How to test backlit Display Type: LED or CCFL?

Question

How to test backlit Display Type: LED or CCFL?

hi

Just bought a MacBook Pro with LED backlight technology (in US). I used it for 2 or 3 days until i returned it because of 3-6 damaged pixels (in Portugal). You can buy MacBook Pro's of the latest generation here but not for that long... in the store, I asked the seller if he was sure that the display type was of the same type (LED), and he said yes but later i clearly understood he wasn't aware of the new technology for the backlight of displays (LED based) when i asked him "is the backlight LED based?" and he answered "yes, this is not a glossy screen...".

Now, with a new display i am not really sure if this isn't a CCFL screen. In fact, I have the feeling that battery life might have decreased but my experience with the other display was short for comparison (5 cycles). I've made some research but i haven't found any way to test this. This is really important to me since I've been waiting for this technology to buy a computer for some time.
Can someone help me?

Thanks in advance

Macbook Pro, Macbook, iMac G3, Mac OS X (10.5.1)

Posted on Dec 15, 2007 9:56 PM

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Answer 1

Top-ranking reply

BSteely

Level 5

7,643 points

Dec 16, 2007 8:51 AM in response to francisco.gtr

It's a good question you ask but I believe the answer is there is no easy way to tell from a simple test. Perhaps in a side-by-side comparison you might be able to tell from things like:

- Absolute brightness; I believe the LED one will be brighter
- Dimming range; I believe the LED will show greater range from high to low brightness
- Spectrum of color; you might be able to judge a subtle difference in color characteristics

But all of these tests require two units to compare. Just trying to test one, stand-alone unit for whether it has an LED backlight or not, I can't think of any way to do this with certainty. Disassembly would be one method, but obviously not a good one.

The fact of the matter is that the technologies are meant to be interchangeable in terms of the function they perform, which makes it very hard to tell one from the other.

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Answer 2

Network 23

Level 6

12,351 points

Dec 21, 2007 4:54 AM in response to fidel-castro

fidel-castro wrote:
b) mbp 17" -> afaik CCFL based -> screen get ON simultaneously
c) mbp 17" -> should be LED based (just a guess) -> screen get ON from top to down

There is a problem here. Apple is not offering LED backlights for the 17" yet. Only on the 15".
If pixels draw slowly from top to bottom, I think it is more to do with unaccelerated video display (video drivers not yet loaded) rather than the backlight type.

If the LEDs are implemented like the CCFL, in that it is a strip along the edge of the screen, then pixels will all light up at once using either technology.

One measurable difference between CCFL and LED backlight performance is in color gamut, as demonstrated here; see the interactive color charts. The difference is great. However, this isn't easy to test without calibration equipment.

I would not recommend the refrigerator cooling test. If you move electronics from a cold temperature immediately to a warm room, moisture in the air may condense all over the cold electronics, even inside the machine. That may damage your expensive computer.

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Answer 3

Dec 16, 2007 6:59 PM in response to francisco.gtr

I found a possible answer to my question! I need your feedback to validate it.

I was seeing youtube videos and i found a pattern...

LED Backlit based screens seem to have a different behavior when computer is turned ON. When you turn a LED backlit based display ON, you notice that your screen pixels get started from top to down. This as nothing to do with brightness getting its maximum instantaneously. It has to do with the way they are started: in a sequence from top to down, like a vertical gradient.
On older Macbook Pro's (CCFL backlit display) you see that all pixels are turned ON at the same time without any order (like from top to down or from left to right).

Here there are two videos where you can notice this difference:
http://www.youtube.com/watch?v=HbZw8zQSDds&feature=related
http://www.youtube.com/watch?v=nl_WJP-jHpA

Please people, give some feedback if you have access to one or both of this machines to confirm my theory that may become a very handy test for backlit display type.

Thanks

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Answer 4

Dec 19, 2007 11:51 PM in response to francisco.gtr

Hi francisco.gtr:

we have discussed yesterday on irc.freenode.net (##mac) about your screen question.

Today i have compared my
a) mbp 15" including a ATI X1600 Graphic Card (first gen mbp)
b) mbp 17" including a ATI X1600 Graphic Card (about 9 month old i guess)
and a brand new
c) mbp 17" hi-res including a NV 8600M GT Graphic Card

Based on the boot-behaviour those screens act like that:
a) mbp 15" -> for sure a CCFL based -> screen get ON simultaneously
b) mbp 17" -> afaik CCFL based -> screen get ON simultaneously
c) mbp 17" -> should be LED based (just a guess) -> screen get ON from top to down

Hopefuly that helps you
Best regards
fidel

Message was edited by: fidel-castro...just found another 17" mbp here

Message was edited by: fidel-castro

Message was edited by: fidel-castro

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Answer 5

BSteely

Level 5

7,643 points

Dec 16, 2007 1:38 PM in response to francisco.gtr

I don't know a way to recover the displays serial number, but your post did give me an idea. If you put your MBP in the refridgerator for a half-hour and then open the lid to wake it up, if the backlight is CCFL, it will start very dim and brighten as the assembly warms up. If it is LED, it will come on at full brightness even from cold. That's the single best test I can think to perform without access to any test equipment.

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Answer 6

Dec 16, 2007 9:22 AM in response to BSteely

Thanks for your answer. I have thought of that...
the ideal situation for a strong test would be a comparison with a identical MacBook Pro and an old (CCFL) one. I haven't does this yet because i don't have the hardware needed for the test available. All i have is a Macbook but there are differences from a common MacBook Pro display (CCFL) and a MacBook's so the test is weak because they are always different.
Besides, i think that full brightness of LED screen is the same of the older ones. The only difference about that, is that the CCFL technology requires some time to reach that brightness (i think it was to do with temperature) and LED make this instantaneous (anyway, good enough for a test).

I also thought about disassemble the screen and see how it's done by myself or better yet, get the serial number of the display and find someone that can recognize it as from one type/brand or other. Unfortunately, this forces me to open the computer and the display almost completely...

If you could tell me an easy way to get the display serial number.......

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Answer 7

BSteely

Level 5

7,643 points

Dec 17, 2007 9:37 PM in response to francisco.gtr

I'm not sure I trust that test. For one thing, I am pretty sure the whole LED array will light simultaneously. I don't see why it wouldn't. They are not wired each individually to a dimming driver. I believe they are all on a common circuit.

What you see may have more to do with the LCD. And if Apple dual sources their LCDs, say for instance from both Samsung and LG Philips, then maybe the behavior is tied to the supplier of the LCD panel and not the backlight. I just don't trust it.

I guessed a half hour in the fridge just based on thickness of the assembly. It seems to me the cool will have no trouble penetrating to that depth in a half hour. In fact, maybe you should try 15 minutes just to make sure you haven't cooled things down too far below their specified range of operation.

I am sure you will be able to see the display is very dim even without a second MBP as a control unit for comparison. The difference is quite noticable. At least that has been my experience those time when my laptop got very cold from being left in a car overnight.

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Answer 8

Dec 18, 2007 12:29 AM in response to BSteely

First of all, thanks a lot for your message.

I know what you mean but the point of my test is not to establish a theorical cause-effect relationship between the fact some displays don't light all pixels simultaneously and that be directly caused by the LED backlight technology.
I am trying to establish an association between screens that i'm sure that have this technology and a behavior that makes them distinct.

Let's say i have feedback for a large number of computers and i verify that screens known to be LED backlit based get ON from top to down and screens known to be CCFL based light up simultaneously. If you imagine this scenario, the odds of being tricked by dual source screen are extremely low since computer parts are created by lines of production and my unit would be the first to break the rule.

What i thought later is that the reason why displays turn ON differently can also be associated with the graphic card. Doesn't seem to be logical but it's the only thing that changed from previous versions of macbook pro that may interfere.

That's why the feedback from MacBook Pro 17" users is very important, since they have the same graphic card but the same old backlit system.

I know your test is powerful and easy... i just don't feel very confortable to put my new macbook pro with my very new screen inside it and i start thinking that i need another machine for comparison since my very old ASUS laptop already handled very low temperatures pretty fine with it's CCFL screen.

Message was edited by: francisco.gtr

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Answer 9

Dec 20, 2007 10:27 AM in response to fidel-castro

Thank you a lot. You just proved my test is worthless.
Well, a CCFL screen can have the same behavior on boot (like your 17") as long as you have the same graphic card (like your 17" computer, again). My test is not accurate.

I will keep searching..

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Answer 10

Dec 26, 2007 2:36 PM in response to Network 23

Hi

I've read your port for a while, now i reply. Thanks, you showed very interesting information. I knew that MacBook Pro 17" didn't have LED screen although they share the same graphic card (that's why i wanted someone to test with it since the macbook's and powerbook g4 are more different for this comparison).

Your test seems good but yes... i don't have calibration equipment. Still, when i get the chance of getting my hands in another macbook pro 15,4" (with LED) i can try share one calibration for the machines and compare the exact color they provide. It should be the same.

I know the LED displays have different greys like (127,127,127) from CCFL.

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Answer 11

Jan 10, 2008 6:09 AM in response to Network 23

ok, thanks for the input.
I wasnt sure about that...thats why i called it a "guess"

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Answer 12

Dec 16, 2007 4:56 PM in response to BSteely

lol
I also thought of that test but I am not sure where can we detect a difference. You say half an hour is enough, is that a guess or are you really sure if you take a CCFL computer to a fridge it will be noticeable ?

I will be on the cold this christmas ( - 9 Celsius ), i will test it there with no need for a fridge. Unfortunately, i won't have a CCFL macbook pro there for comparison...

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