Background light making foggy images...what's wrong?

[budawg]

Hi everyone,

I'll get straight to the point. Over the weekend, I helped a buddy do a photoshoot for a school project. Two AlienBees lights with one white lightninig light on the floor near the white paper backdrop to blow it out. Problem is that it was causing all the images to be extremely foggy even after moving it all around. It was barely off the floor, in front of the backdrop way off to the side.

I guess what I'm asking is, what's the proper way of using a light to blow out a backdrop?

Thanks for the help!

[RTMiller]

Post an example so we can see. Were you smoking while you were shooting?;)

[illy]

Moisture in the air?

[budawg]

let me get one for you guys...hold on....

[René Damkot]

Dirty lens and/or no hood and flare?

[budawg]

here's an example...the light is on the subjects right side, our left.

[budawg]

there was definitely no hood...it was my pos 28-80 3.5-5.6 rebel 2000 kit lens on my 10D. I should mention that with the background light turned off, the photos were fine

[cdifoto]

That looks like low contrast due to flare to me. Usually a background light is concentrated with barn doors or some other type of modifier.

[magicmikey]

Also, if you hit the background with too much light, it will cause lens flare like this.

[Ronald S. Jr.]

Gotta turn down your background lights by about 25%, and put a hood on your lens.


166775

[RTMiller]

How close was your subject to the background?

[TMR Design]

Clearly looks like the subject is too close to the background for that amount of light. I agree with others. Turn down the background light and make sure you're not getting spill or too much reflection returning to the subject from the background.

[budawg]

well, the lens hood is definitely a good call...the background light only had three settings low, med, high. also, he wasn't very close to the background at all. so i guess it really doesn't take much light to blow out a background, huh? so for instance, if you had a 400 watt light, probably set it at it's lowest setting?

[TMR Design]

Ideally would do this with a light meter and eliminate all the guess work.

[René Damkot]

How close the subject is to the BG has nothing to do with it.
The amount of light falling on (and thus coming off) the BG does. (So the lights to BG distance does matter).

In this case too much light is coming from the background. Combine that with a not too stellar lense, no hood, possibly a filter, and you get flare.

Shading the lens as much as possible (a couple of black pieces of paper would have done the trick) would have almost completely eliminated this problem.

Easy way to see if you're not overexposing the BG too much in a case like this, would be to check the 'blinkies' (overexposure warning) on the camera display: If the aperture is closed about 1/2 a stop from the setting you are using, most of the blinkies should be gone. That way, the BG is white, but not overly so.

[budawg]

Miss Damkot, you always seem to answer my questions perfectly. Thank you. Also, how did you know I had a filter on there?!?! When you say shade the lens, do you mean to craft a sort of lens hood out of paper?

[René Damkot]

Miss Damkot, you always seem to answer my questions perfectly. Thank you. Also, how did you know I had a filter on there?!?! When you say shade the lens, do you mean to craft a sort of lens hood out of paper?

Mis*ter* if you don't mind ;) Last time I checked I was a boy. René is fine however.

The filter: Let's say: Educated guess: Been there, removed that ;)

Shading the lens: Place a piece of paper (or a 'flag') between the light source and the lens, just like you would when you were for instance shading your eyes from the sun.
It's more effective then the hood can be, because you can place it exactely where you want: just along the borders of the frame.

[budawg]

i always thought rené was a female name...how 'bout it. Hey, my name is Alain which is like "joe" in france and canada...do you have any idea how many times I get mistaken for a stupid Seinfeld character?

[Ronald S. Jr.]

......"Alain" was a Seinfeld character? :|

[budawg]

Elaine dude...Alain...Elaine...the phonetic spelling of Alain...

[Ronald S. Jr.]

Didn't even think about it like that. Not a name I'll ever hear in the US, really.

Gotcha.

See, some people will say "uh-lane" and some will say "E-lane". I will often pronounce the long e, which is also why I was unfamiliar with what you said.

[René Damkot]

i always thought rené was a female name...how 'bout it.

Happens more... In the Netherlands it (used to) be common to spell "René" for a boy and "Renee" for a girl...
Over here Alain would probabely be pronounced Ah-lehn or so. (don't know phonetic spelling too well, let alone how to type it)

[RTMiller]

How close the subject is to the BG has nothing to do with it.
I have to disagree with you Rene. If the subject is very close to the BG, the light will spill on to the subject. It is like standing next to a big soft box. If you are far away the light will only hit the rear of the subject. If you are too close the light will wrap around, i.e., the light from the top of the BG will fall on the front of the shoulders. If the light on the BG is too strong, this will reduce the contrast between the BG and subject.

[René Damkot]

Agree on the spill and 'wrap around', but that's not what's happening here IMO.