BetterPhoto Q&A
Category: New Questions

Photography Question 
karyl  dalbey
BetterPhoto Member Since: 2/1/2005
 

What is the extent of usage of a CP Filter?


A few questions I guess on the usage of Circular Polarizer Filters. What are their limitations if any and best use. Example, I know they're great for most outdoor photographs. What about portraits shots in a studio situation. Nightime shots, indoor and outside. I've tried several of these and have had a fair amount of success. The color and clarity is great! But, is their intendned use? Wondered what the parameter's where? Some guidelines would be helpful. Thanks! I'd appreciate your insights! Karyl Dalbey


To love this question, log in above
10/14/2007 10:27:12 PM

 
Tareq M. Alhamrani
BetterPhoto Member Since: 6/26/2006
  This is a good topic, I will keep watching it to get the answer as well.


To love this comment, log in above
10/15/2007 1:19:45 AM

 
W.   
"What about portraits shots in a studio situation. Nightime shots, indoor and outside. I've tried several of these and have had a fair amount of success. The color and clarity is great!"

Really? That's very interesting, Karyl.
Care to share some of those "fairly successful portrait shots in a studio situation. Nightime shots, indoor and outside", that you took with a CP filter?


To love this comment, log in above
10/28/2007 11:44:50 AM

 
Carlton Ward
BetterPhoto Member Since: 12/13/2005
Contact Carlton
Carlton's Gallery
carltonwardphoto.com
  Hello Karyl,
I believe there are previous threads about Circular Polarizers you may want to look through to get more perspectives.
I use my circular polarizer for landscape & waterfall photos. You can vary the reflection off the water and get a little more color & saturation using the CP but I have & would never try using one for portraits or indoor shots. My CP loses 2 stops which requires longer shutter speeds which is why I also use my tripod with the CP and usually have my DOF set at f/16 thru f/22 on my wide angle lens to get as much detail and saturation as possible. To use properly you should have the sun at a 45 degree angle and as you look through the viewfinder and rotate the CP, you will see the effect it is having on the sky and water reflections. Its really about the only filter I use because I paid a pretty penny for my lenses and do not like having another optic placed in front of them. I dont even use UV filters but I do like my CP for my landscape photos.


To love this comment, log in above
10/28/2007 12:32:43 PM

 
Gregory LaGrange
BetterPhoto Member Since: 11/11/2003
gregorylagrange.org
  You don't usually try a polarizer with flashes, but you can use them for portraits.
They don't have too many limitations because they're really made for a specific purpose. They don't cut glare or reflections on all surfaces, so that can be a limitation.
They polarize and can also be used as a neutral density. That's about it.


To love this comment, log in above
10/28/2007 1:55:18 PM

 
Bob Cammarata
BetterPhoto Member Since: 7/17/2003
  Why compromise the integrity of your optics if there's really no benefit?

ANY filter will degrade image quality (albeit slightly) and should be applied only for corrective purposes or when a particular effect is intended.
I see no benefit in the use of a polarizer in a studio set up where you have complete control of lighting.


To love this comment, log in above
10/28/2007 5:01:01 PM

 
Pete H
BetterPhoto Member Since: 8/9/2005
  Hello Karyl;

Studio use of a CP filter is an excercise in futility unless for some odd reason you need to dial down the light.

1)Strobes, incandescent etc are artificial light sources and are VERY polarized..so a CP will not "re-polarize" the light reflected from a human subject to any real measurable degree. No; a CP will NOT remove the strobe reflection.

2) (Reflections) from inanimate hard objects such as a counter top often "scatter" man made light sources and a CP will be of some value in this limited situation. Repositioning of the light sources is the better method if you have this problem.

The only "limitation" in the use of ANY filter is as some have said already; they DO indeed degrade light transmission somewhat. Cheap filters moreso than good filters.

Without delving into a physics lesson, light from man-made sources are generally (Wave Length) specific and quite narrow.
Remember the prisms we looked at in school? A rainbow of colors when sunlight passed thru it..Not much of a rainbow from a lightbulb.

The sun combined with atmospheric elements (scatter) light tremendously. The wavelength of this light is quite broad. This is why the sky "appears" blue. It is the scattering of the longer wavelengths of light; Red in particular is scattered and absorbed.
Blue; being a much shorter wavelength passes easily thru the atmosphere.
The sky really isn't blue..ask any astronaut. LOL

A polarizer does NOTHING but (re-align) the scatterd light...it is particularly biased in the Blue & Green area of the visible spectrum.

So; one can make the sky appear more blue..or less blue..Green up foliage more too.

Another reason inter-related to the (green) spectrum is a reduction of (greens) refractory properties. Leaves appear more green as well because a CP will "polarize" or (re-align) if you prefer, the green spectrum. To the eye it appears as though it has reduced the glare coming from the green leaves.

Glare on water: This is a big one for many. It goes hand in hand with (window) glare. Again; the CP is simply (re-aligning) the scatterd light in the visible wavelengths.

Limitations? Hmm? Well, they don't work at all when the light source is either at Zero or 180 degrees.
If you desire to know about (incident angle refraction) I suggest you consult a good physics book. LOL

Nightime use of a polarizer? Hmmm? Guess you need to explain that one to me.


all the best,

Pete


To love this comment, log in above
10/28/2007 6:54:23 PM

 
Amanda  M. Freese
BetterPhoto Member Since: 10/18/2007
 
 
 
Well I was going to ask this seperately, but since we're on the subject.. . I actually used mine for the first time today (brand- Quantaray) and I didn't get the results I expected. Shots were done of a Neptune statue in Virginia Beach at about 300pm today- extremely sunny clear blue sky. I wanted to use the polarizer to really show that blue sky.. My first shot came out completely dark despite the blinding sun behind me. . . and the second was good. The dramatic difference I found out was due to the shutter speed. In the first shot I was in (Canon) M mode, shutter speed- 1/2000, AV- 22, ISO 100, 28mm focal range, WB- Daylight...
2nd shot- M mode, shutter sp.- 1/50, AV-22, ISO 200, focal range 28mm, WB- daylight.... pretty drastic difference...
I think I learned from that experience that the polarizers are good for slower shutter speeds? Please correct me if im wrong on that- I actually would like to know what I did wrong on this...


To love this comment, log in above
10/30/2007 5:41:21 PM

 
Carlton Ward
BetterPhoto Member Since: 12/13/2005
Contact Carlton
Carlton's Gallery
carltonwardphoto.com
  Hi Amanda, When you are looking through your viewfinder are you paying attention to the exposure bar along the bottom ? If it is centered, you should have a good exposure. If you are not you will need to adjust your shutter speed, f-stop & possibly iso setting. I also use the histogram setup on my review display for a quick check after taking a shot and if the histogram is too heavy on one side or the other (dark & light) I will adjust and re-shoot the shot.
When I first started with an SLR, I would sometimes place the camera in "auto", then frame the shot & press the shutter half way down to see what the camera displayed the settings as. I would then put the camera back in manual mode and set my settings to what the auto settings displayed. I would then add or subtract the f-stop to get the depth of field I wanted and would adjust my shutter speed to get the exposure dialed in again. I found this worked like a little cheat sheet until I became more knowledgeable & confident.


To love this comment, log in above
10/30/2007 6:00:10 PM

 
Amanda  M. Freese
BetterPhoto Member Since: 10/18/2007
  hmmm.... lesson 1,432,943,9923 for this week.. . lol... thanks so much...
SO then it is normal for what happened to have happened? I just have to pay attention to either my exposure bar or the shot that appears on my LCD to see if I got it. . . if not redo it. .

I was thinking that I bought a cheap CP... there was an option to get this Pro version that had slightly thinner material for digital shooting, although I was advised there is little difference I was kicking myself in the butt when I saw these pics. . .
Love digital, if you don't like what you shot, redo it on the spot. . . .


To love this comment, log in above
10/30/2007 6:34:16 PM

 
Gregory LaGrange
BetterPhoto Member Since: 11/11/2003
gregorylagrange.org
  Polarizers are good for polarizing. What they are also good for is being used as a neutral density because they do cut the light amount coming thru.
So if you're going to be on manual, you need to compensate when you put a polarizer on. Maybe about 2 stops.
And polarizers are good when the sun is at an angle from your shooting point. 30-90 degrees, be it to the side or above. The sun behind you doesn't have much effect with it.


To love this comment, log in above
10/31/2007 1:22:52 PM

 
Amanda  M. Freese
BetterPhoto Member Since: 10/18/2007
  Well I was going to ask this seperately, but since we're on the subject.. . I actually used mine for the first time today (brand- Quantaray) and I didn't get the results I expected. Shots were done of a Neptune statue in Virginia Beach at about 300pm today- extremely sunny clear blue sky. I wanted to use the polarizer to really show that blue sky.. My first shot came out completely dark despite the blinding sun behind me. . . and the second was good. The dramatic difference I found out was due to the shutter speed. In the first shot I was in (Canon) M mode, shutter speed- 1/2000, AV- 22, ISO 100, 28mm focal range, WB- Daylight...
2nd shot- M mode, shutter sp.- 1/50, AV-22, ISO 200, focal range 28mm, WB- daylight.... pretty drastic difference...
I think I learned from that experience that the polarizers are good for slower shutter speeds? Please correct me if im wrong on that- I actually would like to know what I did wrong on this...


To love this comment, log in above
10/31/2007 5:57:33 PM

 
Amanda  M. Freese
BetterPhoto Member Since: 10/18/2007
 
 
 
These are the pics that go with the post above, somehow I deleted them by mistake. apologize for the double post as well.

Thanks!


To love this comment, log in above
10/31/2007 5:58:31 PM

 
Amanda  M. Freese
BetterPhoto Member Since: 10/18/2007
  Thankyou Greg, that explains why the shot was black. I did have the sun behind me, although it was really bright all around what needed to be polarized was the glare and strength of the light, but not when it's behind me. . . Ok. .. I was thinking to myself "what's the good of these things when you have to turn your shutter speed down so low?" Thanks you guys, this was helpful..


To love this comment, log in above
10/31/2007 6:10:11 PM

 
Tareq M. Alhamrani
BetterPhoto Member Since: 6/26/2006
  Keep practicing to use polarizer then you will find how and when to use it, I love to use my polarizer anyway, so blue clear sky i've got so far [but with dust from sensor :-)]


To love this comment, log in above
11/5/2007 4:26:33 AM

 
Log in to respond or ask your own question.