Happiness – is when you understand
On the meaning of words did not argue too much sense. It is more advisable to agree on terminology. Reasonable people often just do so. But exceptions do occur. If for any reason, highly technical terms beyond the special knowledge, his broader interpretation often causes irritation and resistance from the experts. And if in this context, a dispute, its outcome is likely to be just senselessly lost time and the mass death of nerve cells.
Such problematic situations are typical for most of linguistics. Any language rule not to enter legally. After all, enforceable language norms can not be ensured. Language – is a living process. Has the language practice – it means it’s time to change the language norm. The author of this article is very rarely brought to hear the word “loop” with standard accent on the first syllable. Maybe it’s time to change the normative pronunciation of the word? However, give address this issue for linguists and return to the world of photography.
In the field of photography not so “lucky” to the term “vignette”. In the good old classic sense prevailing in optics, a vignette understand shading the periphery of the visual field neaperturnymi diaphragms, resulting in a drop-light images from the center outwards. That is understood vignetting experts in the field of optics.
In a broader nonspecial used the word “vignette” means any shading edges of the image, whatever the reasons it was not due. Mistake? Maybe so … But, on the other hand, such use is quite natural, since it is directly connected with the word “vignette”, which in its widest sense is understood as any frame or decoration, for example, a plate or ornament (see, for example , Fig. 1).
Fig. 1. Vignette as a design technique
Causes shading edges pictures
The reasons for the fall of brightness at the edges of the photographic image may be several.
Firstly, the brightness may decrease because of the limitations of the light beam various obstacles, falling in the design of the lens. This is a vignette in the classic sense of opticians. When aperturing lens uneven illumination caused by these reasons, decreases.
Secondly, the light beam can be limited by external (relative to the lens) structural elements. When it comes to blends, filter and so forth, the diaphragm, again, can reduce uneven illumination. If, however, cause additional shadowing are design features of a digital pixel matrix, the diaphragm can not save the situation.
Thirdly, the reduction of brightness in peripheral areas due to the law “cosine to the fourth degree.” This law is described in some detail in various articles (see, eg, [1]) and there will not be discussed in detail. It is based on geometrical factors determining the decrease of illumination at the edges of the image. Stopping down the lens against the law cos4 (alpha) »helplessly.
Some examples
Example № 1. Consider a camera obscura (pinhole camera), in which the photosensitive material is located on the plane (Fig. 2).
Do not require any special mathematical knowledge to understand that in this case, we will inevitably face the shading of the peripheral zone of the image. Indeed, as seen from Fig. 2, F> f, that is, light travels a longer path to the brim. And the difference between F and f will be greater than the wide-angle camera obscura.
Fig. 2. Camera obscura
Vignetting it? In the classic sense – no. In terms of general practice – yes. Not coincidentally, many sites dedicated camera obscura, say it is about vignetting, but not to shade the edges. And the easiest way to combat it – place the light-sensitive material on a cylindrical surface, and not on the plane.
Example № 2. Let’s look at two pictures (Fig. 3).
Fig. 3
Can we say that the right image there is an eerie vignette? In terms of optics, we must first understand the causes. If blames the restriction of the beam structural elements of the lens, then yes, this vignetting. Well, if – no, then no. Maybe shading angles in this case generally has nothing to do with optics, and achieved, for example, a graphical editor?
It means that, looking at the image, not to judge vignetting. Of course, in terms of daily practice is inconvenient, since it is necessary to very similar effects on the result using different words.
A reasonable way out of the terminological difficulties
Until the situation is not stabilized with the terminology, each forced himself to choose a reasonable course of action. According to the author of this article, the main thing – to treat interlocutors with understanding and refrain from mutual harsh judgments.
From a more practical approach can offer the following.
First of all, you can separate the terms “lens vignetting” and “image vignetting. In the first case should follow the standard definition of the textbooks on optics. In the second – to judge by the final image.
The other takes a balanced approach in its publications, Paul van Walroy (Paul van Walree) [1]. He proposes to allocate three meanings of the word “vignette”:
1. optical vignetting (the understanding of vignetting in classical optics);
2. natural vignetting (due to the law «cos4»);
3. mechanical vignetting (due to the use of blends, filters and other external devices).
In the English-language Wikipedia (Wikipedia) is also the term “pixel vignetting.This phenomenon is unique to digital cameras. It is connected with the fact that each pixel digital matrix has a finite non-zero depth (as it is at the bottom of the tiny cup-well). As a result, the rays falling on the pixel at large angles are cut off. Many digital cameras are equipped with software to combat this phenomenon.
Thus, it is reasonable in conjunction with the word “vignette” to use the additional clarifying words. As a result, reasons for misunderstanding will be less.
Findings
Alas, to make any definite conclusions until early. Wait and see! Whichever approach you choose for themselves either, it is advisable from the outset clearly communicate it to the interlocutor. To avoid misunderstanding and mutual resentment….