February 2026

How to Meter Without a Built-In Meter

Your TLR camera's meter is dead. Here's how to expose your film correctly anyway.

Most twin-lens reflex cameras fall into one of two categories: those that never had a light meter, and those that had one which stopped working thirty years ago. The Yashica A has no meter. The Rolleiflex 2.8F has a selenium meter that may or may not still respond to light. The Yashica-Mat 124G has a CdS meter that requires a mercury battery no longer manufactured.

None of this matters. Photographers exposed film correctly for decades before built-in meters existed, and the tools available today are better than anything those photographers had. You just need to understand light well enough to measure it.

What metering actually is

Metering is the act of measuring the brightness of a scene and translating that measurement into camera settings — an aperture and a shutter speed — that will produce a correctly exposed negative.

The brightness of a scene is expressed as an exposure value (EV). A sunny day is around EV 15. Open shade is around EV 12. A well-lit interior might be EV 8. A candlelit room is EV 4. Each step of one EV represents a doubling or halving of the light.

Given an EV and a film speed (ISO), there are many combinations of aperture and shutter speed that will produce a correct exposure. EV 15 at ISO 400 could be f/16 at 1/400, or f/11 at 1/800, or f/8 at 1/1600, or f/22 at 1/200. They're all equivalent. The meter tells you how much light there is; you decide how to divide it between the aperture and the shutter.

This is worth understanding because different metering methods — the sunny 16 rule, a handheld meter, a phone app — are all doing the same thing. They're measuring EV. The only question is how accurately and how conveniently.

Method 1: The sunny 16 rule

The oldest and simplest metering method requires no equipment at all. On a sunny day with hard shadows, set your aperture to f/16 and your shutter speed to the reciprocal of your ISO. Shooting ISO 400 film? f/16 at 1/400 (or the nearest available speed, like 1/500).

From there, you adjust for conditions:

Each step from f/16 to f/11 to f/8 to f/5.6 doubles the light reaching the film, compensating for the dimmer conditions. If you want a different aperture for depth-of-field reasons, adjust the shutter speed to compensate. Open up one stop from f/16 to f/11? Double the shutter speed from 1/400 to 1/800.

The sunny 16 rule works remarkably well in consistent outdoor light. It falls apart indoors, in mixed lighting, at dawn and dusk, and in any situation where the light is uneven or changing quickly. It's a good fallback and a useful way to sanity-check other metering methods, but it shouldn't be your only tool.

Method 2: Handheld light meters

A dedicated handheld meter — a Sekonic, Gossen, or Minolta — is the gold standard. These instruments measure light with high accuracy and offer two modes that phone apps cannot easily replicate.

Incident metering measures the light falling on the subject, not the light reflecting off it. You hold the meter at the subject's position, point the white dome toward the camera, and press the button. The reading tells you exactly how much light is illuminating the scene, regardless of whether the subject is wearing a white shirt or a black one. This eliminates the most common source of metering error: subject reflectance.

Spot metering measures reflected light from a very narrow angle — typically 1 to 5 degrees. This lets you meter a specific part of the scene: the highlight on a cheek, the shadow under a tree, the bright sky, the dark doorway. Combined with the zone system (Ansel Adams' method for placing tones precisely on the negative), spot metering gives you complete control over exposure.

The disadvantage of handheld meters is that they're another thing to carry, another thing to buy ($100-300 for a good used meter), and another step in the shooting process. For many photographers, a phone app has replaced the handheld meter entirely.

Method 3: Phone light meter apps

Your phone's camera sensor can measure reflected light. A light meter app reads that measurement, applies the ISO you've set, and suggests an aperture and shutter speed.

Phone meters are reflected meters — they measure light bouncing off the scene, like a camera's built-in meter. This means they're subject to the same errors: they'll underexpose a snowy scene (too much reflected light tricks the meter into thinking it's brighter than it is) and overexpose a dark scene. Once you understand this tendency, you can compensate for it.

The real advantage of a phone meter is that you always have it with you. The camera in your pocket is a surprisingly capable light-measuring instrument. But most light meter apps have a significant limitation when it comes to TLR cameras.

The translation problem

Here's where things get specific. A generic light meter app measures the scene and says: f/5.6 at 1/350 at ISO 400. Good. Now set that on your Yashica A.

Except the Yashica A doesn't have 1/350. Its shutter speeds are 1/25, 1/50, 1/100, and 1/300. Is 1/300 close enough? Probably. What about f/5.6? The Yashica A's aperture ring clicks at f/3.5, f/4, f/5.6, f/8, f/11, f/16, and f/22 — so f/5.6 is fine. But what if the app had said f/6.3? That's not a marked position on the Yashica A's aperture ring. Do you set it between f/5.6 and f/8? How precisely can you estimate half a click-stop on a sixty-year-old lens?

This is the translation problem. Generic meter apps give you mathematically correct exposures in a continuous space of possible values. But your camera operates in a discrete space of specific click-stops. The gap between the two requires mental math, estimation, and compromise — every single time you meter a scene.

For a single frame, it's a minor annoyance. Over twelve frames on a roll, across dozens of rolls, it's friction that adds up. It slows you down when you should be looking at the light. It's one more thing between you and the photograph.

Method 4: Camera-specific metering

This is why we built TLR Companion. When you select a camera in the app — not a generic "medium format camera" but your specific Yashica-Mat 124G or Rolleicord Vb or Mamiya C330f with its 80mm f/2.8 lens — the app knows every aperture detent and every shutter speed that camera offers.

When you meter a scene, the app doesn't give you theoretical values. It gives you the nearest correct combination of aperture and shutter speed that actually exist as click-stops on your camera. The reading you see is the setting you set. No rounding, no mental math, no translation.

If the light is too low for your camera's fastest combination, the app tells you. If the exposure requires bulb mode, the app switches to bulb and shows the calculated time — corrected for reciprocity failure on your specific film stock. If you've attached an ND filter, the app accounts for the filter's light reduction before selecting the camera-appropriate settings.

This approach solves the translation problem entirely. It also means that when you switch cameras — from a Yashica-Mat to a Rolleiflex, say, with a different range of shutter speeds — the meter adapts automatically. Same scene, same light, different camera, different (but correct) settings.

Spot metering vs. average metering

Whether you're using a handheld meter, a phone app, or TLR Companion, you'll encounter two metering modes: average (sometimes called matrix or evaluative) and spot.

Average metering reads the entire scene and computes a single exposure value. It assumes the scene averages out to a middle tone — roughly 18% gray. For most outdoor scenes in even light, this works well. Landscapes, street scenes, group photos, architecture in daylight — average metering handles all of these reliably.

Spot metering reads a small area at the center of the frame. This gives you control over exactly what you're metering. In a backlit portrait, you can meter the subject's face and ignore the bright sky behind them. In a dark interior with a bright window, you can meter the interior and let the window blow out, or meter the window and let the interior go dark.

The general guidance:

The exposure latitude safety net

Here's the most reassuring thing about metering for film: negative film is forgiving. Modern black-and-white and color negative films have remarkable exposure latitude — typically two stops of overexposure and one stop of underexposure will still produce a printable negative.

Ilford HP5 Plus at ISO 400 can be shot anywhere from ISO 200 to ISO 1600 and produce usable results with appropriate development. Kodak Portra 400 is legendary for its ability to handle overexposure — some photographers routinely overexpose it by one or two stops and prefer the results.

This means your metering doesn't need to be perfect. It needs to be close. Within a stop is good. Within half a stop is excellent. The sunny 16 rule on a sunny day gets you within a stop. A phone app gets you within half a stop. A camera-specific app like TLR Companion, which eliminates the rounding error from translating to your camera's actual settings, gets you as close as reflected metering can.

The exception is slide film (color reversal). Slide film has very narrow latitude — half a stop in either direction is visible, and a full stop off is often ruined. If you're shooting Fuji Velvia or Provia, your metering needs to be precise. Use a meter, not the sunny 16 rule, and bracket your exposures if the shot matters.

A practical workflow

Here's how metering fits into the rhythm of shooting a TLR:

1. Read the light. Before you even raise the camera, look at the scene. Where is the light coming from? Is it direct or diffused? Are there deep shadows? Bright highlights? Get a sense of the contrast range.

2. Meter. Point your phone at the scene (or use the sunny 16 rule if the light is straightforward). If you're using TLR Companion, the reading will already be in your camera's language — a specific f-stop and a specific shutter speed that you can set directly.

3. Set the camera. Turn the aperture ring to the indicated f-stop. Set the shutter speed. These are physical, tactile adjustments — you can feel the detents click. On a TLR, this takes two seconds.

4. Compose and focus. Look down into the waist-level finder. Find your frame. Turn the focus knob until the ground glass image is sharp.

5. Shoot. Press the shutter release. Advance the film. You've used one of your twelve frames. Make it count.

With practice, steps 1 through 3 become nearly automatic. You learn to read light without thinking about it. You learn what f/8 at 1/250 looks like. You meter less often because you already know what the meter will say. The tool becomes invisible, which is exactly what a good tool should be.

TLR Companion is a free light meter app built for TLR and medium format photographers. Select your camera, select your film, and get exposure settings that match your camera's actual controls.

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