Copy stand - polarizing the lights to remove glass reflections?

[Jeff Bannow]

I've heard talk of being able to do this, but am not sure the actual process.

I have one of these -Dead Link Removed. The lights are a little different, but close enough. I see a kit for $900 that will add polarization to the lights, but there is no way I'm spending anywhere near that much.

Is it as simple as adding polarizing screens over the lights? I just want to remove reflections from shiny objects when shooting from the copy stand.

 

[Mainecoonmaniac]

Roscoe makes polarizing gels. You also have to polarize the lens. Once the set up is finished, you look through the camera lens and put a coin on the copy surface then turn the polarizing filter on your lens until the the coin has no reflections. When this happens, the coin will turn black. You probably get a polarizing copy stand on Ebay for cheap with the advent of the flat bed scanner.

Here's a link to some polarizing gels for your lights.

http://www.filmandvideolighting.com/pofish19x20i.html

Good luck.

 

[DWThomas]

One word of warning (don't ask me how I know): if you're using hot lights of any power, the heat can damage the polarizing gels unless they are spaced a decent distance from the lens. Even with two inches or so of airspace in front of some 500 W halogen worklights with glass covers, the polarizing sheet was starting to buckle in a matter of a minute or two.

 

[Jeff Bannow]

Interesting - I guess the $900 polarizers are glass instead of gels then?

 

[DWThomas]

Interesting - I guess the $900 polarizers are glass instead of gels then?

I honestly don't know; it could be they set the polarizers a long distance from the lights and then to filter the expanded beam width have to use large sheets of the material which fattens up that price. I was pretty amazed at what that stuff costs.

I had the vague impression that even glass polarizers are actually a sandwich with a plastic layer that has the eye of newt and batwings for polarizing, but I'm a few kilometers out of my depth!

I'm also assuming here that you are talking of photographing three-dimensional shiny objects, as opposed to paintings and flat artwork under glass which isn't really that bad to do without polarizers, until you get into oil paintings with lots of surface texture and shiny varnish or art with embedded glitter.

 

[Q.G.]

All polarizers are indeed polyester or polyvinyl (i forget) sheets, even those glass ones: they are such sheets sandwiched between two glass blanks. The structure of the polyester/polyvinyl (whatever it is) is what does the business that makes them polarizers.
Not having tried this myself (they cost too much) i don't know how they absorb heat, and what they then do.

 

[Steve Smith]

Polyvinyl dipped in iodine and stretched (from what I can remember). I'm sure there are other methods but that was Edwin Land's method to make large and cheap polarisers.


Steve

 

[Mainecoonmaniac]

Mount them at a distance and...

Interesting - I guess the $900 polarizers are glass instead of gels then?

Mount them about a foot away and get a copy stand with a foot switch to turn on the lights when you need them. That way they don't have be on constantly. The bulbs won't last as long, but it will allow you to cool off also.

 

[waynecrider]

It's possible to put a heat resistant diffuser over the lights which are at a 45 degree angle, and there might be a heat resistant PL but if not it's easy enough to improvise a mat gel holder. There is also the shooting tents for table top items that has a hole on top for the camera. You light thru the sides with a strobe. Any glare can be controlled at the lens.

 

[Smudger]

If your lights are set at the correct angle,normally 45 degrees,you should not have any problem with glass reflections.
If the camera /tripod are reflecting in the glass a black card with a hole cut for the lens will do the trick.

 

[2F/2F]

You should be able to shoot through glass just by using a polarizing filter on the lens. I have done it many times. (Copy work is, in fact, my only use for polarizing filters.) Place the lights at identical angles and distances to the original. 45 degrees is standard, but this need not be adhered to. All you need is light that sculpts the artwork in the desired manner, but which provides the same amount of illumination to all dimensions of the piece. In other words, an incident meter should read the same no matter where you place it over the piece. Even if not using a 1:1 ratio, for a more sculpted effect, light evens out across the surface if you move it back from the subject.

If you are still having trouble, try fine grids (10 degree or narrower square or honeycomb pattern) instead of polarizing gels. The shape of the reflectors of the lamps should ideally be rectangular, but this is rarely the case on copy stand. Most have round reflectors. Backing the lamps off will eliminate hot spots that may form with the grids on. Ideally you use free-standing big rectangular lamps instead of those tiny round ones that mount to the stand. I do all my copy work on a wall or sometimes a table with Mole-Richardson 1000W Super Softlites. They provide a large reflected (read even) light, which I modify more by using the stock M-R grids for these lamps. Glass or not, I use a polarizing filter unless the surface is dead matte.

3D objects are a different story. You need reflections to make them look realistic (i.e. not 2 dimensional).

FWIW, I use my SINAR with the Rodenstock 210 or 90 lenses, often with a roll film back, and Ilford Ortho in HC-110 for continuous tone or Rollei ATP 1.1 in D-19 for halftone.

 

[Jeff Bannow]

Great information here - thanks to everyone chiming in and providing so much detail. I've got lots to test out now.