This page was translated by AI. Please be forgiving of any mistakes.
‹ Photo Notes · 15 ledna, 2012
When looking at a photograph we perceive its content and form – the way it was captured and processed, ideally some emotional charge. But has it ever occurred to you how many different numbers can hide behind a single photograph?
In seconds or, more often, their fractions (e.g. 1/125) we express the time for which the shutter was open and light fell on the film or electronic medium.
With a number (2.8, 5.6, 11, 16 …) we describe the aperture value of the lens, where a higher number means a larger stop – a smaller opening through which light can fall on the medium.
The ISO value, expressed e.g. by the numbers 50, 100, 400, 800 etc., informs us about the sensitivity of the film or about the increase or, conversely, decrease of the sensitivity of a digital sensor.
All three numerical values mentioned above, in mutual harmony, ensure the correct exposure of the photograph. Sometimes, though, we want to under- or overexpose a photograph and then we use exposure compensation (e.g. -1/3 EV, +2 EV).
For this or that shot we choose ideal lenses.
Basically we divide them into two groups – with a fixed or variable (zoom) focal length, defined in millimetres (28, 50, 85 etc. for fixed-focal lenses, 17-35, 24-70, 70-200 etc. for zoom lenses).
Another important factor of every lens is its speed (1.8, 2.8, 3.6, 2.8-5.6 etc.), that is the minimum possible aperture value.
In connection with lenses we can further talk about their diameter (62, 77) – we need it for the correct choice of filters, caps, lens hood etc., and it is again given in millimetres. Other factors, such as the number of optical elements – lenses (e.g. 14) in a certain number of groups (e.g. 4) or the quality of optical resolution (e.g. 120 lpm – lines per millimetre), the number of aperture blades and others, inform more about the quality and sophistication of the lens than about a direct influence on a particular photograph.
We mostly record a photograph on a film or electronic image medium. We distinguish the size – the format of the medium (e.g. 35mm film 36×24 mm, medium and large format 4.5×6, 6×6, 7×6, 9×6, 18×24, 24×30 cm etc.) and also the mutual ratio of its sides (e.g. 3:2, 4:3, 1:1).
With digital cameras the resolution of the image chip also plays a role, given in megapixels (e.g. 12 Mpx), and the maximum image resolution (e.g. 4256×2832 px).
A film has a certain number of frames (e.g. 12, 16, 36 …).
A digital photograph is captured by a chip but mostly stored on a memory card, whose data capacity (e.g. 8 GB) and often speed are important – as a marketing trick various numbers such as 133x etc. are given, but in reality what matters is the amount of data transferred per second when reading and writing (e.g. 10 MB/s).
Digital photographs are in most cases stored in the RGB colour mode (red, green, blue), where each of these three colour components can record 256 shades, and by multiplying them together we arrive at a total of 16,777,216 colours. We can also talk about the quality of the A/D converter (e.g. 14 bit) and so on.
All digital data is in fact just ones and zeros.
With digital photography we also work with colour temperature, that is the balancing of white with regard to the surrounding light. We give colour temperature in Kelvins (e.g. 5500 K).
When composing a photograph we think in ratios and proportions of mathematically expressible squares, rectangles, diagonals, triangles and circles or their parts… the middle, that is halves and quarters, thirds, the golden section (the number Phi – Greek φ – with the value 1.618033988749894848…) etc.
We work with the distance of individual objects in the scene, the intensity, direction and often the size of the cone of light, the depth of field and so on.
When a photograph succeeds, the output and its format matter to us – today most often for a computer monitor (formats given in pixels, e.g. 900×600 px), ideally on paper (formats mostly in centimetres or inches, e.g. 60×40 cm, 36×24 „). When choosing suitable photo paper its grammage – weight per 1 square metre (e.g. 290 g) – is also important, and when printing from a digital medium we should, among other things, check the print resolution of the photograph (e.g. 300 dpi – dots per 1 inch).
Terrible? Yes.
One could find still many, many more numbers around a photograph. It is good to know about them, even though it is often not essential. Their practical use should happen rather in our subconscious; it is hard to imagine an author of artistic, let alone reportage photography, where often fractions of a second matter, running around the scene with paper, pencil and calculator, counting, writing down, combining.
For example, music or poetry are also quite well describable mathematically, yet they act on an ordinary listener mostly in an emotional way, and most people will distinguish at most a waltz and the rest. A beautiful example from the musical world is the Beatles song Yesterday. It is atypically written in a seven-bar scheme – in complete contradiction to the most common and for us most natural eight-bar one. Yet it sounds very natural; on the contrary, it would sound very unnatural played in eight bars. This small „anomaly“ was not noticed by a number of musicians, and quite possibly not even Lennon and McCartney were aware of it at the moment of its creation.
Numbers should help us and in no case should they bind us. The photographer-creator should always concern himself with the content of the scene and the way he conveys the shot to his audience, because the viewer doesn’t want to see tables densely covered with numbers, but an interesting photograph that works on his emotions and to which he gladly returns sometimes like to his favourite song.