there are many way to do it and I will touch on one way that I know well.
for this shot
I used a long exposure (about 5 seconds) and fired an external flash at the background, which was a white bed sheet. The room was dimly lit so I cold see , and I used a flash light to shine on the fan to aid in focusing.
This photo has ZERO edits done to it.
Again this is just one way to do it that I know works well
i use a custom white balance setting, sometimes taking a shot of the illuminated BG item, and using that for the custom white balance choice.
if you can get it close doing that - post processing can tune it up...
EDIT: i have found a significant jump in meter readings as well, allowing me to trust the meter more for indoor shots, to shoot at 1/640th with low wattage lamps.
long exposures add lots of noise, especially with a black BG - so bear that in mind - shake is an issue as well if you dont have a remote
Is 'noise' a product of long exposures and/or the camera one is using? I took the photo below at a 3 second exposure (would that be considered long?) with little noise.
How or what is the best way to get a pure black or white background in a photograph?
If I try to bump up or down the exposure, I can get good blacks and whites but then the subject gets all screwed up.??
It's a great subject to practice. It's mainly in your lighting. If you don't have enough light on your background, getting it to white will be difficult. Here's an example snapshot I did recently that is unedited other than a resize:
I used a combination of ambient light, a long exposure, and my flash.
Black background are much easier to get, IMO. You just have to make sure your subject has ample light and the background has none (or as little as possible. In many cases, you can put too much light on your subject, underexpose the shot, and your background will go to black with the underexposure.
How or what is the best way to get a pure black or white background in a photograph?
If I try to bump up or down the exposure, I can get good blacks and whites but then the subject gets all screwed up.??
You have the right idea about bumping up or down the exposure - but it is the relative difference between the subject and the background that is of interest, not the absolute exposure value you select.
Your eye can see a lot more stops than your camera can. As a rough rule of thumb, I assume that I can get detail for about +- 2.5 stops around the actual exposure I set. So to get a really good black background, you want your subject to be generally illuminated about 2 or more stops above the background - similarly for a good white background, you need the background to be about 2 to 3 stops brighter than your subject.
If you have these relative light levels correct then the backgrounds will end up black or white as you want them - otherwise you'll end up with detail that you don't want. You can work within these ranges or close to them and fix things up with adjustments but in generally having a wide dynamic range in the scene is the easiest and most repeatable way to achieve this.
E.g., using flash to lighten the subject, pushing the background towards black
Or shooting towards a much darker, non illuminated area (in this case I've kept some of the background detail for texture - this was about 2 stops difference)
or picking a really well lit background for a subject mostly in shadow
In all of these cases, my eye could see a lot more detail than is captured by the camera, but by using my meter I could see where the backgrounds would start blowing out and set the subject/ background exposures accordingly to get the result I wanted.
i would think, and if my camera made it a simple task in manual mode, spot metering is also a way to acheive the same end.
eventually i will buy an external meter for indoor studio shots, but for now, custom white balance seems to help.
light source, and intensity is also a factor with white BG's
and the custom white balance seems to help with that mostly.
i don't have a lot of wattage to work with, nor clean light...
i am curious if others have tried similar things as i mention.
@ casualguy - no i dont think 3secs is all that long an exposure. post the full size shot though.
if your subject is brightly lit, and the background isn't?...
and you want a black background.
Then the dynamic range of the image gives your the opportunity to get a black background, if you expose it correctly. You don't need a spot meter or hand held meter to do that.
yeah i suppose, but i saw the cat like that, and knew the camera didn't, and adjusted the white balance, and exposure -2 stops to try to acheive what I saw...
Originally posted by Gordon:
honestly, I think that that is backwards - its about knowing how a camera sees, and learning how to identify it and see it yourself.
