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Basic Colour Management: C1 & PS

Smeggypants
Posted 14/10/2009 - 22:49 Link
Hi folks

Hope this isn't a stupid question but could I sensibly use my K20D to colour balance my Computer monitors using the RGB histograms on the camera by taking a picture of a pure white pic displayed on the screen?

Just before the K20D battery ran out I did try it and the RGB histograms showed narrow band peaks at different places on the x- axis of the histograms. I'm assuming that for a proper colour balance the R, G and B peaks should be at the same position on the histogram to indicate equal brightness of each colour.

And can you show a histogram in live mode with the K20D as that would avoid the cycle of taking a pic, tweaking the monitor, taking another pic, etc,etc
[i]Bodies: 1x K-5IIs, 2x K-5, Sony TX-5, Nokia 808
Lenses: Pentax DA 10-17mm ED(IF) Fish Eye, Pentax DA 14mm f/2.8, Sigma 17-70mm f/2.8, Pentax-A 28mm f/2.8, Sigma 30mm F1.4 EX DC, Pentax-A 50mm f/1.2, Pentax-A 50mm f/1.4, Pentax-FA 50mm f/1.4, Pentax-A 50mm f/1.7, Pentax DA* 50-135mm f/2.8, Sigma 135-400mm APO DG, and more ..
Flash: AF-540FGZ, Vivitar 283
Smeggypants
Posted 15/10/2009 - 01:56 Link
I think i've had a bit of success using a camera to measure the colour calibration of a monitor.

I set the K20D to 1sec shutter speed to avoid the black bars from the monitor sync. I set the white balance of the K20Dto manual and neutral

I then took a photo of a white pic displayed on the monitor.

I then had a look at the R, G and B histograms in both the camera and more accurately in Photoshop. It was then pretty easy to tweak the RGB colour settings on the monitor, take another pic, look at histogram and adjust.

I'm sure it's not as accurate as using a proper colour meter, but It's certainly helped a lot. And it's free!

It's amazing how much you get used to a colour balance. My 2 computer monitors had far too much blue bias
[i]Bodies: 1x K-5IIs, 2x K-5, Sony TX-5, Nokia 808
Lenses: Pentax DA 10-17mm ED(IF) Fish Eye, Pentax DA 14mm f/2.8, Sigma 17-70mm f/2.8, Pentax-A 28mm f/2.8, Sigma 30mm F1.4 EX DC, Pentax-A 50mm f/1.2, Pentax-A 50mm f/1.4, Pentax-FA 50mm f/1.4, Pentax-A 50mm f/1.7, Pentax DA* 50-135mm f/2.8, Sigma 135-400mm APO DG, and more ..
Flash: AF-540FGZ, Vivitar 283
MattMatic
Posted 15/10/2009 - 14:35 Link
Smeggy,
That's a fair idea... definitely worth experimenting with.
But watch out that the histogram on the camera (or PS) will vary with the white balance of the camera, and the camera has its own colour response curve too!

However a hardware calibration (say with a Huey) isn't that expensive (especially when compared with the cost of say the K20D or K7D!). The Argyll CMS software will take a whole pile of measurements at different intensities to create a profile for the monitor - it's not just a "balance R, G, and B at one level" (which is what you're doing).

Typically, displays need some serious calibration at the low and high ends - the curves produced by Argyll can be all over the place!

Just some thoughts
Matt
http://www.mattmatic.co.uk
(For gallery, tips and links)
Smeggypants
Posted 15/10/2009 - 17:10 Link
MattMatic wrote:
Smeggy,
That's a fair idea... definitely worth experimenting with.
But watch out that the histogram on the camera (or PS) will vary with the white balance of the camera, and the camera has its own colour response curve too!

Yeah I first tried it with the AMB balance of the K20D enabled Comment Image
and then switched it to manual.

I did wonder whether the camera would have an inherent resposne curve even with any white balancing switched off

Quote:

However a hardware calibration (say with a Huey) isn't that expensive (especially when compared with the cost of say the K20D or K7D!). The Argyll CMS software will take a whole pile of measurements at different intensities to create a profile for the monitor - it's not just a "balance R, G, and B at one level" (which is what you're doing).

Typically, displays need some serious calibration at the low and high ends - the curves produced by Argyll can be all over the place!

Just some thoughts
Matt

I hadn't considered a dynamic change in colour response. I suppose for testing purposes you use the camera to take a photo of the monitor at different intensities just for kicks, but ultimately, as you say a proper monitor profile is the way to go.

I'll check out this Huey contraption
[i]Bodies: 1x K-5IIs, 2x K-5, Sony TX-5, Nokia 808
Lenses: Pentax DA 10-17mm ED(IF) Fish Eye, Pentax DA 14mm f/2.8, Sigma 17-70mm f/2.8, Pentax-A 28mm f/2.8, Sigma 30mm F1.4 EX DC, Pentax-A 50mm f/1.2, Pentax-A 50mm f/1.4, Pentax-FA 50mm f/1.4, Pentax-A 50mm f/1.7, Pentax DA* 50-135mm f/2.8, Sigma 135-400mm APO DG, and more ..
Flash: AF-540FGZ, Vivitar 283
MattMatic
Posted 15/10/2009 - 22:20 Link
Quote:
I'll check out this Huey contraption

You can get the cheapest Huey or Pantone Spyder, or Gretag Macbeth Eye One - they all work with Argyll CMS + dispcalGUI.

The software is free to use and, IMHO, works far better than the software supplied with the hardware So, go for the cheap consumer version (or second hand) and use decent free software

EDIT: But the Huey is easier to install and faster than the Spyder for display calibration

Matt
http://www.mattmatic.co.uk
(For gallery, tips and links)
Edited by MattMatic: 15/10/2009 - 22:21
Smeggypants
Posted 15/10/2009 - 22:48 Link
Cool - cheers Matt
[i]Bodies: 1x K-5IIs, 2x K-5, Sony TX-5, Nokia 808
Lenses: Pentax DA 10-17mm ED(IF) Fish Eye, Pentax DA 14mm f/2.8, Sigma 17-70mm f/2.8, Pentax-A 28mm f/2.8, Sigma 30mm F1.4 EX DC, Pentax-A 50mm f/1.2, Pentax-A 50mm f/1.4, Pentax-FA 50mm f/1.4, Pentax-A 50mm f/1.7, Pentax DA* 50-135mm f/2.8, Sigma 135-400mm APO DG, and more ..
Flash: AF-540FGZ, Vivitar 283
Smeggypants
Posted 18/10/2009 - 17:29 Link
MattMatic wrote:
Quote:
I'll check out this Huey contraption

You can get the cheapest Huey or Pantone Spyder, or Gretag Macbeth Eye One - they all work with Argyll CMS + dispcalGUI.

The software is free to use and, IMHO, works far better than the software supplied with the hardware So, go for the cheap consumer version (or second hand) and use decent free software

EDIT: But the Huey is easier to install and faster than the Spyder for display calibration

Matt

I took the plunge and bought a Huey today. I'm away from Monday to Wednesday so hopefully it'll arrive in time for me to play with it on Thursday.

I take it that this http://hoech.net/dispcalGUI/ is the way to go?
[i]Bodies: 1x K-5IIs, 2x K-5, Sony TX-5, Nokia 808
Lenses: Pentax DA 10-17mm ED(IF) Fish Eye, Pentax DA 14mm f/2.8, Sigma 17-70mm f/2.8, Pentax-A 28mm f/2.8, Sigma 30mm F1.4 EX DC, Pentax-A 50mm f/1.2, Pentax-A 50mm f/1.4, Pentax-FA 50mm f/1.4, Pentax-A 50mm f/1.7, Pentax DA* 50-135mm f/2.8, Sigma 135-400mm APO DG, and more ..
Flash: AF-540FGZ, Vivitar 283
MattMatic
Posted 19/10/2009 - 08:57 Link
Yes, that's the dispcalGUI. You also need to install ArgyllCMS first: http://www.argyllcms.com/

Argyll is command line based. Works on Mac, Linux and Windows. dispcalGUI provides a much easier way of calibrating, rather than fumbling around with loads of command line stuff.

At the bottom on the options, choose "Profile Type: LUT" for a better calibration (especially if the display hasn't got a very good black point). Be aware of the following points:
* It's a good idea to have the screen on for an hour before calibration
* LUT calibration can take an age (30 - 60 minutes on Medium quality)

Hope that helps!
Matt
http://www.mattmatic.co.uk
(For gallery, tips and links)
Edited by MattMatic: 19/10/2009 - 09:00
Smeggypants
Posted 22/10/2009 - 14:13 Link
Cheers Matt

I've had enough of command line madness from the old days of DOS.

My Huey Arrived today ( beat the postal strike my milliseconds it seems! ).

Anyway I tried it out with the bundled software and I wasn't impressed. it made things a lot worse. I actually had better results using my camera as described in posts above.

Using the Huey everything was washed out and had a hideous green tint.

I'm now going to try Mr Argyll
[i]Bodies: 1x K-5IIs, 2x K-5, Sony TX-5, Nokia 808
Lenses: Pentax DA 10-17mm ED(IF) Fish Eye, Pentax DA 14mm f/2.8, Sigma 17-70mm f/2.8, Pentax-A 28mm f/2.8, Sigma 30mm F1.4 EX DC, Pentax-A 50mm f/1.2, Pentax-A 50mm f/1.4, Pentax-FA 50mm f/1.4, Pentax-A 50mm f/1.7, Pentax DA* 50-135mm f/2.8, Sigma 135-400mm APO DG, and more ..
Flash: AF-540FGZ, Vivitar 283
MattMatic
Posted 22/10/2009 - 14:36 Link
Mr Argyll is definitely the way to go
http://www.mattmatic.co.uk
(For gallery, tips and links)
Smeggypants
Posted 22/10/2009 - 15:59 Link
I've been having a go with Mr Argyll in command line mode ) I couldn't' wait to set up the GUI add-on. I'll do that later.

What I'm finding is that I need to decide upon a target colour temperature for the monitor. Using Argyll without a target temperature gives me a far too warm display. like it's lacking in blue.
[i]Bodies: 1x K-5IIs, 2x K-5, Sony TX-5, Nokia 808
Lenses: Pentax DA 10-17mm ED(IF) Fish Eye, Pentax DA 14mm f/2.8, Sigma 17-70mm f/2.8, Pentax-A 28mm f/2.8, Sigma 30mm F1.4 EX DC, Pentax-A 50mm f/1.2, Pentax-A 50mm f/1.4, Pentax-FA 50mm f/1.4, Pentax-A 50mm f/1.7, Pentax DA* 50-135mm f/2.8, Sigma 135-400mm APO DG, and more ..
Flash: AF-540FGZ, Vivitar 283
MattMatic
Posted 22/10/2009 - 16:53 Link
Sigh... use dispcalGUI It really isn't hard.
My iMac is set to:
Whitepoint: Native
White Level: Maximal
Black Level: Minimal
Tone Curve: 2.4
Calibration Quality: High

Profile Quality: Medium; Profile Type: LUT

With those settings you should get a "correct" display. You can then go from there... but be warned! Your eyes may take some time getting used to a calibrated screen

Obviously you can set your whitepoint to something representative of the medium you are targetting (e.g. print). Do some Googling

Have fun!
Matt
http://www.mattmatic.co.uk
(For gallery, tips and links)
Smeggypants
Posted 22/10/2009 - 20:03 Link
I isntalled dispalGUI and I'm now running another session.

I'm trying:

Whitepoint: 6500k
White Level: Maximal
Black Level: Minimal
Tone Curve: 2.4
Calibration Quality: Medium

It's still got a while to go, it's running dispread.exe at the moment.

I'll let ya know how it goes
[i]Bodies: 1x K-5IIs, 2x K-5, Sony TX-5, Nokia 808
Lenses: Pentax DA 10-17mm ED(IF) Fish Eye, Pentax DA 14mm f/2.8, Sigma 17-70mm f/2.8, Pentax-A 28mm f/2.8, Sigma 30mm F1.4 EX DC, Pentax-A 50mm f/1.2, Pentax-A 50mm f/1.4, Pentax-FA 50mm f/1.4, Pentax-A 50mm f/1.7, Pentax DA* 50-135mm f/2.8, Sigma 135-400mm APO DG, and more ..
Flash: AF-540FGZ, Vivitar 283
Smeggypants
Posted 24/10/2009 - 15:46 Link
well I've had a couple of days playing with the Huey + Argyll/DispcalGUI and I'm still trying to find a calibration that I'm happy with.

I think part of the problem is the inability of my CRT monitors ( 21" NEC diamnondtron FE2111 ) to resolve the darker end of the greyscale. Without calibration the first 4 levels of this look black ...

Comment Image


Once calibrated I can resolve all levels but then the display lacks contrast and looks washed out.

I'm currently compiling some calibration curves using different levels of "Black output offset" to see if that helps.
[i]Bodies: 1x K-5IIs, 2x K-5, Sony TX-5, Nokia 808
Lenses: Pentax DA 10-17mm ED(IF) Fish Eye, Pentax DA 14mm f/2.8, Sigma 17-70mm f/2.8, Pentax-A 28mm f/2.8, Sigma 30mm F1.4 EX DC, Pentax-A 50mm f/1.2, Pentax-A 50mm f/1.4, Pentax-FA 50mm f/1.4, Pentax-A 50mm f/1.7, Pentax DA* 50-135mm f/2.8, Sigma 135-400mm APO DG, and more ..
Flash: AF-540FGZ, Vivitar 283
MattMatic
Posted 26/10/2009 - 09:03 Link
Did you set the profile type to LUT?
If you didn't - that's your problem
(My Toshiba laptop has a very poor black point, and only by using LUT does everything fall into place.)
HTH
Matt
http://www.mattmatic.co.uk
(For gallery, tips and links)

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