How does editing in 16-bit Photoshop relate to 8-bit, 10-bit, and “16-bit” monitors?
Asked 4/26/2017
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I edit photos in 16-bit mode in Photoshop to preserve more tonal precision and reduce issues like banding during adjustments. But Photoshop also has an option for 30-bit display output (10 bits per channel) on supported systems and monitors.
What is the relationship between a 16-bit image and an 8-bit or 10-bit display? If my monitor only shows 8 bits per channel, how can I still work meaningfully in 16-bit mode?
Also, some monitor specs mention 16-bit processing or 16-bit LUTs. How does that fit in if Photoshop and the operating system are not actually displaying a full 16 bits per channel to the screen?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
9y ago
2 Answers
6
When you work in 16 bits mode, the pixel data have 16 bits/channel, thus 65536 shades per channel.
Your display has 8 or 10 bits/channel, thus 256 or 1024 shades per channel.
The way you convert the source data to the display is by resizing the color space. You have different strategies called render intent.
The more simple, the perceptive intent, is a proportionnal resizing :
- the 0 value of the source data is matched with the 0 value of the display,
- the 65535 value of the source is matched with the 255 value of the display.
- the n value of the source is matched with the n × (254 - 0) / (65535 - 0) of the display.
This is assuming that the color profile of the picture (let's say sRGB) is the same as the display. If not, you have to adjust the gamut in addition (dealing with the color values that the display will never be able to reproduce physically) and the computation is not that simple.
If the display (Eizo 16 bits) has more shades than the source image, Photoshop probably sends 8 or 10 bits data and then, on the operating system or on the screen itself, some algorithm resize them to 16 bits by doing the opposite operation : the n value of the source is matched with the n × (65535 - 0) / (254 - 0) value of the display.
Originally by user51051. Source · Licensed CC BY-SA 4.0
user51051
9y ago
0
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They are different stages of the pipeline.
A 16-bit image in Photoshop means the image data has far more tonal steps per channel than an 8-bit image. That extra precision is useful while editing because curves, levels, and other adjustments can be applied with less rounding error and less risk of banding.
Your monitor does not need to display all 16 bits per channel for that to help. Before the image is shown, Photoshop/OS/GPU converts the image data to the display’s output depth and color gamut using color management. So a 16-bit source can still be edited advantageously even if the display is only 8-bit.
A 30-bit display path means 10 bits per channel are sent to the monitor, which can show smoother gradients than 8-bit if the whole chain supports it.
When monitor makers advertise “16-bit,” that usually refers to internal processing, such as a 16-bit LUT or internal color calculations, not that the panel is literally showing 16 bits per channel to your eyes. The monitor uses that higher internal precision to map image values more accurately to its actual panel output.
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