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In this issue of Photo Shop, we are going to spend a lot of time looking at - PhotoShop!

Adobe PhotoShop, that is, the premier picture editing tool used by digital photographers. Currently in Version 7, this popular image manipulation software has come a long way in terms of functionality, if not exactly in ease of use.

PhotoShop is the preferred tool for image manipulators everywhere, and is very often sold bundled with digital cameras, personal computers, scanners and other image capture devices.

However, if this is how you obtained your copy of PhotoShop, chances are that what you got was the "Light Edition", sometimes called PhotoShop LE or Adobe Elements.

This does not concern us here, because whether you have the full-blown version or a light edition, the functions we are going to use in this article are available in all of the versions anyway.

So, what are we going to cover today ? PhotoShop is an immensely feature-rich tool. Based on a quick look at the PhotoShop shelf in my local Borders, I would estimate that well over 100,000 pages have been written about how to use this particular piece of software. Clearly, therefore, it is way beyond the scope of this article to cover more than a fraction of its functionalities, so I will limit myself to those that every digital photographer should know: Image sizing, cropping, color manipulation, sharpening and saving, in that order.

In future articles, we will delve deeper into the rich menu of choices that PhotoShop offers those who want to explore and experiment. But a word of warning is in order: If you decide to become a PhotoShop guru, either don't start a family, or at least notify the one you already have that you won't be available evenings any more. The learning curve is steep, and there are many detours along the way.

Let's roll!

The large toolbar on the left is your main toolbox, and where you find the all important Selection tool (top left corner, highlighted)

On the right are various other toolboxes, with the most important one being the History tool (bottom box on the right). This tool is your multi-level "Oops!" corrector, and as you work on a picture, the actions you have performed are listed. You can use this tool to undo any changes you have made, up to a point. You specify the number of undo levels in the Preferences menu (found under Edit), but beware! Once you save a file, the History tool is reset to the new state of your picture, and you can no longer undo anything you did before saving.

The first action is clearly to open a picture, and you do this just like you would open any other file in a typical Windows program, by selecting Open under the File menu.

Unless you are supremely confident, or like living on the edge, or both, the first thing to do is to make a copy of the picture, and work on that copy. this means saving the picture under another name.

It is important to take a little detour here, and discuss file formats. There is a dizzying array of file extensions and formats available, and you can work with them all in PhotoShop. But the first thing to remember is to NEVER save a file you are working on as a JPG file!

Chances are the picture that came from you digital camera is a JPG file. Without spending a lot of time on the details, suffice it to say that JPG is a file format that employs a compression algorithm. This means that the computer will seek to "optimize" your picture, or rather the file size, to keep it as small as possible. It achieves this by discarding picture information whose loss will not make a substantial difference to the naked eye anyway. This makes good sense if you want to display pictures on the Web, for example, but for our purposes, this is no good. You see, the compression is applied EVERY TIME you save the picture, and this means that every time you save, compression is heaped upon compression, with picture information being lost every time! Soon, a print of your picture will look horrible, because the changes made in compression will show up quite clearly on a print.

The dialog box that pops up will probably tell you that your picture presently is of an outrageous size, like 80 centimeters wide or something. Clearly we need to change this, but what we do NOT want to do is to change the picture to the size in which we want to print it. At least not yet. You see, we are going to crop the picture in a minute, and if we size the image to our intended print size now and then crop it, the picture will no longer be of that print size, will it?

So, since I have an idea that I want this image to fit nicely on an A4 page, which is roughly 29 centimeters wide, I'll give myself some wiggle room and specify 40 centimeters as the width. The height will be set automatically by PhotoShop, in proportion to the original picture size and the new specified width.

The next vital change we must make is the Resolution. If you have been paying attention to the last two articles, resolution refers to how many dots (or pixels) per-inch we want to print. By default, PhotoShop opens your picture at a resolution of 72 dpi. This is because a typical computer monitor only displays 72 dpi, and so for monitor display, there is no need to display anything more. No matter how many dpi you set in this dialog box, the picture will look exactly the same on your monitor. But I assure you, it will not look the same when printed!

You could set it to 1200 dpi if you felt like it (and had a huge hard disk on your PC), but for printing purposes, 300 dpi is the standard, and plenty adequate, so change the 72 to 300 and press enter.

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Cropping for a Better Composition

Now sit back, take a sip from your drink, put your feet up, and contemplate the picture before you. What (if anything) is wrong with it ? Well, in this case, there is way too much sand. Whoever looks at this picture want to see an eagle ray up close and personal. Sand they can see anywhere!

So we need to crop this picture, put the focus back on the star of the show, as it were.

The easiest way to do this is to make sure the Rectangular Selection Tool in the top left corner of the main toolbox is highlighted, then with our mouse draw a nice outline around the area we would like to print, like so:

This is much better! We've eliminated vast amounts of not terribly exciting sand, placed the eagle ray more or less in the middle, and already the focus of the image has shifted. We have action in the picture, too, with a clear focus on the swirling sand kicked up by the flapping wings.

Cropping is of course also an excellent way to remove irritating elements such as half-divers, sea urchin spines, fish tails et cetera, that have a habit of intruding around the edges of a picture, especially if you are in the water with a large crowd.

Manipulating Color

Now comes the hard part. Color manipulation is a science in its own right, and way too large of a subject for this article to deal with in any meaningful way.

So what we will do this time is simply change some of the highlight-characteristics of this picture. Especially since this particular image consists almost solely of blue and green anyway.

Highlights and shadows are dealt with through manipulation of something called "Levels".

PhotoShop comes with an Auto-Levels option, found under the Image, Adjustments menu. But, while Auto-Levels sometimes does a reasonable job, it is not a very subtle tool, and it gives you no options other than to accept the output, which can sometimes be outrageous. The image can virtually be destroyed by Auto-Levels, because it tries to average everything and give you what it believes to be the best result. But this method can best be likened to someone using a sledge hammer to drive in a 1-inch nail. Not pretty, and not recommended.

The colors on the ray are not bad, actually, but we appear to be in a field of green cheese, some of which has rubbed off on our winged friend!

No, what we want to do is to manipulate the Levels all right, but we want control over the process. So we select the Levels option from the Image, Adjustments menu, and get a dialog box that looks something like this:

You can actually work in the entire color range here, by selecting the individual Red, Green or Blue color channels individually and working on them.

But we are still amateurs here, so we will opt to work on the picture in its entirety, so leave the box set to "RGB" (Red, Green, Blue, well guessed!), and turn your attention instead to the histogram (the mountain range in the middle of the box).

Now, the way we manipulate levels is by using the mouse to grab the little adjustment arrows you see underneath the X-axis of the histogram. The left arrow adjusts Shadows, the middle adjusts mid-tones, and the one on the right adjusts highlights in the picture.

You can play around with the arrows and instantly see the effect on your picture. There is no universally perfect setting, but initially, what you want to do is adjust the Shadows by moving the arrow to the point where the left-most part of the histogram starts, and the Highlights by moving the arrow to (you guessed it!) the point where the right-most part ends. Like so:

Sharpening the Picture

One of the best things about digital photography is that we can work with the image sharpness, and achieve some pretty neat results. Clearly, you can not do too much with a picture you took one-handed out of your car window as you were traveling across a recently plowed field at 60 km/h, but if the image is reasonably crisp, we can make it crisper!

Tools for doing this are found in the Filter, Sharpen menu, but wait!

The makers of PhotoShop are real pranksters. They know that if they call a tool "Sharpen", most users will assume that they have just found the tool used to actually sharpen an image. And to make it that easy would detract from their reputations as makers of amazing and complex software.

The Sharpen tool will, in fact, sharpen your image, but like the Auto-Levels tool, it is best left alone. Why ? For the same reason that Auto-Levels is best left alone. Sharpen is not a subtle tool, and the changes it makes to your pictures are rough and irrevocable, especially when printed.
To get more control, the jokers at Adobe have incorporated a much more powerful tool. And like the comedians they are, they have chosen to call it the "Unsharp Mask" tool.

The technique of masking the outlines of objects, thus making them look sharper to the naked eye, was first developed in Hollywood as a means of sharpening moving pictures. If you want to know how it works, try http://www.pixilver.com/tutor_usm.html for a great guide.

For now, select Filter, Sharpen, Unsharp Mask and you get a dialog box that looks something like this:

The settings in this dialog box are mercifully few, and easy to play around with. PhotoShop will give you instant feed-back on the result, but no changes are made to your picture until you press OK. For an excellent lecture on the Unsharp Mask settings, visit

http://www.creativepro.com/story/feature/11242.html

In this case, I played around for a little bit, until I found the most pleasing result, which - for me - was a Radius of 2, a Threshold of 4 levels, and sharpening of 300%.

Along the way, we changed the resolution of the picture to 300 dpi, so we can print it, and in the process of doing that, we learned how to change the physical size of the picture.

I would encourage you to try these actions on pictures of your own. These are the basic skill required to master PhotoShop, and give you a good grounding for the next article, where we will start working with some more complicated pictures, and see how we can remove irritating objects such as bits of backscatter, and how using something known as "Layers " can dramatically improve our pictures.

About the author

Bjorn is a PADI Master Scuba Diver Trainer living and working in Singapore.
He has been a passionate underwater photographer for 5 years, and is widely
published on the World Wide Web. His "Guide to Underwater Photography",
which can be read http://www.seapix.com/basicuw.htm was recommended by
Rodale's Scuba Diving, and he has won several amateur underwater photo
competitions.