Help in preventing background burn

[djmorgan]

I am trying to get a white background using a white drop cloth and illuminating the background to f13 with subject at f8 but I am finding that around the hair on the top of the subject I am getting purple fringing I assume from the burn out of the background.

The background is about 5 feet from the subject I'm using a key light at about 90 degrees to the subject and a distant fill light at about 45 degrees.

If I drop the light intensity to avoid the burn out I get a grey background!

Please any pros with some tips, I'm getting to the point of chucking it all away and heading for the great outdoors!

David

[Curtis N]

More distance between subject and background. Barndoors on the background to avoid illuminating a larger area than needed.

[djmorgan]

More distance between subject and background. Barndoors on the background to avoid illuminating a larger area than needed.

Thanks I am on limited space and the ceiling is about 7 feet, I note what you didn't say was drop the light intensity on the back lights! which when I think about what you said makes sense, the background is white so I need to cut the reflection back to the subject!

If anything I want more coverage as I am battling with a single 180Ws flash for the background, I guess a second is in order?

is there say a ratio between distance and Ws? in a case like this, maybe just do black backgrounds :confused:

[doidinho]

Here (http://www.zarias.com/?p=71) is a good read for you.

It echos what Curtis said, but goes into way more detail. Enjoy.

[djmorgan]

Here (http://www.zarias.com/?p=71) is a good read for you.

It echos what Curtis said, but goes into way more detail. Enjoy.

Fantastic! can't thank you enough great read that make me realise I am going to have major problems getting what I want :(

[steveathome]

You say you have a drop cloth for background? what are its reflective qualities like compared to say a purpose made white background paper?
Also, what sort of lighting are you using, and what control do you have over it?

I can rarely achieve a large distance between subject and background as I don't normally have studio facilities. However, when using a bright paper, i see no need to go much more than 1/2 stop above its normal exposure (having said that, distance is a great advantage).

This will differ between different set-ups etc, but firstly it would be an advantage to have a good background with reasonably high reflectance. It would also be preferable to illuminate it as evenly as possible with two lights - one either side.

This needs to be set up first before key and fill lights, and can easily be checked with your histogram/blinkies screen. Get the exposure as low as possible, whilst maintaining total blow out of the background, then increase this very slightly.

Your key and fill lights may also contribute to the background intensity, so when they are set up, check again with the histogram and blinkies screen, and see if you can reduce the background illumination a little further (equal adjustment of both background lights)

There really is no need to go over the top when blowing a background out, when the highlights are blown, they are blown. Increasing exposure even further can then have a detrimental effect by starting to act as a rear light source.

[djmorgan]

It's a commercial white cotton back drop.
My first attempt had a 180Ws strobe behind a chair I was sitting on (self portrait - practice) this was at full power and only basically gave a halo around the body the sides were grey background, not a big problem in PS.

The key and fill are 400Ws strobes the key was at about 1/4 power, the fill less.

After taking the practice shots at approx f11 - 100 ISO 1/125 and looking at them I found purple fringing around the body and hair this I feel is blow back from the background.

Since writing here I moved the 2 x 400ws strobes to the background shooting through softboxes and used the less powered 180Ws with a brolly as a single light but it does not wrap that well but it did solve the blow back problem.

My thought now is to get a second 180Ws so I can have 2 for back lighting as 1 just does not fill the area and distance/power is not controllable enough.

Thanks for your interest and advice

David

[steveathome]

Even illumination of the background is really the key, and with two even powered strobes with soft boxes, you are definitely on the right track.

I Look forward to seeing what you produce.

One thing I found when experimenting with white backgrounds - depending on surrounding walls etc as well, you don't normally need as much fill as you generally would, due to refections everywhere.

Make sure you don't overexpose the subject at all, if anything err towards slightly under if not spot on. The reason for that is, when doing PP in photoshop, if the skin tones are slightly over, you will find when bringing them back down again, your background will follow, and you may start to find slight grey area's in parts.

Edit:
If not getting enough fill with the one light, try a reflector on the shadow side, it will work a treat.

[agedbriar]

Great tips, thanks.