EDU: Using Studio Gels

[coreypolis]

I get asked about thisfrom time to time, so I thaught I would share.


One of the cheapest and easiest ways to change the background of an image is a studio environment is to add gels to the lights. Getting the desired result is the hard part.


You can use any color seamless. White is one of the easiest to work with, but requires some knowledge of proper exposure. Gray and black are other popular choices.


The first thing is to try and have the background light on a separate power system, so that you can control it independently. You also need to make sure that the key light and or fill light doesn't contaminate the background. Any white light will change the color of the background light. Using black flags and aiming the lights is key. You also want the subject as close to the key light and as far from the background light as possible.

Instead of buying every gel under the sun, you can change the color by adjusting the intensity of the background light. For the following test, we took a gel (labeled to the left), used a light meter to measure the incident light on the seamless paper, and adjusted the location of the lights to obtain a normally exposed image at f/8. We did this because it is in the middle of a 9 stop range (We used a 135mm L F/2 from Canon, one of the few lenses to have this large of a range) instead of using another lens and having to adjust the light intensity for the extreme values. This allowed us to change the exposure in 4 stops in either direction. The example shows a range from f/2 at +4 stops of light to f/32 at -4 stops of light.

We took the gel, cut it in 2, and used laundry pins to attach it. DO NOT let it touch the actual bulb, it will melt it, and white light will go through and ruin the shot/lose intensity in the color.

Cliff notes:
Adjust the intensity of the light changes the color.
The results can be seen below.

[Wilt]

Great illustration of a single gel creating many different tonal renditions of the same fundament color. Your shot also illustrates why one needs to separate the model from the background, because of the color cast onto her skin and hair by the light bouncing from the background.

I might also suggest that a series of shots of gray background paper with differing levels of light falling on the paper can alter its tonal rendition from black to white!

[nanko]

where did you get the gel material? what is it?

[coreypolis]

this was a Lee gel, and is available at most pro photo/video stores.

[akhoopes]

are you using a steady light for this gel or a flash, and if you are using a steady light, how many watss does it have to be to show up on the camera, ive tried 250 watts steady and nothing, but my ab800 flash it shows up but i cant get it quite right at all

[Benji]

Using a gel on a white background will give you highlights in the hair like the OP has shown. If your client doesn't mind having blue, green. red or orange hair this is great, but if they would like to have their real hair color use a low key background. My tutorial on using gels can be found here http://www.photocamel.com/index.php/topic,15518.0.html

Benji

[Blackey Cole]

There was a link to a you tube video that showed and English photographer demonstrating how to light a subject and a big part of it was on using gels to get different effects from a neutral background also flooding it with light for a white bg and blocking light from it for a black bg.

I lost my link and was wondering if someone could post it so I can go review these videos. I believe it was a series of three or more you tube videos.