Polarizing filter woes...

[Kyle]

Hi guys

I'm about to buy a polarizing filter, though i'm looking through the long list on b&h to find the right one, and i'm stumped...

http://www.bhphotovideo.com/bnh/control ... &Submit=Go


I shoot motorsport and still auto photog mostly, so thats what i's main purpose is

Anyone able to give me some direction at all?

Cheers

[fozzie]

Kyle - you may want to have a look at this:-

http://www.schneideroptics.com/info/han ... k12_15.pdf

Remarks: for a wide angle lens you will a slim CPL filter.

If you shoot Nikon, they make a line of CPL, and said to be excellent quality.

Hope this helps you out.

fozzie

[Yi-P]

B+W CPL are very good quality polarizers, but they are bit on the expensive side.

Nikon seconds from that quality, and Hoya follows from the budget line.


But for cars, polarizers are not able to remove reflections from metal objects, be ware... It is only to remove certain non-metallic reflections, such as water and glass reflections as most, but will not remove hotspots or reflections from metallic car bodies.

[Kyle]

Any way to do it then yi-p?

[Yi-P]

If you are talking about motor shows, then I dont think you can do anything with it, at least that what I know.

If you have control over the cars, then taking it outdoors into an open area or sometimes the reflections will help to make the shot more interesting (ie clouds or surrounding buildings)

On motorsports, I dont think it really matters (cars are not clean and shiny anyway), but polarizer can get you a more interesting sky and contrast nonetheless. But will greatly slow your shutter speed down.

If you think of those studio kind of effects, you may need a really large backdrop and huge diffusers

[Matt. K]

I'm stuffed if I know what the attraction is to PL filters! I know some photographers who never take the bloody things off their cameras! Let's get back to basics...what does a PL filter do? It reduces reflections in glass and water...but not metal. It may darken the blue sky and give you that 'Womens Weekly' landscape shot look ( a crappy look overall and one that yells....fake!) It does nothing else! Downside is...it costs you nearly 2 stops of light! In other words...it turns your F2.8 $2000 lens into a F5.6 $300 lens! So folk....yes, there are times when the filter is useful. Shooting into water or through shop windows, But just to darken a blue sky? Well, you can do that in PhotoShop and not lose 2 stops of speed? I rarely, rarely, rarely use a PL filter. I need a good reason to put one on my camera. I have one in a drawer and hardly ever take it out! And a good PL filter costs nearly 200 bucks! Better to put that money towards your next lens...an 85mm F1.4. Now that's worth having.

[Kyle]

True true, up until now i've never used a filter for motorsport, but recently people have been telling me to.... only reason I asked...

Hmm, wonder if that 85 would be any good at the drag strip

Better off with a 70-200

[gstark]

Kyle,

For motorsport, I would respectfully suggest that it's worthless.

Its uage depends upon correct orientation wrt the sun and your subject, and it needs to oriented for each shot.

Not the sort of thing one will be doing as cars go shooting past.

By all means, get one to use in landscape and stockon-site photography.

But not for action.

[Kyle]

Ok cool thanks for that gary

An ND filter might be better for bright days to pull back shutter speed to around 1.160-200 for panning perhaps

Also, will the CP filter pull the reflected reds in this perhaps?
http://www.ks-photog.net/gallery/d/3222 ... ugs001.jpg

Thanks for your help guys

[Steffen]

I respectfully disagree (with Gary and partly with Matt). The polariser's dependance on the angle of sunlight is only for reducing atmospheric dispersion, i.e. for making washed-out skies bluer and white clouds more standing out.

However, polarisers can cancel out all kinds of non-metallic reflections, including those on car paint, produced by any light source. Even though car paint is frequently metallic or mica these days, the primary reflection (glare) is mostly caused by the clear coat. Hence, using a polariser for shooting cars will produce more pure colour and more detail, even if a shimmer from the metal particles remains. It won't remove glare from chrome parts, obviously.

I don't use polarisers much myself (heck, I rarely use any kind of filter), but polarisers can have an effect that is impossible to mimick in Photoshop (unlike any other filter).

Cheers
Steffen.

[gstark]

Steffan,


What you say is sort of fine, as long as the vehicles are stationary. Kyle has stated that he wants this for motorsport, where the cars are expected to be mobile.

The reduction effect of the reflectance, off glass, water, paint, whatever, is always dependant upon the alignment of the angles through which the rays of light are travelling.

A polariser is directional, and cancels out some of those directional rays, and you basically adjust the filter to achieve the maximum amount of cancellation, thus improving the relative transmission of the remainder of the light.

As the cars are going to be mobile, and it's the reflection of the light from the sun that you will typically be trying to address, the relative angles between the sun, vehicles, and yourself will always be changing, and thus the effectiveness of the polariser will be rendered to be of variable effect, often to a point of being totally useless, unless you can adjust the polariser while you're following the cars.

Not something I would suggest as being being easy to do, especially when trying to simply follow focus.

The polariser's dependance on the angle of sunlight is only for reducing atmospheric dispersion,

Actually, I don't accept this particular point. Were this the case, then there would be zero effect when you are using a polariser to see "through" a reflection off, say, a glass windscreen or window into the interior of a building or vehicle.

But we know that by simply rotating the polariser we can dial in the effect of the polariser by cancelling out light rays that travel in just the one particular direction. With a stationary car windshield less than, say, two meters away, this is a most effective technique, and there is unlikely to be very much atmospheric dispersion involved over that short a distance.

But that isn't the scenario that Kyle is thinking about.

[gstark]

Kyle,

Also, will the CP filter pull the reflected reds in this perhaps?

Difficult to say, but the reds in that are very subtle: I'm seeing them on the glass, and also on the keyhole on the door.

I see a lot of reflections though in the paintwork, but they're an artefact of the lighting/technique used for the making of this shot. Basically, this was made in an open environment, and, without taking suitable measures, the result that you see contains reflections of that environment.

Difficult to control outside of a studio, and to be honest, I don't see this as an issue in this sort of image.

[Matt. K]

Steffen
I partly agree with part of what you have said part of the time.