Photo editing software has a large price spectrum from free to those costing many hundreds of dollars. There are programs that are very basic and limited, and the more expensive programs that have an almost endless variety of features. Whether you use a free program or one with endless features depends on your needs and expectations, as well as your computer skills and patience to learn new features. One thing is certain: to some extent, you get what you pay for in photo editing software.
As a genealogist, before making a purchase you really need to assess your needs for photo editing software. Are you ready to spend days and maybe weeks learning a complex program or do you just need to adjust some photos and add labels and perhaps a description? One way to determine what you need is to try several free programs and then decide if you need a more complex alternative.
How does an inexpensive photo editing software program compare to the top-of-the-line Adobe Photoshop? Do you need all of the features of the more expensive program? For comparison, I choose a recent addition to the photo editing line-up, Pixelmator, an England-based software product available for $29.99 from the Mac App Store, and Adobe's Photoshop at about $800. I will also throw in some comments about Photoshop Elements, the less-expensive version of Photoshop priced at about $60 to $80. I do all my photo editing on an Apple iMac, but there are comparable programs for Windows. Pixelmator is a Mac-only program, but Adobe's products run on Windows and Mac platforms.
Many of the features of the newer photo editing software programs do not pertain to editing at all. The programs are expanding to include ways to share your photos and to connect with social networking sites. Most of the programs have features that allow you to format and publish your photos to the Web. Programs like Photoshop and Photoshop Elements also have either built-in photo organizers (Photoshop Elements 10) or like Photoshop have a dedicated program for organizing photos called Adobe Bridge. Photoshop also includes a sophisticated editing program called Camera Raw. Out of fairness, I have to admit that Adobe Bridge and Adobe Camera Raw are extremely valuable tools for editing, organizing and adding metadata to photos. Adobe Bridge and Adobe's Camera Raw programs come with the purchase of the full version of Photoshop.
Pixelmator and the Adobe programs are available in free 30-day trial versions. In deciding what to purchase, one challenge is that Adobe's products, including both versions of Photoshop, also come in standard and expanded versions. It takes quite a bit of time examining the Adobe.com website to really understand the differences between the various levels of the programs. For example, there is also a program called Adobe Premiere Elements 10 which adds video editing capabilities but is a separate program. Yes, it gets very confusing very quickly.
What are the most common features of these programs? The idea of a photo editing program is the ability to change the content of the photo, not just adjust the color cast or lighten or darken the image or add special effects. You could work with any one of the these programs for quite a while before you discovered the real differences. Let me show you a how the programs work with removing an unwanted element from a picture.
Here is a photo of a cemetery with an unwanted shadow of the photographer:

The object here is to remove the shadow so that the photo appears as if the shadow was never there. Before I get started, remember to make a copy of any photo you intend to edit. Never work on your only or master copy. You might make a mistake that cannot be reversed.
First, I will use the tools in Pixelmator to try to remove the shadow. To simplify the process, I am not going to create layers in the photo or work with masks which are more advanced tools. There are entire books of instructions about how to use all of the tools and create layers and masks in Photoshop, and to avoid all of this extensive complication I will use the basic tools of the programs.
Pixelmator has a Healing Tool that removes unwanted objects from the photo. You essentially paint over the object you want to remove and the program fills in the area from the surrounding parts of the photo. Photoshop also has the same type of feature. As a rule, Photoshop has several other ways to achieve the same results. Here is my first try with Pixelmator:

Hmm. Didn't work too well. I changed tools and used the clone tool with Pixelmator. Here is the photo without the shadow:

If I spent some more time, I could do a better job of blending the rocks so that you really couldn't tell that something had been removed. Now, I could go on with a long discussion and comparison of the tools in Photoshop and Pixelmator, but here is the same photo with the shadow removed in Photoshop (you will have to take my word that I really did use Photoshop for the second photo).

Any differences are due to the time I took in removing the shadow. One thing you will notice, if you look carefully, in both photos there are duplicates of some of the rocks so you would have to work with the photos for some time to make the copy look random. Also, the area you choose to clone makes a huge difference in how the finished product appears.
This looks like a draw between the two programs. Both have the basic capability to edit the photos. If I were to take a few dozen pages, I could demonstrate why I will still use Photoshop. The main reasons deal with the way it handles Camera Raw images and other details dealing with file management and other issues. For example, one feature I use all the time in Photoshop's Camera Raw program is the fill in flash, where you can lighten the foreground without overexposing the entire image. This tool seems to be missing from Pixelmator but you can adjust the foreground and the background sort of independently. The differences may be a more a matter of degree of control rather than missing the entire feature. Please be aware that I have only skimmed the surface of the features of these programs. If you need a program like the full version of Photoshop, you will know it from experience.
But all in all, for the price, a program like Pixelmator gives you the ability to make substantial and real edits to your photos without spending a lot of money in the process. Will you outgrow the capabilities of the less expensive programs? That depends on how far you want to go with photo editing. What about Photoshop Elements? I could do exactly the same edits in Elements as I did in both the other programs. The main differences reside in the added features of organizing and sharing photos.