Where you combine values, you have flat areas.Where you have gaps (ie jumps in values) you can get "banding" in the image.So all in all you have lost 10 values, about 5% of the range.In the 127-255 range, things are worse, because we are mapping 127-255 to 137-255, so we are missing 10 "slots", so some of the 137-255 values will correspond to two values (or even three in the bad cases) from the 127-255 range.Some of the 0-137 values won't correspond to anything in the original 0-127 range, so you will have gaps. All the values in the 0-127 range are mapped to values in the 0-137 range.You make a rather minor brightness adjustment in your image, so mid-gray (127) becomes 137.When you are working with 8-bit per channel, things degrade very quickly. The real difference is in the processing. You won't see a difference usually because your screen electronics use 8-bit/channel (and in fact probably the whole chain between Gimp and the display is 8-bits). Just trying to lower file size without reducing resolution or detail by much. And don't worry, I'm definitely not messing with indexing. But what I'm getting is that unless there's MORE than the 16 million color limit in the original 16-bit image, then converting it into 8-bit won't change much. Okay, I'm not that techy so I might need a rephrase. (08-22-2021, 08:01 AM)rich2005 Wrote: 8 bit and 16 bit for RGB images are the number of bits per channel so 8 bit = 24 bits per pixel, 16 bit = 48 bits per channel/ Does this mean that if I don't index, no actual visible information is lost by converting it to 8-bit?Īs far as I know, colourcube is stuck in the past and is only 8 bit ( 24 bit 16 million colours) Obviously, the indexed version only has 256. Quote:Edit: Looking at the colorcube analysis, both the original 16-bit and converted 8-bit PNGs have the same amount of unique colors. and can 'dither' the boundary between colours to give an impression of a smooth transition. Converting from RGB to Indexed will try and make the best colormap from the image. Indexed Images are very different, each pixel is assigned a colour from a colormap, the colour map only contains 256 values so you only get what is available in the color map. Covert from 16 bit to 8 bit and colours are lost but it all depends on the image, it might not be as severe as it sounds. That determines the number of colours available. Does this mean that if I don't index, no actual visible information is lost by converting it to 8-bit?Ĩ bit and 16 bit for RGB images are the number of bits per channel so 8 bit = 24 bits per pixel, 16 bit = 48 bits per channel/ I'd really like to know how much information I'm losing if I switch to 8-bit precision, without indexing, after I'm already done editing the original 16-bit photo.Įdit: Looking at the colorcube analysis, both the original 16-bit and converted 8-bit PNGs have the same amount of unique colors. Does anyone know what actually happens to the photo if I switch to the 8-bit precision after I'm done editing? And what's the difference between just using 8-bit precision and using indexed colors, since I can see a VERY visible difference if I index the colors as well. It seems to me that if I edit a photo in 16-bit and then convert it to 8-bit precision after I'm done, it still makes it may smaller in size.and flipping between 16-bit and 8-bit via the history tab, I can't see an actual difference. However, I'm VERY interested in the reduced file size. I have no trouble with RAM usage, and I shoot a lot of my photos in 16-bit RAW format, so I edit photos with that. Online, it says that editing a photo with 8-bit precision is easier on a computer's RAM, and reduces file size. Just a couple questions that I can't seem to find the answer for online, so I figured I would ask here.
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