CameraCrazy

A few cheap items and a little bit of work and you won’t have to worry about post-processing white balance issues.

There are many good ways to determine white balance (grey cards, auto settings on the camera, Expodisc, etc…) The latter is a great white balance tool because it is simple, you put the product over the top of your lens, aim it at the light source, and set the custom white balance. It saves time on using grey cards and with post-processing a RAW file.

I was going to pick one up, but after hearing the cost ($159), both my bank account and my morality wouldn’t allow me to purchase an item that looked like it has a profit margin of 200+%. After looking at its construction and reading of other ways to set WB (grey cards, old Pringles lids, coffee filters), I realized that setting proper white balance is nothing more than using a white lid and a diffuser. So here is my attempt at making one.

The first thing I acquired was the diffuser. This is definitely the toughest piece to get. I used some scrap screening from a fluorescent light. You can acquire this from hardware stores or just ask a building manager for any broken or scrap pieces.

Now for the tools, I tried this a couple of ways and the easiest and most precise way I found was to purchase a cheap hole saw that attaches to a drill. A hole saw is the tool used to install door knobs.

The bigger you can get the better, after all a big homemade white balance disc will fit over top of small lens, but not the reverse. For estimates on size, a 3 inch diameter hole saw ends up being about a 70mm diameter. The only problem I found is that after 3” the next common size is 4”. I couldn’t find any sizes in between.

It would be good to pick up a grinder bit and/or sandpaper to remove burs that occur from the drilling and grind down any chunks of plastic that didn’t get properly cut. When drilling out a circle, your going to want to raise the drill bit in the middle of the hole saw upwards so you don’t have a hole in the middle of your diffuser. However before you do this, I suggest drilling out a template with the drill bit lowered, this creates a large hole that you can place your hole saw in as a guide. I tried drilling directly with the bit raised and without a guide and ended up scratching the diffuser sheet. Once the circular diffuser is cut out, grind down any abnormalities and smooth the edges with sandpaper.

The other key component to making a homemade white balance disc is finding a uniform translucent material that can accurately reflect 18% grey. I tested out several materials that have been suggested from searching the web (tissue paper, lens paper, filter paper, coffee lid) under several lighting conditions (incandescent, fluorescent, overcast, sunny). It appears that a white plastic lid works best for accurately obtaining the proper white balance.

Most companies, produce lids that have writing or a picture on them, making them not usable for measuring white balance, however I know of two products that produce completely white lids: GoodHost iced tea and diet Nestle iced tea.

Edwin Leong did a comparison of an Expodisc and a plastic lid, he found that although the lid did a pretty good job at capturing the white balance, there was a color cast associated with it. This is why I added the diffuser. The light coming in is first diffused on to the plastic lid and then converted to a 18% equivalent by the lid. My thinking is that the diffuser minimizes color casts.

The only thing left to do is stick them together, I would suggest using some glue on the outer edges (so it doesn’t interfere with the incoming light). You can also stick it to a UV filter or adapter ring.

Thats it, a few cheap simple supplies and a little bit of work and you have a great white balance tool. I think fundamentally there is not much of a difference between the homemade version and the real thing. Attaching a lanyard to it to hang around your neck is a good idea to quickly access and change white balance as the light conditions change.