What is the “right” exposure?

Exposure is a key concept in photography. Especially in film photography, where you can’t see your images until you develop the film.

Let’s talk about proper exposure: what it means for the final result and how to properly expose. This is especially important given that we’re learning how to shoot properly on every film, and it’s all about getting the exposure right everywhere.

If you don’t understand the term “exposure” itself, it’s simply the amount of light hitting the film. The emulsion needs light to form a latent image. It’s a chemical process that requires light. It can be a lot of light, it can be little light. Our job is to give the film the right amount of light and that’s what we’re learning.

We begin by defining “transparent” and “dense” film negatives.

"Transparent" and "dense" film negatives

When a negative film is exposed and then developed, the areas that receive light appear dark and opaque, which is where the silver halide crystals form what we call the graininess of the film.

The light or transparent areas on the developed film negatives received less light and retained fewer crystals. When there is not enough light at all to activate the crystals, the emulsion remains completely transparent – without any light information.

Areas of the developed film that received a lot of light look dark, filled with crystals (“dense”). It can be difficult to distinguish hues in these areas, but such areas are usually more useful than areas where no crystals are forming. You can think of dense areas as paintings painted with barely distinguishable shades of black paint on a black canvas: it may be hard to tell what’s there, but it’s definitely better than a completely blank canvas with no image at all.

There is usually a better chance of recovering overexposed images (i.e., “dense” negatives) when scanned or printed than underexposed (i.e., “clear” negatives). Note that this rule is reversed for slides (positive film).

Shadow Metering

Some photographers advise beginners to aim the exposure meter at the shadows. This is more likely to exclude the brightest spots from the exposure meter calculations, giving readings with slower shutter speeds and wider apertures. This method ensures that the darker areas, which often suffer from loss of detail, get more light by allowing the bright (dense spots of the negative) to retain enough information.

However, in my experience, measuring shadows does not guarantee a good result.

If you point the spot meter at a dark spot in a brightly lit scene, your image will probably be severely overexposed with these camera settings.

As mentioned above, “dense” negatives are preferable because they can contain some information, as opposed to “transparent” negatives. But this method has a limit, which is easily overstepped by mindless light measurements, ignoring the bright areas.

Selective metering

The best exposure is achieved by ensuring that the key subject has the optimum amount of light on the film. After all, this is who you are photographing, and you need as much visual information on film as possible for your subject.

Everything that surrounds your subject should take a back seat when you are measuring your scene. The best tools for taking these measurements are spot meters, incident light meters and your own eyes.

Spot meters measure the reflected light from your scene in a narrow corner – a spot. They help you get spot readings, although they are not always built into the camera. In that case, I download a smartphone app like Lumu. Light measurement apps can be more accurate than built-in meters.

However, you have to remember that spot meters have to target 18% gray (see below). This means that if you are pointing at something white, your readings can cause underexposure in the midtones, and if you are pointing at something black, your readings can cause overexposure. There are two things you can do in these situations:

Find something in your scene that looks like medium gray, and measure it instead;
Estimate how many steps your focus point is darker/lighter than the average gray, and compensate your exposure meter reading with that.

For example, the mushroom in the photo above is light gray, so the photographer pointed the spot meter at it and corrected the reading by about +1 step to make sure it stayed bright at my exposure. The original value gave a shutter speed of 1/125s, after compensation it became 1/60s. It takes a bit of experience to know exactly how many stops to compensate for. Practice randomly measuring the reading using the exposure meter app on your phone.

Ambient light meters are suitable for complex light measurements, and with them you don’t have to worry about compensation. Instead, they measure the available light where you are measuring.

If the photographer were to use one on the same mushroom above, he would have to walk up to the mushroom and hold the incident light meter next to his hat, pointing to the light source. That’s not always practical, especially when you’re photographing objects that are far away or trying to take a quick measurement. Incandescent light meters, moreover, are expensive.

Sun Rule 16 guarantees a good exposure if your subject is in bright sunlight, you set the aperture to 𝒇16, and the shutter speed is about 1/ISO of the film. For example, a film with ISO 100 in bright sunshine and 16 would best be exposed at a shutter speed of 1/125. Of course, you can change the camera setting to 𝒇8 (add +2 stops of light) and 1/500 (-2 stops) to get the same exposure. Over time, you will learn how to set your camera settings just by looking at your scene.

18% gray

Every scene with white and black dots has many scattered shades. If we were to sort them and line them up according to their brightness, where 100% would be white and 0% would be black, the 18% mark would be perceived by the human eye as the “average” brightness.

The exposure meter will analyze your scene and use the 18% mark as a guide to set your camera’s shutter speed and aperture so that the average gray color roughly corresponds to the midpoint of your film’s dynamic range. For example, for ISO 100 film, your meter might show an aperture of 8 and a shutter speed of 1/500 second on a bright sunny day.

Film exposure is about detail, not brightness

Exposure is only the first step to the finished photographic process. In the darkroom, you can easily make your prints darker or brighter. Your scanner software will automatically adjust the brightness of your image.

The evidence of the quality of your exposure will only be visible in the negative itself and in the amount of detail you can extract from it. If you have given the film too much light, you may notice a change in color and a loss of detail in the highlights. Too little light will result in noise and graininess in the shadows, color shift and loss of detail in the dark spots.

The goal of exposure is to get as much detail as possible in the most interesting area of your scene.

The brightness of the final image can be corrected by scanning or printing.

The choice of exposure can be subjective

This article aims to get as much detail as possible in the area of interest. Following this advice, especially in combination with film with a narrow photographic latitude, can produce images that may appear very dark or very bright. Some areas may lose information, but this does not always mean the wrong exposure.

There are times when the photographer doesn’t care about preserving all the details, aiming for a certain effect. As long as he is happy with the results and the results match his vision, the exposure is correct.