Polarizing Strobe Lighting

[Streetwise]

I have a job to shoot a bunch of flat "art" that has a lot of glossy tape on it. Typically, I would shoot with strobes on umbrellas at around a 30-40 degree angle to the artwork with good results. This time, however, is a lot different with the anticipated reflections.

I have a couple sheets (10" x 19") of polarizing material, but I'm wondering if it's possible to Polarize light that's reflected from an umbrella? I almost think not.

The other option would be to shoot without umbrellas and just use straight reflectors, shooting through the polarizing material (maybe include a sheet of diffusion material?).

Of course this process assumes that I also have the lens polarized as well to work with the filters in canceling out glare.

Any experience with this type of thing? Does diffusion defeat the effect of polarization?

Thanks.

Dave

[Kevin W Smith]

I have a job to shoot a bunch of flat "art" that has a lot of glossy tape on it. Typically, I would shoot with strobes on umbrellas at around a 30-40 degree angle to the artwork with good results. This time, however, is a lot different with the anticipated reflections.

I have a couple sheets (10" x 19") of polarizing material, but I'm wondering if it's possible to Polarize light that's reflected from an umbrella? I almost think not.

The other option would be to shoot without umbrellas and just use straight reflectors, shooting through the polarizing material (maybe include a sheet of diffusion material?).

Of course this process assumes that I also have the lens polarized as well to work with the filters in canceling out glare.

Any experience with this type of thing? Does diffusion defeat the effect of polarization?

Thanks.

Dave
[a href=\"index.php?act=findpost&pid=141599\"][{POST_SNAPBACK}][/a]

Light is either polarized or it isn't, diffusion doesn't change that. That's why your polarized sunglasses still work on a cloudy day.

That said, I haven't done exactly what you're trying to do but have shot flat art with  reflectors with polarizing gels over them, no diffusion. The harder light, in my experience, brings out texture better.

[Alaska]

In your experience, have you found that the modeling lights vs flash provide a reasonable guide as to the correct rotation of the polarizing filter on the lens?  i.e. if the light has a different polarizing angle; modeling lamp vs flash tube, then it would be difficult to remove the appropriate glare without taking a number of images to actually see the effect of lens filter.

The reason I ask, is that a future project will involve this exact issue using oil paintings two strobes and polarizing sheets in front of the strobes.

Jim

[peterhorsley]

I have a couple sheets (10" x 19") of polarizing material, but I'm wondering if it's possible to Polarize light that's reflected from an umbrella? I almost think not.

The other option would be to shoot without umbrellas and just use straight reflectors, shooting through the polarizing material (maybe include a sheet of diffusion material?).

[a href=\"index.php?act=findpost&pid=141599\"][{POST_SNAPBACK}][/a]

Bouncing light off things or shooting through translucent material tends to "depolarize' it.  (and change it's colour).
You're on the right track of shooting the light through a diffusion material and then the polarizing sheet.  
It's worth trying to contain any light spill, perhaps by making a a large (A2) card with a 9" x 18" cut out and attaching diffusion material on the light source side and the polarizing sheet on the subject side. That way you can rotate the card and hence the polarized light 'coming' from the cut-out and observe the effect on the image.

In your experience, have you found that the modeling lights vs flash provide a reasonable guide as to the correct rotation of the polarizing filter on the lens?  [a href=\"index.php?act=findpost&pid=141626\"][{POST_SNAPBACK}][/a]

Generally the is a high correlation between the strobe and modeling light, at least from an orientation point of view, but the effect can be slightly more or less intense.  It's easy to see in a digital preview.

Cheers

Peter

[Streetwise]

Bouncing light off things or shooting through translucent material tends to "depolarize' it.  (and change it's colour).
You're on the right track of shooting the light through a diffusion material and then the polarizing sheet. 
It's worth trying to contain any light spill, perhaps by making a a large (A2) card with a 9" x 18" cut out and attaching diffusion material on the light source side and the polarizing sheet on the subject side. That way you can rotate the card and hence the polarized light 'coming' from the cut-out and observe the effect on the image.
Generally the is a high correlation between the strobe and modeling light, at least from an orientation point of view, but the effect can be slightly more or less intense.  It's easy to see in a digital preview.

Cheers

Peter
[a href=\"index.php?act=findpost&pid=141657\"][{POST_SNAPBACK}][/a]

Thanks for the input everyone. I kind of thought the same thing that polarizing the light, but then bouncing it off of an umbrella would more or less defeat its purpose. That's why I mentioned the diffusion material and polarize that. I like your idea of mounting the material on some cards. I'll have to give that a try.

Does anyone know where I could purchase larger pieces of Polarizer material?

Dave

[Craig Murphy]

Seems you have the polarizing answers.  Even with the polarizing I have to really look close at the files to make sure that its working correctly.  Sometimes it looks great but then I notice some spotty reflections in a corner etc.  Usually is a matter of moving the lights some.
    I shoot flat art for reproduction for a number of artists. Oils, acrylics, watercolors and find it to be a little bit of a PITA.  Hard to make money at considering all the time involved.  I print reproes for them with my 9800 and they have been satisfied so far.  First thing I tell them though is that they are never going to totally match the originals in color.  I take this as a failing on my part because I really don't know how to match all the complex subtle colors that can be in a painting.  Have anyone ever gone to the Epson site and linked to the Museum in Boston that claims they are getting accurate repros with the 9600.  Would love to know their hardware and workflow.

[fnagy]

Seems you have the polarizing answers.  Even with the polarizing I have to really look close at the files to make sure that its working correctly.  Sometimes it looks great but then I notice some spotty reflections in a corner etc.  Usually is a matter of moving the lights some.
    I shoot flat art for reproduction for a number of artists. Oils, acrylics, watercolors and find it to be a little bit of a PITA.  Hard to make money at considering all the time involved.  I print reproes for them with my 9800 and they have been satisfied so far.  First thing I tell them though is that they are never going to totally match the originals in color.  I take this as a failing on my part because I really don't know how to match all the complex subtle colors that can be in a painting.  Have anyone ever gone to the Epson site and linked to the Museum in Boston that claims they are getting accurate repros with the 9600.  Would love to know their hardware and workflow.
[a href=\"index.php?act=findpost&pid=141936\"][{POST_SNAPBACK}][/a]

Craig,

Not much has changed since the conversion to Digi, when I shot 35 mm slides and 4x5 Tranies, they were never an exact match, in fact I used to switch between Provia, Fuji tungsten and Kodak (both )depending on the type of artwork and client??? artists on a limited budget.  Prints from them were never the exact, each paper had it's own characteristics, repro to CMYK printer depended on the expertise of the set up man (why else shoot a colour card?) and printing budget?

Take a look at some Catalogues from art exhibits, walk around and compare to what is on the wall, most galleries have comlimentary copies out.

As long as the artists are satisfied, you have done your job well.

[Streetwise]

Seems you have the polarizing answers.  Even with the polarizing I have to really look close at the files to make sure that its working correctly.  Sometimes it looks great but then I notice some spotty reflections in a corner etc.  Usually is a matter of moving the lights some.
    I shoot flat art for reproduction for a number of artists. Oils, acrylics, watercolors and find it to be a little bit of a PITA.  Hard to make money at considering all the time involved.  I print reproes for them with my 9800 and they have been satisfied so far.  First thing I tell them though is that they are never going to totally match the originals in color.  I take this as a failing on my part because I really don't know how to match all the complex subtle colors that can be in a painting.  Have anyone ever gone to the Epson site and linked to the Museum in Boston that claims they are getting accurate repros with the 9600.  Would love to know their hardware and workflow.
[a href=\"index.php?act=findpost&pid=141936\"][{POST_SNAPBACK}][/a]

It is really hard to make money with art repro, at least in my small town. However, I am able to get almost dead-on reproductions with watercolor originals on my 9600. The downside is that it takes a LOT of time and paper/ink to come up with a good artist proof. I have yet to invest in a good calibration system beyond my monitor calibration, or a RIP. Maybe down the road. For now, Photoshop know-how with adjustment layers is the rule of the day (and night).


Dave

[paulhu]

I have seen Chuck Modlin of DTG (Data Technology Group) using two strobes with just reflectors and polarizing sheets tapes to each strobe.  He demonstrated the technique at a seminar, while capturing art images on the wall, then print the image on canvas. Each strobe was approximately 45 degree to the art object on the wall. The printed copies look verly close to the originals.

The only thing that I was not sure of was that he used the strobe or just the modeling lights.  I will call him tomorrow and ask him exactly how he did it, then post in this forum again.

[Craig Murphy]

I don't think it really matters if you use strobe or tungsten lights.  Modeling lights would probably make the exposure time excessively long.