Will a polarizer work ....?

I'm shooting some car rallying tomorrow and am considering popping out and getting a polarizing filter so I can get the driver and his number 2 showing through the windscreens.

I know, when shooting landscapes they really only work on sunny days. The weather forecast is cloudy for tomorrow morning, so I'm wondering if it is worth the effort to go and get one, will it still do what I want if it is cloudy and grey?

All help appreciated, thanks.

Yes. CPL's reduce or (almost) eliminate reflections on glass, and other surfaces. It won't matter about the sun in this case.

I doubt you will get much, or any, effect from a CPL in those conditions. I would also hesitate to use a CPL for windscreens anyway, as it can result in bad stress patterns showing in the glass.

I have had little trouble with seeing the occupants in rally / racing cars without using a CPL, you just need to avoid standing in a position where your angle to the cars catches the light being reflected back at the camera.

I also doubt that you will be fast enough to turn the CPL fast enough to get a good effect on moving rally cars. Additionally, the CPL requires about one stop (light that is) that you don't want to miss in a fast paced situation.

I have used a CPL successfully before. But beware, that some windscreens (lexan ?) will show the rainbow stress marks instead of glare with the CPL.

Here is are a couple examples. These were on sunny days. I don't bother with one on cloudy days.

Wow, thanks for your replies guys, very conflicting.

I went out and bought one, a B&W. It's not just for tomorrow.

I'll try it on the safety cars and maybe a few on the road to test.

I'll post results.

Again thanks.

The CPL effect on surfaces is still there with most overcast sky, although weaker of course. What looks to you like you can't see the sun anymore still have stronger sun from where it is. That's how that Viking stone worked, it intensified the sunlight so that you can see where the sun is even though the naked eye cannot.

Having said that, if it's overcast it sounds like a bad idea to use a CPL that drops a couple f-stops since your exposure time or ISO would go up. Unless you want that for panning.

When I shoot my pal taking his Evo out on track days I always use a CPL.

• Yes, it does cut down on reflections making it easier to see the driver.
  
• Yes, some windscreens will show stress patterns - not so many nowadays.
  
• Just set the correct orientation once on a stationary car - that'll work for them all. Angle to the sun doesn't matter.
  
• I always use a slow shutter speed (otherwise you may as well shoot parked cars) so 2-stops isn't important.