Friday, 23 April 2010

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?


Post a Comment