Dropper Tool and values for RGB and TIF

[hartpaul]

Was explaining to a friend about shades of colour -- human eye has Red, Green and Blue sensitive cones and each can detect about 100 shades givin a combined total of about 1 million shades that we can normally distinguish, well within the 16 million shades that a jpeg can show (256 x 256 x 256) or the 64,000,000,000 shades (4096 x 4096 x 4096) that a TIF can show.

I used the eyedropper on a jpeg to show how the values went from 0 to 255 for each of Red Green and Blue, but when I went to a TIF expecting the RGB components to go from 0 to 4096 it showed 0 to 65535. To me this is an inaccuracy in the eyedropper tool at least for Tifs

I was trying to emphasise that while we may think that by having a greater range of shades available in the TIF we can produce richer images with more variety of images it all boils down to the lowest common denominator - that our eyes are not capable of determining a range of shades more than 1 million.

Try this test -- set your foregrond colour to RGB 128,128,128 grey and using the paintbrush tool draw a line. Then double click on the foreground box in the materials palette and change say the red value to 129 and draw another line overlapping the first one. Repeat increasing the red value and see when the difference in shading becomes obvious to your eyes. For me I had to go from 128 to 135 before I could recognise a difference so that is 7 values which look the same to me. So I cannot see even the 16 million colours of a lowly jpg let alone the small differences in a Tif.

[wds937]

I used the eyedropper on a jpeg to show how the values went from 0 to 255 for each of Red Green and Blue, but when I went to a TIF expecting the RGB components to go from 0 to 4096 it showed 0 to 65535. To me this is an inaccuracy in the eyedropper tool at least for Tifs

PSP and some image file formats support a color depth of 16 bits/channel. The Dropper Tool will show these values ranging to 65535. The next step down is 8 bits/channel, which will show values ranging to 255. I don't think PSP supports anything in between that would allow values ranging from 0 to 4096.