Filter Question

[Plato]

So I checked it out and I won't really be able to tell by just looking at it, but after rereading the post by plato above about the frisbee I understand the concept a little better. I also understand the more technical post by Dao because I can just relate it to going fishing.

Bear in mind that the polarizer will have no effect if no polarized light is present. Actually, it will act like a 1-stop neutral density filter because it will block frisbees in all directions equally.

 

[EleanorW]

phifer - I chat lots, ask the guys but I do my research... just not sure about "how" to use it yet.

plato - I understand the concept of what you said, but what I think I'm struggling with is, how do you know when you have the filter set right?

 

[Plato]

Technically, polarizer filter is used for selectively filtering light. As the name imply, it filter polarized light.

Light wave normally oscillate in many direction. But in certain condition, it only oscillate in one plane. And we called it polarized light.

Reflected lights are usually polarized. Hence, polarizer filter can be used on reduce the amount of light from a reflected surface such as the surface of a pond or glass.

Lights can be polarized by scattering. The blue sky was the result of that. However, some of the partially polarized light will make the sky kind of wash out. So block those light from entering the camera can make the sky deeper blue.

As for why circular and rotatable, since you want to rotate the polarizer so that the invisible slits are perpendicular to the polarized light oscillating plane. In that way, it will stop those light from passing through.

Pretty close but not exactly correct. Probably easier to explain if you first read my earlier post with the frisbee analogy.

lol .. I did not see your post when I reply ... I learned about the polarization more than 20 years ago (yeah .. i am old) ... I am glad I still remember some of them!!

Your post was accurate except for the explanation for "circular" (as opposed to linear). By the way, I first learned about polarizers in 1962! (They were all linear then.)

 

[Dao]

If you have 2 CPL, you can stack them together and rotate one ring slowly. You will see what happened.

 

[Dao]

Pretty close but not exactly correct. Probably easier to explain if you first read my earlier post with the frisbee analogy.

lol .. I did not see your post when I reply ... I learned about the polarization more than 20 years ago (yeah .. i am old) ... I am glad I still remember some of them!!

Your post was accurate except for the explanation for "circular" (as opposed to linear). By the way, I first learned about polarizers in 1962! (They were all linear then.)

:hail:

 

[phifer8390]

plato - I understand the concept of what you said, but what I think I'm struggling with is, how do you know when you have the filter set right?

I know what you mean here I still need to get out and snap a lot more photos. The only advice that seems to be agreed upon is just to practice taking photos different ways. I cannot wait until I can go out and fill up my 16gb card this weekend playing with different settings and filters!

 

[Plato]

phifer - I chat lots, ask the guys but I do my research... just not sure about "how" to use it yet.

plato - I understand the concept of what you said, but what I think I'm struggling with is, how do you know when you have the filter set right?

Two ways, depending on personal preference. One way is to simply watch the scene and you will actually see the effect of the polarizer as you rotate it. You'll see reflections disappear and the sky darken. (For dark skies, your camera MUST be aimed 90 degrees from the angle of the sun.) Here is a very simple example of what you can see in the viewfinder.

Another way is to watch your camera's metering. If, for example, you're set for aperture priority (you set the aperture and the camera sets the shutter speed), you watch the shutter speed. As you block more frisbees, the shutter speed will slow down to keep a good exposure.

 

[kundalini]

The CPL filter is most effective when at 90° from the light source (sun).

Two excersizes to test the effectiveness.
1) On a nice sunny day with white puffy clouds in the sky turn so that you're 90° from the sun. Point your lens towards the clouds.... look through the viewfinder. Slowlyy rotate the outer ring of the filter and take note of the change/contrast the clouds have as well as the blue color of the sky. See any change?

2) On a nice sunny day go out to your car, turn so that you're 90° from the sun. Point your lens towards your windshield. Slowly rotate the outer ring of the filter and take note of the change of reflection from "I can't see anything but the reflection" to "Hey, I can see the interior of my car. It really needs to be cleaned up".

The CPL filter reduces reflections, increases contrast and increases saturation (particularly blue & green).

Outside, I usually like to have it on. If the effect is more than I want.... rotate it. Have fun.

 

[phifer8390]

Here is a very simple example of what you can see in the viewfinder.

Great examples in the link! Huge difference

 

[kundalini]

Dang, lots of typing going on while I was responding...... and filling the wine glass.

 

[Bitter Jeweler]

plato - I understand the concept of what you said, but what I think I'm struggling with is, how do you know when you have the filter set right?

Just look through it and rotate it.
Look at reflections on glass, and rotate it.
Reflections will mostly dissappear at one point.

Look at the sky through it, and do it in different directions.
You will see the sky darken.

Keep in mind if you put this on a lens that rotates as it focuses, you have to adjust it after you focus.

 

[phifer8390]

Dang, lots of typing going on while I was responding...... and filling the wine glass.

This is a very hot thread at the moment!

 

[EleanorW]

The CPL filter is most effective when at 90° from the light source (sun).

Two excersizes to test the effectiveness.
1) On a nice sunny day with white puffy clouds in the sky turn so that you're 90° from the sun. Point your lens towards the clouds.... look through the viewfinder. Slowlyy rotate the outer ring of the filter and take note of the change/contrast the clouds have as well as the blue color of the sky. See any change?

2) On a nice sunny day go out to your car, turn so that you're 90° from the sun. Point your lens towards your windshield. Slowly rotate the outer ring of the filter and take note of the change of reflection from "I can't see anything but the reflection" to "Hey, I can see the interior of my car. It really needs to be cleaned up".

The CPL filter reduces reflections, increases contrast and increases saturation (particularly blue & green).

Outside, I usually like to have it on. If the effect is more than I want.... rotate it. Have fun.

Ok this is all making more sense now - thanks kundalini and Plato. That brings me to another question then . Lets say I'm outside taking photo's of people. If I follow the be 90° from the sun thought, then wouldn't that also put the people whose photo's I'm taking with 1/2 of their face in the shade?

 

[Plato]

plato - I understand the concept of what you said, but what I think I'm struggling with is, how do you know when you have the filter set right?

Just look through it and rotate it.
Look at reflections on glass, and rotate it.
Reflections will mostly dissappear at one point.

Look at the sky through it, and do it in different directions.
You will see the sky darken.

Keep in mind if you put this on a lens that rotates as it focuses, you have to adjust it after you focus.

Many years ago I bought the first SLR with a built-in meter. It didn't control the camera; it merely gave needle movement. With that camera, it was easier (and much more accurate) to watch the needle and pick the one of the two valleys.

 

[kundalini]

Here's another tip for CPL filters. DO NOT CHEAP OUT!

Anything under $50, I would pass on. Really IMO, from $80-200 range you are more likely to get a quality filter.

Popular brands: B+W (probaly one of the best), Singh-Ray (perhaps a little better), Hoya, Tiffen, .... there's a couple more but they elude me at the moment. The wine, the wine.......