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Zone System help needed

Doug Kerr

Well-known member
I never use the Zone System for exposure planning, but of course my work on exposure metering brings me into contact with it here and there.

I am mystified by the following.

Conceptually, the full Zone System range comprises 11 zones, identified as 0 through X. Often only zones 1-IX are actually considered.

Purportedly, the zones are at intervals of one stop (or a 2:1 difference in exposure).

Often Zone V is spoken of as sort of the "anchor" of the system, intended to receive objects of a "mid gray" reflectance, often thought to be a reflectance of perhaps 18% (and accordingly, the photometric exposure for such items should be, in a digital context where this has clear meaning, something like 18% of saturation).

But if we assume that the top of zone X would correspond to saturation, then the middle of zone V (5.5 stops down from that) would have a reflectance implication of about 2.2%, not close at all to 18%.

If we think of a "zone V placement" as receiving a photometric exposure of 18% of saturation, then the brightest object we could accommodate (it would get a photometric exposure a little less than saturation) be thought of as ending up in zone VII.

What am I missing here?

Thanks.

Best regards,

Doug
 

Asher Kelman

OPF Owner/Editor-in-Chief
Doug,

I think it's most helpful to consider the Ansel Adams-Fred Archer zone system from the standpoint of visible detail in the brightest and darkest parts of the scene. So where does there appear to be detectable texture and detail in the blacks and then in the whites. These establish Zones III and VIIII find this simplified explanation useful to remind me of the zones.

BTW, how are you using "saturation" here, as there is no hue to equal RGB components?

Asher
 

Doug Kerr

Well-known member
Hi, Asher,

I think it's most helpful to consider the Ansel Adams-Fred Archer zone system from the standpoint of visible detail in the brightest and darkest parts of the scene. So where does there appear to be detectable texture and detail in the blacks and then in the whites. These establish Zones III and VIIII find this simplified explanation useful to remind me of the zones.
Thanks.

The reference is nice.

It basically says there are no zones VIII, IX, and X. That works.

BTW, how are you using "saturation" here, as there is no hue to equal RGB components?

I was speaking of saturation photometric exposure, the highest photometric exposure to which the sensor can uniquely respond, not saturation as an aspect of chromaticity.

Sorry for any confusion.

Best regards,

Doug
 
Doug,

I think it's most helpful to consider the Ansel Adams-Fred Archer zone system from the standpoint of visible detail in the brightest and darkest parts of the scene. So where does there appear to be detectable texture and detail in the blacks and then in the whites. These establish Zones III and VIIII find this simplified explanation useful to remind me of the zones.

Hi Asher,

And in addition, I believe it was mostly based on film negative captures, and with film processing in mind. I do not think it is as valuable a system with the post-processing capabilities we have nowadays. The concept of 'placing' a certain scene brightness at a certain receiving medium level of density is somewhat moot, I would say. We can do much more and do it better with the tools we have today.

Cheers,
Bart
 

Doug Kerr

Well-known member
Hi, Bart,

And in addition, I believe it was mostly based on film negative captures, and processing in mind. I do not think it is as valuable a system with the post-processing capabilities we have nowadays. The concept of 'placing' a certain scene brightness at a certain receiving medium level of density is somewhat moot, I would say. We can do much more and do it better with the tools we have today.

A good point.

And thus I should not worry that "Zone V" has an impossible definition!

One thing I have learned over the years is to ignore anything related to photographic exposure and/or metering that has "18%" in it.

Best regards,

Doug
 
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