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Without wishing to kick of a blue I must say at the outset that I do not agree at all with using a light tent to copy oil paintings. It would change small specular highlights on the brush-strokes into an overall sheen which would reduce contrast and colour saturation. In part the situation could possibly be remedied in POST PRODUCTION - but then again, perhaps it could not. Well, not so precisely, anyway.

Now, Adam, the foirst thing to come to grips with is why you wish to copy all these paintings. Is it simply to catalogue them as a reference and for possible on-line promotion, or do you wish to make reproductions from them for sale and possible printing as posters, post-cards, calendars, etc. The intended use will greatly influence the lengths you go to in the copying.

For the ULTIMATE result I suggest copying the paintings in cross-polarised light. What is 'cross-polarised light?' I hear you ask. Well you place a sheet of Polarising foil over each lamp orientated in the same direction (usually indicated by a mark of either your own or the manufacturer's addition) and then you place another Polariser over the taking lens of the camera orientated so as not to allow any reflections to show.

Because so much of the light is being blocked by the filters, exposures can become quite lengthy affairs and so this is all best carried out in a room capable of total darkness so that other (ambient) non-polarised light does not affect the exposure. The simplest thing if you don't have a light-tight studio or copy-room is to work at night woth the lights turned off.

I use standard dish reflectors on my flash units because being smaller the reflections are smaller. The lights are placed at about 45º either side of the artwork at sufficient distance to give an even illumination without hot-spots. Obviously the lamps should be positioned in such a way as to cause minimal relections to begin with.

I used this technique just a few weeks ago and wrote of it here. I used flashes of 1500WS and, using a view camera and macro lens, I needed f22 to assure even image quality across the image. The flashes with all the filtration gave me f4 and so it was necessary for me to open the shutter on 'B' and then fire the flashes 32 times to attain enough exposure for f22. (I ended up cheating and using f16 which only required 16 flash 'POPS'.

Included adjacent to the painting should be a Kodah Colour-Separation guide and a Step-Wedge (greyscale) if you intend to have the pictures reproduced by a commercial printer They provide an industry standard reference which relates directly to the ink that goes onto the paper.

Good luck with the project.

Well I've been busy sinking all this in and have a few questions still.

I have been looking for a 67 mm polarising filter and my choices, it would seem, are plentiful.

This site shows a hint of what I mean - Circular polarising, HMC Circular Polarising, Super HMC Circular Polarising, Ultra-UV Circular polarising, Linear Polarising... though they do give another link to read - so off I go on yet another exploratory read here.

OK I'm back after a lengthy read. I take it I need either a standard Circular Polarising, HMC Circular Polarising, or a Super HMC Circular Polarising filter. Priced at $79.40, $139.55, and $156.10 respectively. OUCH!
So be it. Advice on which to buy here would be greatly appreciated.

The lens I am using here is the 18-70 G kit lens that comes with the D70. My budget does not yet allow the lens lust that the lust so desires. If I were to spend over $100 on a filter for this lens, I would hope that the eventual replacement to this lens would also be 67mm. But if I were to spend less on the filter and it doesn't do the job, well that's false economy, like buying a beach spade to dig foundations. At least I can get a 67 to 62mm step ring and use the filter/s on my 70-300 G lens as well...

So on to the other tricky bit - Polarising Foil... ??
I am in northern Tasmania. The camera shops around here are such that if you like the look of a D70 or a 20D they'll happily take your money... but when seeking specialist information and the products to match, well I could read the book if I wanted to as well... Maybe I will find a local photographer and have a chat if he/she can afford me the time.

Where can one purchase (/obtain) polarising foil? Would it be a bad idea to get a bit extra to put in the front of the camera as well instead of a filter - for this art photography challenge only? Or am I being too cheap there? You say I need to orientate the filter on the front of the camera so as to not to allow reflections to show. That would allude to the fact you're not talking about circular polarising lenses for the front of the camera in this instance? Are you indeed referring to the orientation of the polarising foil you mention?

Dazed and confused...

While on the subject, I am also looking out for neutral density filters - x2, x4, x8, and maybe the x400 just for fun. Is about $50 each correct?

For those that missed the intro to the creation of this thread, it can be found here.

More on polarizing lenses here.
Answers to the most common polarizer/UV questions

Perhaps it should have been called "Detailed, scientific answers..."

Der Mr Sheetshooter.
Thank you.
I bought my linear polarizer film some years ago. Well, I now have an SB900 and have borrowed an SB600, so I have set up one either side, and the built in flash on commander mode with the built in flash turned off.
Linear film over both SB units and the inbuilt flash, and linerar film over the lens at 90 degrees to the orientation of the film over all the flashes.
Here is the result on one of my framed photos. Taken using D700, 50mm f1.4 at f8

Film removed from front of lens


Film applied to front of lens


Smaller, animated gif of both images, to compare -


Now I have a heap of photography to do, about time eh?
Thanks again

For those that are interested, the timber frame is made by me, hand crafted from Tasmanian timbers. This one is Tas Oak.

Adam.

Thanks for this most informative post Adam. I think this post should be a sticky or something...

surenj wrote:Thanks for this most informative post Adam. I think this post should be a sticky or something...

Most of the reflections you are seeing in the first photo are from the PopUp. Even with it set to "off" in commander mode, you get some contribution to the final image, most often seen in direct reflections like here.

For a simple approach, you could put a card in front of the PopUp so the remotes see it, but the glass doesn't. Or you could use the SB900 as master and trigger it using a cord. An SC17...29 should work. Or two or more coupled together if you need more distance.

I am interested that you are using a linear polariser over the lens. Everything I have read says these don't work well with Digital. Something to do with the sensors as I recall. Do you need to be finicky with the orientation of the LPL in an absolute sense (i.e. relative to the camera, or just make sure you cross it with the light sources?

Having done lots of copy work both in and out of studio....there's no reason you can't take your artwork outside and copy it using natural light. Do a white balance pre set and put a Kodak colour strip in the first frame if you need absolute colour fidelity. Do it in open shade or in sunlight...try a couple of test shots first and make sure the camera back is squared up and centered to the frame. Avoid using wide angle lenses....50mm or longer is better. Avoid using very small F/stops as you will lose sharpness due to diffraction. F/8 or f/11 would be best.