said 9:58AM on 9-12-2007
@Don
Nope, 262k is reported as "Millions" due to dithering. Look at the specs for the last generation 17" iMac which was clearly a 18 bit panel.
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Matt Sayler said 10:17AM on 9-12-2007
"LCD panel in the new 20" iMacs is not a 24bit color panel as in the previous generation, but an 18bit panel instead. "
Previous gen iMac 20" (I'm typing on one now) are 18-bit. It kind of sucks, and is most visible in Windows/Boot Camp (Supposedly the ATI driver on Windows is less clever with zee dithering).
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Don MacPherson said 10:59AM on 9-12-2007
@Eric
Good to know. I knew there was dithering involved, but I wasn't sure if it was enough to break the millions mark. Any idea exactly what it reports as? I've been told it's ~16.2 million with dithering, but there seems to be some debate on that (particularly between brands and device types).
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Entica said 11:27AM on 9-12-2007
Come on, isn't the glossy screen enough of deal breaker on it's own for serious photo/graphics work? This is just icing on the cake.
There's a lot of crappy low end panels out there (even at 20+ size). I hate it when friends get some gigantic panel and brag. Yeah so you got a 28" panel for $400... you know what? It's $400 for a reason - it sucks.
@1 There's some seriously great LCD's out there now that rival CRT. They just cost an arm and a leg. You have to be willing to pay the big $ for quality. A decent LCD will easily be almost double the price of a crap one for the same screen size.
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Buckingham said 12:41PM on 9-12-2007
There was also a discussion about this for the Macbook Pro. Basically, the millions-of-colors claim isn't really accurate.
http://discussions.apple.com/thread.jspa?messageID=5089692
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John Sample said 2:56PM on 9-12-2007
Ok I think there's more to this. To my understanding this is how these panels work in general:
In order to do things like making the panel light weight, low-power, affordable, high viewable-angle, and so forth and yet still display 24 bits per pixel, the manufacturer got clever... Each color has 6-bits R, G, B, yielding 18 bits total per pixel. However, since the goal is to display 24-bits, they 'dither' to add 2 more bits per channel but thats not quite right; they dither through time: By flickering the panel between two states, your persistence of vision that makes video appear fluid kicks in and you see 24 bit even though the panel isn't *technically* displaying it.
The artifacting 'shelf' you see in places in color ramps is because in one panel-state you can see it, and that pattern recognition 'trumps' the persistence of vision blurring.
So, are these panels delivering 24 bits to your brain? Yes.
Is a true non-time-dithering 24 bit panel better? Yes.
However, for most applications you wont' be able to see any difference because the continuous color-shifting ramps simply won't be seen. That is a test pattern designed to highlight the artifact, not a real-world example.
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rimshak said 10:40PM on 9-13-2007
I was surprised also when i got my brand new Imac 20 (i'm a switcher).
i'm playing a game called Eve online, and the flickering used creates some very bad bandings problems. This game is very dark in its UI design.
First i thought i was running the game in 16 bits depth but when i checked i was in 24 bits.
I'm very very pleased by the Imac, but this 18 bits screen issue is a big problem for me.
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Phosphor said 8:13PM on 9-12-2007
@John Smaple:
Do you have links to any documentation or discussion about the "two-state P.O.V/time-based dithering" of 6 bit/channel LCD monitors?
No offense, but I'm not ready to give you a "Pass" on that theory until I see it corroborated by a known reliable source.
Thanks!
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lostmyheadnmind said 9:49PM on 9-12-2007
Yeah, my new iMac is up stairs with a shitty monitor and my network card is messed up. I have an apple genius to check out the problem on friday night and hope to have this resolved. I did hear if using a calibration on the monitor seems to work really well. I wish I still had my macbook.
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TestYourColor said 11:16PM on 9-12-2007
Read the article and test the bit depth of your display here:
http://www.leppik.net/david/blog/?p=58
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Kakaze said 12:15AM on 9-13-2007
My aunt got a 20 inch iMac in July of 06 and the screen annoys the hell out of me. Whenever I move anything on the screen or move my eye just right I see dithering all over the screen and I can't stand it. I would have taken my PowerBook back if I could see, in my opinion, horrible artefacting like that on it.
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Phosphor said 4:12AM on 9-13-2007
@ TestYourColor/reply#15:
I don't have to test my monitors' bit depth.
I use CRT's. GOOD ones, calibrated weekly.
:p
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Shaun said 5:09AM on 9-13-2007
The specs on the LG Philiips page for the LM201WE3 list it as 16.7m 8 bit(FRC). This is a little misleading as you'd not use FRC if it was truly 8 bit.
It is in fact 6 bit with FRC to achieve 8 bits per colour. See http://en.wikipedia.org/wiki/TFT_LCD for an explanation.
It's also anti glare coated underneath that glass panel so you get the worst of all possible combinations - reflective glass followed by colour reducing anti-glare coat, followed by a crappy 6bit panel. Welcome to the new Apple iMac. You can never be too crappy.
The 24" quite possibly uses a 6bit panel too as LG Phillips make a 24" model with the exact same specs as the 20", the LM240WU3(TN).
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