Monitor Calibration Tools

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 grid.

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 you want.

Colors
The image below should appear as a rainbow starting and ending with red.
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 (colour bands):

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).

The minimum 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.

Monitor Adjustment Target

This target 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).

The contrast 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 Target

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.

Another Option
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.

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