Short Backdrops- Composite?
Sometimes despite your best planning, backdrops just do not work for a particular project. Sometimes they are not quite wide enough, sometimes not quite long enough. You are then left with an arm of legs often hanging outside of the border or trying to microadjust the background for each pose. Is there an option? I will add that this point that this post requires that the user have at least a moderate understanding of photoshop.
Solid background are typically not a problem especially if your subject is just barely over the border. Photoshop for quite some time has had the warp and transform tools that allow you to adjust a portion of the image. Of course, this has limits, and after a point you loose quality. Content aware scale is also possible for areas without a great amount of detail, depending on how far you wish to stretch the pixels, but then again after a point you will loose quality of the image. If you plan of blurring the backdrop slightly, you may even be able to paint in a portion of the missing backdrop. Cloning is also an option, but can be very tedious.
The above solutions tend to fall short though if you have a detailed backdrop or if there are significant gaps between the subject and the backdrop. At this point you may want to consider a composite.
In the left image above, the detail and varied colors tended to rule out anything other than a composite. At one point this was a very detailed and tedious project that almost needed to be performed with the pen tool in photoshop. Recent advances in the software however have made this just a bit easier. Using the Select Subject or Select Object (Select Menu) tend to provide a very good selection in most cases.
It is typically important to follow up with the Select and Mask tool next which will let you see your selection and refine it is necessary with the brush tool, or refine edge tool. Once everything looks good, be sure to feather and smooth your image to avoid a cutout look. A feather of 2 px and a smoothing of 5 px is often enough for many images. You may output this to a selection.
Whenever I photograph a subject onto a background, I ALWAYS photograph the background FIRST prior to placing my subject in frame. This give me a decent starting point for exposure, as well as a BLANK PLATE for my project.
From this point, it is a relatively easy job to cut and paste or just move my selection on to the blank plate. I resize my subject to assure that it is proportional to other objects in the image by scaling down. Scaling up will cause some major resolution issues if done to excess. Blending the subject into the background can be another entire post to itself, but lighting, contrast, and color are often important points. Working with the Adobe camera raw editor (ACR) can be valuable here. Photoshop also has in a beta release the Harmonize Beta Release which can be found under Neural Filters (Filter menu) which I have found to be partially helpful in some cases (Be sure you are in the 8 bit editing mode for this to work).
Sometimes a composite can save a project and if you are challenged by this project Realistic composites may be able to help.