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Lens to use and copy table

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Old 10-25-2009, 07:23 PM
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grannysdc grannysdc is offline
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Join Date: Nov 2006
Location: Kansas USA
Posts: 280
Re: Lens to use and copy table

my 2 cents worth to what has already been said. .

Polarizing filters (Gels) indoors with portable flash and studio strobes/floods has been around for quite awhile. It is often done with a combination of lens filter and gel filters on the light units. The general idea is to polarize the light coming from the light units and then match that polarization with a filter on the lens. The benefits are generally the same as polarizing filters used outdoors - reduced reflected light resulting in richer colors and less reflections on glassware and other shiny surfaces. "Cross polarization" can reduce this glare to provide richer color saturation. Transmission is around 38% (one and a half to two stops). This neutral Gray linear polarizing film is used in front of lights to reduce the glare caused by smooth surfaces such as glass, water, paper and certain metallic objects. Especially effective when used in conjunction with a polarizing filter at the lens (cross polarization). Be aware that these Gels should be placed at a distance from hot lights.

For the polarizing filter on your camera lens to work indoors you must first polarize your light source. This can be done by putting a polarizing film or gel over your flash unit or light source (and turning off all other ambient light sources). Covering your soft box with a polarizing sheet gives your lens-mounted filter additional reflection-blocking power because more of the light reflected from your subject is polarized. The technique works equally well with reflective objects in product shots. Use a fairly bright light with a modeling lamp so you can get an idea of what the effect will be before the film or sensor is exposed-- The filters will absorbed almost 2 stops of light, so use 300Ws or brighter to avoid having to crank the ISO to 800 or higher. Light your copy work just as bright as you would a person and shoot with the same care as you would as shooting a human subject to capture all the fine details. . a simple on-camera flash won't do (The angle will not work if you try to polarize an on-camera flash. . The closer the light is to the lens axis, the less effective a lens mounted polarizer will be at controlling sheen or glare. ) Polarize in one direction with polarizers over the flash(es). Place the flash heads at 45%. Put a polarizer on the lens, turned 90 deg from the direction the flash is polarized. You may use either a circular or linear polarizer on the camera; however, the polarizer on the flash should be linear. You might want some gobos or barn doors to avoid spill onto the camera, but you shouldn't have to worry about it that much if the light on the subject is strong. Keep in mind that you can add back as much reflection intensity as you like just by giving the on-camera filter a twist. You can also use a long lens for greater camera to subject distance. The longer the lens and greater the camera to subject distance, the less perspective distortion and correction you'll have to deal with.

A couple sources for linear gels: http: // http: //

Reflections in glass are very simple to deal with without polarization. . Position a large black card, a large piece of black velvetine or velvet, a black piece of foamcore or art board. . . cut a hole in whatever material you use for the lens to poke through, . . . . cover the camera, tripod legs and yourself with something black and turn off any ambient light to keep the environment from being illuminated. light the subject at the proper angles for a good exposure. . The main point is to have a surface facing the glass that has no reflective properties.
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