# Calculating snow exposure with a spot meter

I've been using a Sekonic light meter in spot mode for over a year now with the zone system, and I have consistent issues with snow. Despite putting the snow on zone 8, that area of the negative ends up being very dense, more like I would expect zone 9.5 to be. I originally thought I was doing my calculations incorrectly, or that I was measuring snow + rock and therefore not really reading the snow, but I've recently confirmed that a solid zone 8 placement was dramatically overexposed and required significant burning to get any detail. To correctly expose snow I have to assume 1-2 stops of light beyond what the light meter records.

Is this an issue with my light meter? How do others correctly expose snow in their black and white film shots? Do you just assume an overexposure and underdevelop the negative?

• Have you calibrated your development? You may be metering okay; but, metering goes with development and you may be over developing. The Zone System does its magic by exactly matching the gamma to the display print capability. Snow is your detailed highlight. Don't forget your shadow density.
– Stan
Commented Oct 30, 2017 at 15:53
• @Stan Every other subject that I shoot seems to place correctly. Snow is my outlier. Commented Oct 30, 2017 at 16:19
• Both the question and the sole answer (at this point in time) seem to make the assumption that one zone in Adams' "Zone System" is equal to one stop. That is far from necessarily the case! Please see How do the 11+ stops of dynamic range from a modern DSLR fit into the 10 stops of the zone system? and both answers for more. Commented Oct 30, 2017 at 19:18
• @MichaelClark very astute, I was making that simplification. Thank you. Commented Oct 30, 2017 at 21:42
• @steel Without looking at the specific page (because I don't have the 2015 version available), I'm guessing it is in the context of a base of N before the concept of different values of N is introduced later on. N+2 would spread 8 stops of DR over the 11 zones (0-10 inclusive is eleven zones). N-3 would spread 13 stops of DR over the 11 zones. Commented Nov 18, 2017 at 7:46

## 2 Answers

I divide the ISO of the film by 5 and then set the meter to this value. I then spot read the snow and set my camera to via this reading. That's a compensation of 2 1/3 f-stops. Works for me!

• is this something you do only for snow, or for all subjects? How do you handle an image where snow is only a fraction of the subject, say 1/5? Commented Oct 30, 2017 at 16:20
• @ steel -- To correctly expose, I often took readings from a gray card. In my youth, light meters usually failed in feeble light. I would substitute a white card and take a reading. Dividing the ISO by 5 simulates the same reading as if taken using a gray card. When imaging snow, best to substitute a gray card for the snow. Using the same logic, I read the snow as if it were a white card. Then divide by 5 to simulate a gray card. Works for me! Commented Oct 30, 2017 at 16:56
• I see. That's another way of putting the snow on zone 5 then, it seems? Commented Oct 30, 2017 at 17:03
• @ steel -- the deviser can be adjusted to place snow on a different zone. Seems to me, one could experiment to achieve the desired zone. Commented Oct 30, 2017 at 17:29
• @steel You understand that whatever you meter is "zone 5" by definition. If you take a reading of a patch of snow, your indicated exposure will produce a density for mid-grey. To make the metered area white, you must change the indicated exposure by the difference between the grey and the white you want - about 2-½ stops as Alan mentioned. But that alone is not the "Zone System."
– Stan
Commented Oct 30, 2017 at 18:15

You mention a few different issues which I shall try to pull together: snow, Zone system, spot meter. There are different phases of the whole Zone System too involved to discus here, now. Briefly, the Zone system is a process to reduce the subject luminance range to fit within the density (reflectance) range of a photographic print (reproduction).

Note also that the resulting Zone system negatives are used to make a "straight print;" one that requires little if any manipulation (masking, dodging, or burning-in detail). It is exposed, and processed according to a standardized procedure according to an initial calibration phase to determine actual film speed, standardized processing, and printing procedure along with a myriad of other variables.

Snow is not a trivial material to photograph. It is high luminance but has a narrow luminance range. It is crystalline and highly prone to specular high-lights. It can be dead-white line across a line of distant mountain peaks or it can be depicted as a full range of tones from deep texture to paper white You must determine how it will be rendered.
It is a fragile material in a dynamic natural harsh environment.
Conditions often change from the time you make readings and when you press the shutter release.

Pre-visualize your subject to determine what you want represented in your print.

Meter your scene, making notes of values for later calculation of the necessary processing for contrast control. (Normal, compression, or expansion.)

The Zone system assigns ten zones of subject luminance values to be represented as print values from:
Zone 0: Photo paper black; maximum black representing emptiness; nothing; openings into unlit rooms. Seems solid rather than mysterious.
Zone 1: Nearly black, the beginnings of a sense of empty space. Unlit rooms; forests; depths; shadows in dim light.
Zone 2: The first sense of an emergence of texture, Othe the border line between visible and invisible texture—mysterious.
Zone 3: TEXTURED SHADOW. Texture and detail are firm and full of the sense of substance in dark materials such as black garments leather. Visible creases and folds encourage the sense of touch.
Zone 4: Average dark foliage, dark stone, shadow in landscape or buildings. Recommended shadow zone for portraits in sunlight or floodlight.
Zone 5: The pivotal zone for both paper and film. Middle gray; 18% neutral test card. Dark or sunburned skin in sunlight; clear North sky on panchromatic film; average weathered wood or stone, light foliage.
Zone 6: Caucasian skin with sunlight, but not glare or highlights. Snow in shadow when both sun and shadow are in the same picture. Clear North sky with orthochromatic film. Poured concrete buildings in overcast light.
Zone 7: TEXTURED BRIGHTS. Light skin entirely in diffuse light. Average snow in raking sun; light gray concrete bright colours. "Whites" with textures and delicate values. Sense of substance remains tactile.
Zone 8: Last vestige of texture. Glaring surfaces; snow in flat light; whites without texture.
Zone 9: Threshhold gray into pure white of the paper. Tends to feel solid representing only itself. Loss of sense of substance. Represents highlights (as opposed to brights) such as chrome trim, or specular reflections.

Use the above "scale" to identify and visualize subject values in zones. Snow is mentioned specifically, here. Photographically, the difference from one value to the next IS EQUAL TO ONE FULL STOP DIFFERENCE IN EXPOSURE. This is fundamental to the understanding and using the zone system. (I checked my notes.)

Metering for the Zone system. (Are you batteries good - remember it's cold and you rely on the meter's accuracy.)

1. When taking a luminance reading, whether it be an overall average or a closeup of a shadow area, cheekbone, or the highlight of a snowdrift, always point the meter along the lens-to-subject axis. Different angles of view may include reflection and brightnesses different from those seen from the point of view of the camera lens.
2. Take every precaution to prevent the shadow of the meter, your hand, or your body from falling on the subject while the reading is being made, or a false reading will be obtained. With back-lighted subjects, be careful that your body does not act as a reflector filling in the shadow area as you meter it. Light sources should not be in included in the field of view of the meter.
3. Consider carefully the acceptance angle and coverage. Spot meters allow as little as 1° of light to enter, and make readings of small or distant areas quite simple.
4. Determining luminance values in fog or heavy mist is most accurate when the subject is metered from the camera position. The light falling on the subject (incident light) has been scattered by the fog. The luminance reflected from the subject is then further scattered and diffused as it travels to the camera position. A exposure reading made close to the subject will read he immendiate amount of diffuse light reflected from the subjct, but not the quantity that finally gets to the camera.
5. A luminance meter is an instrument that gives a physical measurement of eth quantity of light flux reflected from various areas of a scene. The luminance measured is purely objective. How you decide to represent the luminances of a scene as print values is subjective.