backdrops - What is the best way to photograph an object when the background has to be replaced in post?

I plan to shoot an object (a banana peel to be precise) and then replace the background with another image¹. What would be the most effective approach given the following conditions:

• Canon 550D


• Sigma 18-55mm f/2.8-4.5


• Maximum camera to subject distance: 1.5m



• Distance from object to wall: around 0.5m


• No flash, but continuous household lighting²


• I have a black cardboard backdrop of 1x0.6m. It's not a requirement to use it.


• The background should be able to be replaced automatically. There will be a lot of photos (it will be a stop-motion), so I can't manually mask every single one.

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Footnotes:
(1): The full story for those interested, (I think) this is not relevant to the question: I want to make a stop-motion featuring a banana peel as a person. I can place the peel in different positions and hold it with transparent thin fishing lines. However, I would also like to animate the background. Doing this simultaneously with the banana animation is tedious. My plan is to do a stop-motion of the background separately and then replace the banana background through some keying process.

(2): I do have an off-camera flash, but no way of syncing it. If I hook it up to my DSLR it would probably fry it as it is an old 300V flash. Household lights range from 10 to 150W.

Answer

Here are all the ways I know of for removing the background (in order of my preference):

1. 
   

   White Background

   
   

   This is done by using a white-ish background and lighting the background about 3 stops brighter than the subjects (exact lighting depending on your camera).

   
   

   There's no way you can do this with household lights but a flash aimed at the wall behind the subject does this easily, you can do it by shooting your subject with a very slow shutter speed and using your flash's test button or you can get a $40 flash from ebay (plus about $10 for adapters and cables to sync it off-camera).

   
   

   Note: you will want to get the subject as far from the background as possible to minimize light bouncing from the background hitting the subject.

   
   


2. 
   

   Chroma-key

   
   
   

   Use a solid color background (most commonly green), make sure the background is lighted evenly and that there are no shadows falling on the background.

   
   

   You can sort of do it with household lights but here it is even more important to not have light from the background hitting the subject (because it will cause a green color cast) so you will need some distance between the background and subject.

   
   


3. 
   

   Black background

   
   

   This is done by simply placing the lights very close to the subject and letting the light falloff turn the background black, the more powerful the light the easier it is to get a black background.

   
   

   Here distance to background is also important but you can manage without it if the light is powerful and very close (but a powerful light very close will create very dramatic hard light - so if you want even soft lighting this is not for you).

   
   


4. 
   

   Masking in software

   
   
   

   If you just carefully paint the mark for each photo you don't care what the original background is - and you don't need any special lights, however, this is obviously very tedious.

   
   

   You can make an almost-white or almost-black background, use automatic selection and then just refine the mask to save some time.

   
   

Whatever you do all of those will confuse the camera's auto mode, don't forget to meter for the subject and use manual mode and manual white balance - and to take test shots and watch them on the computer before starting with the stop motion animation.