Jargon: Key Words

I was just reading over the last couple of posts I made and realised I'm jabbering away about RAW and post-processing terms like "Unsharp Mask", all terms which will pass a new starter by completely. I will cover the whole RAW vs JPEG debate in a later post, as well as some of the basic post-processing techniques, but let me just fill you in on the basics of what some other terms mean.

Shooting in RAW

In basic terms, if someone says they are shooting in RAW they are referring to the file format of the shot in the camera. A RAW file is the digital equivalent of the negative in 35mm cameras; it captures the raw data of the shot without applying any processing whatsoever. This means that every possible pixel of data within the parameters of the settings you have chosen, will be captured and made available to process with.

On the flipside, shooting in JPEG, your camera will apply a certain amount of processing to a shot as soon as it is taken; most notably it is a "lossy" file format, and the automatic compression applied to the file within the camera makes much of the detail unchangeable in post-processing. For example, if I underexpose a shot slightly, with the JPEG file I will be limited as to what detail I can recover in the darker areas; with RAW there is a lot more that can be recovered, which is handy for me as my camera tends to shoot a little dark anyway.

RAW files themselves are not viewable as a preview or thumbnail and you have to install special software to view and edit the images. RAW files also tend to be anywhere from two to six times the size of a JPEG file.

I shoot RAW+JPEG -- it uses a huge amount of space on my memory card and hard drive, but it enables me to pick and choose via the JPEG preview which shot I want to edit and publish.

I really need to clear some of those old shots out, actually.

Post-Processing Terms

For starters, in future posts you may see me mentioning "PP" -- that refers to post-processing, which is adjusting the shot in software such as Photoshop or, in my case, GIMP.

Unsharp Mask -- confusingly-named tool for sharpening an image. This method is preferred to any generic "Sharpen" tool you may have as it offers more control.

Levels -- the Levels tool is for adjusting colour and contrast using the image's histogram as a guide. I'm not totally au fait with the science behind it, but it involves moving sliders around to get the desired contrast and level for the overall image or for each colour channel.

 

Curves -- similar to the Levels tool, the Curves tool shows you the image histogram with an initially straight diagonal line running through it, which can be adjusted as needed to increase or decrease the various tones of the image. For example if you pull down the lower end of the line, and pull up the higher end, you are darkening the dark tones and brightening the bright tones, thus adjusting your contrast.  Again, you can choose each colour channel for more specific results.

Both Levels and Curves are tools I use instead of the standard Brightness/Contrast tool, as they both offer a lot more control over how bright and dark you make the different tones.

Focal Length

Focal length is a term used to describe the length of a lens. It is always shown in millimetres and describes what level of zoom it offers. Exactly what the distance is measuring is something a little too sciency for me but you can find a very wordy explanation at Wikipedia.

The human eye sees roughly at a focal length of 45-50mm. The longer the lens, the further in it will zoom. Anything shorter than 50mm is described as "wide-angle", it offers (obviously) a wider angle of vision than the longer lenses.

Incidentally I am on the verge of dropping £150 on a 70-300mm zoom lens. Purchasing everything on my Amazon Wish List will require me to win a small fortune on the lottery at some point.

That covers most of the basic stuff I prattle on about.

I think?

Jargon: The Exposure Triangle Part III -- ISO.

Ugh, totally lazy late update from me. Believe it or not I've been so caught up in actual photography I've had no time to blog about it. :)

So far I've described how aperture and shutter speed can control the amount of light that falls onto your camera's sensor. ISO is more about light sensitivity. In the old film days you would have to buy different types of film for indoor or outdoor shooting; the indoor film would have a higher sensitivity to light, meaning it was able to detect it better.

These days with the nifty DSLRs we have, we have more control over what ISO setting we use, as well as being able to ramp it up to much, much higher than was available in the past.

The lowest ISO setting available on most DSLRs is ISO100. This setting pretty much allows us to control the exposure of the shot purely using aperture and shutter speed. If you're in a position to shoot in darker conditions and allow for increased shutter speed (i.e. through use of a tripod) then the lower ISO is still the way to go, to maintain the integrity of the shot. However if you find yourself in a dark condition with nothing but your hands to stabilise the image, bumping up the ISO can allow you to keep your shutter speed relatively fast - noise is always preferable to blur, and some editing software even comes with a noise reduction feature which can help.

In the below pic I was in a fairly crowded bar with no choice but to ramp up the ISO to keep the shutter speed fast enough to reduce blur. In this instance it actually works really well, giving the shot a gritty, "rock star" edge to it:



Of all the settings I use, this is the one I always, without fail, forget to set back if I then shoot in brighter conditions. If you look closer at the sky you can see what I mean:



Blech, I hate looking at shots from when I first started.

So there you go. Higher ISO can enable shorter shutter speeds but compromises the quality of the shot with digital noise.

Thus concludes my crappy explanations of the exposure triangle!

Jargon: The Exposure Triangle Part II -- Shutter Speed

So we've talked about Aperture and its role in the Exposure Triangle, and how to create bokeh using shallow depth of field. The next part of the triangle is the shutter speed.

Where aperture is the size of the opening which allows light into the lens, the shutter speed is the length of time your camera's sensor is exposed to the light. Use faster shutter speeds to capture instant moments and sharp images where the subject (or you yourself) is moving.



In this shot the wind was blowing a little, but where the exposure is set to 1/250th of a second, there is no movement blur.

If the light is low, the shutter speed will need to be increased in order for enough light to fall on the sensor and your shot to be correctly exposed. You can balance this somewhat by opening up the aperture wider (and increasing your ISO... more on this in a later post).



This shot was taken in the evening in my living room -- we only have two 60-watt uplighters lighting the room, and as I had the camera in Aperture Priority mode, the camera automatically chose an exposure of 0.5 seconds. This may not seem a lot but if you're shooting a moving subject or hand-holding the camera it can be an age. I had my elbows propped on the table to reduce hand-shake.

So for moving subjects or bright-light situations, a faster shutter speed is required. You can set your camera to Shutter Priority mode to control the shutter speed and let the camera work out the other particulars.

There will also be instances where you are actually aiming for a longer exposure; because you want to illustrate movement, or during night-time shooting, shooting fireworks or similar.



Here I was actually deliberately trying to capture the movement of the carousel so I switched to shutter priority mode and stopped down to 1/8th of a second. I wanted to go for longer but the shots were coming out way over-exposed even with the smallest aperture. Normally in long-exposure situations you absolutely MUST use a tripod (to avoid movement blur due to hand-shake) but miraculously I managed to stay still enough for this.

So, to capture crisp blur-free shots, a faster shutter speed is required (and wider aperture to compensate the light). To illustrate movement or shoot outdoors, a longer shutter speed is needed.

Next jargon post will be on ISO.

Jargon: The Exposure Triangle Part I - Aperture (and Bokeh)

There are a million blogs and a million articles on the web that will explain these terms in more eloquent or technical ways than I can, but I will give it my best shot.

When taking any photograph, the first consideration has to be the exposure. The exposure is exactly that: how well the camera's sensor was exposed to the light at the moment the shot was taken. There are three main things to consider when aiming for the right exposure: Aperture, Shutter Speed, and ISO; known collectively as The Exposure Triangle.

Aperture

Aperture was, for me, the more confusing term when I first started out. The aperture setting controls the size of the lens opening to allow more or less light into the camera. If you consider your camera lens to be like the human eye, the aperture would be the size of the pupil. Bigger = more light, smaller = less light.

As well as controlling the amount of light let in, the aperture also controls something called Depth of Field; that is, the area or amount of the shot that is in focus. A narrow depth of field means that only a small area of the shot is sharply in focus:



See how just a small part of the fence is sharp, but the foreground and background are all out of focus? That's what a wide aperture will do to a shot, especially one where your focus is very close.

A smaller aperture limits the amount of light coming into the camera, but also ensure more of the shot is in focus:



Here you can see the sundial in the foreground is just as in-focus as the trees and sky in the background.

Ok so here's where it gets confusing, and why it is this way, I couldn't tell you. To select a larger aperture on your camera, you have to choose a smaller number, and to select a smaller aperture, you choose a higher number.

Narrow depth of field = smaller number = wider aperture.
Wide depth of field = larger number = narrower aperture.

In order for your shot to be correctly exposed, if you limit your aperture you must then slow your shutter speed to allow enough light in to the camera. I'll go over shutter speed in more detail in a later post.

If you select your camera's Auto mode, you will have no control over any of the settings; however all DSLR cameras and even some Point and Shoot models have an Aperture Priority mode. This will allow you to select the aperture size you want, and the camera will then work out the optimum shutter speed to correctly expose the shot. I currently shoot almost exclusively in Aperture Priority mode.

Bokeh

Ahh, bokeh. I've come to realise from my reading that bokeh is a notion that is more pleasing to amateurs, and the more experienced photographers out there don't really consider it that much.

The word "bokeh" (pronounced "bock-eh", not "bow-kay") is a Japanese word and it refers to the part of a photograph that is out of focus. A lot of people, myself included, will compose a shot not just to capture a subject, but also to capture some attractive bokeh in the background. I find it pleasing to the eye; in the professional world I don't know how much weight it carries. To achieve bokeh, one must open up their aperture really wide when photographing a foreground subject; the subject will be in focus, the background out of focus, and this blurry background is the bokeh.



See how the cute little flower is sharp and then there's loads of out-of-focus jazz in the background? That background jazz is bokeh. The best bokeh, in my opinion, is created with a really narrow depth-of-field (the capability for which, my current lens just doesn't have) and contrasting colours or lights in the background. Bokeh itself can be an artistic device, or can be used to highlight the subject of the shot even more.



My next Jargon post will be about shutter speed.

Happy snapping.
xxx