Bright White Background Exposure

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mike weeks

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I often find that people quote a 1.5 to 2 stop difference between subject and a bright white background (often wrongly called high key). The only way to get it right is to try and so using a Lastolite Hi-Lite that is what I did.

First step was to set the Hi-Lite to f11 and then meter the light falling on the subject, first test at f4 (background 3 stops brighter)

f4.jpg


Second test was to leave the Hi-Lite at f11 and then meter the light falling on the subject at f5.6 (background 2 stops brighter)

f56.jpg


third test was to leave the Hi-Lite at f11 and then meter the light falling on the subject at f8 (background 1 stop brighter)

f8.jpg


Fourth test was to leave the Hi-Lite at f11 and then meter the light falling on the subject at f11 (background same level)

f11.jpg


Notice the problems caused with the background being too bright and that when using the Hi-Lite there actually needs to be very little difference.

Mike
 
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Would be an awesome post if the images had worked, Mike.
 
Yes, that shows clearly that a whole stop works well, but even half a stop brighter is often enough.
 
Impressive!

How did you light the Hilite?
One flash or two? High or Low?

Now I'm thinking of getting one....
 
I have the largest i.e the 9'x7' Hi-Lite and used two Bowens 500s in the middle of the 7' sides to get an even light and Letitia was light with just 1 further 500 in a Wafer 75 softbox. This was just done as a demo to prove that you should not just take printed "facts" as gospel. Each type of bright white background needs a different level of light due to its reflective qualities.

Note how little difference in the images there is between no difference and +1 stop lighting difference.

Mike
 
Cheers!

I can see a slight difference between the last two pictures, where there is a slight darkening of the background at the bottom of the picture. The outline of the model is OK in both pictures.

How many people soes it take to fold the Hi Lite afterwards? :)
 
Well, your test proves what I've been saying for years, not only is excessive overexposure of the background totally unecessary, it also destroys the contrast, creates flare and results in far too much wrap. I always suggest something like a half stop of overexposure with film, 0.7 stop with digital.

All you have to do now Mike is to convince Lastolite to remove that rubbish info from their website:)
 
Gary,

like you I believe in doing the tests myself and there should be a difference between a Hi-Lite and other white backgrounds because here you are reading the light being transmitted through as opposed to falling on to a surface and as we know each surface has its own reflective properties and not all whites are equally white.

I totally agree that there is a lot of nonsense written on may sites about such matters and yes you would hope that Lastolite would understand how their own lighting device works, but if nothing else we understand.

Mike
 
mike weeks said:
First step was to set the Hi-Lite to f11 and then meter the light falling on the subject, first test at f4 (background 3 stops brighter)
Click to expand...
So we all agree there is too much wrap around your subject.
Second test was to leave the Hi-Lite at f11 and then meter the light falling on the subject at f5.6 (background 2 stops brighter)
Click to expand...
Again a bit too much wrap, a combination of 2 stops from a hi-lite and background to subject distance.

third test was to leave the Hi-Lite at f11 and then meter the light falling on the subject at f8 (background 1 stop brighter)
Click to expand...
Looks ok, about right for a hi-lite.

This was just done as a demo to prove that you should not just take printed "facts" as gospel. Each type of bright white background needs a different level of light due to its reflective qualities.

Note how little difference in the images there is between no difference and +1 stop lighting difference.
Click to expand...
I haven't tried printing (haven't even loaded to PS), but the background in the 4th image isn't white. Like you say 'there should be a difference between a Hi-Lite and other white backgrounds because here you are reading the light being transmitted through as opposed to falling on to a surface', but if you want a white background it looks like you still need 1 stop brighter with a hi-lite, or 1.5 stops for most white reflective backgrounds.
 
I think if you look at the setup you will see that the right hand light as I look at it was actually a bit high, causing the bottom of the Hi-Lite to be a bit darker. You will always get a degree of fall off which is why I am with Gary and go for between 0.5 and 0.7 stops difference, no need for a full stop of difference

setup.jpg


On site I will shoot a full frame of the Hi-Lite and do a quick measure to ensure that it is not dark in the corners.

Mike
 
I couldn't see mention of how you metered the background?

I'm having a bit of a blank as to how i'd go about doing that
 
nano said:
I couldn't see mention of how you metered the background?

I'm having a bit of a blank as to how i'd go about doing that
Click to expand...
Do you have a dedicated light meter? Very useful for setting things like this up.
 
studio light photography without a meter - virtually unthinkable however I could set the Hi-Lite using the flashing highlights on the camera or Photoshop but a meter is much easier and designed for the job. The clue should be in the term "I metered the background" - I use the Sekonic 308 and have done for about 15 years.

Mike
 
I actually do have a lightmeter :D I was asking how you metered the background (using a lightmeter)

With a reflective background i usually place the meter on the surface facing back to the light and take a few pops along to check its fairly even. Are you doing the same thing just with the meter facing the surface?
 
nano said:
I actually do have a lightmeter :D I was asking how you metered the background (using a lightmeter)

With a reflective background i usually place the meter on the surface facing back to the light and take a few pops along to check its fairly even. Are you doing the same thing just with the meter facing the surface?
Click to expand...

Using an incident reading meter, it should be against the background. With a HiLite it should face the background, with a paper/reflective background it should face the camera/lights.

Personally, I use blinkies for final settings. Set the main front light and then turn up the background until the blinkies are just flashing. Gives me about 0.3 to 0.5 stops over, though if you could get it to 0.1 stops that would be enough to blow to white. Blown is blown, whether its 1% or 1000% over.

You do hear people say +2 stops quite often, but they usually get pounced on round here. The reality is that even with a HiLite it's never perfectly even so if it's 0.1 over in the corners the middle is going to be a bit more than that. Personally I make sure the middle is just over and clean up the edges in post if needs be.

The only justification I can think of for +2, and it's a bit of a dangerous game, is that if you're shooting full length a bit more exposure on the background helps to lift the foreground train quite a bit, if that's the kind of compromise that's acceptable. I don't think it is. Bleached hair around the main centre of interest, the face, never looks good and I'd rather fudge it a bit and clean up around the feet in post.

I find the most difficult subject is kids lying on the floor. Getting both a clean background and floor there is tricky!

Edit: Nice examples Mike :) A lot of the flare in the first couple of shots is due to the large size HiLite being used for a small subject. It would be greatly reduced if the unused area was screened off, or the background moved fruther back.
 
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HoppyUK said:
Edit: Nice examples Mike :) A lot of the flare in the first couple of shots is due to the large size HiLite being used for a small subject. It would be greatly reduced if the unused area was screened off, or the background moved fruther back.
Click to expand...

Subject was 5 to 6 feet in front of the Hi-Lite which is typical for event work and in events we go from individuals to large groups - I was demonstrating to event photographers so they would not be in the situation to make the changes you have suggested, but more importantly was to get the idea of testing setups across to them - far too much duff information out there about what settings to use.

I totally agree with the method of metering and as a last resort I will use the flashing highlights on the camera but prefer to check in Photoshop.

Mike
 
An interesting thread guys. I bought a 6x7 Hilite for home use. I was planning on using an old Courtney 300 Solar flash I have to light the background. Doing some initial set up tests I was struggling to get anything above f11 at full power. I was thinking the light might be failing but it sounds that to light the hilite to f16 you would need a more powerful light. However from what I'm reading above f11 shouldn't present any problem.

Alan.
 
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In answer to an earlier question it can be seen that there is a point where the lighting on a background can be a factor in the main subject lighting (still getting a little burn when background is 1 stop brighter) however when background & foreground are the same there is no effect on the subject caused by the background lighting.
One of the factors that was brought up was size of subject vs background but what needs to be factored in is the distance between background and subject. Lighting is not done in isolation of each other for the final result.

Mike
 
I use 1x300ws strobe in my 7x8 hilite aimed at the back about 3' from the bottom.

In camera whiteout metering to make sure I have no dark spots..

This method works well as long as you can put your model at least 3 feet away so you can get separation ..
Especially when your eventing and setting up in a hurry..

If I have time I'd meter it as the great mike weeks has explained ..
 
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