Digital Darkroom

Screw-In Or Modular Filters?
Filters are available in many different shapes, sizes, and materials and their use can affect contrast, sharpness, highlight flare, color, light intensity, or create an array of special effects. They are available as delicate gelatin filters that drop into special holders or lens hood, threaded glass filters that screw onto the front of your lenses and square or rectangular plastic modular filters that slip into holders than can be attached to different lenses using adapter rings.

If you have a variety of fixed focal length and zoom lenses of different focal lengths you can easily find yourself owning lenses requiring many different filter sizes. Modular filters overcome this obstacle by letting you purchase one filter that fits all your different lenses. These filters fit a standard filter holder and work with various-sized adapter rings, allowing them to fit different lenses and even different format cameras. All you need is a single, inexpensive adapter ring for each of your different lenses’ thread sizes. That means you only need to own one ND, gradient, or polarizer filter and it will fit all of your lenses.

Modular filters are typically square or rectangular, although some companies, such as Cokin, offer round filters, too.

These filters are also more than likely be made out of plastic. Don’t let that word “plastic” conjure up the optical quality found in toy cameras or even my favorite Holga. Plastic filters are usually constructed from the same kind of optical resin material that’s used in eyeglasses. The sizes of filters and the type of adapters used are different for some modular filter manufacturers, but some filters are compatible with other systems.

The Cokin modular filter holder is available in four sizes (A, P, Z-Pro and X-Pro) and all use a three-slot system for holding filters. While filters can be placed in any and each of them, the slot nearest the camera lens is specifically designed for Cokin’s round filters, including polarizers and is the slot that must be used when a Polarizer is used with another filter. This means you can simultaneously use other filters such as Neutral Density graduated filters and control the position of both independently.

Cokin’s original A filter system uses 75x75mm filters. The larger P (84x84mm) filter system was designed for professional use on medium format cameras, but an A/P adapter lets you use the A filters in a P holder so it’s not necessary to buy P filters if you already own equivalent A versions.

TIP: When using A filters on shorter focal length lenses some vignetting may occur so watch out for this problem on your LCD preview screen. Cokin offers the even larger (6.7x5.1”) X-Pro size that use a holder similar to the A and P series but with more rugged construction. Later, Cokin launched their grande 130mm wide Z-Pro series. A Z/P adapter lets you use Z filters on a P holder and the Z/P wide angle adapter lets you use Z filters on a P wide angle holder.

Filter Factors
Many lens filters absorb light and that light loss must be compensated for when calculating exposure. Fortunately, digital SLR in-camera metering systems compensate for these differences, but the rated “filter factors” are still a good measure of the number of stops that must be compensated for by either automatically or otherwise altering shutter speed, aperture, or ISO setting. Filter factors are multiples of the unfiltered exposure so that a factor of two is equal to a one-stop increase. My preferred method of making photographs when using filters is to change the shutter speed, using a tripod if necessary to maintain the same depth of field for either the filtered or unfiltered exposure.

Using Cokin’s Gradual Tobacco T2 Soft filter changes the mood once again. Cokin claims that it’s supposed to look “stormy” but I like the dramatic look it adds to an image. Exposure in Shutter Priority mode was 1⁄60 sec at f/11.

Pushing Cokin’s Gradual Tobacco T2 Soft filter down into the holder adds color to the entire image and creates a sunset look. Exposure in Shutter Priority mode was 1/100 sec at f/7.1.

Filter Companies
Many different kinds of filters are produced by camera manufacturers as well as filter companies, including:

HP Marketing Corp.
(Heliopan)
16 Chapin Rd.
Pine Brook, NJ 07058
(800) 735-4373
www.hpmarketingcorp.com

LEE Filters USA
2237 N. Hollywood Way
Burbank, CA 91505
(800) 576-5055
www.leefiltersusa.com

OmegaSatter
(Cokin)
1041 S. Carroll St.
Hampstead, MD 21074
(410) 374-3250
www.cokin.com

Schneider Optics
(B+W)
285 Oser Ave.
Hauppauge, NY 11788
(800) 645-7239
www.schneideroptics.com

Singh-Ray Filters
2721 SE Highway 31
Arcadia, FL 34266
(800) 486-5501
www.singh-ray.com

The Tiffen Company
(Tiffen)
90 Oser Ave.
Hauppauge, NY 11788
(585) 426-1073
www.tiffen.com

THK Photo Products Inc.
(Hoya)
2360 Mira Mar Ave.
Long Beach, CA 90815
(800) 421-1141
www.thkphoto.com

ToCAD America Inc.
(Sunpak)
53 Green Pond Rd.
Rockaway, NJ 07866
(800) 886-2236
www.tocad.com