Cross polarisation

melekalikimaka

I'm pursuing a project on still life, and i want to go down the cross polarisation route, has anyone tried this before.... can i use two filters or do i need polarising paper?

thedarkroom

What exactly do you want to do with cross polarization when you say you want to use it in still life?
Do you want to show the effect of stress patterns when photographing transparent subjects such as plastic or are you using it to cut surface reflections when photographing glossy subjects?

melekalikimaka

stress patterns

thedarkroom

What you need is a polarizing sheet for below the subject and then a circular polarizer on the lens. The last time I did it I used a light box behind the subject (Plastic cassette cases) and it worked great, fantastic rainbow colours. very abstract. I don't know how things would work if you are using studio lighting shining on to a subject. You could experiment with a polarizing gel on the studio light and one on the lens and see how that works but I suspect that the system referred to above is the way to go as you are photographing light diffraction being effected by the stress patterns in a transparent object, which, in effect, is transmitted light. Using studio lights to shine on to your subject is using reflected light from your subject and different rules apply.

I have used this on my studio lights for removing glare and reflections when copying paintings and it works fine
http://www.adorama.com/RO7300.html
I'm not sure how it would work for cross polarization but it should be fine. It's a linear polarizer rather than a circular but the time I did the dross polarization pictures it was with a small Kodak Wrattan 100x100mm linear type and it was fine.

A word of caution, as it is a coated flexible gel filter, it will be quite fragile and easy to scratch so you will need to be careful when handling it.

If you decide to go for the link above, don't forget that there will be duty payable on importing but it still represents excellent value. I bought two of them about 8 months ago and all in it cost about €100. I could have sourced them directly from Rosco in the UK and it was going to cost me nearly the same price for just one.

thedarkroom

If you are interested, I will do a test with my filters to see if it works and post the results after the weekend so you will see then if it works for what you are after,

David

thedarkroom

I've attached a sample with three shots to show the before and after using the set up above. I use the Rosco Cinegel Polarizing Filter No #7300 on the light box and on the lens i used a Hoya High Quality Cir-polarizing. It was a quick test so the quality is only OK and the depth of field is zero as I used a 60mm macro at f2.8 but the results show what you're after (I hope). Its of the transparent from cover of a CD case.

melekalikimaka

lovely stuff, iust what i wanted to do... now to save cash... i'm considering using 2 polarising fiolters, a big one over light source, small on lens? any idea if it'd work?

thedarkroom

To be honest, I'm not too sure. I did it by putting the large sheet over a light box and placing the subject on top of that and then photographing it with a polarizer on the camera lens. Remember that the object is transparent and that it is a photograph of the stress patterns in this transparency that you are photographing. A light box, shining through the filter and cd case towards the camera is using transmitted light where as if you are using the gel over the light source, ie a desk light or some sort of flash, then you will be photographing the light bounced back from the subject and this is reflected light.
I don't know how this will effect the results but I would imagine that it would not be as dramatic. All I can say is to try it and see. What you could do is put a small gel on a small flash gun and use that as your light source with a filter then on your lens. At least this way you won't need to source a large lighting gel, which can take time and would be more expensive. You should be able to get a small Kodak Wrattan Filter 100mm x 100mm (or thereabouts) from Photoglogic (Kodak Agents) (01-2350888) or DML (01-4658600) for a reasonable price.
If you have a problem sourcing a small Wrattan filter let me know and I'll have a look at home, I might have one some where that you could try out,

David

Fiona

Hi

There was an article about this in the Jan edition of Digital Camera magazine, I can email you a copy of it if you want?

Mrs Crilly

melekalikimaka

well i shall be giving it a shot tonight with two polarising filters, so i shall let you know..

and yes i'd love a copy of the article, i shall pm you my email thanks

melekalikimaka

first attempt...

not great, will be investing in polarising paper