How to: Gelling Large Light Sources
Do you shoot with soft boxes, beauty dishes and/or umbrellas?
If you shoot exclusively with small lights, you can just tape a couple of square inches of gel to your flash head, as with my permanently mounted warming gel seen above. No matter what the mod, the light is gelled before it gets there.
But if you sometimes shoot with big lights, things can get a little more complicated. Here are some ideas to help you gel the big mods as efficiently as possible.
Basically, the idea is that you want complete coverage without using a ton of gel material. If I can gel a mod with a single 20x24" sheet of gel, I am much happier than if I have to buy several sheets of gel to do the job. Bearing that in mind, let's run through how to gel some of the more common big mods.
Beauty dishes, typically 22" in diameter, are great portrait mods for a number of reasons. They give beautiful light, and they stand up to wind outdoors. And happily, you can gel the whole front surface with a single 20x24" sheet of gel if you tweak the dimensions with some scissors and scotch tape.
You do this by cutting a two-inch strip off of a standard 20x24" sheet to make it 20x22". You have to get it pretty exact, too—you'll need every bit of gel on both dimensions. Then you tape the 2" strip to the side to make a 22x22" sheet with a couple of chopped up corners.
No worries, as that the corners will be waste after you trace and cut the gel to fit your dish. (But remember to save the scraps for your speedlights.)
Alternately, some people prefer to cut a smaller circle and put a Velcro® dot in the center. You can then stick it to another Velcro® dot on the shield that sits in front of your tube.
I like the full-sheet version here, as you can sometimes lose full coverage with a floppy gel if you go the other route. After all, it's just one sheet so it is not too expensive to do it right. Also, by using a full sheet you can work without the flash tube tube shield if you want more specular light
UPDATE, from commenter Andrei Popovici, below:
Here's an alternative way to gel your dish with less material.
Just cut a strip, tape it into a donut and slide it around your centerpost light blocker/reflector. (Thanks Andrei!)
Pain in the butt to gel an umbrella, right? Wrong. It's dead simple if you use a cheap spill-kill reflector with a tiny hole in it to account for the shaft. Spill kills are cheap, and they also make an umbrella into a much better light source.
(Note: For clarity, this is shown without the umbrella shaft inserted.)
You can tape the corners back to ensure no ungelled light leakage on the light that is headed to the umbrella. But be careful to make sure there is some ventilation space between the gel and your modeling light. Even so, use the modeling light as sparingly as possible to prevent melting.
Of course you'll have to snip a tiny hole in your gel to account for the umbrella shaft. You can still use this small gel sheet over standard reflectors when needed by sticking a small piece of gaff over that hole to block raw white light spilling through it.
This method also holds true for anything that it umbrella-based, such as umbrella/diffuser mods like my go-to Photek Softlighters.
Gelling a Paul Buff PLM couldn't be simpler and takes very little gel material. If you are using it with an umbrella shaft mount, gel it as seen above.
If you are using the speed ring mount for perfect parabolic positioning of your light, you'll need even less material. Use the triangular "Death Star" area of the frame to wrap a small piece of gel thusly:
You'll easily get full, absolute coverage with a minimal amount of gel. Just remember to vent it a tad up top or down below at the back edge for heat dissipation.
To be honest, gelling issues are one reason I really am not a huge fan of soft boxes. With some boxes you can velcro a smallish piece of gel inside and get full coverage. But it is always clunky at best, and difficult not to get some white light leakage.
With small- to medium-sized boxes you can gel the front completely, which is something I did for many years when I used my 24x36" soft box literally to death in the 1990s. But to do so you'll need two sheets of 20x24" gel, which you tape together to make a single 40x24" sheet. Trim 4" off one side and you're set.
Not ideal, as it is not very efficient. But if that is your go-to key light, it's probably worth the effort and cash to have some full-front gels for it.
Just use sticky Velcro® tabs on the corners of the soft box and the gels and you are golden. Or fluorescent green. Or whatever. If you shoot a lot of head shots in tungsten or fluorescent environments, it's worth having a color correction set (CTOs, window green, etc.)
And you can also stack gels (for instance, green correction + key light warmth) by putting a set of Velcro® hooks on one side of the gels and loops on the others.
It's not an ideal solution, but if that is your go-to source that will be your best route.
Because of their size, which is generally small in terms of raw square inches, (i.e., 10x36", etc.) strips can be treated like small boxes. Which is to say you can gel the on the outside with a single 20x24" sheet of gel, which makes it pretty doable.
Take one 20x24" sheet and cut it down the middle to make two 20X12" strips. Tape those end-to-end to make a 40x12" strip and trim to fit your box. Mount to the front with Velcro® as described above. As always, when custom-fitting gels save the scraps for your speedlights—especially since they will usually be the colors you use most often.
Good news is, with strip boxes you are often going to be rim lighting someone anyway. Which usually lends itself to a fairly standard selection of color correction gels (CTO's, CTB's. etc.).
So it might make sense to keep a set of those colors (remember to do two of each if for rims). But for anything crazy, you'll likely be reverting to standard reflectors to make gelling easier/cheaper when using whack colors.