Rays of light

[codyderek]

Hi all,
I hope I chose the right section to post my question. I am wondering about techniques to capture rays or beams of light. I am planning a shot where I need a beam, and I might need to create it myself. Are there any things to take into consideration concerning exposure? Also, is there anything for a set-up shot that I could use to disperse the light? I would appreciate any advice.


Cody

 

[payasam]

A cloud of dust or smoke might be the answer: though it has nothing to do with optics other than being bad for them.

 

[Roger Hicks]

If I understand you correctly, you want to shoot e.g. a beam from a spotlight.

The only way you will see that is if it reflects off something, which means (as Payasam has already suggested) dust or smoke. Exposure is going to be a bugger, as keeping the density of smoke constant is extremely difficult, and the amount it reflects will change according to the density.

I'd go for a spot reading of the beam, and memory to guess when the beam density you are about to photograph is equivalent to the density when you read it.

A long lens will enable you to work at a convenient distance from the contaminants, and a dark background will make the beam most visible.

Cheers,

Roger

 

[Sparrow]

Water vapour, from a kettle may be less hazardous to your lungs.

You would need to get the camera and lens warmer than the ambient temperature to avoid condensation being too great.

PS, or one of those dry-ice “smoke” machines they use at discos

 

[delft]

A small laser would also produce a nice ray of light, if it is reflected off some dust / smoke / water vapor / mist or wat have you. If you choose a long exposure, you could move the laser during that exposure.
For getting the exposure right, you could use digital: shoot, chimp, adjust, shoot, chimp etc. until satisfied.

Greetings,
Dirk

 

[delft]

P.S. Please show us your results.

 

[codyderek]

Thanks for the replies guys!

I am thinking of a beam from a flashlight. It is for only a small amount of area, not a full landscape, just a portrait/still life in the woods. I have a photo I took in the Redwoods (not where I am doing this shot) that fortunately had dust kicked up by some walkers, and I was able to capture them.

For a set up shot like this, dust or smoke doesn't seem too feasible. I like the dry ice suggestion. I think I read somewhere that you should use a high f stop, is this true?

I'll post the result when I am done. It will be a while since I am gathering some other supplies and have to find a location. It is a complicated shot, but hopefully it will be worth it. I am entering it in a local contest.

Thanks again for your replies. I appreciate it much.

Cody

 

[Sparrow]

Exposure is going to be very tricky, with no light at all in the shadows it won’t matter what you do you’re just not going to get any detail without a second light. You could do with finding someone who has already tried this.

If I had to guess; for someone’s portrait, and if you have a spot metre that reads 18% grey, you could take a reading off their face and open up two or three stops (assuming that’s the brightest bit of the photo). A second reading of the illuminated particles would tell you weather the beam was lighter or darker than their face and you could adjust the amount of that (again assuming you want the beam darker than the face).

You would then need a second ambient light in the shadows perhaps 4-5 stops darker than the original reading. I’d probably do a set at +1 +2 as well.

Anybody got a better idea?

 

[Pherdinand]

here's a trick we used in our laser labs (where our boss strictly forbid us to use smoke - smoke is just fine dust that deposits on optics):
IF your setup is static, you can do this: Put your camera on tripod, make the room dark as much as u can, set the shutter on bulb, fix the light beam, and move a piece of white paper in the beam following its path.
Even if you don't do it with a uniform speed, it will come out nice and ..different.

 

[rxmd]

I guess since there's always some dust around, a sufficiently powerful laser pointer would do the job (got to be rather careful with those, of course, and for a toy it's a little pricy)