Req: Zone System compatibility

[photoken]

The Zone System (developed by Adams and Archer), although a great process for working with images in the era of film, paper and chemicals, is still valid in this day and age of digital imaging -- Thinking, Pre-Visualizing, and placing areas in exposure zones can always help in getting an excellent image.

The Curves adjustment is probably the most important tool we have in this regard, and I have a suggestion:
The curve area in the Curves adjustment is divided by a grid into 10 areas. If PL would divide that curve area into 11 areas, that would instantly make PL directly compatible with a Zone System of exposure compenstation.

[bkh]

Dividing the diagram into 11 columns doesn't give you the intervals of the zone system – and the division is dependent on the colour space used. For example. for sRGB, the zones map to RGB values as follows (assuming that Zone 5 is at 18% exposure) – note that the ranges become wider for brighter zones.

Zone 0 from 13 to 22
Zone 1 from 22 to 34
Zone 2 from 34 to 50
Zone 3 from 50 to 71
Zone 4 from 71 to 100
Zone 5 from 100 to 138
Zone 6 from 138 to 189
Zone 7 from 189 to 257
(Zone 8 from 257 to 348)
(Zone 9 from 348 to 469)
(Zone 10 from 469 to 631)

(Zone 8, and sometimes 9 and 10, are accessible only in raw files, otherwise you have to underexposure to be able to use the full range of zones, there are enough dark zones below 0 in a digital image.)

I wouldn't mind having a Curves adjustment panel which uses a logarithmic scale on both the x and y axes (divided into f-stops, independenly of the colour space used) – which would essentially correspond to the zone system.

Cheers

Burkhard.

[photoken]

Dividing the diagram into 11 columns doesn't give you the intervals of the zone system – and the division is dependent on the colour space used. For example. for sRGB, the zones map to RGB values as follows (assuming that Zone 5 is at 18% exposure) – note that the ranges become wider for brighter zones.

I don't understand how you arrived at this analysis of the current diagram, but I'll take your word for it.

I wouldn't mind having a Curves adjustment panel which uses a logarithmic scale on both the x and y axes (divided into f-stops, independenly of the colour space used) – which would essentially correspond to the zone system.

Yes, that's the functionality I was looking for. Having both axes using a logarithmic scale as you suggest would also keep the "line" depiction of the curve as the diagonal.

It seems to me that the current grid is purely arbitrary and doesn't serve any particular purpose. Using log scales as you mention and dividing the diagram into 11 zones would make the Curves adjustment a precision tool, compatible with the Zone System, and more useful for exposure compensation. Highlighting the middle Zone (V) with thicker grid lines would be a nice touch....