High Key Images - How to get the white background white

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FrattonFreak

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Hi,

I'm using a white vinyl background and off camera flash via a softbox.

Whilst I'm pleased with subject lighting I'm not getting the "extreme" white in the background. I'm assuming I need to somewhow light this.

I'm using an on camera SU800 as commander and an SB900 shooting through a softbox.

I'm assuming I need to somehow light the background with a 2nd flash (which I have and could be controlled by the commander), ensuring it doesn't impact the subject nor visible in frame.

Any advice / suggestions of what people have set-up and worked OK for them?
This is a link to an example of what I currently am getting with the high key background:
http://www.flickr.com/photos/61780014@N08/8602958400/in/photostream

Thanks in advance
 
2nd Flash at any white/pale wall if its close enough not to interfere with the subject i.e. place the flash to the side, making sure its headed towards the wall/backdrop will do it.
 
Lighting the background half to a full stop brighter than the subject is all you need to do to get white...........Just watch out for any light spilling back.......
 
Gypsy_Biker said:
I posted details of a set-up last week, that I had used for achieving a white background for the first time:

http://www.talkphotography.co.uk/forums/showthread.php?t=473392

You'll see from the replies that it really created a storm of interest, however I think it answers some of your questions and is with equipment similer to yours.

Thanks!
Click to expand...
I must have missed that post Pat :bonk: but even without a flash meter you can set your flashes to say 1/2 power on background and 1/4 power on subject that's your stop of light and then adjust iso and shutter and aperture to suit
 
k4stn said:
I must have missed that post Pat :bonk: but even without a flash meter you can set your flashes to say 1/2 power on background and 1/4 power on subject that's your stop of light and then adjust iso and shutter and aperture to suit
Click to expand...

Thanks Shane, that's a really interesting comment you make. And one that formed the basis of a eurika moment for me last week! Let me know if I've got this right.

I started off exactly as you discribe, I'd read that I needed 1 stop of differance between the background and subject to get a pure white background without blowing the edges of the subject. So I set 1/4 power on subject and 1/2 power of background (or something similar) and started from there. I was dissappointed that the subject was blown out and the background very grey....

Then I realised that it surely has to be the f stop of light reaching the subject/background that needs to be a stop differance, not the power dialled into the flashes. As the flash power alone would not take into effect the distance the flashes were from the subject/background or any light modifiers that the light was passing through.
 
FrattonFreak said:
Hi,

I'm using a white vinyl background and off camera flash via a softbox.

Whilst I'm pleased with subject lighting I'm not getting the "extreme" white in the background. I'm assuming I need to somewhow light this.

I'm using an on camera SU800 as commander and an SB900 shooting through a softbox.

I'm assuming I need to somehow light the background with a 2nd flash (which I have and could be controlled by the commander), ensuring it doesn't impact the subject nor visible in frame.

Any advice / suggestions of what people have set-up and worked OK for them?
This is a link to an example of what I currently am getting with the high key background:
http://www.flickr.com/photos/61780014@N08/8602958400/in/photostream

Thanks in advance
Click to expand...

There are a lot of good threads on the pure white background look, but it's not easy to do well.

The background should be 'only just' over-exposed (aim for half a stop, one stop max) and it needs to be even all over. For anything more than a tight head and shoulders portrait, you need two lights on the background to achieve that.
 
HoppyUK said:
There are a lot of good threads on the pure white background look, but it's not easy to do well.

The background should be 'only just' over-exposed (aim for half a stop, one stop max) and it needs to be even all over. For anything more than a tight head and shoulders portrait, you need two lights on the background to achieve that.
Click to expand...

Out of curiosity, why do you need to limit the level of over-exposure on the background?

Is it to avoid producing a 'back light' on the subject?
 
Faldrax said:
Out of curiosity, why do you need to limit the level of over-exposure on the background?

Is it to avoid producing a 'back light' on the subject?
Click to expand...

Again, there are lot of long theads on this with illustrations.

Over-cooking the background is one of the most common mistakes, possibly because there's a theory running around photo forums saying it should be two stops over exposed. This is wrong.

Blown is blown, 1% over or 1000% over, both are pure white. But if you overdo it, it bleaches the subject outline and eats away at fine detail. Blonde hair is particularly prone and white tops will vanish into the background.

Outline bleaching is one thing, and the other is lens flare with tons of very bright light blasting at the lens dramatically reducing contrast and saturation. Lens hoods are almost useless at preventing this. It's a very good idea to screen off all areas of the background not actually in the frame, or even right up to the edge of the subject because it's easy to remove this in post-processing.

The 'back light' you refer to sounds like wrap - basically the background 'reflecting' off the subject. This can be moderated either by screening off the background, or by moving the subject forward. If screens are positioned between the subject and background, they will moderate both wrap and flare. If they're positioned between the subject and camera, they will reduce flare but not wrap.

Doing this technique well is not easy ;)
 
HoppyUK said:
Again, there are lot of long theads on this with illustrations.

Over-cooking the background is one of the most common mistakes, possibly because there's a theory running around photo forums saying it should be two stops over exposed. This is wrong.

Blown is blown, 1% over or 1000% over, both are pure white. But if you overdo it, it bleaches the subject outline and eats away at fine detail. Blonde hair is particularly prone and white tops will vanish into the background.

Outline bleaching is one thing, and the other is lens flare with tons of very bright light blasting at the lens dramatically reducing contrast and saturation. Lens hoods are almost useless at preventing this. It's a very good idea to screen off all areas of the background not actually in the frame, or even right up to the edge of the subject because it's easy to remove this in post-processing.

The 'back light' you refer to sounds like wrap - basically the background 'reflecting' off the subject. This can be moderated either by screening off the background, or by moving the subject forward. If screens are positioned between the subject and background, they will moderate both wrap and flare. If they're positioned between the subject and camera, they will reduce flare but not wrap.

Doing this technique well is not easy ;)
Click to expand...

Thanks, that does explain it.

What I meant by 'back light' was that the blown background would act as a light source - which is the effect you are detailing (IE I had figured out the problem, but not what all the effects of that problem could be :) ).
 
Here's the theory.The reason for the 2.5 stops over is based on the 18% grey that all digital cameras are calibrated to. Mid way between pure white and pure black is mid grey which reflects 18% of light. Each time you double the light intensity from 18% you add a stop of light. Therefore 36% is one full stop, double that to 72% is another stop, thus leaving 28% of 100% which is pure white. Totalled up that makes 2.28 stops over 18% is pure white.

This is the theory, but where this falls down is that it doesn't take into consideration the reflective qualities of different surfaces.
 
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The Noir Dude said:
Here's the theory.The reason for the 2.5 stops over is based on the 18% grey that all digital cameras are calibrated to. Mid way between pure white and pure black is mid grey which reflects 18% of light. Each time you double the light intensity from 18% you add a stop of light. Therefore 36% is one full stop, double that to 72% is another stop, thus leaving 28% of 100% which is pure white. Totalled up that makes 2.28 stops over 18% is pure white.

This is the theory, but where this falls down is that it doesn't take into consideration the reflective qualities of different surfaces.
Click to expand...

18% worked to some extent with film, digital is closer to 13%. But facts don't get in the way of internet opinions:)
 
Faldrax said:
Thanks, that does explain it.

What I meant by 'back light' was that the blown background would act as a light source - which is the effect you are detailing (IE I had figured out the problem, but not what all the effects of that problem could be :) ).
Click to expand...

Yes, the bright backgound acts as a very important light source. It obviously illuminates the back of the subject, hidden from the camera, but also the sides - this is known as 'wrap'. The wider the background is, relative to the subject, the more wrap you get, so that can be moderated by screening off the background (making it smaller) or by moving the subject forward which has the same effect (by making the background relatively smaller).

Wrap is all part of the pure white background look. For example, if you were to shoot the subject against a dark background and then cut it out in Photoshop and change to white, it would look totally different and unnatural.
 
The Noir Dude said:
Here's the theory.The reason for the 2.5 stops over is based on the 18% grey that all digital cameras are calibrated to. Mid way between pure white and pure black is mid grey which reflects 18% of light. Each time you double the light intensity from 18% you add a stop of light. Therefore 36% is one full stop, double that to 72% is another stop, thus leaving 28% of 100% which is pure white. Totalled up that makes 2.28 stops over 18% is pure white.

This is the theory, but where this falls down is that it doesn't take into consideration the reflective qualities of different surfaces.
Click to expand...

No, not if I've understood you correctly.

If you take an incident meter reading, it will peg 18% grey (for sake of argument) to the mid-tone area regardless of the subject, eg middle of the histogram. Therefore white will automatically be about three stops brighter than that and will be on the brink of blowing. Therefore it only takes a small nudge of over-exposure to blow it completely.

The exact amount of over-exposure necessary depends on a few other variables that a hand meter knows nothing about, so I always use the histogram and blinkies for this, so I know exactly where the blowing point is.

Apologies if I've misunderstood your post :)
 
Paul,

at Coventry last year Keith explained that their ezybalance was no longer 18% grey but 12% as this is an historical mistake - I said so in that case I get a new one because the other is faulty - sadly he just chuckled.

The idea of the 2 1/2 stops sounds good when using a reflected light meter but when using an incident light reading it is of course wrong.

When using incident light readings what is needed is just enough light above what would be the right level to compensate for shadows, unevenness of lighting etc. & colour of background (as well as overcoming the latitude of the film) - 2 stops will certainly be enough. Unfortunately many carry this through to use of the Hi-Lite and make a big error.

Mike
 
mike weeks said:
Paul,

at Coventry last year Keith explained that their ezybalance was no longer 18% grey but 12% as this is an historical mistake - I said so in that case I get a new one because the other is faulty - sadly he just chuckled.

The idea of the 2 1/2 stops sounds good when using a reflected light meter but when using an incident light reading it is of course wrong.

When using incident light readings what is needed is just enough light above what would be the right level to compensate for shadows, unevenness of lighting etc. & colour of background (as well as overcoming the latitude of the film) - 2 stops will certainly be enough. Unfortunately many carry this through to use of the Hi-Lite and make a big error.

Mike
Click to expand...

Agreed. And unfortunately this seems to be an inevitable by product of the "trainer syndrome" - hmm, photography is getting to be too competitive, so I'll teach other people how to do it instead and make my fortune that way.
 
HoppyUK said:
No, not if I've understood you correctly.

If you take an incident meter reading, it will peg 18% grey (for sake of argument) to the mid-tone area regardless of the subject, eg middle of the histogram. Therefore white will automatically be about three stops brighter than that and will be on the brink of blowing. Therefore it only takes a small nudge of over-exposure to blow it completely.

The exact amount of over-exposure necessary depends on a few other variables that a hand meter knows nothing about, so I always use the histogram and blinkies for this, so I know exactly where the blowing point is.

Apologies if I've misunderstood your post :)
Click to expand...

I do agree Richard. I quoted it as the general "theory" as to why some people sometimes quote the 2.5 stops technique to obtain a pure white background. That is why I also added the caveat that it did depend upon the surface and it's reflective qualities.
 
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