08-22-2021, 01:04 PM
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). The real difference is in the processing.
When you are working with 8-bit per channel, things degrade very quickly. Consider this:
In 16-bit this can happen to, but to a much lesser extent
Also, in 8-bit, there is a "gamma-compression", which means that the actual values are corrected (power 2.2) to give more range to the darks. This hjelp to keep details in the shadows, but at the expense of the lights.
In practice, Gimp now works in high-precision internally (32-bit floating-point), so the image precision only tells it how to store intermediate values (ie, your layers, channels, selections). If your image is 32-bit floatin-point, you skip conversion steps and the processing can be faster.
Last, to give you an idea the usefulness of using high-precision even for your layers:
The high precision in 2.10 avoids some artefacts (less moiré in 2.10 even in 8-bit) but the result is still choppy, because the bump map could only have 256 values (the bump map was produced by filling a feathered circle selection).
When you are working with 8-bit per channel, things degrade very quickly. Consider this:
- You make a rather minor brightness adjustment in your image, so mid-gray (127) becomes 137.
- All the values in the 0-127 range are mapped to values in the 0-137 range. Some of the 0-137 values won't correspond to anything in the original 0-127 range, so you will have gaps.
- 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.
- So all in all you have lost 10 values, about 5% of the range.
- Where you have gaps (ie jumps in values) you can get "banding" in the image.
- Where you combine values, you have flat areas
In 16-bit this can happen to, but to a much lesser extent
Also, in 8-bit, there is a "gamma-compression", which means that the actual values are corrected (power 2.2) to give more range to the darks. This hjelp to keep details in the shadows, but at the expense of the lights.
In practice, Gimp now works in high-precision internally (32-bit floating-point), so the image precision only tells it how to store intermediate values (ie, your layers, channels, selections). If your image is 32-bit floatin-point, you skip conversion steps and the processing can be faster.
Last, to give you an idea the usefulness of using high-precision even for your layers:
The high precision in 2.10 avoids some artefacts (less moiré in 2.10 even in 8-bit) but the result is still choppy, because the bump map could only have 256 values (the bump map was produced by filling a feathered circle selection).