Polarizers: What They Do - DPChallenge Forums

Nikon AF-S DX Zoom-Nikkor 55-200mm f/4.0-5.6G ED

10/15/2005 08:46:17 AM · #2

I think, I wonder, and bear music has the answer..

I am going to have to get you to follow me around all day long.

AzCKelly

Nikon D70s

10/15/2005 09:17:25 AM · #3

I don't have any filters for my camera, is there a software filter that might get this effect? I have photoshop elements and everything I have tried so far just darkens the entire picture. I live in the desert with LOTS of sun so this is something that could definately help.

Bear_Music

Samsung Galaxy S24 Ultra

Sony 24-70mm F4 Vario-Tessar T* FE OSS

10/15/2005 09:59:19 AM · #4

Originally posted by AzCKelly:

There's no software filter that can do this. It's one of the few things you cannot emulate with software. It's why the polarizer is the essesntial filter. It only admits to the the sensor light traveling in parallel rays, so eliminates all the scattered reflections that rob color and contrast.

Robt.

peecee

Canon EOS-5D

10/15/2005 10:03:06 AM · #5

Good examples Robert, of course there are times when the filter can make water shots much more interesting also.
Maybe not the best examples but they improved these shots for me.
And also helped in extending the exposure times.

bucket

Canon EOS-30D

Canon EF-S 18-55mm f/3.5-5.6

10/15/2005 10:40:07 AM · #6

Originally posted by bear_music:

Originally posted by AzCKelly:
I don't have any filters for my camera, is there a software filter that might get this effect? I have photoshop elements and everything I have tried so far just darkens the entire picture. I live in the desert with LOTS of sun so this is something that could definately help.

There's no software filter that can do this. It's one of the few things you cannot emulate with software. It's why the polarizer is the essesntial filter. It only admits to the the sensor light traveling in parallel rays, so eliminates all the scattered reflections that rob color and contrast.

Robt.

text

if you had to choose having only ONE filter..would you go with a UV or polarizer?
I remember reading in another forum that a number of people don't like to use filters unless there are elements such as lots of dust or ocean spray, and I had always thought (thanks to camera stores) that you HAD to use a filter or you were crazy..asking because Tamron 28-75 is on order..

BlackDot

Canon EOS-20D

10/15/2005 10:48:42 AM · #7

Personally I order the UV the same time as the lens. Put it on as soon as I get them and never take it off. Price of scratched UV replacement is a mere fraction of replacing the lens.

It might be worthy to note that polarisers reduce speed by one to two stops and the effect of the filter increases as you approach 90degrees perpendicular to the sun.

Any ideas what the little white arrow is for on the circular polariser ?

AzCKelly

Nikon D70s

Nikon AF-S DX Zoom-Nikkor 55-200mm f/4.0-5.6G ED

10/15/2005 11:07:59 AM · #8

OK, Dumb question...the UV is different than the polarizer? Where I live, the sun is pretty intense no matter what time of year it is. Most of my daytime shots are too bright.

ElGordo

Canon EOS-400D Rebel XTi

Sigma 18-200mm f/3.5-6.3 DC OS for Canon

10/15/2005 12:31:26 PM · #9

Originally posted by AzCKelly:

OK, Dumb question...the UV is different than the polarizer? Where I live, the sun is pretty intense no matter what time of year it is. Most of my daytime shots are too bright.

The UV filter blocks short wavelength light (ultra-violet). Your camera sensor is somewhat sensitive to UV and the presence of that light tends to reduce contrast in your image, especially in the blue part of the spectrum. Polarizers work over a broad spectrum of light, dramatically reducing randomly scattered light. Linear polarizers accept light in one plane only and can be rotated to vary the effect.

Rikki

Canon EOS-20D

10/15/2005 02:05:34 PM · #10

Great post Rob't. I think it would also be a good idea to let folks know that having a CPL when taking fast action shots doesn't help either. I've noticed a slight difference in sharpness with and without the CPL. I think it puts you a few stops down right?

Carl Zeiss 35mm f2.4 Jena/Flektogon MC

10/15/2005 02:09:09 PM · #11

Does anyone like Cokin make a top half only gradient polarizer? Is that even possible?

Uusilehto

Canon EOS-1D

10/15/2005 02:15:26 PM · #12

How polarisers affect foliage:
//koti.mbnet.fi/uuslehto/img/test/CPLno.jpg
//koti.mbnet.fi/uuslehto/img/test/CPLyes.jpg

The first one is with the filter at minimum effect, and the second with max.

10/15/2005 02:16:41 PM · #13

Originally posted by AzCKelly:

OK, Dumb question...the UV is different than the polarizer? Where I live, the sun is pretty intense no matter what time of year it is. Most of my daytime shots are too bright.

Yes, polarizers decrease the amount of depolarized(diffuse)/reflected light. Sunlight coming directly into your lens will not be affected, and many reflections off of solid object will not be either. Water and cloud vapor tend to diffuse light and increase un-polarized light. I think the atmosphere actually act as a polarizer to Solar light. may be wrong. I probably screwed all that up in my head, and bear will have to explain it correctly.

Message edited by author 2005-10-15 14:16:57.

10/15/2005 02:22:17 PM · #14

Hey! i was right, but I explained it badly.

Here's a link to smart people who can write well :o)

//micro.magnet.fsu.edu/optics/lightandcolor/polarization.html

Canon EF 70-200mm f/4.0L USM

10/15/2005 02:30:33 PM · #15

See also:

//dpfwiw.com/polarizer.htm#scatter

I should become a web research assistant.

troberge

Canon EOS-20D

10/15/2005 03:28:46 PM · #16

Originally posted by AzCKelly:

OK, Dumb question...the UV is different than the polarizer? Where I live, the sun is pretty intense no matter what time of year it is. Most of my daytime shots are too bright.

I read somewhere on here that if you dont have the polorizer you can try taking the shot through your sunglasses. I tried that on a bright, sunny day and it worked really well. It may help you.

AzCKelly

Nikon D70s

Nikon AF-S DX Zoom-Nikkor 55-200mm f/4.0-5.6G ED

10/15/2005 03:42:04 PM · #17

Hey, thanks for explaining and examples. I can definately see problems with my pictures because of this. I will try the sunglass trick then probabily hit the camera store to get the right one.

...see, I knew there was a Reason I wasn't winning any ribbons, I wasn't using any filters. Live and Learn!

KarenNfld

10/15/2005 03:44:37 PM · #18

I love my polarizing filter.....does a great job when photographing boats in still waters, the reflections are really nice. And on a day with big puffy clouds in a blue sky the couds really pop.

Pentax DA 18-55mm f/3.5-5.6 AF

12/25/2005 11:06:14 PM · #19

Looking for input on polarizers and UV.
Have the new 70-200 f2.8L IS

Do you have both a UV and a polarizer filter on at the same time? Would you leave the polarizer on all the time?

I have the Canon 77mm circular - can someone explain what changes when the filter is spun? Why I would spin it?

faidoi

Pentax K10D

12/25/2005 11:08:43 PM · #20

Originally posted by autumncat:

Really no reason to put on a UV when you have a polarizer, unless you are trying to get vignetting :P

Spinning the polarizer changes where the effect is. If you want to get bluer skies spin it and the sky will get bluer and the clouds really stick out. If you don't want a reflection in water spin it and it will help you see through the water.

Message edited by author 2005-12-25 23:10:22.

Bear_Music

Samsung Galaxy S24 Ultra

Sony 24-70mm F4 Vario-Tessar T* FE OSS

12/25/2005 11:16:07 PM · #21

Originally posted by autumncat:

Digital cameras basically have UV filtration already built in, in a "cover" right above the sensor I think. I have seen no benefots other than glass protection to using a UV filter on a dSLR.

As for rotation, a polarizing filter is designed to only admit light rays that are parallel to each other and in a particular orientation to the filter. Rotating the filter allows you to control how much of the "scattered" light is allowed to pass through. If you stand looking at a blue sky through a polarizing filter at mid-morning or mid-afternoon with the sun at right angles to your direction-of-looking, and rotate the filter, the effect will be obvious; the sky will get noticeably darker as you approach the angle of maximum polarization.

More subtle but equally important is the effect the filter has on light that is bounced and scattered from surfaces within the field of view. For example, color saturation on leaves and other foliage will improve dramatically when polarization is used, and water will often become much more transparent under maximum polarization; so much so that it's possible to OVERpolarize shots with reflections and lose the essence of the shot.

Robt.

* the foregoing was a layman's description of the effect of polarization, not a technical one...

Pentax DA 18-55mm f/3.5-5.6 AF

12/25/2005 11:22:39 PM · #22

Originally posted by faidoi:

Thank you - good to know I only need the one type.
Just trying to understand better - a circular filter will be different on one portion of the filter so that you need to spin it to effect different parts of the landscape? Should I be able to see a significant (if any) difference through the viewfinder?

faidoi

Pentax K10D

12/25/2005 11:27:33 PM · #23

Originally posted by autumncat:

Should I be able to see a significant (if any) difference through the viewfinder?

Noticed a couple diner pictures in your portfolio. If you were to be outside on a sunny day you can spin it and see only the reflection, spin it again and you can see through the window.

Shot through a window. Good thing I had a polarizer on or it would've just been a reflection of myself.

Message edited by author 2005-12-25 23:29:42.

12/25/2005 11:31:10 PM · #24

Thank you, Bear.
That helps - layman terms are appreciated.

I've been photographing for years - but never learned enough about all the technical aspects - including utilizing filters and good glass.