Quote:
Originally Posted by j.p.s
...But pupil dilation is likely significantly more inside, so a big chunk of that 30:1 ratio goes away. If the color temperature of the display is significantly higher than an overcast sky, the blue brightness ratio comes down even more, and might even go below 1. So I don't think the 30 hours inside for every hour outside is a good estimate (for blue light).
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The 30 times exposure estimate was referring to the exposure of the eye, not a comparison of the environment intensity. Also, just in case of any other misunderstanding, when I referred to latitude, etc. that was not inferring that the color temperature of the sky changed with it but that the intensity of the light radiation varies with it.
If pupil dilation is more then it means that the intensity of the light radiation is less i.e. the light source is weaker, so the iris manages the light entering the eye accordingly; one can assume under normal indoor and exterior lighting conditions the iris manages the light so that the intensity entering the lens is approximately constant (in the same way as a camera works if speed is fixed and exposure controlled by the diaphragm alone).
It is very unlikely that the color temperature of the display is higher than that of the sky. Because:
The color displays that we are ever likely to employ use the sRGB Color Space and the sRGB White Point is 6500Kelvin and most displays will be set around that when delivered. As most displays are used inside it is more likely that if the user were to reset the color temperature it will be set warmer (say towards 5500Kelvin) than cooler (Note that when talking about displays "warmer" is normally taken to mean towards the red, and "cooler" meaning towards the blue, whereas in fact, in black body color temperature terms, blue is "hotter" which can lead to some confusion). If a display is used outside it may be set at a higher color temperature (say towards 7500Kelvin). All that assuming the user actually enters the display's setup and manually changes the color temperature, something the vast majority of users never do unless the display is on a simple device that just gives a "normal" and a "warm" checkbox selection (rather than the incremental adjustment one has on a monitor, say) in which case they can never set a color temperature greater than around 6500Kelvin. Some months ago I actually gathered up all the tablets and phones around here and with their displays set to normal (i.e. not to "warm" or "blue filtered") they were all almost exactly 6500Kelvin. I also checked 2 monitors and 2 notebooks with the same result (those all were still at those factory settings as they are used for photography).
The color temperature of an overcast sky (as any well versed photographer will know) varies between 6500-7500Kelvin and that of a blue sky may exceed 9000Kelvin. So, it can be easily seen that it is very unlikely that displays in in typical uses will have a color temperature higher than that of the external environment.