Ambitious hobby photographers can’t but help themselves to try their hand at adjusting the sharpness of the photo themselves. Technical utilities can be used to assist in this endeavour. When using a DSLR camera with a live view, a central portion of an image can be enlarged and later perfectly focused after some manual adjustments. This, however, takes a lot more time to do than just using an autofocus system to find the right focus.
Older analogue cameras did not come with an AF system. In order to focus the camera, the photographer had to rotate the lens until the correct focus was found. In the early days of photography, however, that wasn’t so easy. The photographer first had to estimate the distance of the camera to the object being photographed. This was later made a bit easier by using technical aids such as a rangefinder. The simplest of such devices is the double-image range finder. These are plugged into the camera’s hot shoe. The system has two transparent mirrors and a rotatable prism. The goal is to gather two identical image sections of the object being photographed. The value is then set on the lens. One could only see the results when viewing the developed photo.
In older SLR cameras, the distance to the object was set directly in the lens. In comparison to normal analogue small-format cameras, this was a lot more convenient for the photographer. Here, the light takes a small detour via an upward-folding mirror and goes through an adjustment disc (with a split-image indicator and micro prisms). With their help, the photographer can focus on the object by rotating the lens. This of course means that the sharpness of the photo completely depends on the visually perceived sharpness from the view of the photographer.
Photographing with a manual focus doesn’t only require of practice, but also a lot of patience. That’s why it’s not really suitable for just taking quick snapshots. It’s especially worthwhile to take the time to manually focus on an object when the sensor of the autofocus in unable to correctly focus the object due to conditions in your surroundings. Manually adjusting the focus is also advantageous when you want to photograph the same motif multiple times using the same focus settings. A camera with an AF system is unable to do this in certain circumstances since the sensor will sometimes choose a different point of focus every time.