Tutorial - Isolations
'How do you isolate objects off their background" is probably one of the most frequently asked post-processing questions in photography. Certaintly a lot of people have asked me that. Everybody wants to know how to achieve perfect isolations and to extract objects from their backgrounds. In this two sequel tutorial I will deal with tricks of isolation - from basics (Part I), to more advanced, such as hair, fur and complex objects, isolations (Part II).
We know that there is high demand for images "over white" : many designers want their images over white because white is what they publish on and it offers designers many versatile opportunities to be creative. Stock photographers want their images over white - they sell better as designers would much rather prefer a concept/product image over white than over gray, blue, pink, or yellow. And yet, matters of correct lighting and exposure aside, many stock photogrpahers who use home-made light tents, home-made lights or both still frequently do need to clean their images up to make surse their background is purely white. People who sell their work on ebay prefer the clean, uncluttered, professional look of "over white" isolations. And yet I've heard many times from e-bay sellers that they purchased equipment to shoot their products "over white" but could never really achieve perfectly white background and instead ended up with shots "over gray".
Strictly speaking, depending on your subject matter and your needs, some of what you may need to do can be done by pure color manipulation and the use of an eraser tool. The pen tools is necessary only in certain, more complex, cases. Let me walk you through a couple of representative examples. Starting from a basic, simple one.
Basics (Part 1)
Option A: Use Levels to Whiten the Background, Use Eraser to Correct the Foreground
All right, how do you get from A to B?
(Note: sometimes the gray background may appear as white, but in fact be not a pure white. (Note: To double check if your background is pure white use the color-picker/eyedropper tool pointed at the background. If the numeric values of the color picked by the eyedropper are different from #FFFFFF or 255/255/255, then your background color is not pure white and you need to change it)
Well, the first solution (and the less helpful to those of you who are already looking for isolation tips) is to do all the work in the camera: compose right, have a correct exposure, and voi la. However, only a tiny percentage of all the isolations done in-camera do not require any post processing. In most cases even correctly lit products shot over white background would need at least some kind of clean-up and post processing. Just like the shot of this red christmas ornament, most of my "over white" shots have original grayish background. For example, 'love letters' above is such a case: theoretically, pure "white" background is achieved by lighting the background (NOT lighting your subject, but pointing much of your light at the background) to achieve pure white and then exposing for the foreground. In my case, since 'love letters' are positioned flat on the surface, it is impossible to light the background separately from the background and I exposed for the letters and then "cleaned up" the gray of the surface surrounding the letters. In any case, back to isolations...
Isolating simple objects, like these christmas ornaments is extremely easy! In fact, it's a three step procedure!
First you need to create a copy of the original background: this new layer can be created by using CTRL+J (or by using layer-> duplicate layer command). Later you will understand why we've duplicated this layer. Now on to the background. The simplest and the most effective way to to achieve a pure white (255/255/255) background and to turn this gray (or any monotone) background into white is by using the CTR+L (or the image -> adjustment -> levels) option. What you do is drag the right-most slider to the left while holding the ALT key down. When you start dragging, you will notice that much of the image is black, as you drag the slider more to the right you will notice that the area of the gray background changes color from black to blue or green to bright yellow and then to pure white. Keep dragging until the full area of gray background is white. In the end you will get something like image "C" below: your background will be completely white.
The problem is that after you have corrected the background and turned it from gray to white you have also over exposed your main subject - your red Christmas ornaments are now extremely overexposed, unnaturally red, with washed out details and crude color transitions. What do we do? A-ha! That's why we created a copy of the background layer. If you look at your "layers" window (window->layers), you will notice that you have to layers there: the original layer and the layer with a pure white background. Step 3 is to "fix" the ornament and revert it back to its nice, original, natural red color. Easy.
The logic is that you have to "erase" the overexposed, bright red ornament from the white-corrected background layer so that the original ornament from the underlying, original layer shows. So, what you need to do is select your eraser tool, and set it to a large soft brush. It is very important to select a large brush because it will make it easier for you to stroke around the contours of the area where you need to erase, and it is extremely important to select a soft brush because it will give you a smooth transition between the erased and the non-erased areas (I will demonstrate this below).
You are almost done! All you need to do now is erase the ornament from the upper level so that the original layer with original ornament shows through. You work on the upper level (make sure it's highlighted in blue in your layers palette), and "erase" the area where the ornament is. You will see the original, normal looking ornament peeking through. To double check how well you've erased the ornament, make the original level invisible in the layers palette (see green arrows in the image below), and you will see what parts you have erased (transparency shown as a grid) and what parts remain.
Since you have selected a soft brush, it is okay to leave some edges of the ornament not perfectly erased. What soft brush does is creates a gradated "transparency" from "fully transparent" closer to the center of the brush to nearly non-transparent closer to the edges of the brush. The red edges that you see remaining are no problem as they are not rough, hard edges. They are soft, gradated edges, and will assure soft, smooth color transition from erased areas of the ornament to the pure white background.
Flatten the image (layers --> flatten). And you are done!
Of course, every effect can be achieved in Photoshop in more than one ways. Other ways to make the background white while keeping the ornament correctly exposed are:
- Option B: Paint the background white (Page 2)
- Option C: Magic wand selection & Pen tool selection (Page 3)