Is there a better way to determine which gel to use?

[jcblitz]

I just starting to play with gels so I picked up a Rosco sample pack. I'm still learning the color correction gels and wanted to see if this was a good technique to determine the correct gelling.

I first use my gray card without flash to set a custom white balance and make sure that looks appropriate. I then pop on my flash and take another shot and decide which family of gel I need to apply. Then I basically try and feel it out from there whether to go up or down based by taking shots with various cuts and comparing it to the original, control image. I've been semi successful doing this but it does take some time (and battery life).

Another thought I had, but not sure if it's possible, was to try and get the color temperature from the initial balanced photo and just use a formula to determine which cut I need to adjust my SB-600 to that color. Anyone know if that's possible with the Nikon D90? I know I can dial temperatures in, but wasn't sure about getting them back out with a custom WB.

 

[JerryPH]

I know through trial and error what camera setting to apply to a specific gel to get a specific result. I also know when to match the gel to the current conditions and more importantly, when to set my camera to match the gel conditions which do NOT match ambient conditions for artistic reasons.

It all comes down to experience.

There are times I gel slightly warmer:

... totally neutral:

... or for artistic reasons, totally against the ambient:

Practice, knowledge and needs define methods. Just don't get stuck thinking gels are just for corrective purposes... they do a whole lot more.

Want to have some fun? Take a totally weird colour like pink... gel your flashes pink and then correct for it in post process... tell me what colour the background goes to once you colour correct your pink coloured subject to a natural colour... if you guessed yellow (yeah, yellow!), you would have been right.

Gels are fun.

 

[jcblitz]

Yeah, they are fun, the Rosco kit I have has a bunch of colors in it. I started playing with the funky colors by putting them in totally different rooms and just having the color leak out. Tons of potential and one of the reasons I've asked my wife to buy me another flash for Christmas.

I did melt a red one with my first attempt though...oops. You live and you learn.

 

[Derrel]

" and get the color temperature from the initial balanced photo and just use a formula to determine which cut I need to adjust my SB-600 to that color."

This is where old-school knowledge comes in handy. There are ample references available telling you the color offset/shift of each and every gel,and there is the WB you have dialed into your camera. Charts and tables are available from the manufacturer's web site describing the exact number of degrees Kelvin for each and every gel made.

Have you searched the manufacturer web sites for the needed technical info? It's there for free. all you need is a small piece of paper and a good pen to make a cheat sheet you can refer to, then shoot some test shots to see how the results look.

How do you suppose color correction was handled in the pre-digital era? With charts and tables and notes and actual tests. Today, it takes 5 seconds to see the effect of a particular gel on an image, not four hours on a sheet of E-6. If you spend a Saturday or two, you'll be able to accomplish weeks' worth of "shoot-develop-examine-re-shoot-develop-re-examine" trial and error work.

 

[JerryPH]

I did melt a red one with my first attempt though...oops. You live and you learn.

Careful. I can tell you 2 things right off the bat... you are placing the gel flat against the fresnel, and that is a huge no-no.

If it melts on the fresnel, it won't come off and that flash is whatever colour is melted for life... or until you replace the fresnel of that flash.

Gels are made to survive in high temperature environments. For maximum effectiveness, you are supposed to leave an airgap between the gel and the fresnel. What I do is place 2 pieces of velcro on the flash and extend the size of the gel by adding tape to it (I used gaffers tape), and then placing the opposing velcro piece on the tape attached to the gel. Then I simply slap the gels on and off and they are not flat on the fresnel... never melt, even after thousands of flashes within a single 8-10 hour time-span.