About noise and distortion in photographs

Sometimes photographed bouquets of flowers appear disproportionately large or small compared to other objects. Why is this happening? Everything is very simple: a person sees any object with two eyes, our viewing angle is 45°.

A lens with the same viewing angle is called normal and is designated by the index F50 (focal length 50 mm). A lens with a different designation (that is, viewing angle) distorts space. Look at photos taken with lenses that have different focal lengths (viewing angles). If the index is less than F50 (the viewing angle is wider), then near objects will appear closer, and distant objects will appear further, the space seems to expand.

Such lenses are called wide-angle. If the index on the lens is greater than F50, then distant and near objects will seem to be next to each other, the space will seem to be compressed. Such lenses are called long-focus lenses. Point-and-shoot cameras have lenses with variable focal lengths.

So, in order to get the “correct” frame, with an undistorted perspective, you need to choose a focal length close to F50. But what if we don’t have the opportunity to set the desired value, for example, we can’t move away from the object at a sufficient distance so that it fits completely into the frame?

Then we use a wide-angle lens (a value greater than F50), and correct the resulting distortions by moving objects in the frame. Background objects should be placed closer to foreground objects, that is, objects should be placed almost in the same plane. This way you can slightly correct the perspective distortion.

Now let’s talk about image quality. Look at the two photos of the rose. The photo above is a clear shot. The rose is detailed in the frame: smooth transitions of halftones and distinct edges of the petals are clearly visible.

In another photograph, the flower seems to consist of separate details, dots, there are almost no halftones, which spoils the impression of the photograph. When shooting the first frame, the sensitivity was set to low (ISO 200), when shooting the second – high (ISO 6400).

The matrix of a digital camera, like photographic film, consists of photosensitive cells. Light hitting the cells of the matrix causes voltage in them. At low sensitivity values, the voltage in the cells is insignificant and the electrical charges remain within their cells.

At high values, the voltage in the cells increases, and charge can “jump” from one cell to another. This is why color and other noises arise. A simple tip: set the sensitivity to low if possible.

What to do if there is not enough natural light? In this case, it is better to illuminate the object with a flash without setting high sensitivity. Then the pictures will be bright and clear.

We wish you creative success!

Author of the article: Alexey Popov.

Floristry: Anna Tchaikovskaya (“Lady Rosette”).