Depending on what area of photography you’re pursuing, there are several mainstream programs you can use to edit your images. Your post process workflow is the most important factor to consider when making your choice - such as the volume of images and the extent of your editing. Whether you batch edit your images lightly or do intensive editing sessions on a select few, there is a program for your specific style.
Lightroom was developed with the photographer in mind. Whie you can certainly do many wonderful things in Photoshop, the workflow is not always as friendly to photographers as Lightroom can be.
Essentially, Lightroom provides you with many tools and processes that streamlines your editing (such as Modules and the film strip). This is fantastic for photographers who have a large volume of work (think wedding or sports photographers) and would like to apply relatively simple edits to many images at once. Techniques such as black and white conversions, white balance changes, simple blemish removal and skin softening, etc. can be performed easily.
You can also apply similar edits to several images in Photoshop as an action, but Lightroom does it in a more simple, straightforward, and easily reversible manner.
Also, the interface is a bit more user-friendly than Photoshop since the more advanced tools have been omitted to focus more on streamlining your work. Unless you know your way around Photoshop, it may take you a while to figure out where your tools are and how to perform certain techniques. So not only can you perform edits easier and to multiple images in Lightroom, but you can also access your tools more efficiently for the ultimate streamlining of your work.
If you have a Mac, then you also have the option of using Aperture, which is much like Lightroom. Comparing these two programs is much like comparing Nikons and Canons, so I’ll try to not get too technical.
Aperture has many great organizational features like Lightroom, although the interface is a bit different. For example, Lightroom has the Develop Module while Aperture has Adjustments. Some users say that Aperture is a bit more streamlined in organizing your images (mainly due to the Books feature), while Lightroom is considered to be better for printing your work.
While there are many “pros and cons” articles comparing these two programs, the reality is that both perform with little difference. The best way to decide on the best program is to download the trial version and give both a test run. One interface will eventually seem more natural to your workflow and style than the other, which is the most important step in choosing the right program (at least when your choices are either Aperture or Lightroom).
While Lightroom/Aperture is perfect for the casual editor who has many images, Photoshop is where the advanced post processing takes place. Exposure blending, panoramic stitching, cloning and other detailed work is done in Photoshop as the previous two programs are not equipped to handle that kind of intricacy.
The biggest benefit of Photoshop is layers – more importantly, the ability to mask and blend layers to create a mosaic of edits in just the right combination. The learning curve is rather steep, but the reward is most certainly worth it.
Photoshop is for sophisticated photo editing, much more suitable for those who spend a few hours on an image but only produce one or two at a time (such as fine art photographers), or for those rogue images from a wedding that need special attention.
As you can see, photographers have several editing options for their images. The best part about these programs is that they all have free trials allowing you to use the program before making an investment. Many photographers will employ Lightroom/Aperture AND Photoshop to get a full spectrum of editing capabilities. For example, a photographer may use Lightroom to go through simple editing and preparing images for the web, but will switch to Photoshop for the more serious edits.