verify calibration

[shacharoren79]

hi,

i'm trying to calibrate a 30" apple cinema display monitor with the new i1 display pro.

i ran the very basic calibration on it with CCFL as monitor type, 120 for luminance and D65 as a white point.

it finished the process rather quick and insert the profile into the OS (windows 7)

now when i work on lightroom i feel like the monitor is a bit reddish!

the gray background that i use in lightroom looks bit reddish.

is there a way to verify that my calibration was good?

as i understood people take the time until they achieve a good calibration. how can actually one can tell if one calibration was better than the other.

thanks. 

[digitaldog]

now when i work on lightroom i feel like the monitor is a bit reddish!
the gray background that i use in lightroom looks bit reddish.

IF your prints and display match, you have your verification. If it is too red, you need to adjust the white point.

[shacharoren79]

i haven't got to the point of matching to my prints as i print at an outside lab.

secondly, i don't want to use my "eyes" to judge the redness of the monitor,

that's why i was using a colorimeter.

i'm saying it looks reddish, but i'm not sure. how can i be sure without trusting my eyes?

[Rainer Ots]

If you make a black to white gradient in photoshop is it all reddish? Or only parts of it?
If only a part of it is reddish then that would imply a bad calibration.
Also have you used monitors calibrated to D65 for a long time? D65 can look extremely weird at first if you are used to quite blueish defaults many monitors have.
Have you tried using native white point?

[digitaldog]

i haven't got to the point of matching to my prints as i print at an outside lab.

You don’t want them to match? What’s the point of calibration then?

secondly, i don't want to use my "eyes" to judge the redness of the monitor,

They when even use a color display?

that's why i was using a colorimeter.

You use such an instrument to produce consistent calibration once you hit the ideal target calibration aim points (White Point, Luminance, and if possible, contrast ratio).

[shacharoren79]

well Rainer,

as a beginning this is the first time i'm trying to calibrate, so no reference.

second, the BW gradient did show only parts reddish like.

so i tried going to the native white point and now it looks much better as far as the reddish look, BUT,

when i zoom in the gradient in PS i can still see something uneven (reddish looks) in the pixel level.

and once again i find myself judging the monitor with my eyes.

what am i doing wrong?

[Rainer Ots]

You have to decide whether you trust your eyes or not.
If you don't then just believe what the calibrator is doing and don't try to judge it with your eyes.
If you do trust your eyes then try to find out what the problem might be.

[Tim Lookingbill]

well Rainer,

as a beginning this is the first time i'm trying to calibrate, so no reference.

second, the BW gradient did show only parts reddish like.

so i tried going to the native white point and now it looks much better as far as the reddish look, BUT,

when i zoom in the gradient in PS i can still see something uneven (reddish looks) in the pixel level.

and once again i find myself judging the monitor with my eyes.

what am i doing wrong?

You may need to go several rounds of recalibration placing the colorimeter in different locations on the display until you get a completely neutral grayramp with no red/green banding issues viewed in Photoshop.

I had to do this calibrating with the original i1Display package on my 2004 G5 iMac which uses a similar CCFL panel as your Apple display. i1Display has a different interpretation on what D65/6500K color cast hue looks like when choosing it as a target in the software as apposed to calibrating to native WP. i1Display target 6500K makes my entire G5 iMac screen look noticeably pinkish blue or a kind of magenta because its native looks so green/yellow by comparison.

When I set the iMac to native I still got a reading of 6500K from the software. Go figure.

It boils down to just picking a color cast that yields the smoothest grayramp. I've done this on two CCFL panels that have the green/yellow native WP but I have to go several rounds. I even got good results after several rounds going with i1Display's pinkish/blue 6500K target WP but it just got too uncomfortable to edit images.

[shacharoren79]

so how did you know finally that you nailed it?

i mean the only reference is looking at a gradient in PS and see that it is as natural as possible?

[Nigel Johnson]

…i1Display target 6500K makes my entire G5 iMac screen look noticeably pinkish blue or a kind of magenta because its native looks so green/yellow by comparison.

When I set the iMac to native I still got a reading of 6500K from the software. Go figure.

The correlated colour temperature reading, in your case 6500 K, only takes account of approximately blue-yellow colour changes and does not take account of magenta-green colour variation. Hence, two different whites may have a correlated colour temperature of 6500 K but differ in the amount of magenta-green; in your case the native white has a green tint whereas the calibrated screen should be neutral (it probably only looks magenta because of the greenness of the uncalibrated screen although this might also be a result of the colour of the room lighting or decor).

The fact that correlated colour temperature does not uniquely define a white is also the reason why raw convertors such as Lightroom and Camera Raw have both a temperature slider (blue-yellow) and a tint slider (magenta-green) in their white balance settings.

Regards
Nigel

[Tim Lookingbill]

so how did you know finally that you nailed it?

i mean the only reference is looking at a gradient in PS and see that it is as natural as possible?

Sorry, I forgot to mention that I load as a desktop pattern a grayramp that I made applying a gradient in a new document in Lab space and then posterizing the top half to 21 steps. Since Mac OS is colormanaged right down to the desktop pattern you don't have to have Photoshop open.

The reason for making the gradient/21 stepwedge desktop pattern in Lab is that it distributes a smoother linear role off into the shadow right down to the last step right next to black. It also provides less banding as the midtone roles off into black. Gradients created in 2.2 gamma encoded space like AdobeRGB will always show some slight banding as there are fewer steps used to distribute shadow detail into the shadows due to an 8 bit video system.

You're never going to completely get rid of all banding in a gradient made in Photoshop unless you get a display that does this directly through the hardware LUT of a higher end display like an Eizo or NEC which allows this.

The thing is I've never had or seen one of those displays to verify this. I have to rely on Andrew Rodney and others who can afford those type of displays for confirmation.

I can tell you in my ten years relying on 8 bit video manipulation to get a grayramp to look linear through calibration with minimal banding on a sub $700 CRT and LCD, it's never been a problem in getting screen to print matches, thus that's how I know I nailed it.