Focal length is one of main parameters of any lens. This is the distance from the optical center of a lens to the camera sensor when the lens is focused to infinity. It is usually measured in millimeters (mm). Optical center of a lens is the light rays convergence point inside the lens. Focal length determines useful angle of view for specific frame size in vertical and horizontal planes. Shorter focal length means wider angle of view both in the objects plane and in the image plane. Longer focal length lenses give larger image of the object.

The "normal" focal length is generally considered to be around 50mm on a full-frame camera. A 50mm lens provides a field of view similar to what the human eye perceives, making it versatile for various types of photography.

Interestingly enough, the Agfa pocket series that you recall offered several models with a variety of advanced features. As 110 cameras go they were fairly high end. Built-in telephoto or macro converters that slid in front of the main lens, variable shutter speeds up to and including electronically controlled shutters that could be set from 1/15 to 1/1000 second, and even wider aperture lenses with manual focus wheels were offered in various models. Yet Agfa only offered one 110 pocket series camera model with a built-in electronic flash - the 3000 that lacked any other advanced features. Most of the Agfa 110s had a receptacle for 'flip flashes' that were an 8 or 10 bulb card version similar to earlier 4 bulb flashcubes. The reason it was called a flip flash is that after firing the first four or five bulbs in sequence on one side of the card the user had to pull it out, flip it over, and plug the other end of the card into the camera's flash receptacle to use the other half of the card. Agfa did offer an optional electronic flash unit that attached to some models via an end mounted hot shoe foot that could also hold a tripod socket adapter. Another version flash screwed directly into the tripod socket on other models. It had a cable that plugged into the flip flash port.

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Eventually semiconductor electronics reached the point where automation for exposure became more sophisticated and accurate. Manufacturing electronics became cheaper through the widespread use of printed circuit boards. The popularity of the cheap 110 cameras and the 110 film format they supported waned in the face of new point and shoot cameras in the 135/35mm film format that provided higher quality images with much of the same ease of operation the 110 cameras had. The emergence of autofocusing 35mm lenses in the late 1980s that trickled down to compact 35mm point and shoots by the early 1990s put the final nail in the coffin of widespread 110 usage.

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Wide-angle lenses have shorter focal lengths, typically less than 35mm, providing a broad field of view. Telephoto lenses have longer focal lengths, often above 70mm, allowing for magnification and bringing distant subjects closer.

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Focallength formula

Focallength

On the diagram below the object is located at the same distance from the camera sensor. But due to the lens optical center is farther frome the sensor, a 75mm lens produces larger image than a 35mm lens.

View angle of a lens is formed by the lines connecting center of the lens front element with border points of the space pictured by the lens with acceptable sharpness and brightness. The lens can be used for shooting on the frame size with diagonal that is less or equal to diameter of the image circle of the lens. Many cine lenses have larger image circle than size of the acceptable image quality circle, so actual view angle of most lenses is greater than view angle determined by the frame size.

In some countries, these were colloquially simply called "Pocket cameras" (eg german "Pocketkamera"), probably often pseudo-anglistically.

Please don't mess a lens focal length, flange focal distance and back focal distance. These are three different parameters as you can see on the diagram below.

Deviation of the actual focal lengths from the values listed above should not exceed ±2% for lenses with F<=22mm, and ±3% for all other lenses.

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Shorter focal lengths (wide-angle) tend to have a deeper depth of field, keeping more of the scene in focus. Longer focal lengths (telephoto) can create a shallower depth of field, isolating the subject from the background.

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Shorter focal lengths (wide-angle lenses) capture more of the scene in the frame, making them suitable for landscapes and tight spaces. Longer focal lengths (telephoto lenses) bring distant subjects closer, making them ideal for sports and wildlife photography.

The choice of focal length depends on the intended use. Higher focal lengths are not necessarily better; it depends on the photographer's creative vision and the type of photography. Each focal length has its advantages in different situations.

That's an old point and shoot camera that took 110-format film. For that reason, they're usually called 110 cameras. You can even see that term, "110 CAMERA," on the label on the camera in your photo.

I am trying to find what was my first camera (brand/model) but my memory is weak. All I can remember is that it had the same shape than the one on the picture, it was small, black, had a big round red button on top to release the shutter and you had to do a kind of "shotgun reloading" movement to advance the film.

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Understanding focal length is essential for photographers, as it plays a crucial role in composition, perspective, and the overall look of an image.

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You don't want to know what I called the cheap 110 Instamatic I was forced to use when I was young and couldn't afford anything better! The reason they were called 110 cameras is because they used the 110 film format introduced by Eastman Kodak in 1972.

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When the 110 film format was introduced by Kodak in 1972 typical 35mm cameras required a fairly steep learning curve to operate - both in terms of exposure and focusing. Particularly among the lower priced offerings, 35mm cameras and their lenses were heavy and bulky and still a bit pricy for many people. The 110 format introduced a cheap, easy to use small and lightweight camera to the masses in much the same way that the Kodak Brownie had offered the masses an alternative to medium format view and rail cameras a generation or two earlier.

Crop factor, associated with cameras with smaller sensors, effectively multiplies the focal length of a lens. For example, a 50mm lens on a camera with a crop factor of 1.5x behaves like a 75mm lens (50mm x 1.5).

A zoom lens has a variable focal length, allowing the photographer to adjust the magnification level. For example, a 24-70mm lens is a zoom lens that can be set to 24mm for wide shots, 50mm for a normal view, and 70mm for a closer view.