Luminous Landscape Forum
Raw & Post Processing, Printing => Digital Image Processing => Topic started by: Irwin on January 19, 2008, 06:40:12 pm
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When profiling an LCD does the screen brightness matter or will the calibration take brightness into account ?
I can think of reasons why both might be true so, obviously, I don't know.
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When profiling an LCD does the screen brightness matter or will the calibration take brightness into account ?
I can think of reasons why both might be true so, obviously, I don't know.
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Yes it matters! At the default 75% on mine the screen is so bright that the prints all come out too dark. I'm now down to 22 or 23% for 125.9cdm (according to my eyeone!)
Mike
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When profiling an LCD does the screen brightness matter or will the calibration take brightness into account ?
Yes it's important. Adjust to 120/cdm and see how it works for you...that's what works for me.
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What I do is create a 40 step wedge in PS (gradient then posterize) and adjust the brightness and contrast to give me as much apparent different in the bottom and top couple of wedge as possible.
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What I do is create a 40 step wedge...
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Tim,
Why 40 ?
-Irwin
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I should add that on my three day old 23" ACD, turning the brightness as far down, or as far up, as it will go still lets me see a difference between areas 1 and 2 and area 39 and 40. It's more obvious with the brightness at maximum.
Why not 255 steps ?
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The luminance target you choose should be based on your ambient viewing conditions. If you work in a cave you will not like a monitor at 140. if you work in a photostudio you may find 120 too dark. It has to be based on real live conditions. There is a proportional relationship and some ability to adapt to various conditions. It is also possible to see tonal separation as suggested above at more than one luminance level so that has little bearing here. I would start at 120 in dim but not dark ambient conditions. If you get a good print to screen match, assuming you have a good print profile then you are in the neighborhood. If not you need to assess both your lighting and monitor levels and decide which to modify. There is no standard.
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When profiling an LCD does the screen brightness matter or will the calibration take brightness into account ?
I can think of reasons why both might be true so, obviously, I don't know.
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And to further answer this question, screen luminance should be set to match the your target luminance either before profiling or during using ddc like hardware control. The more you adjust the monitor brightness to match your luminance target the less will be done in the video card.
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Tim,
Why 40 ?
-Irwin
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Mostly arbitrary, but 20 (ie 5%) doesn't seem to allow for sufficient differentiation in the bottom-most and top-most wedge. Once I've set brightness and contrast by eye to a 40 step wedge, I can see pretty well see one step gradations between 0 0 0 and 100,100,100 (actually the blacks aren't apparent until 98).
Going from memory of a method Michael described in his review a few years ago of the Sony Artisan, you can test the final results something like this...
Create a white 1000x1000 image (size is arbitrary) select the left half and turn off the marching ants. Create a curves layer (select pigment/ink% under curve display options) and select the bottom left point, using the up arrow you can move that point up one increment at a time. I can see the difference in left and right with output of 1 and input of 0. For the blacks fill the selection with black, invert the selection, hide the "ants" again. Drag the bottom left point up to the top and both halves will be black, (output 100, input 0) incrementally drop the output using the cursor and see at what point you can detect a difference between the 2 halves. If Pigment/ink% isn't selected just use the opposite end points.
This worked well for my Dell 1420 laptop. Of course what you can see in print is a whole different issue.
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The ducks you need in order are not only the ambient light around the display but the means in which you'll view prints (assuming your goal is to view a print and the display and get some reasonable match). The Ambient light can be quite different from the viewing booth but it needs to be low (it actually can't be too low, it can be too high). This also affects the perception of contrast ratio of the display to print matching: In a pitch black room, the black calibration of your display is obviously unaffected. As the ambient light increases, it can't not in some way strike the display and affect black and this the contrast ratio which ideally matches the print. So, lower is always better (unless the light is so low you can't see anything and start bumping into the furniture). You're far better off aiming for luminance that matches visually how you'll view the prints, the luminance of the viewing box.
http://www.ppmag.com/reviews/200411_rodneycm.pdf (http://www.ppmag.com/reviews/200411_rodneycm.pdf)
Most new, LCD's out of the box are going to have a tough time running at 120cd/m2; too low. In fact, they really need a few hundred hours to stabilize and provide the ability to calibrate even close to that low value.
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Create a white 1000x1000 image (size is arbitrary) select the left half and turn off the marching ants. Create a curves layer (select pigment/ink% under curve display options) and select the bottom left point, using the up arrow you can move that point up one increment at a time. I can see the difference in left and right with output of 1 and input of 0.
You need to Assign the display profile to this document. That's critical to the test:
http://www.ppmag.com/reviews/200412_rodneycm.pdf (http://www.ppmag.com/reviews/200412_rodneycm.pdf)