My Favourite Polariser Trick

[Garbz]

Ok so not really photography, but here's a little physics phenomenon for you, posted here because well we all have these filters at home to play with.

Lets start with a poorly resized image of a computer monitor, and LCD, and something about LCDs is that they have a large linear polariser across their surface:

So now to add our camera's linear to circular polariser and adjust the rotation angle so the screen's polariser and our polariser are 90 degrees out of phase:

A few notes here: This could be an interesting backlighting project seeing how linear polarised light changes polarisation angle when it scatters off a surface creating the weird backlit effect off my calibrator, ... and all the dust on my screen.

And now we add another polariser into the picture. This time a Linear to Circular Polariser, in phase with the screen's linear polariser. This means the light going through the polariser is not cut out, but rather returned to a circular polarisation. The camera polariser has no effect on the circular polarised light beyond it's own insertion loss.

Volah if this doesn't get your kids interested in optical physics nothing will... I am serious... this is exactly why there are so few optical physicists in the world.

 

[jlykins]

That's cool. I'm going to have to try that when I get home...

 

[ksmattfish]

Sometimes when I'm out in bright light I'll look to the LCDs on my camera, and it'll be very hard to see. I'll be like "What the!?!?", and then "Oh yeah, I'm wearing polarized sunglasses."

 

[Big Mike]

Sometimes when I'm out in bright light I'll look to the LCDs on my camera, and it'll be very hard to see. I'll be like "What the!?!?", and then "Oh yeah, I'm wearing polarized sunglasses."

Happens to me ALL THE TIME!

 

[Judge Sharpe]

The one that Got me was when I was flying in a rental C-172, and the radio setting would not come a cross with Polarizing sunglasses on. I thought the rasio was dead.
If you cross 2 linear polarixing filters, the closer they come to 90 degrees, the darker the light becomes untill allis blocked out. An adjustable ND filter. Many times privacy glass in windows has a ploarizing film on it and you can clear it by looking through a polarizing filter turned 90 degrees in its axis. Not that anyone would want to do that.
JS