The magazine of the Melbourne PC User Group Enhancing Your Digital Photos Geoffrey Heard

A common problem in any photography is control of the brightness or dynamic range. Our eyes can handle a huge range of levels of brightness — some say unlimited — while an 8-bit digital photo has a range of 256. We all know that on a bright day with some nice black shadows, even our eyes with their great range are struggling to cope. So how can we get enough shadow and highlight detail in our precious photos so that they look "normal" to us?

One way is to reduce the range — add light to the shadows with flash fill, reflectors, etc. or limit or disperse light with shades or diffusers at the time you are taking the photograph. But what would you do about a shadowed landscape? How big is your flash?

Other solutions are in the processing. The first stop is manipulating your curves. Professionals I know who work with images all day do this with amazing speed and success but my experience is that we ordinary users simply don't do enough of it to gain and, importantly, maintain the necessary expertise.

There are plug-ins to help. A good one is ShadowFixer from FixerLabs. But while it is opening up the shadows, in my experience it is also lightening (to a lesser extent) the highlights and mid tones. Okay for a quick fix over a somewhat limited range, but not a complete answer.

Photoshop CS2 boasts a new tool to help fix this — Merge to HDR (High Dynamic Range) — which combines three or more images, over-exposed (for shadow detail), correctly exposed (for mid-tones) and under-exposed (for highlight detail) and it works in 32 bits. Adobe's note on it talks about scenic views with as many as seven different exposures of the same picture taken from exactly the same viewpoint with the camera on a tripod.

I can see that could be a great help to architectural or landscape professionals. But do you plan your pictures that far ahead? No, neither do I. What happens if there are moving elements in the picture? I would hope the Merge to HDR tool would also work with a reasonable image plus over- and under-exposed versions you generate in your computer, but the Adobe note does not mention that. It looks as though this is a Rolls Royce tool that runs only on smooth roads!

Back To the Future!
 
But here comes the cavalry! You don't need to be a curves expert, or go to the expense of plug-ins, or run the latest Photoshop to get more open shadows and highlight detail in your pictures. There is a fast, efficient and easy way to control contrast that gets results, indistinguishable to the ordinary eye for most purposes, from those of the Merge to HDR tool. In fact, once you know how, it is hardly any more trouble in the computer
than the automated Merge to HDR process — it literally takes two minutes maximum — and you work from a single image so it is much less trouble at the picture taking end of things.

The essence is simple, you do exactly what the old time photographer did when grappling with a high contrast picture on film — you make a transparent, reversed, blurred mask and combine that with the image, adding detail to both ends of the contrast spectrum. Once you know the trick, you can play with stuff like how dark or light you make your mask, how sharp it should be and the type of transparency to use for the most pleasing result.

Here is a step-by-step guide to the process using Canvas's raster image mode. In Canvas, I have separated the images on the page to make it easier to see what is going on. Normally, Canvas users would leave the two pictures in register while working on the top image. The process is virtually the same in Photoshop, Paint Shop and other photo/raster programs with the basic tools. As a guide, in Photoshop you copy the layer your original is on, name the copy "Contrast" (or whatever you like) for convenience, then go to work as described in the captions.

Is the result up to snuff? You decide!

And speaking of automated — in Canvas you can set this up as a sequence (a recording of your actions) so that you have a macro to do the job; in Photoshop that would be an Action (from Photoshop 4 on). You could tie that in with a simple Visual Basic script to automatically process a whole bunch of similar problem pics.

About the Author
Geoffrey Heard is a Melbourne writer, photographer and Desktop Publisher. He is the Publisher of The Worsley Press. http://www.worsleypress.com/

Reprinted from the July 2006 issue of PC Update, the magazine of Melbourne PC User Group, Australia

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