Easy Cross Polarisation

Cross polarising effect is where you use a pair of polarising filters - one on the camera and one on the light source (behind the subject) to show stress in plastic which appears as wonderful multicoloured pattern. It used to be quite difficult as the filter needed for the backlight needed to be large and polarising gels are not only hard to find but also quite expensive. But there is a modern day solution and it's staring right at you! Your LCD computer monitor. Yes this can be used as the light source and even though you didn't realise - it has the polariser built in.

Gear
Any camera with a polarising filter either attached or positioned in front of the lens. An LCD computer monitor. A steady support. A tripod is idea but it could just be a pile of books to get the camera to the correct height.

Some clear hard plastic items - filter cases, plastic cutlery, plastic glasses, cassette and cd cases or geometry sets (my favourite) are a few options. Something to hold the plastic item steady in front of the computer monitor.


Technique
Turn the monitor on and remove any desktop clutter and change the screen saver to a neutral colour.

I find the quickest way is to create a grey file. Just a plain mid grey image about 800x600 pixels and call it grey.jpb.

Then drag this to the web browser to display it. And then hit the f11 key to display the browser full frame without menus. And then hold down the ctrl key and tap the + key until the grey image fills the monitor window.

Next position the plastic item in front and in the centre of the monitor. In the illustrations I bought a cheap geometry set from Poundland. It was unused so has no scratches as they can spoil the effect.

I used a McClamp to hold the piece in the centre. But you could use a tripod leg, large book or glass and tape the item to the edge. Anything to get the area you want to photograph in the centre of the monitor.

Now attach the polarising filter to you camera and position the camera in fron of the plastic so all you see is an area of the plastic with the grey image totally filling the background. If you can't get close with your camera use the lens at its telephoto setting to fill the frame and avoid edges of the monitor showing. If you still can't get close enough you will have to crop off areas you don't want later.

Now rotate the polarising filter and watch the colours of the plastic become stronger and the grey go darker. If you have it set up correctly the grey monitor will go totally black, and the colours in the plastic will be brilliant.

You can use any exposure mode and shooting at the metered setting should be fine. Under expose a little if you want even more dramatic colours.

As an extra level of abstractness I tried shooting with another piece of my geometry set slightly out of focus in front of the original piece. The result was rubbish, but I then realised that if you brought the item even closer to the lens it made the whole image have a multicoloured filter. By experimenting you can often find undiscovered gems. 




You've read the article, now go take some fantastic images. You can then upload the pictures, plus any advice and suggestions you have into the dedicated Photo Month forum for everyone at ePHOTOzine to enjoy.