At 6:24 PM +0000 1/30/02, olympus-digest wrote:
>Date: Wed, 30 Jan 2002 09:25:36 -0600
>From: "Dean C. Hansen" <hanse112@xxxxxxxxxx>
>Subject: Re: [OM] Ack! Macro flash help, please
>
>Jim Brokow suggested a light tent, and Daan suggested diffusers, to help
>reduce reflections when photographing gems. Yet another possibility to
>consider is using cross-polarization with your flashes. See a photo of
>amathest crystals photographed with cross-polarized flashes in George
>Lepp's "Beyond the Basics. Innovative Techniques for Outdoor/Nature
>Photography," p. 41. I use cross-polarization with good results to
>photograph insects and spiders (OM4T, 2 T32's, 50mm or 38mm macro OM
>lenses).
Cross polarizers will not do well with the metallic parts of the jewelry -- it
will render as black. The gemstone will be interesting, but isolated from its
setting. Cross polarization works very well with organic objects such as
insects and spiders, because surface reflections are supressed, allowing the
true color of the organic objects to be seen. However, metals are all surface
reflection; take this away, and nothing remains.
The traditional way to photograph shiny metal objects is with a light tent and
one or two lights (or strobes). The tent is in effect a translucent white
hemisphere with a round hole in the top just large enough for the camera lens
to poke through. What the camera sees in the shiney metal is the out-of-focus
reflection of the tent. (It's best to ensure that the depth of focus does not
include the tent.)
Even if the tent is lit evenly, the varing angles and radii of the metal will
cause variations in effective brightness, so one will see the needed modelling.
One can also emphasize this effect by uneven illumination of the tent.
The "hemisphere" need not be hemispherical, but be aware that reflections of
any seams may be visible when reflected in the metal object being photographed.
If the hole doesn't fit the lens tightly, it may be possible to see the camera
as well.
One can buy hemispherical tents intended for the purpose, but they are
expensive.
One low-cost dodge is to use a big sheet of frosted mylar or acetate drawing
film with a hole in the center for the lens. Seamless white nylon fabric, the
kind used for softboxes and the like, should also work. This sheet is stapled
to a wooden frame and held horizontal over the tabletop where the object being
photographed sits. The sheet, being far larger than the spacing between sheet
and table, dominates the reflections. One can use a vertical fence made of
white foamcore to both hold the sheet up and to block all sight lines from
object to beyond the sheet's edges.
Joe Gwinn
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