Ramblings of a Grouch

OK, so the DigitalMemoriesonline photo has got the background fixed (unless we decide to tweak it toward the end of the restoration) and it's time to look at the main subject.

Now the original photo was very flat and washed out. If I start restoring the main parts now I will only have a rough idea of the finished effect, so I need to boost the contrast to see what I am really working with.

As with most things, Photoshop offers an 'easy fix' for contrast - it is found in Image, Adjustments, Brightness & Contrast. The tool opens to reveal sliders to alter (you guessed it) the brightness of the image and the contrast. These controls would certainly improve the image, the trouble is that they work globally - the whole image is adjusted by the same amount. While this may seem a reasonable course of action, it isn't. And the reason why can be seen in the Histogram.

A Histogram is just a way of showing what is going on in an image in a way that we can easily understand. In Photoshop, go to Image, Adjustments, Levels and the Histogram will pop up (along with the controls to adjust the image). This is the Histogram for our photo:

So what on earth does that tell us? Basically it's a graph just like you studied at school, with zero at the far left and 255 at the far right. And this one has a dark blodge (technical, eh?) in the middle. On a Histogram, zero corresponds to pure black (full shading) while 255 corresponds to pure white (no shading). The values between represent the various shades of grey between white and black. The height of the blodge shows how much of a particular shade of grey is present in the image.

"So what?" you may say, as did I when I first saw a Histogram. But it turns out that it is an essential tool for photographic work - essential enough that all decent digital cameras allow you to see the histogram before you take a photograph. And this is what our Histogram is telling us.

The Histogram doesn't actually start at zero - it only really has any value around 82 on the horizontal scale (the blodge starts climbing up at that point). And it has died away aorund a value of 186. So there is no pure black and no pure white in the image, which we can tell by looking at the image itself. What is not to obvious is that we actually have a pale grey as the lightest tone and a dark grey as the darkest tone. The tones actually run from 82 to 186 and it is this small range which causes the photo to lack contrast and look washed out. Our 'white' and 'black' are actually the grey tones shown below.

The cure? Below the horizontal scale on the Histogram are triangular sliders (not very obvious in the picture above) which allow us to adjust the tonal range of the image - the lightest parts are made pure white, the darkest parts pure black and the tones between are 'stretched out' between the two. This is a very easy adjustment to make and, if you only make one adjustment to your photographs then this is the one to go for.

Photoshop also has another way to adjust the tonal range, known as the Curves adjustment tool. This is a very powerful weapon that can at once seem intimidating, awkward and downright confusing. It is based on the same adjustments as the Levels tool, but whereas the Levels tool affects the all the tones in an image, the Curves tool lets us adjust shadows, highlights and midtones separately (and indeed, in a colour photograph the individual colours can be adjusted separately). This is the tool I used to bring back the contrast and clarity in our photo to allow me to see the blemishes more clearly and to judge the effects of the restoration as it will be seen on the finished work. It also had the advantage of putting a little texture into the background, which I think is quite a pleasing effect.

Compare the image at the top of this article with that from the previous article here and you will see the power of the Curves tool.

And here is the Histogram of after using the Curves tool, showing the tones running evenly from white to black.

And I've now run out of time, so I'll start restoring in the next article.

Until next time ...

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