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:::Why I saying "If human eye is capable to adaptation", because human eye iris size changing can be [[Rudiment (disambiguation)|rudiment]], because at strong light hard to tell difference between 1 and 5 (from 0-255 possible if 5 appears at strong weak light and 1 at strong light). But more than this is, that strong light, especially sun light by passing into eye iris through lens reflecting from eye iris and eye white "ball" thing and then by physics laws light passing from one matter to another (from eye lens to air) makes light reflection first from iris and white part of eye and then this light goes, where eye lens and air intersects and reflects from air back to iris (you can check how laser pointer reflecting from air if you direct it into window). So this from air reflection in eye lens probably makes most, if not all, light blooms, glows, glares and so on and so pretty weak colours (say from 0 to 20-50 from 0-255 possible) are overgrayed (overlighted, overtaken) with this strong light refection inside lens from air. And even from iris itself due to not ideal flat surface of eye iris, light from strong riris illuminated point goes to near bumpy iris receptors and very weak light near strong light is mixed with strong light shining halo, glare. Also iris physical size difference not necessary must give 5-7 times bigger sensitivity at maximum eye iris size than at minimum eye iris size, but can give only 2 or 1.5 or 1.3 times bigger sensitivity at maximum eye iris size than at minimum eye iris size (this would mean, that monitor maximum white colour is 1.3-2 times weaker than white paper illuminated by sun and that lamp light at 1-3 metters distance not so weak compare with sun light, but then two such lamps must stronger illuminate than direct sunlight). So if, say, 2 times stronger weak colour at maximum eye iris size than at minimum eye iris size, then at maximum eye iris size human seeing 1-128 (from 0-255 possible, 0 is black) and at minimum eye iris size human see 2-255 (from 0-255 possible, 0 is black). But say human eye, probably not selecting only this two ranges or 1-128 or 2-255, but between also, like 1.5-191 and hard to see difference and hard to tell if there is some darker objects at strong light (or near strong light/luminance) due to eye iris adaptation or due to blanking effect of various blooms and glows due to reflection light from air inside eye lens. And at all colours comparison is hard task even if they are on monitor separated by black space and one is RGB(255:0:0) and over RGB(191:0:0), then if they not near each over hard to tell which is which. Maybe iris size becoming not rudiment only when it is from average to big and from average to small nothing changing at all, etc.
:::BTW I make all possible tests to see if red or green or blue turning to gray if this basic colour is very very weak (need to have monitor with big contrast ratio, some stupid CRT monitors can be even better with too big contrast ratio, that less than 50 is not seen, so need to do display driver software contrast and brightness calibration if you still want to use it). So RGB colours if they are very very weak then from first look it's harded to tell diference between blue and green and much easier between red and any over, but don't matter how weak they are there still possible to say colour at any time with 90-99% correct answer, especially for red and if all weak colours of red, green and blue a displayed together. Specular highlights of all 3 colours and threshold of colour RGB(1:0.4:0) makes it say red raver than orange so number of possible colours decreasing in dark and if object is of two mixed channels RGB, then stronger channel will be seen only at very weak light and weaker will be under threshold of visibility. They are pretty weak so need concentration, maybe thats why hard to recognise colours in dark. So on monitor either you see ver very weak colour of separate chaneel red, green, or blue or don't see nothing at all at night. So don't dare to say about some gray colours bullshit at night, that you have something in eye to see everything monochrome. Dark colours just look dark and thats how it is. If you want to look in game at night, then specular highlights must dominate of material, but this in most cases comes naturally and especially and most LCD monitors with small contrast 300:1, there even 0 shining like 30-50 on monitor with big contrast like 1000:1 or bigger. So such monitors with small contrast better suited to use at day and of course this LCD led light still almost overcoming number 3 or 5 or ten so you still don't see this weak colours or if see they not pure red or gree or blue, but they turned from pure red or green or blue to such like they strong analogs RGB(255:200:200) for red, RGB(200:255:200) for green, RGB(200:200:255) for blue, so there no need in game to simulate gray for dark illumination, because LCD monitor Led backlight and room light graying weak colours pretty much itself already. But I have to admit, that with too big contrast monitors turning all colours spectrum little bit in direction into 6 basic colours, like my unmodified algorithm, red, green, blue, cyan, yellow, pink, because 128 is no more two times weaker than 255, but about 2.2 times and 64 is not 2 times weaker than 128, but about 2.5 times. http://imageshack.us/g/827/rgbcolorsdark2.png/
:So contrast is each pixel color multiplication by some number (or division). Brightness is some number addition (or subtraction) to all pixels colours. And if you want use combination of brightness and contrast that line in AMD display drivers control center in up right corner would be precisely in right upper edge and bottom of line would be higher than in bottom left edge, then you need to brightness add 2.55 more, than from contrast subtract, for example, brightness=100, contrast=100-100/2.55=61 (defaults brightness=0, contrast=100).
:Now I tell you about gamma algorithm, which used widely as brightness and contrast. Gamma can be controlled by changing <math>k_g</math>; <math>0.5<k_g<3.5</math>. Gamma algorithm is this:
:<math>final.rgb=(color.rgb)^{1/k_g}.</math>
:Gamma algorithm almost the same as this algorithm "final.rgb=color.rgb*2/(1+color.rgb)" if compare with <math>k_g=2</math> or this "final.rgb=color.rgb*3/(1+2*color.rgb)" if compare, when <math>k_g=3</math>, but gamma in both cases increasing colours values little bit more, then those two respectively.
:And I admit, that for monitors with very big contrast ratio like 1:10000, little bit of gamma can correct colours ratio for example 255 must be 2 times brighter 128; 128 must be 2 brighter than 64; 64 must be two times brighter than 32 and so on. For big contrast monitors 64 is about 3 times brighter than 32; 32 is about 4 times brighter than 16. You must see the same colour don't matter if it is RGB(255:100:0) or RGB(128:50:0) or RGB(64:25:0).
:For HDR gamma can be used for compressed luminance:
:<math>final.rgb=(color.rgb)^{1/2}.</math>
:But in this way you will get colours graying, because orange colour will become almost like yellow, so algorithm should be this:
:<math>final.rgb=color.rgb / sqrt(max(color.r, max(color.g, color.b)));</math> 0<color.rgb<1. Function "sqrt()" is square root in programing language (HLSL). Function "max(,)" choosing bigger number from two numbers. Compressed luminance is good for adding weak and strong light and don't get overbright light; and weak light still be looking pretty strong alone. But then why need such things like light attenuation so perhaps better use normal HDR without compressed luminance. BTW sky light is blue, lamp light is yellow, together white, thats how they not overbirighting each over perhaps.
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