This article is not about the actual technique used to replace the background but the complications that comes with the idea in the first place.
It always makes me chuckle a little inside when someone says “just replace the background”…
Replacing a background is simple enough providing several but rather critical and sometimes complicated criteria are met. Normally backgrounds are replaced with the scene already in the art directors mind. The models are shot and lit in such a way to match the background, or vice versa. The models will be shot on a neutral background making it easy to cut out and replace onto the new backdrop. All assets with be with the commercial photo retoucher.
In an everyday situation this is not the case. Often a client will ask for a “background replacement”. With what kind or background? where from? who is going to shoot it? find it and buy it?
Sourcing a background requires some criteria to be met.
1. The new image background must be in the same lighting as the original
It is of little use if the new background image has dull lighting with no strong shadows if the original was shot in bright sunshine. Likewise if the original was shot with a softbox or in dull lighting and the background was shot in the mid day sun. Care has be to taken to match them as if they were both taken on the same day or in the same conditions. Sun position in the sky must be noted if the shots are outside, long shadows mixed with over head sun light will be a retouching Fopa.
2. Height of camera
Camera height is also important especially for near objects or when shooting backgrounds. If the subject was shot at eye level but the background shot at waist level criteria 3 can easily look wrong. Angles start to look wonky or incorrect. Height of camera is most important when positioning a person into a line up. Waist level positions mixed with high or eye level positions can lead to looking up the nostrils of the person being dropped in, where the rest of line up have noses where you cannot see their nostrils at all.
Trying to insert a person or object into a scene where the scale or perspective does not match that of the original will have you messing with an image for hours only to give up, it will never look right.
4. Focal length of lens
The focal length of a lens can also have an effect on if two images will blend together. A person taken from an image shot with a long lens will look odd in an image shot on wide angle unless 1 2 and 3 can be met perfectly. Long lenses compress depth of field and facial features. A very flattering portrait can be made with a long lens. A wide angle lens produces very enhanced features and the two will not mix.
5. Licensing and cost.
Probably the most important when it comes to replacing a background is the licensing.
Each image has set licensing that the image can be used for. These terms must be met when the image is reproduced. It may be that the image can be used for website advertising but not be sold on for profit or gain. It’s important that you as the client, understand the implications should be handed over to your legal department to ensure no breaches will be made.
Ideal images are not free, they come from stock agencies. Not all stock agencies have the same images. We retouchers cannot have an account at every single stock agency so we will end up paying the same you do for the image. The only difference being is that we have to find the image in the first place. If it is to meet the above 5 criteria then it could take a while. There is this search time to pay for.
When it is asked “can you replace the background” these many factors have to be considered even before the retouching begins.