Zone Metering was a technique made famous by Ansel Adams and Fred Archer. It's fairly new to me, so I am using it in a very simple format which I'll go over here. I plan to update this post as I learn to use it better. This will be the most basic overview possible to reflect the minimal extent to which I am using the system. We'll call it overly simplified.
Zone Metering - What is it?
The Zone Metering technique was designed for shooting black and white back in the 30's and is used to adjust exposure based on highlights and shadows. As meters are designed to give you a reading for middle gray (18% reflectivity) this system was developed to adjust the readings to show shadow detail or not blow highlights. Again, keeping this overly basic.
The scale is ranged:
- 0 - Pure Black (no detail)
- III - Where I adjust for shadow
- V - Middle gray (18% / gray card)
- VI- Where to theoretically adjust for skin tone
- X - Pure White (blown highlights)
When your meter evaluates a scene (in a nutshell) it is giving you the exposure for middle gray (18%) or Zone V in this system. Now, depending on your meter, that's the average light in the scene or area you are metering.
For this reason, I have moved to a 1% spot meter (Pentax V Spot Meter to be accurate). With a spot meter, you can get very accurate readings from distance on specific areas of your scene. As you can see to the right, the small circle in the middle on the corner of the barn door is all the meter is reading.
In the past, I used a regular meter to check the light in shadows and shot at half box speed. This usually gave the scene +2 stops and kept the shadows and highlights in check. Now, I am looking to either retain shadows or nail skin tones.
For this system, I am metering a box speeds - then adjusting. I'll give examples.
Zone Metering: Shadows
If I am looking to keep detail in shadows, I place the spot meter on a dark area of my scene - an area where I need to retain some information. Upon clicking the meter, the needle will move to a EV Scale light reading (let's just say EV 10 2/3 as that matches the photo to the right) and I turn the wheel until the white arrow is on the EV 10 2/3.
This is Zone V - but not how I want to expose shadows.
For shadows, the simplified rule of thumb is the darkest acceptable zone to retain detail is Zone III. Now, my meter doesn't have the Zone System sticker on here, but I know it's a 2-stop difference.UPDATE: I have since added a Zone System sticker onto my meter to make life simple (Thanks to Craig for his sample sticker notes and helping me understand the dev time formulas in practice). Now, what I do is rotate the wheel counterclockwise until the EV 10 2/3 is under the Zone III in pink. I like to have my metered EV to be in the left third of Zone III (closer to Zone IV than to Zone II).
To further clarify, if I meter for EV 10 2/3, the meter is saying for a Zone V exposure of the shadows I need to shoot for 1/60 seconds at f/5.6. To shoot this in Zone III, it'll be 1/250 seconds at f/5.6 - two stops darker than metered.
Also, at this point, I meter for the highlights to see what zone they fall in (without turning the wheel). Again, this comes in handy while developing for the shadows. In this example, if my highlights were EV 16 - sitting in Zone VIII - I know there are 5 zones between shadow and highlight. This means I'll need to develop for N-1 with N being the box development time. If my developer should go for 10 minutes, then N-1 stop would be 8 minutes instead. I'll explain further later on.
Zone Metering: Skin Tone
I am not getting into skin tone differences here (pale Irishman vs black and so on) to keep it simple. The theory is, to meter for a portrait, place the spot meter circle right on the cheek of my subject. This is, as before, a Zone V reading.
The simplified rule of thumb for skin tones is to shoot in Zone VI. So, if I am metered at EV 14 (Zone V) I need to adjust one stop clockwise. So rather than the EV 14 being under the triangle, you'll rotate clockwise until EV 14 is under the Zone VI (one stop).
If I meter for EV 14, the meter is saying for a Zone V exposure of the skin tone I need to shoot for 1/500 second at f/5.6. To shoot this in Zone VI, it'll be 1/250 seconds at f/5.6 - on stop brighter than metered.
*NOTE: Now that I've actually went through the steps here, I am finding that shadows get clipped with this process. In this photo to the right, I metered exactly as noted above, set to Zone VI and the light on the skin looks good, but notice the shadow by her neck - gone.
My current thought is just to always meter for the shadows and set to Zone III. I need to experiment much more. Below is an example of a Zone III meter for shadows only - with a n-1 adjustment in dev to pull the highlights.
What Zone Meter Does for Development Times
Basic rule is meter for the shadows, develop for the highlights. The range should ideally be 4 stops between shadow and light - for example - f/4 in the shadows and f/16 in the highlights. More than 4 stops (say f/4 shadows and f/22 highlights) will require less development time (roughly 20% per stop) as there will be more contrast in the scene. If less than 4 stops (say f/4 and f/11), then more development time (roughly 20% per stop) to increase contrast. For this formula, N is the box development time. The number is stops to add or remove.
This is why I take notes on shadow and highlight metered zones. Here's some quick development notes (see this post for a more complete breakdown):
Developing Ilford Delta 100 in Kodak D-76
Box Development Time: 9 minutes at 68°F
- N-3: 3 minutes 36 seconds
- N-2: 5 minutes 24 seconds
- N-1: 7 minutes 12 seconds
- N: 9 minutes
- N+1: 10 minutes 48 seconds
- N+2: 12 minutes 35 seconds
- N+3: 14 minutes 24 seconds
Developing Ilford HP5 Plus 400 in Kodak D-76
Box Development Time: 7:30 minutes at 68°F
- N-3: 3 minutes 0 seconds
- N-2: 4 minutes 30 seconds
- N-1: 6 minutes 0 seconds
- N: 7 minutes 30 seconds
- N+1: 9 minutes 0 seconds
- N+2: 10 minutes 30 seconds
- N+3: 12 minutes 0 seconds
Caveats to Zone III Shadows + Portraits in Dev
As Craig helped me understand, there's another step you can take in development times with portraits in terms of metering for Zone III shadows.
If you are metered for shadows as described above, but the cheek is metering for Zone V, you can move the shadows up to Zone IV to bring the skin up to Zone VI (and then note the range from shadows to highlights for development).
If you are metered for shadows as above, but the cheek is metering for Zone VII, give a minus development time (N-1) to bring the skin tones into Zone VI (more flattering for female subjects).
As I get more of these great tips, I'll keep adding them to this post. Bookmark it!
I kept this very crude in manner of explanation and detail, but it gives you an idea of how I am using Zone Metering for my large format Chamonix 45n-2 camera. I have even begun to do this on the Plaubel-Makina 670 camera. There's a whole other part to this system when it comes to developing and darkroom printing - again, I am not there yet.