The scene contains high key highlights (a X/10 on Ansell's System PLUS Black (0 on Ansell's).

Your subject - a mountain - is a mid range (5 - Ansell again).

To get the best exposure in the photograph you spot meter (with a handheld meter) say the 10, the 0 and the 5.

Meter Readings: 0 = 125 at f1.4 10 = 125 at f8 5 = 125 at f4

[For this discussion, I'm ignoring my camera and the matrix meter mode, as I am learning about handheld meters to hopefully get a better outcome and more often.]

Questions: I 'hear' that one combines these three figures, in some fashion, and takes the square root of the same?

If this is correct? What's the best method to ensure correct exposure, as best as possible, for the entire scene? Or is this simply not possible?

  • With only five stops between your desired zone 0 and your desired zone X, this one is pretty easy with pretty much any digital camera and almost any type of film. It's only five stops! You can miss the center by a couple of stops in either direction and still have room for error. – Michael C Jan 9 at 7:21
  • 1
    With film, we (and Ansel Adams) say to expose for the shadows and develop for the highlights. With digital it's the opposite: We expose for the highlights and develop for the shadows. To get the cleanest digital file with which to work, expose so that Zone IX (that is, the brightest thing in the frame that you desire to show any details - Zone X in Adams' system is pure white and has no details) is just short of clipping. You'll need to test your camera to see how many stops above 18% (which is what the meter wants everything to be) that is. It will be more stops for raw than for JPEG. – Michael C Jan 9 at 7:30
  • Keep in mind that Zone X is not a specific brightness, it is the brightness which you select at which anything that bright or brighter should be pure white in your photo. Likewise, Zone 0 is not a specific (lack of) brightness, either. It is the brightness in the scene, along with anything else that is even less bright, which you decide can be depicted as pure black in your photo. – Michael C Jan 9 at 7:34

The problem: (This is likely both over simplified, and wrong in detail. The last time I read about the zone system was 30 some years ago.)

Ansel regarded film as portraying 11 signficiantly different levels of grey.

Black and white film of the Pan-X (ISO 100) could handle about 10 stops. Tri-X was higher contrast and cold do something like 7-8 stops.

Satin finish paper has about a 100:1 contrast ratio. Or about 8 stops.

Modern digital cameras handle about 12-13 stops.

With film you don't have the ability the same way you do digitally to adjust the contrast curve easily. Instead there were a whole bunch of recipes for adjusting the exposure and development conditions. (Hence , "expose for the shadows, develop for the highlights." And there were variations that increased mid tone contrast but left highlights/shadows more or less the same.

What are we to do?

In the digital world we have it easy. Sort of.

Situation 1: Your scene has less than 8 stops luminance. Take the picture. Adjust mid tones. Print it.

Situation 2: Your scene has more than 8, but less than 12 stops difference in luminance. Take the picture. Adjust the range of luminance to match your output medium. Adjust the mid tines. Print it.

Situation 3: Your scene has more than 12 stops difference in luminance. Shoot a series of HDR pictures, map the range of exposures to your output medium...


The Zone System has 5 zones of significant use/importance; zones 3-8. With zone 3 being the minimum black exposure that reveals adequate detail, and zone 8 being the lightest exposure that retains adequate detail. Which correlates with the 5 stops of exposure most camera meters display; and the 5 zones of exposure editing controls/sliders in programs like Lightroom (blacks/shadows/exposure/highlights/whites).

But the zone system is not particularly special in terms of metering; you look at the scene, determine what is most important to you, and then you expose it accordingly... just like any other scene/exposure/method.

Say you determine that what is most important is that you record a minimum amount of details in this particular dark area of a scene... you simply meter that area and expose it at zone 3 (2 stops under). Or similarly, you meter and expose the lightest area you want to retain details in at zone 8 (2 stops over). And the other tones simply fall where they may. If you have tones/zones that fall outside of your ability to record them then it is simply not possible to bias the exposure adequately with a single image.

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