How Does an SLR Camera Work?

A few days ago I stumbled upon a video where a kid got completely puzzled and didn’t know what to do when he was given a cassette player and a tape. A similar thing may happen to beginner and enthusiast photographers who never shot film and are given a retro 35mm camera back from the 1960’s.

The mechanism in SLR cameras works simply enough and resembles the way DSLRs function. But still an old film camera may have a few little things that may surprise or even take the modern photographer aback. Lets talk about them and get you familiar with the basics of using an SLR camera.

When you compare SLR cameras and DSLRs, you understand that they are different only in the form of recording the image. DSLRs use a digital mechanism that processes the received data and records it using the camera sensor, whilst SLRs record information about every image on a separate exposure of the film.

The typical film size is 36x24mm. This is why the modern professional DSLRs are sometimes called 35mm cameras or full-frame cameras.

We already talked about how digital single lens reflex cameras function. And SLR are not too different, even the pentaprism/pentamirror system is the same. However, the layout of the most essential settings—aperture, ISO, and shutter speed—as well as the ergonomics may become a stumbling point.

Since the SLR camera lacks an electronic system, these settings are adjusted mechanically either on the body of the camera or the lens. For example, in most SLR cameras the aperture should be set manually using the aperture ring on the lens. You will notice changes in lighting straight away by looking through the viewfinder.


Unless your SLR is really old, the shutter speed dial is probably the first thing you will notice on the settings panel. You simply can’t miss it because it’ll include values you are accustomed to seeing—1/500, 1/250, 1/125, and so on—and B mode that stands for bulb. Older film cameras had weird shutter speed values that will be difficult to understand.

ISO settings in SLR cameras are a bit different though because you need to use the same ISO value of the film you are using. Modern SLRs won’t feature an ISO dial because the camera will read the film sensitivity using the electronic contacts located on the film cartridge. If your SLR lacks these contacts, then you will need to select the same ISO of your film with the ISO dial located anywhere on the settings panel of your camera.

The most important element in the camera is the film compartment, located on the back of the camera, that is divided in several interconnected elements.

You can open the film compartment using a button located either on the side of the camera or on its back. That is where the film is inserted. Some older cameras have a rewind crank that you will need to press after taking every photo in order to wind the film back into the fulm compartment and pass on to the next exposure.

When you have shot the whole film, you will need to rewind it into its case. This is done in two steps. Firstly, you should find a special button located on your camera that unblocks the camera rewind and then press and hold it. Secondly, you will need to roll the film back into the case using the rewind release. In the contrary case, the film will turn out torn.

Apart from all of it, your SLR may have a timer and timer release button located on its front panel near the lens as well as a remote shutter release port.

Now you only need to get a good grip on your SLR, slip the film into it, adjust the shutter speed and ISO, and make a photo. Good luck!

We hope that this article was of help to you and we’ll be glad to answer your questions in comments. Feel free to shoot us a message!

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