Flat panel monitors revisited

There was discussion here a while ago on whether flat panel monitors are
good enough for photographic work. Since then I've done a lot of digging to
try and get to the bottom of this subject, and thought I'd summarise my
conclusions as to why exactly LCD monitors generally don't seem to cut the
mustard. If anyone has any additional comments or recommendations on
monitors that are good enough but don't cost the earth, feel free to chip
in. Any prices below are for 20" 1600x1200 monitors, which is what I was
looking for.

Despite claiming 16.7 million colours, most LCDs have 6 bit LUTs (6 bits
per channel colour) whereas we all know that 8 bits is required for true
colour. Samsung monitors (around £600) seem to have 8 bit LUTs, and the
better NEC models have 10 bit LUTs (but cost £900+).

The fluorescent backlights use by LCDs have colour deficient spectrums and
only cover 70% of the NTSC colour gamut, whereas CRTs cover 90%. White LED
backlights are better but are only just starting to become available.

Most LCDs are around 500:1 contrast. CRTs are around 3500:1, which is the
same as 35mm film. The difference is largely in the black level. At least
1500:1 is needed for convincing blacks.

The optimum brightness of a display in normal conditions is about 90cd/m2,
which is what CRTs give. LCDs are 2-3 timed brighter (probably to punch out
a bit more contrast, albeit at the expense of even worse black levels).

In summary, for photo use a monitor should have an 8 or 10 bit LUT, and the
highest contrast you can find at the lowest brightness level. Unfortunately
most monitor specs do not say how many bit colour they have but simply say
(almost certainly wrongly) that they give 16.7 million colours. Go for LED
backlighting if available/affordable. A photo-quality 20" LCD will probably
cost £900-1000, though it's possible that some £600 displays are suitable
(I haven't been able to determine this for sure because of the LUT issue).
In contrast, a 22" Diamondtron can be had for £350-400 these days.

 

I'm surprised that you recommend white LEDs. Those I've seen have had a
distinctive blue cast - are you saying that this has been fixed, at a cost?
Do you comments include the expensive Sony displays which appear to have a
decent black level? (Sorry can't remember the model.)
I'm currently enjoying using a 17" EIZO Trinitron. Last time I did a search
for a larger Trinitron or Diamondtron I drew a blank. Can you post a link?
Thanks

 

Re. comment on LEDs I'm going mainly by a technical article on the
NEC/Mitsubishi website on how the backlight constrains the available gamut.
I've also read a user comment elsewhere that says a new $6000 NEC LED/LCD
monitor (2180WG) (WG=wide gamut) really does cover the whole Adobe RGB
gamut. The only difference from the standard 2180 monitor appears to be the
LED backlight. There is some question though about how long the LEDs last.

Re. blue cast, are you referring to LED monitors, or white LEDs generally?
I can imagine that general purpose LEDs might be optimised for brightness
rather than whiteness.

Do you comments include the expensive Sony displays which

Apart from a quick look at the potential benefits of LED backlights, I
haven't seriously looked into anything costing much over a £1000 - my
concern is to find something that performs as well as a CRT at a comparable
price. However LEDs do seem to address the black level issue somewhat, with
much better shadow detail being visible according to one review, however
the overall contrast still seems to be in the 500:1 range.

At the moment it seems that although you can get a 20" LCD for £450 (e.g.
Belinea), £900 is the minimum at which you can be confident it's adequate
for photographic use (ie. 10 bit LUT), but it may be that some £600
monitors are also good enough. (These are VAT inclusive prices I'm looking
at.) For me, £900 is still too much so I'm trying to get more info on the
less expensive ones such as the £600 NEC 2080UXi (the 'i' seems to be
important - online shops seem to be selling off the older version at
present).

One pitfall is that monitors that may seem to be stablemates, e.g. Iiyama
prolite H2010 (=20.1") & H2130 (=21.3"), or the NEC 2080 (=20") & 2180
(=21"), are actually very different beasts, using completely different
types of LCD panel! The 21" ones from each company are apparently suited to
photo use, but the (much cheaper) 20" ones might not be.

You can get a 22" Iiyama Diamontron for about £360, e.g.
http://www.monitors-online.co.uk/22_inch_CRT_Monitors.php
http://www.cclonline.com/categories/MON-C21PL
http://www.microdirect.co.uk/Productinfo.aspx?productid=3334

 

Thanks for your reply. Six years ago a colleague who was more in to
monitors than I am had QA problems with the Iiyama he bought. So I'll be on
the alert.
My 17" Sony Trinitron, bought new, failed within the 1st year due to a
circuit board problem. Domestic illness matters stopped me taking advantage
of the warranty before its time was up, so I bought a used 17" Eizo, and
it's been fine with a much more professional interface than the Sony had.
And it's still going strong after 40 months hard daily and night usage after
my s/h purchase.

 

I'm using a 17" Iiyama diamondtron now, and until recently it has been
very good. However it's now 7 years old and having been driven hard
throughout its life has developed horizontal deflection problems which mean
I have to hit it quite hard to get a full width image.

Anyhow I have no qualms about getting the 22" Iiyama if I decide to stick
with a CRT.

The only bad thing about the Iiyama is the stupid push button controls, but
most monitors seem to suffer from those nowadays. The worst bit is that to
exit the onscreen display you have to press two buttons simultaneously,
which I still can't manage some of the time even after 7 years. (It does
exit of its own accord after about 10 seconds though if you're patient.)

For critical work I think the main problem with CRTs (possibly any display
device?) is slight discolouration that creeps in after a while, in my case
one side of the screen now gives a slightly creamy white compared to the
other (probably phosphor burn from uneven usage of the screen). It's only
about 2% difference in luminance terms but when photo-editing I sometimes
have to flip an image across to the other side of the screen to decide
whether what I'm seeing is really off-white or just the monitor. If I were
a rich artist I would probably replace the monitor very 3 years to maintain
perfect colour purity. As it is I can live with it (but not with the
deflection problems!).

 

Hi,

If you wish to keep your old CRT, the deflection problems are most likely to
be caused by poor
solder connections on the circuit board. Something that can be very easily
fixed by even the most
humble TV repair shop.

As for LCD monitors, I would like one too for photo editing, to replace an
ageing 20" Sony Trinitron,
still working fine after nearly 10 years. From surveying the market it is
very difficult to judge what TFT
would be any good, most PC retailers sell on price and might have only one
or two large TFT's on display.

You might like to take a look at this month's PC Pro magazine who have
reviews of 20" TFTs and Computer Shopper
who are also reviewing a range of TFT's this month. Personally I would buy
the Eizo L887 or their new 21" wide model
if I could justify the price!

As for White LED backlighting, I have not seen such displays except in
phones or PDAs where white LEDs are generally used.
For larger panels white leds would not be a sensible option, as a white led
actually is made from a very intense blue or
ultra-violet led covered in a phosphor which changes the colour to 'white
light' the disadvantage is that the light has a
colour spectrum with a strong blue content. Conventional TFTs use
fluorescent tubes (CCFL), these tend to have a bias towards
green in their colour spectrum, with less output at the 'red end'. White
LEDs also have a wear-out mechanism as the phosphor
will deteriorate over time reducing the output, in a similar way to CCFL
backlights, CRTs wear out too so there's nothing new there!

The real benefit from LED backlighting will come when manufacturer's start
to use RED, GREEN & BLUE leds combined to make
the backlight , giving even amounts of each colour in the light output and
neutral white colour, I have heard this talked about
for TV displays but not yet seen a computer display that features this
technology.

Philip