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Using Your Camera To Check Monitor Luminance
One of the most common complaints that we hear about matching the print to the
monitor image is that the prints are too dark. Usually the fault is not with the
print but with the monitor luminance (brightness). If the monitor is too bright,
you will invariably reduce the image brightness to make it look "right". Result
- dark prints.
The factory settings for modern LCD monitors are always far too bright for photo
editing so, unless you use a hardware calibrator to set luminance, it is
worthwhile spending a few minutes to check that you are at least in the right
ball-park. A good quality camera will allow you to do this.
If you are reasonably confident that your camera gives correct exposure, follow
this procedure to check or set your monitor luminance.
| 1 |
In your image editing application, open a new, blank document with a
white background. Open this document in full-screen mode so that most of
the screen is filled with white.
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| 2 |
Set your camera to manual focus and set the focus to infinity. Do
not use a close focus mode because this will change the effective
aperture of the lens and your readings will be inaccurate.
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| 3 |
Set your camera as follows: ISO 400; Aperture Priority; f/5.6
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| 4 |
Point your camera at the centre of the screen at
close range (50cm or less) so that the viewfinder is completely filled with white. Don't
worry that the image is completely out of focus - it will not affect the
exposure reading. In fact, you should find that moving the camera back
and forth between 20cm and 50cm does not affect the exposure reading.
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| 5 |
Note the exposure reading. This will normally be displayed as a
fraction of a second - in other words, 1/60th
will be displayed simply as 60. This displayed number will be the luminance of
your monitor in candelas per square metre (cd/m2)
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| 6 |
The recommended luminance for photo editing is 120 cd/m2 so you
should adjust your monitor brightness to get an exposure reading of
between 100 and 125. (1/100th to
1/125th) |
Naturally, this procedure will not guarantee you a precise
measurement of luminance, but it is at least objective. We have no innate
reference for luminance so any measurement technique is probably better than
doing it by eye.For some monitors the lowest achievable luminance will be
higher than 120cd/m2; the iMac is one well known
example of this. If your monitor cannot be set to 120cd/m2
don't be tempted to use one of the software methods to reduce the luminance.
These methods usually reduce the number of colours that you can display, and may
well produce colour banding where smooth colour gradients have visible steps.
Better to live with the higher luminance and adjust to it mentally!
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