Color Deficiency Type

In this drop-down list you can select among:

Protanopia

Don't be afraid of this barbaric name. It is made of three Greek roots: “op” for eye, vision; “an” for negation; “proto” for first, the first color in the RGB Color System. So, protanopia is vision deficiency of Red color. It's the well-known daltonism.

Protanopia is actually more complex: red but green also are not seen. Protanope remains sensible to yellow and blue. Besides, there is a loss of luminance and a shift of hues to short wave lengths.

Deuteranopia

Green vision is deficient. Deuteraopia is actually like protanopia, with a loss of green and red vision, but without luminance loss nor hue shift.

Tritanopia

Blue but also yellow are deficient. There is actually a loss of Blue and Yellow vision; Red and Green are preserved, with luminance loss and a shift of hues to long waves.

Examples

Figure 10.44.  Example of protanopia on a text

As you can note, a red-blind person will not see your red (255,0,0) text on a black (0,0,0) background. You will have to change color text. Daltonism is frequent in the population.

Figure 10.45.  Examples of the three vision deficiencies on an image

From top to bottom: normal vision, protanopia, deuteranopia, tritanopia. It seems that filter doesn't give a fair reflection of medical data. In deuteranopia yellow is shifted to red. In tritanopia, green should be present: it is replaced by blue...

Intent

You can apply the filter you will select according four methods:

Perceptual

The Perceptual method is the best to reproduce photographs on ink-jet printers. Adjustment is minimum and visual relationships between colors are preserved so that they are perceived in a natural way by the human eye.

Relative Colorimetric

This method compares source white and black points to those of destination gamut and scales hues accordingly. It well suits printing photographs on ink-jet printers. It tends to darken result: compensate black point is often necessary.

Saturation

This intent preserves the saturation values of original pixels. It is used for documents where color punch is more important than their accuracy, as for logos. Continuously variating colors are badly represented, with color leaps.

Absolute Colorimetric

This method leaves colors inside the destination gamut unchanged. Colors out of gamut are cut out. Color accuracy is preserved, but color relationships are not.

Profile

This text box and its browser button allow you to select the profile you want on a storage device.

Black Point Compensation

Black point Compensation scales hues from black point of the original image when result is too different from original.