Tagged: chroma

11th October 2018 – Arthur Kingdon

Arthur Kingdon was our guest speaker and a very well received evening of his (mainly) underwater pictures. Our own Julie Kaye introduced us to this genre last year. Arthur took us around some of the worlds hotspots for underwater photography and took us back a few years too.

The equipment needs to keep a diver live aside, the hostile environment, and days when a diver cannot see their hand in front of their face, aside, pretty much most sorts of cameras can be used given a functioning housing. This is an equipment heavy branch of photography.

But all that equipment does, plus a heap of research and local knowledge, is get us to the photo opportunity. Then the photography begins. Less light to no light depending on depth, colour shifts also dependent on depth and things with big teeth and a bad attitude looming in the dark.

So among the other environmental factors and the need to master shooting close up using wide angle lenses (fish eye lenses are not uncommon but that is not where they got there tag from), there is also a need to shoot at high ISO’s. And high ISO’s mean noise in the image. So, something common to us all.

Our personal attitude to noise is the key to its perception and thereafter our attitude to an image that contains it. Noise in digital photography is caused by the action of electricity passing threw circuitry where it encounters impurities and as a result generates signals that are not part of the designed outcomes. It is just part of the physics of electrical circuits.

When we increase the ISO we boost the signal. When we boost the signal we boost the noise in that signal. At low ISO’s, that is around the base ISO that the sensor was designed for, usually 100, there is so little noise that we cannot or do not perceive it. Double the ISO to 200 and we double the amount of noise in the image. This maybe equally undetectable but eventually it does become obvious.

There are two sorts of noise we can detect in our images. Luminance, which manifest as little points of light and which we are likely to be far more tolerant of because their visual impact is less, and chromatic or colour noise, which can be hideous over fairly limited levels.

Luminance noise, as the name suggests, comes about under restricted light conditions. It can be caused by bumping up the signal via the ISO or through long exposures. Its source is the sensor heating up as it does its complex job very rapidly using very small channels which create resistance and therefore heat. It produces “Hot pixels”, little squares of white, which are usually quite easily dealt with in post.

Chromatic noise manifests itself as tiny worms of colour, especially in very dark or very light areas in an image. It comes across as tonal aberrations in an image. It can be lessened in post production through noise reduction software, but it comes at the price of a certain smudging of the image.

Whereas it is true that the newest sensors are a lot, lot better at handling noise than they were even five years ago it is still a by-product of boosting the signal and causing heating of the circuitry. It is also true that the situation of the photograph is also important to our perception of noise in an image from a sensor of pretty much any size or age.

Getting the focus spot on is probably the greatest distractor from noise that there is, especially when we fill the frame with it. It is also the easiest of the solutions to our perception of noise in any given image to enact. It doesn’t alter the amount of noise in a frame but it does fool our senses about the amount of it.

A correctly exposed image will draw less of our attention to high ISO image noise than an underexposed one – though there is lesser noise obvious in an overexposed exposed one.

So a frame filling, sharply focused, correctly exposed image will go a long way to positively influencing our perception of any photograph, a high grain one just as much lower, though, again, none actually reduce the physical amount of noise but does diminish our perception of it.

JPEG is also, because of the nature of its algorithms, not a good option for shooting in, especially when you further process it. Shooting in RAW is a better option if any post processing is going to be involved. The reason being JPEG applies noise reduction, giving that loss of fine detail we alluded to above, RAW comes with everything left in. That means we can apply noise reduction manually as we see fit. With JPEG we have to take what we are given.

 

101 Corner

Light is everything in photography, but to make a photograph we have to do something with it. Basically we have a frame, what the viewfinder shows us, and we move around or move what is in the frame around to make an image that shows us something interesting.

Arranging things in the frame, however we do it, is called composition. Composition is the second most important thing in photography after light. Every photograph ever taken, or ever will be taken, combine these two things. Consciously using these two things is the absolute basis of making better pictures and they have evolved over centuries.

Although they are usually referred to as “The Rules of Composition” that is not helpful, as rules imply something that is absolute. They are better thought of as the Tools of Composition. We select the appropriate tools to make a photograph, just as we would select a hammer not a screwdriver to drive a nail into a plank of wood.

There are many such tools, some get used more often than others, some in combination. We will revisit this several times, but at the moment get your camera out for 20 minutes every day over the next week and use these three tools: “Thirds”, “Frame within a frame” and “Leading lines” to make half a dozen images a day. It can be in doors or out, with your phone or another sort of camera, the important thing is to go looking for these opportunities, or making them.