Setting Gamma (brightness and contrast)
Step back from your monitor or squint.
One of these numbered boxes is about the same shade as the surrounding
This is your "screen gamma".
Most photographer's web pages are designed for 1.8 Gamma
(TV monitors are calibrated for 2.2 Gamma).
If your monitor is much off from 1.8 Gamma, you can adjust your
contrast control to bring it closer. You can juggle the brightness
and contrast to get the correct gamma while getting the brightness
The image below should appear as a rainbow starting and ending with
There should be a smooth transition from color to color with no
banding and no little dots.
The following image is NOT a smooth transition. If you have only
limited colors ( i.e. 16 levels of colour) the above rainbow would
look something like this (colours dithered, mixed dots):
or like this
If your picture
looks like either of the bottom two rainbows above, you need to
check the settings in your computer for numbers of colours (for
Windows users, right click the desk top, select Properties, then
Settings, then select colour settings).
acceptable number of colours should be 256 but 16 bit, 24 bit, 32
bit, or "millions" of colours is the preferred setting
(this can slow down games).
Ok, that's colour,
now let's deal with gamma, brightness and contrast.
Below are some
boxes, one should be absolute black. Nothing on your monitor should
be darker than the black box. Look at the black border around your
monitor. It should be as black as that box. And nothing should be
lighter than the white box.
The two grey boxes and compleatly neutral shades (the same values
for red, green and blue) therefore should have no colour tint to
them. If you can see a pink or blue colour tint in these shade,
adjust the colour settings on your monitor until they appear neutral.
can be used to judge whether your monitor is adjusted for best viewing
This target was designed to allow computer users to adjust the contrast
and brightness of their computer monitor so that graphic images,
such as scans of photographs, textual documents, or maps, look their
best. After making the gamma adjustments above, the target below
should be clear.
The target consists
of two scales of shades of gray ranging from white to black. The
top scale illustrates the full range of tones that a computer monitor
can represent when set to 256 or more colors (8 bits or higher).
The lower scale consists of three sets of shades, including two
dark shades, three middle gray shades and two light shades. The
shades in each set on the lower scale should be just distinguishable
from the adjacent similar shade(s).
and brightness control on your monitor adust the appearance of the
top scale. You should see a broad range of shades from white to
black and all seven shades on the lower scale should be distinguishable.
The following are the exact target shades from the
National Archives and Records Administration's Monitor Adjustment
11 Shades from White (R 255, G 255,
B 255) to Black (R 0, G 0, B 0)
7 Shades. 2 White, 3 Grey and 2 Black.
Each should be just distinguishable from the adjacent similar shades.
Calibrate your monitor using Colour Vision OptiCal at the (fairly
well accepted) PC normal gamma 2.2, this means that on your monitor
you can make out the difference between all of the (computer generated)
grayscale blocks below.
It's recommend that you should be able to see the
difference (at least) between X,Y and Z and ideally A,B and C.
Note that this is not in agreement with the 1.8 setting above. Everyone
seems to agree that a setting between 1.8 and 2.2 is where your
gamma should be set. In any case, you should be able to see the
difference in the individual sections in the grayscale block.