A simplified zone system calculation table for field use

Discussion in 'Black and White' started by kevin_moloney, May 8, 2020.

  1. I'm sharing here a simple zone system table I developed after working to learn the zone system a dozen years ago. Please feel free to use it or share it with attribution. I find it quite a lot simpler and faster than any formulas or logging techniques. It is a PNG set up to print as a 3X5 card or to be loaded onto your mobile phone for quick field calculations.


    Here's a link for an easily printable PDF version of the card:
    A Simplified Zone System Calculator Table

    Simple instructions are on the card, but here's how you use it:
    • From the scene in front of your camera, previsualize the area of full shadow detail (zone III) and of full highlight detail (zone VII). These aren't true black or true white, but the areas that should show some detail in the final image.
    • Meter the area for zone III first, and find on the table the row where that aperture lands under zone III. Shutter speeds do not appear on the table, so set the shutter speed that pairs with your selected aperture in this reading and leave it.
    • Meter for zone VII next. Looking down the same row where your chosen aperture was for zone III, find the aperture listed in the zone VII column.
    • Set your aperture to expose for the aperture in the zone V column from that same row. You now have your exposure.
    • In that same row, find the aperture you metered for zone VII. Look at the top of the column for the development N number.
    • Develop according to that N number above your zone VII aperture.
    An example:

    You arrive at a scene and pull out your spot meter. You meter for the shadow that you would like to hold just a little bit of detail in the final print. That reading is 1/125 sec. @ f/5.6. Set your shutter to 1/125 and then look in the zone III column of the table for 5.6. See it? Sixth row below the zone numbers.

    Next, meter the highlight where you'd like just some readable detail in that print. Meter also for 1/125. It reads f/32.

    On that same row, look in the pink zone V column. It says f/11. That's your exposure aperture. Set the camera to 1/125 @ f/11.

    Look at the table one last time. Finding that VII reading (f/32) look to the top of the column where f/32 sits. It says N-1. That's your development factor for that exposure. Scribble it on your film holder, in a notebook, on the roll itself, or on a memo on your phone. You might find your own process for using the table, too. For example, I have come to quickly read for zone III, jump to the zone V entry on the same row, set and shoot, then circle back to meter zone VII and find the development factor.

    I don't have a densitometer and never dialed in my materials the way maestro Ansel did. I use Chris Johnson's basic development factors to adjust development times for most film/dev combos:

    Standard films_____T-grain films

    If the results are not perfect, they are at least very good. My negatives all land nicely in the range of very small and easy printing adjustments, particularly with the flexibility of variable contrast papers. Frequently I land a perfect grade 2 negative.
    jose_angel and bgelfand like this.
  2. I must be reading it wrong Kevin. Z V11 on table says f22 not f32 and normal development. What am I doing wrong?
  3. Hi Jim,

    All the numbers I'm using in the example are along the row that starts with 2.8 on the left (under zone I).

    If you took a reading in the area you previsualize as landing in zone 3, and the result was f/5.6@1/125; then you took a reading for an area you want to land in zone VII and the reading was f/32@1/125; you would expose at f/11@1/125 (under zone V) and give N-1 development (above the f/32 in that row on the table).

    In this example the scene is contrasty. The area you would like to have zone VII tones is a stop too bright for normal development, so N-1 development would lower those highlights by a stop and have them land right where you want them.

    However, if your zone VII meter reading happened to be f/22, you would have a normal contrast range and N (normal) development. No change in development time needed.

    If your zone VII reading was f/16, it is a low-contrast situation. You would give N+1 development to increase the density in the highlights and stretch the contrast.

    Maybe those additions will help. If not, feel free to let me know and I'll see how I might better describe it.


  4. Kevin,

    That makes sense, thank you. I had assumed you were using the chart as is, as your example. I have printed your chart and hatched all rows except the one you mentioned (starting with 2.8 under Z1).

    In this case f22 would fall on V11 with normal development.

    I think I had taken your original post as referring to the chart Look at the table one last time. Finding that VII reading (f/32) look to the top of the column where f/32 sits. It says N-1. Whereas -on the chart- V11 reads f22, not f32.

    I understand that your text was an example of where it may fall, not where it actually falls in the chart.

    I am getting it or have I lost it completely?

    Many thanks,

  5. By Jove, I think you’ve got it!
  6. Thanks Kevin for your answer and the work you put into the chart.

    I have just been reading another thread about the end of Photo.net. I dont get notifications anymore and cant change my email address.

    What a shame to lose such a great forum.


  7. I've never used the zone system. But I have a question. Don't you get different reading in the shadow areas depending on the reflectivity of the shadow detail. In other words, if the shadow area has a white rock vs a dark rock, wouldn't you get different reading. How do you account for that?
  8. Indeed you would Alan. But with the zone system you decide before the exposure which zone you would like that black rock in the shade to be -- dark but with some visible detail (zone III) -- and that white rock in the sun to be bright but with texture (zone VII). Rather than them telling me how bright they are in reality, I am deciding how bright I want them to be in the print (or scan).

    I decide the dark rock in the shade should be in zone III in the print. I read the dark rock and get some numbers. I look for that aperture number under the zone III column. Sliding my finger two columns to the right I see what aperture I should set on the camera, with the shutter speed the meter gave me on that reading. Then I decide I want the white rock in the sun to be in zone VII and I take a reading on it. Using the same shutter speed as before I look for the aperture given on that reading on the same row of the table. Sliding up to the N numbers I see how I should develop the film to have that white rock end up as zone VII on the print.

    It's truly expose for the shadows and develop for the highlights.
    Last edited: May 10, 2020
    jim_gardner|4 likes this.
  9. Kevin, you explained that almost as well as Ansel himself.
    Alan, I cannot recommend highly enough, the 3 book series by Ansel adams. The Camera, The Negative, The Print. Years ago I learnt more from those 3 books than every other book I have read.
    kevin_moloney likes this.
  10. jim_gardner|4 +1

    But no reason to re-invent the wheel.

    Adams himself and others wrote succinct accounts of using the Zone System for 35mm:

    Zone system (Adams) 1981-11 Popular Photography
    Zone System for 35mm 1962-06 Popular Photography
  11. It's all very well pointing a meter at something in the real world, but how do you account for lens and camera-body flare, which will reduce the contrast at the image plane?

    And how do you chop up a cassette of 35mm or roll of 120 to apply N-titty-N development to individual frames?

    Those of us that don't want to carry multiple backs or camera bodies labelled N, N+1, N-1, etc. simply use a digital camera set to shoot RAW, and get about 12 stops SBR to play with as a matter of course. Plus the ability to apply any colour of filter you care to name during conversion to B&W.

    And if you insist on using film, almost any C-41 process film will give you nearly the same flexibility.

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