polarizer at night?

[RoB_m]

just wondering if there's any purpose for them for night photography?

[timmyquest]

same reasons you'd use it for day photography

[RoB_m]

alright, i'm wanting to experiment with it. er.. i have a polarizer for my canon A-1. can i just hold the filter up to the lens of my A80 without any adverse effects?

[Jesper]

Yes, you can use a polarizer at night too. Beware that a polarizer takes away between 1 and 2 stops of light, which means you'll have to make the shutter speed 2 to 4 times as long as without the filter (the camera will do this automatically ofcourse if you have it on auto exposure mode), but it probably means you can't shoot hand-held. I don't know what happens if you use a polarizer with flash, but I guess you won't get a really nice photo....

[Bodryn]

I haven't tried a polarizer for night photography, just for day photography. However, I am quite sure it would affect moonlit sky the same way it affects sunlit sky during the daytime. For example if you want better views of the stars through a moonlit sky, it might help quite a bit if you didn't want to wait a few days for the moon phase to change. I suppose it might have similar effects on a sky illuminated by city lights if they are coming predominately from one direction, for example if you live outside a nearby large city.

[Persian-Rice]

You can use a polariser at night, no one has made a rule that you cant.

The only thing I would suggest is to take a tripod along, you are going to need one.

[PacAce]

Yes and I can wear my sunglasses at night, too, but why would I want to? ???

[mwinog2777]

There is absolutely no reason to it at night. All you will be doing is taking away 1-2 stops. If you wish to waste time experimenting, go ahead.

[Bodryn]

Some people DO wear sunglasses at night. Why would they want to?
Didja ever hear of Ray Charles? Well, sadly enough, he doesn't wear them anymore :(

Seriously, there might be a very good reason to use a polarizing filter at night; maybe I'll try it myself and try to prove the point.

Losing 1 or 2 stops of light is no barrier - think "time exposure".

Any amateur astronomer knows that various kinds of filters can be useful at night and I'd venture to say that in certain instances one could stand to gain with a polarizer as well. As I hinted at previously, it might be worth seeing whether one could use a polarizer to cut through some light pollution as for example when shooting a celestial object; I seem to recall reading that some stars emit light which is more polarized in one direction than another. The more imaginative among us humans are always trying new things, breaking new ground.... others, well...

[PhotosGuy]

Hold it in front of your eye. Rotate it. If you see something you like, try it. If not, then not! :wink:

[Bodryn]

Good advice perhaps; unfortunately at very low light levels, such as are used for astronomical photography, where images may take several minutes to accumulate on a CCD, one could not tell much just by looking through a polarizer - the human eye just can't see objects as dim as that; one would have to try the photo process itself to find out very much....

[nosquare2003]

Good advice perhaps; unfortunately at very low light levels, such as are used for astronomical photography, where images may take several minutes to accumulate on a CCD, one could not tell much just by looking through a polarizer - the human eye just can't see objects as dim as that; one would have to try the photo process itself to find out very much....

If human eyes can't judge the effects of polariser, then how to use it?

I'm not good at Physics while I don't understand the astronomical part. Anyway, I don't see the advantage of using a polariser directly to the light source, the star. It will cause a loss of light. Can you still get the star for several minutes exposure -- since the Earth has been moved? I'm afraid you will get a star trail. (Stacking of under-exposed photos may be a better choice but it needs a lot of work.)

I can't rule out the use of polariser at night. For example, the cutting of the reflection in windows of a shop.

[Bodryn]

I don't know much more about polarized light coming from celestial objects other than that I read about it some years back. Many of these would be too dim for the human eye to detect but could be seen photographically and one would have to use trial and error. I can guess that nebulae illuminated by nearby stars might well be polarized in some way.

Astronomers have routinely hooked cameras up to clock driven telescope drives that keep up with the sky so that they can take photographs, sometimes hours in duration. Now with CCDs, they've been able to greatly shorten the times on these but I understand that they are limited now by noise in how long they can make each exposure.

I don't know what the person who originally asked the question had in mind but from what I know, there might well be a use in cutting down some photographic light pollution in a time exposure if you orient the polarizer in a direction that would be basically at a right angle to the source of the light, whether it be a bright moon or city lights, and thus cut that light down more than the other light sources such as bright stars and thus be able to bring them out more than otherwise. I think it could be quite interesting to try this on city skylines at night just to see how different orientations might affect the ambient sky brightness, because the lights would be mainly in one direction from the camera lens.

The way to know which way to orient the polarizer would be to first check it out in sunlight; make a mark on it closest to the direction of the sun at the point where it dims the sky the most; then, at night, find out the direction of the light source and orient the polarizer towards that. I did that on my polarizer for day shots just so I wouldn't have to repeatedly check the image before shooting which can be hard in bright daylight. I just turn the polarizer towards the direction of the sun and shoot. I made several dozen great cloud photos last month just this way while on a trip. Marking the filter saved me lots of time and trouble.

[RoB_m]

There is absolutely no reason to it at night. All you will be doing is taking away 1-2 stops. If you wish to waste time experimenting, go ahead.

a little closed minded are we?


thanks for the input everyone. haven't really messed around with this yet, but i will soon.

[timmyquest]

a little closed minded are we?

My thoughts exactly...

:roll:

[ltdedorc]

I've used a linear polarizer in special situations to take sunsets thru a reflective window. A fellow on a tour in June had a Sony 828(?) and a linear polrizer but was not using it. So at dinner I rotated my linear and showed him the results on the LCD while taking these two pics seconds apart to eliminate the reflection of a in-direct light fixture on a ledge adjoining the window:

First polarized
http://a4.cpimg.com/image/CA/7A/35461834-6253-02000180-.jpg
Next not polarized
http://a2.cpimg.com/image/B2/F5/35362482-2330-02000180-.jpg

[Bodryn]

Those photos are great examples. The way I understand it is that polarizers are most effective to cut through reflective surfaces like water or glass when used at about a 45 degree angle to the surface. Naturally, a polarizer could be used just as effectively at night as in the daytime for reflective surfaces such as these - just have to lengthen the exposure.

One of the handiest uses of circular polarizers has been when I made a long trip by Greyhound bus once some years ago and had to use my polarizer to be able to get good video out the side window - without the polarizer I was getting mostly reflection from the front of the bus - so I routinely left the polarizer in place at all times and even used Scotch tape to keep the orientation true. This is also an issue if you're a passenger in a car and want to take routine photos while traveling - you can very effectively cut out windshield or side-window reflections if you orient the polarizer correctly and if you try to shoot at about 45 degrees to the window - most windshields seem to be at about this angle anyway.

[RoB_m]

my polarizer is a solid shade. seems like you guys have maybe a different type than me? it's for a 50mm canon lense and i plan on just holding it up to the lense of my A80. hope it doesn't soften or blur the image.

[Bodryn]

I don't know of any qualitative difference in polarizers, I think they all are directional. Holding it in front should work fine but would be awkward.

Anyway, I have an A70 and I found out that by using the lens adapter I could put my old 52mm polarizers right on that. Sure is easier than holding it in front. They are not expensive and also would provide extra protection for your A80 lens. You also are protecting the zoom mechanism from bumps, etc., when the lens adapter is in place.