Q: Polarizer v Neutral Density

[Night Owl]

I've used a CP in the past with varying results (in fact, I'm not sure I ever really learned to use it correctly) and recently read an article in a photo rag about "gotta have" gear that included a ND filter. I seem to recall they suggested the ND over a CP.

1. Any truth to the ND > CP claim?

2. I shoot heavy metal in varying light and always outdoors. (Shooting a 747 in-flight is a real trick indoors) What would serve me better?

Thanks.

[Hogleg 44]

I wouldn't think it would be of any benefit. It even might cause vignetting on some lenses due to the extended thickness of the extra filters frame.

[Debbi]

They both serve different purposes (sort of). The neutral density filter will bring the range of highlights/shadows closer together so that your camera can capture more of the range. The CP will do that as well (slightly) but really shines in taking out reflections (water, glass, etc.).

I've only had a problem with vignetting using multiple filters if I am using a wide angle lens. Even that has really diminished with the availability of super slim filters.

Bottom line, I have a .6 GND and a CP in my bag at all times but most situations usually only require one or the other.

[CaptainTom]

The ND filter will help control aperture or shutter speed. It does cause some EV shifting.

The CP will attempt to reduce reflection and will darken a clear blue sky dramatically.

If it were me, I'd go for the CP and have the ND in case If wanted to shoot props and needed to control the shutter speed in bright sunlight.

[KeithAlanK]

CP does so many things, it should be the first filter anyone gets.

I use ND4s to lengthen shutter time, to smooth moving water for example, and for IR shooting. A longer shutter isn't what you want for planes in flight.

A CP will cost you a stop of exposure, but it's worth it.
Bluer skies? Control over reflections on painted surfaces? Good stuff.

[jeffkohn]

What Tom (correctly) describes is an ND filter, which is a solid filter that doesn't really do anything except reduce the amount of light coming into the lens. They're mainly used when you have too much light for a given shutterspeed/aperture combination and you don't want to change either one (for instance, if you want to shoot an outdoor portrait with a wide aperture to blur the background, but you also need to keep your shutterspeed below 1/250 in order to use fill-flash). Another reason might be to achieve a long shutter speed for shooting moving water.

What Debbi describes is a graduated ND filter, which is similar but serves a slightly different purpose. Grad filters are clear at one end and transition to darker at the other end (the transition can be either "hard" or "soft", and the amount of filtration at the dark end can also vary). I'm guessing the magazine article was talking about graduated ND's, as they've traditionally been very popular with landscape photographers, particularly when shooting film.

What a grad filter allows a landcape shooter to do is properly expose for the foreground of a scene without over-exposing the sky. As long as you don't have an irregularly shaped horizon and there's somewhere to "hide" the transition, this can work very well. But if you have trees, buildings, or mountain peaks sticking up into the sky, they'll get darkened along with the sky which can look unnatural.

I personally don't see any reason to use grad filters when shooting digital, because you can take multiple bracketed exposures and combine them later to achieve the same effect, only with far greater control over the final result. This approach does require a sturdy tripod, but you should be using one of those for landscape shots anyway. Some people still prefer using grad filters with digital, but I think in a lot of cases it's because that's how they did it with film and that's what they're comfortable with.

As for the difference between a polarizer and a grad filter, both can darken a blue sky, although the effect with a polarizer will depend on the angle of the sun. The polarizer won't affect skies on cloudy overcast days though. A polarizer has some other benefits that make it unique:

- As opposed to just darkening the entire sky, it will actually increase the contrast between the sky and clouds (great for those days when there are a few puffy clouds in the sky).

- The polarizer can increase the saturation of foliage by cutting glare/reflection.

- The polarizer allows you to control reflections on other surfaces including water or glass.

- It can double as a solid ND filter, since it cuts roughtly two stops of light from your exposure.

I shoot the vast majority of my outdoor shots using a polarizer, although it's not always rotated for maximum effect. IMHO a polarizer is the second most useful accessory and landscape photographer can buy (the first being a tripod).

As for your specific questions:

1. Any truth to the ND > CP claim?

IMHO, no.

2. I shoot heavy metal in varying light and always outdoors. (Shooting a 747 in-flight is a real trick indoors) What would serve me better?

Neither will help you with reflections off metallic surfaces. A polarizer would be be more useful in your case because it can darken blue skies without also darkening the plane, and it can also cut glare coming off the windows.

[DJ.]

CP is indeed very valuable for reflections and can even be used to reduce shutter speed a small amount. The ND will have a greater influence on shutter speed and allow you to capture some shots that would otherwise be next to impossible.

I went with the Singh-Ray LB Warming Polarizer for my CP choice and the Singh-Ray Vari-ND to cut down on the need for removing and replacing or stacking of ND filters. I chose the wide-angle ring mount on both to cut down on the possibility of vignetting.

[jeffkohn]

Hey Dave, how do you like that LB polarizer? I like the idea of getting a bit more light through, although the warming function is of no real use shooting digital. Does it still give the full polarizing effect of a traditional CPL? I considered buying one of them before my last trip, but at the time they were backordered.

[DJ.]

Originally Posted by jeffkohn

Hey Dave, how do you like that LB polarizer? I like the idea of getting a bit more light through, although the warming function is of no real use shooting digital. Does it still give the full polarizing effect of a traditional CPL? I considered buying one of them before my last trip, but at the time they were backordered.

It is great and has all if the functionality of the standard CP. The Sing-Ray folks are great to work with also. They were backordered wihen I needed mine for a trip also. I told them my departure date and they had it to me with a little room to spare. They give priority to those situations. The workmanship is great as well and they come in a leather case that provides good protection.

I am going to order the Gold/Blue CP next.

[Night Owl]

Thank you, my Lieges! After the advice given, I think I'll pick up a CP to start (resume?) until I learn a bit more about filter use. Y'all are the best.

[KeithAlanK]

Originally Posted by jeffkohn

Neither will help you with reflections off metallic surfaces.

A CP most certainly WILL help with reflections off a painted metal surface. Most planes are painted. I have done strict A/B testing of an F16 and locomotives to prove this.

[venchka]

A polarizer is a neutral density filter and a lot more.

A neutral density filter is never a polarizer.

So, if you start with a polarizer (as you should for all of it's other benefits), and decide to add a neutral density filter later, make sure that the ND is a couple stops darker than your polarizer. Otherwise you'll end up with duplicate filters as far as the ND filter factor is concerned. Clear as mud? Example: Most polarizers are in the 1.3 to 1.5 stop range. To avoid duplication, look for a 2.5 to 3 stop ND filter.