Photo How To

Ever wish you could make the sky more blue without changing the foreground color and without tweaking the image with software? Or maybe give a daytime shot that sunset look? Welcome to the world of square graduated filters. Welcome to the world of Cokin.

The Cokin holder-and-ring system appeared in the US about 35 years ago. The system consists of a slotted plastic filter holder that attaches to many dissimilar lenses via inexpensive adapters. The filter holder has slots for round and square filters which are made of CR-39 eyeglass resin. The idea is that you can use the same set-up on just about every lens you own, even if they have different size filter threads, instead of buying duplicate filters in different sizes.

Most of the filters, including all of the graduated filters, are square, so can slide them up and down in the holder to preview and adjust the effect. The few round filters (Polarizers, for instance) can easily be rotated in the same fashion. You can download the current catalog here.

Graduated filters have been the hallmark of the Cokin system since the beginning. Even if you’re not into color-punching, graduated filters are still a great tool. Many of us have used the grey or tobacco grads to darken an overly bright sky and emphasize cloud structure. The Graduated ND8 (Cokin number 121) works better. You can easily adjust the gradient’s dividing line to match the horizon. Try using it upside down at the beach to obtain correct exposure of the ground while allowing the sky to completely blow out.

The images at the top of this column were shot with a Canon G1 X and Cokin P (Medium) filters. The filters used are as follows, moving from left to right and from top to bottom:

No Filter

123 B2 Dark Blue Graduated

132 Y1 Yellow Graduated

124 T1 Tobacco Graduated (upside-down)

124 T1 Tobacco Graduated

198 Sunset 2

122 + 123 Blue Graduated (2 filters)

130 E1 Emerald Graduated (low horizon)

Tips: Set your camera’s White Balance manually to Daylight, otherwise it will likely add some compensation that’s hard to predict. Focus normally—AF will work fine in most cases—and adjust the graduated horizon line to your liking. Break the rules—turn the filter upside-down or use two filters, one covering the bottom and the other covering the top. To exaggerate the effect, under expose slightly.

Cokin filters are available in four sizes. The A-series (now called Small) offers adapters from 36mm to 62mm. P-series (Medium) adapters go up to 82mm. Z-Pro (Large) and X-Pro (X-Large) cover bigger sizes up to 96mm and 112mm respectively. Most DSLR shooters will find the P-series most convenient. If you mainly use mirrorless compacts, the smaller (and less expensive) A-series may be your best choice.

What are they made of? A resin named CR-39. It’s an allyl diglycol carbonate monomer patented by Pittsburg Plate Glass (PPG) and is the material most often used to create eyeglass lenses. Introduced more than 60 years ago, it was the 39^th compound formulated by Columbia Resins, a PPG subsidiary, hence the name CR-39. Today it lends its ophthalmologic purity to Cokin photographic filters. Its original use? Combined with other materials, it was used to construct lightweight fuel tanks for B-17 bombers during WWII.

—Jon Sienkiewicz