Contrast ratio of LCD monitors

HEMI-Powered wrote:
Shon Kei Picture company added these comments in the current
discussion du jour ...

Victek wrote:
I'm wondering about the contrast ratio spec of new LCD
monitors. It varies between 1,000 and 3,000 in many cases,
but with the screens all lined up and displaying images in
the store I don't see much difference. Any opinions about
how much difference this makes in the real world, and how you
can actually assess the difference?
There are only a few LCD screen manufacturers in world capable
of producing a monitor with CMYK colour gamut. You can however
use a cheap monitor and provided you follow a few pointers,
only ever miss out of the last section of black on a contrast
wedge.

Although these monitors all seem to come with a 15 pin VGA
plug (or adaptor) DVI (Digital Video Input) will absolutely
improve the contrast range you can see on screen.

I've got a 21" and a 26" Samsung monitor and also an ATI Radeon
video card. I don't at all like the digital interface even if it
is marginally sharper because it doesn't allow the various
controls on the monitor to alter the image. Yes, this can be done
with the video card but then one is altering the actual video
signal at the source rather than how the monitor processes and
displays it. I much prefer to run on the analog side.

If you use a RADEON video card, it comes natively with built
in monitor profiling adjustments. All you need to do is get
the RGB examples right and you have very good colour balance
without profiling the screen.

This is definitely not true in my experience. I've set up both my
Samsungs, one on analog and one on digital, and ran through the
calibration stuff that comes with the Radeon card and with the
color calibration tool Samsung provides. It is not at all a
trivial task to get these things to display what I know is the
correct brightness/contrast and color balance. Worse, similar
settings display entirely differently on each monitor making it
even more problematical to decide what "right" is.

You may need a cheap program called "power strip" to move the
gamma to a low contrast region suitable for photographs but
once you have done these things, a $200 LG monitor will start
to look like a high end Ezio.

The contrast ratio described by LCD makers is all useless. I
have a 2000:1 CR screen that looks no better and no worse than
the $1900 Ezio I bought for editing photos - most of the time.

I use the (wide screen) LG for movie editing but I'd happily
use it for photo editing if I didn't have the Ezio.

Samsung make a screen now they claim will match the CMYK of a
web offset press. Big deal. So will my tweaked LG and it cost
less than half the price of the Samsung.


Use power strip. The shareware version will nag you at boot but
otherwise it works a treat on Samsungs

Victek wrote:
I'm wondering about the contrast ratio spec of new LCD monitors. It
varies between 1,000 and 3,000 in many cases, but with the screens
all lined up and displaying images in the store I don't see much
difference. Any opinions about how much difference this makes in the
real world, and how you can actually assess the difference?

I wonder if someone who knows about densities and prints might care to
comment on this. I'm too rusty! Is a 1000:1 range the same as a density
range of 3.0? What is the best that prints can achieve? I would have
expected less than 3.0, and if so presumably the blacks are compressed a
little to fit the available dynamic range of the print? I remember
sometimes having to do dodging and burning to produce the "best"
black-and-white print.

I have been disappointed with the LINEAR dynamic range of typical (i.e.
inexpensive) LCD monitors - there is very little display of the lower
blacks so that, if you have an image of 0..255, all levels below 8 may
appear as one black. To get the best visible greyscale reproduction, I
have found that you typically need to decrease the contrast (gain)
setting, and increased the brightness (offset) setting, so that the blacks
are actually shown as dark greys. This then works well with colour
images. Note that I print very little, so matching monitor to printer
isn't an issue for me.

Perhaps these new OLED displays are better?

David

saycheez wrote:
The current issue of Maximum PC reviews this subject.
There are also some comments in an interview in the current issue of CPU
that give insight into why LCD television panels are not what they seem
compared to Plasma, DLP and particularly the late CRT, still the
standard of measure. This is particularly so with regard to what
contrast ratio means: if LCD panels cannot display absolute black then
what does contrast ratio really mean?

It is supposed to mean the ratio of lowest to brightest light.

If they could display absolute black, the ratio would be infinite.

Even CRTs don't have an infinite contrast ratio, as long as they
have been on recently, or been in a lighted room, because of phosphorescence.

Anything over 500:1 is perfectly adequate for previewing
photo material meant for halftone printing or photo
printing on paper. It may no be adequate for images
destined for transparencies or better electronic displays.

Doug McDonald

Don Stauffer in Minnesota added these comments in the current
discussion du jour ...

In the end, I think this is a highly subjective issue.

I'm not talking about sharpness though, I'm talking about
contrast graduations.

Keep in mind the human eye can only perceive a 2% contrast
ratio change.

To the extent this is true, why would one pay more if they can't
see the difference? Following that kind of logic would also suggest
that using more mega pixels really doesn't equate to better
pictures. Personally, I'm not at all interested in the theoretical
only the practical, so when shopping for a monitor I look to see if
they look good to me and only then ask about the specs.

--
HP, aka Jerry

Don't be a fop or a blooter, make only pithy comments on Usenet

Check out Sony's 1000000:1 OLED screen and you will see the difference.

Toby

"Victek" wrote in message
...
I'm wondering about the contrast ratio spec of new LCD monitors. It
varies between 1,000 and 3,000 in many cases, but with the screens all
lined up and displaying images in the store I don't see much difference.
Any opinions about how much difference this makes in the real world, and
how you can actually assess the difference?

I'm wondering about the contrast ratio spec of new LCD
monitors. It varies between 1,000 and 3,000 in many cases,
but with the screens all lined up and displaying images in
the store I don't see much difference. Any opinions about how
much difference this makes in the real world, and how you can
actually assess the difference?

If you were looking at a low key images side by side you may
notice a slight difference between a monitor with a low
contrast ratio and one with a high one, but to be honest
1000:1 isn't low at all.

Please see my reply to the OP first, but I would disagree that
1000:1 isn't pretty low. But, unless one is into technical lab
testing to glean some scientific comparisons, it is vitally
important to view real world images and not just the canned
displays in the stores. In my shopping this spring I found the
1000:1 displays were the lowest end monitors with the least sharp
display while the 5000:1 were barely better than the 3000:1 but
usually 2X-3X the price.

In the end, I think this is a highly subjective issue.

It occurred to me to check out the specs of the 19" flat panel I'm currently
using. It's a couple of years old - contrast ratio is 500:1 and response
time is 16ms. These specs are poor by today's standards yet this monitor is
perfectly adequate for me. It's a good example of how specs can suggest
differences that don't matter in the real world (at least not to everyone
under all circumstances).

"Victek" writes:

You anticipated and answered my next question about DVI. My video card
(Nvidia 6600GT) has both VGA and DVI connectors. I'm currently using the
VGA connector, but the new screen I picked up has both so I will invest in a
DVI cable. I don't know if the Nvidia card has the built-in monitor
profiling you mentioned (?) I've read that using DVI eliminates screen
centering issues - is that true?

The main point of a DVI connection is it delivers fully digital data
from the graphics card directly to the controller in the monitor,
eliminating several sources of noise and error.

With an analog connection, the digital RGB values stored in the graphics
card are converted to analog RGB values via a digital to analog
converter, with one pixel following another at a rate determined by an
internal oscillator in the graphics card. These signals, plus a small
amount of noise and hum picked up along the way, are fed to the analog
input of the monitor.

This circuitry has the job of guessing what resolution the graphics
card is working at by looking at the sync frequencies. Then it tries to
generate a local pixel clock oscillator which is as close as possible to
being in sync with the one in the graphics card. An analog to digital
converter converts the voltages in the input signal back into RGB
values, and those are stored in the monitor's local RAM which is used to
update the individual pixels in the display panel.

In a perfect world, the data in the monitor would be a perfect
reconstruction of what was in the graphics card, but in the real world
there are black level and gain errors, noise, and clock rate mismatches.
The DVI connection avoids all the analog stages, sending clock and
RGB intensity data in digital form across the cable.

Dave

"David J Taylor" writes:

I wonder if someone who knows about densities and prints might care to
comment on this. I'm too rusty! Is a 1000:1 range the same as a density
range of 3.0?

Yes, it ought to be, since density is base-10 logarithm. On the other
hand, you need to check what you're comparing. Some monitors are
specifying a "dynamic contrast" rating that includes dimming the
backlight in dark scenes. What you want to know is the largest contrast
available *within one image at the same time*. Even then, this depends
on the test pattern.

What is the best that prints can achieve? I would have
expected less than 3.0, and if so presumably the blacks are compressed a
little to fit the available dynamic range of the print? I remember
sometimes having to do dodging and burning to produce the "best"
black-and-white print.

If I remember correctly, the density range of good B&W paper developed
to have good blacks, and with a glossy surface, is about 100:1, maybe
200:1 in the very best cases. Colour prints are more like 30:1.

You can choose paper contrast during printing to make tradeoffs between
reproducing a relatively small scene brightness range (5-6 stops) with
normal contrast, or a wider scene range with lower than normal contrast.
Dodging and burning in provide local exposure changes to "push"
highlights and shadows towards midtone. You can even use multiple
exposures on vari-contrast paper in combination with
masking/dodging/burning to print different areas with different
contrast.

I have been disappointed with the LINEAR dynamic range of typical (i.e.
inexpensive) LCD monitors - there is very little display of the lower
blacks so that, if you have an image of 0..255, all levels below 8 may
appear as one black. To get the best visible greyscale reproduction, I
have found that you typically need to decrease the contrast (gain)
setting, and increased the brightness (offset) setting, so that the blacks
are actually shown as dark greys. This then works well with colour
images. Note that I print very little, so matching monitor to printer
isn't an issue for me.

That might be deliberate on the part of the LCD makers. Pulling the
darkest tones to blacks causes the rest of the tonal scale to have
higher contrast and more saturated colours. Less accurate, but a lot of
people like the effect.

Dave

Dave Martindale wrote:
"David J Taylor"

writes:

I wonder if someone who knows about densities and prints might care
to comment on this. I'm too rusty! Is a 1000:1 range the same as a
density range of 3.0?

Yes, it ought to be, since density is base-10 logarithm. On the other
hand, you need to check what you're comparing. Some monitors are
specifying a "dynamic contrast" rating that includes dimming the
backlight in dark scenes. What you want to know is the largest
contrast
available *within one image at the same time*. Even then, this
depends
on the test pattern.


Agreed.


If I remember correctly, the density range of good B&W paper developed
to have good blacks, and with a glossy surface, is about 100:1, maybe
200:1 in the very best cases. Colour prints are more like 30:1.

You can choose paper contrast during printing to make tradeoffs
between
reproducing a relatively small scene brightness range (5-6 stops) with
normal contrast, or a wider scene range with lower than normal
contrast.
Dodging and burning in provide local exposure changes to "push"
highlights and shadows towards midtone. You can even use multiple
exposures on vari-contrast paper in combination with
masking/dodging/burning to print different areas with different
contrast.

Thanks for the reminder!

I have been disappointed with the LINEAR dynamic range of typical
(i.e. inexpensive) LCD monitors - there is very little display of
the lower blacks so that, if you have an image of 0..255, all levels
below 8 may appear as one black. To get the best visible greyscale
reproduction, I have found that you typically need to decrease the
contrast (gain) setting, and increased the brightness (offset)
setting, so that the blacks are actually shown as dark greys. This
then works well with colour images. Note that I print very little,
so matching monitor to printer isn't an issue for me.

That might be deliberate on the part of the LCD makers. Pulling the
darkest tones to blacks causes the rest of the tonal scale to have
higher contrast and more saturated colours. Less accurate, but a lot
of
people like the effect.

Dave

Thanks for your reply, Dave. Perhaps there is also some problem about
reproducing dark very greys accurately, so the monitors are designed not
to reproduce them at all? I would much prefer accuracy to the garish
results sometimes seen. From what I hear, I may be in the market for the
OLED displays....

Cheers,
David

Don Stauffer in Minnesota wrote:
[]
The figures I had seen said 2% for the blackest black on fully exposed
printing paper. This corresponds well to about the same value for 3M
Black Velvet paint. I believe inks from printing press are a bit more
reflective.

I worked on a project developing blacks for sunshades on satellite
optical instruments. It was hard to find ANYTHING blacker than 1%.
The best blacks we had were between 1 and 2%.

Thanks, Don. I recall that for TV test targets they once used recessed
boxes (sort of a light sink) lined with black baize to try and get a very
low reflectivity value. However, all this doesn't explain why LCD
monitors, with claimed contrast ratios well in excess of 100:1, can
produce such lousy dark greyscales!

Cheers,
David