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Editing your photographs part 1

John Humber

Posted on Thu 31 Jan 2019

It appears that in this blog feature I can upload only one image per entry. Therefore I will have to make this in four parts.

First off, to work with digital images it’s necessary to understand just a little about how they work.

The image is a grid of pixels that can be thought of as being similar to a graph-paper grid; each square on the graph-paper is a pixel. (See my previous post on Image Resolution).

Each pixel can be a different colour; the arrangement of these colours forms the image.

A full colour image, such as when you photograph your artwork, is termed a 24-bit or an RGB image.

Twenty four bit refers to the amount of digital data needed to record the image. RGB refers to the way that the colours are created from the three light primaries (NB: red, green and blue are the light primaries and are different from the pigmentary primaries used in painting/printing etc.)

The colour image is a combination of the three primaries; in digital imaging they are known as channels. So, an RGB image has three channels, one red, one green, one blue. Combined they form the full-colour picture.

Each channel is an 8-bit image—effectively a monochrome representation of all the red in the image, all the green and all the blue. When combined, 3x8=24, hence 24-bit.

Each of the pixels in each of the three channels can be one of 256 colours, or in digital-speak, Levels.

Adjusting these levels to correct imperfections in the tonal or colour balance of the image is the simplest and most effective adjustment you can make.

I use Photoshop so all of these screenshots are Photoshop, but I repeat, all digital images work in the same way; specifically, they are 24-bit, RGB images. The way that the information is presented and displayed in other editing applications will differ but you should be able to find your way around without too much difficulty.

My example is a photo, taken with my digital camera, of one of my ink and pastel drawings. The first image is the raw image as it came straight out of the camera, so-to-speak. Imported into Photoshop you can see the three colour channels indicated.

Editing your photographs part 1


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