Blog Selenium light meters

Selenium light meters

Selenium light meter

Operating guide, functionality, and the heritage of film photography

What is a Selenium Light Meter?

The selenium light meter is one of the oldest measuring tools used in photography. Its operation is based on the photoelectric effect of selenium, which generates a small electric voltage when exposed to light. As a result, the device does not require any external power supply, and the light measurement is entirely analog and instantaneous. For decades, it was the primary method of determining exposure for both amateur and professional photographers.

Unlike later technologies based on CdS cells or silicon sensors, the selenium light meter measures reflected light and assumes a certain average brightness of the scene. It does not analyze contrast or color of the light, but only its quantity. This limitation is simultaneously its greatest advantage and disadvantage—it simplifies the photography process but requires the user to be aware of what is being measured.

Selenium light meter - how to use it?

The operation of a selenium light meter is best explained with a concrete example, and the Leningrad is perfect for this. On the front of the device, there is a large selenium cell that responds to the amount of incoming light. When light hits the surface of the cell, a current is generated within the system, moving the analog needle.

The first step in working with a selenium light meter is to set the sensitivity of the film you are using. In the case of Soviet-made devices (e.g., popular models like Leningrad or Sverdlovsk), the sensitivity scale is expressed in ГОСТ (GOST) units. In our case, ISO equals 100, so we set the sensitivity to about 90 GOST.

Although GOST mathematically differs from the modern ISO standard, in practical photography, it is assumed that they are almost identical. The simplest conversion rule worth remembering is the "90%" rule: the GOST value is typically about 90% of the ISO value. In everyday use, however, this difference is small enough to fall within the tolerance error of negative materials.

ISO GOST DIN Sensitivity Conversion Table

To make it easier, I have prepared a list of the most popular sensitivities you will encounter while working:

ISO	GOST (USSR)	DIN (Germany)
100	90	21°
200	180	24°
400	350	27°

If your light meter does not have the exact value of your film (e.g., you are looking for 400, but you have 350), set the nearest lower value. In analog photography, a slight excess of light (overexposure) is usually safer for the image than a deficiency.

Have you already set the sensitivity? Let's move on! The next step is the actual measurement. Most selenium light meters have two working ranges: strong light measurement (full sun) and weak light measurement (shade, indoors).

Pay attention to the slider or button usually located on the side or back of the casing. Using it uncovers the selenium photocell (often by sliding away a physical flap or filter). This allows much more light into the sensor, enabling the needle to "come to life" even in challenging lighting conditions.

So, we have two modes:

Bright mode (without button): If you are outside on a sunny day, the light meter will react immediately after being taken out of its case. You then read the result from the first, main scale.
Weak mode (using the slider): In the shade or indoors, the needle might not move at all. In this case, use the slider to open the sensor. However, remember that changing the physical light intake means switching to the second, more sensitive scale on the device's dial.

In our case, after opening the sensor, the needle moves and stops slightly above the number 5. This is our baseline value.

Important: Always make sure which scale you are looking at! If you used the button to increase sensitivity, you must read the result from the row of numbers assigned to the "open" photocell. Incorrect scale reading is the most common reason for spoiled, underexposed photos.

When we know the deflection value of the needle (in our case, it's about 5.5), we need to transfer it to the calculator dial. We rotate the outer ring so that the marker (arrow or chosen digit) aligns with our reading on the scale.

Now the "magic" of the analog computer happens. In the upper part of the dial, you'll see two adjacent rows of numbers:

Inner circle: Aperture values (e.g., 2.8, 4, 5.6, 8).
Outer circle: Corresponding shutter speeds.

How to read the results?

From the dial, you can read ready pairs of parameters. For example:

If you want a shallow depth of field and set the aperture to f/2.8, the light meter will indicate a shutter speed of 1/125 s.
If you stop down the lens to f/5.6, the shutter speed will extend to around 1/30 s or 1/15 s.

Simply transfer the selected pair to the camera rings, and you're done! You can enjoy a correctly exposed frame.

To be sure, I conducted a comparative test with my "standby," modern digital light meter. The results are identical or differ by a fraction of a degree, which is absolutely negligible when shooting on film. This is proof that the old Soviet "selenium" meters, if stored in the dark, are still brilliant and reliable tools.

Famous brands and manufacturers of selenium light meters.

The first portable selenium light meters appeared in the early 1930s when photography began to move beyond professional laboratory environments. One of the earliest and most influential models was the Weston Model 617, introduced around 1932. It was Weston who established many of the measurement standards that would be used in photography for decades to come.

In Europe, Gossen held a special position; its light meters, such as the Weston Master or Sixtus, were synonymous with reliability and precision. Zeiss Ikon developed both standalone light meters and integrated designs with cameras, similar to Agfa, which aimed its products primarily at advanced amateurs. In Japan, the first selenium models were produced by Sekonic before the company transitioned to more sensitive technologies.

Simultaneously, light meters built into cameras were being developed. In the 1950s and 1960s, many rangefinders and SLRs featured characteristic selenium cells mounted on the front of the body. These solutions were entirely battery-independent and operated whenever the camera was exposed to light.

In the Eastern Bloc, Soviet designs gained popularity, with the Leningrad holding a special place. It was a robust, handheld selenium light meter produced in several versions, designed with simplicity, durability, and mass availability in mind. Even today, it remains one of the most frequently encountered models on the secondary market.

Advantages and disadvantages of selenium light meters.

The greatest advantage of selenium light meters is their independence. The absence of batteries means the device is always ready to work, and its operation remains unchanged over the years. The response to light is immediate, and the readings are clear and intuitive. For many photographers, simplicity is also important – a selenium light meter does not make decisions for the user; it only provides raw information.

On the other hand, selenium is a material that degrades. Over the years, the cell loses sensitivity, leading to systematic measurement errors. Selenium light meters are also of little use in low light and are not suitable for precise work in scenes with a wide tonal range. The lack of real calibration options means that each unit must be treated individually.

Selenium light meter today

In the contemporary world, a selenium light meter is no longer a necessary tool, but a conscious choice. Functional units still exist, but their accuracy varies and requires verification. They work best in analog photography with good daylight, where their limitations are not as pronounced.

For many photographers, a selenium light meter is an element of the process that forces a slowdown and greater attentiveness. It does not offer the safety of a histogram or real-time adjustments, but it teaches the observation of light and consistency in working with exposure.

Alternatives

Today's photographer has many alternatives at their disposal. CdS and silicon light meters offer significantly greater sensitivity and precision, modern digital cameras have advanced light metering systems, and mobile applications can provide surprisingly accurate results. Each of these solutions is more versatile than selenium.

Nevertheless, the selenium light meter remains an important point of reference. Not as a technological relic, but as a tool that reminds us that photography relied for a long time on simple physical phenomena and decisions made by humans, not algorithms.