Jump to content
  • Announcements

    • olyclimber

      WELCOME TO THE CASCADECLIMBERS.COM FORUMS   02/03/18

      We have upgraded to new forum software as of late last year, and it makes everything here so much better!  It is now much easier to do pretty much anything, including write Trip Reports, sell gear, schedule climbing related events, and more. There is a new reputation system that allows for positive contributors to be recognized,  it is possible to tag content with identifiers, drag and drop in images, and it is much easier to embed multimedia content from Youtube, Vimeo, and more.  In all, the site is much more user friendly, bug free, and feature rich!   Whether you're a new user or a grizzled cascadeclimbers.com veteran, we think you'll love the new forums. Enjoy!
Sign in to follow this  
mr._happy

circular polarizers

Recommended Posts

ok, strictly speaking, i know this isn't a climbing topic per se, but that doesn't seem to stop others from posting anything/everything on this site. wink.gif" border="0 besides, i know there's a whole legion of competent outdoor photographers that lurk here.

so what i'm wondering is this: when you're using ttl metering thru a circular polarizer, is exposure compensation necessary? i was taking pics this weekend and left the polarizer on the lens. all the pics came out waay overexposed. confused.gif" border="0 i've never had this problem before, so i'm thinking it just might be the place where i had the film developed that's to blame. but i'm wondering if there's something i need to know about using polarizers? thanks in advance for anybody who's willing to answer.

Share this post


Link to post
Share on other sites

You lose two stops with a circular polarizer so if anything your pictures should be underexposed. Maybe you had your film ISO set too low?

Share this post


Link to post
Share on other sites

I've never had any real problems with circular polarizers causing overexposure. The polarizer should be reducing the amount of light making it through to the metering system. It could be that your metering system over corrected, but I doubt that. I would be highly suspicious of where it was developed/printed. If you are lucky, it was just a bad print job.

Charlie Don't Surf could probably enlighten us all.

Maybe

Share this post


Link to post
Share on other sites

quote:

Originally posted by jon:
You lose two stops with a circular polarizer so if anything your pictures should be underexposed. Maybe you had your film ISO set too low?

no, my camera (a nikon n70) is set to automatically read the speed on dx-coded films.

so if i leave the polarizer on, should i generally open up two stops everytime to compensate? maybe that's a dumb question, but i'm a dumb guy.

thanks.

Share this post


Link to post
Share on other sites

If you have TTL metering, you shouldn't have to make any adjustments.

One kind of polarizer messes with TTL metering though... but I think that's linear polarizers, not circular. You may want to verify that your polarizer isn't of the linear variety.

from some website:-------------Q. How do I tell if I have a circular or linear Polarizer?

The most reliable way is to look at the filter ring. It should be marked to indicate that it is a circular type. Look for any of the following markings on the ring: CIR., CIRCULAR. CPL., C-PL

[ 03-21-2002: Message edited by: philfort ]

Share this post


Link to post
Share on other sites

I've used both polarizing filters and a two stop neutral density filter with a through the lens meter, and had not exposure problems. I'd suggest you read what your TTL meter says both with and without the polarizing filter and see if it opens up when you add the filter.

If it does, then your problem lies some place else such as overriding the film speed read off the film or developing error.

Share this post


Link to post
Share on other sites

yeah, i thought about that one, too. yes, linear polarizers can screw with your ttl metering and autofocus, but circulars won't.

one thing i found out is that if you're not sure if you have a linear or circular, just take the filter and look directly thru it into a mirror. then flip it around and look thru it from the opposite side, again into the mirror. circular polarizers will appear black in the mirror when flipped around.

maybe it was just the developers that screwed up my pics. it couldn't have been me, i do everything right! [laf]

Share this post


Link to post
Share on other sites

quote:

Originally posted by Paul K:
I've used both polarizing filters and a two stop neutral density filter with a through the lens meter, and had not exposure problems. I'd suggest you read what your TTL meter says both with and without the polarizing filter and see if it opens up when you add the filter.

If it does, then your problem lies some place else such as overriding the film speed read off the film or developing error.

thanks!

Share this post


Link to post
Share on other sites

I have a bunch of filters that I play around with on my Nikon FE2, F3, and F5. They all have TTL metering and they do not require any compensations (that's the benefit of TTL). If your sure your camera is set to autoDX coding and your also sure it is a circular polarizer then something else has to be set wrong. 1) If it has never happened before I would look to the lab. Shoot another roll (12 exp to keep cost down) with the filter and see how it comes out. 2) Make sure your exposure compensation is set to zero (since I use this one a lot, every now and then I'll forget to zero it). 3) You may need to take the camera in and have the light meter calibrated (this should be done as regular maintenance).

Your shooting situation could also have something to do with it. I don't know how much you know about how the light meter works, but in extreme lighting situations they need the help of our little brain. What were you shooting? Bright snow, backlit, fog, sunrise/sunset, these all require some sort of compensation.

Let me know what you come up with. It may help me out some day. Good luck.

Share this post


Link to post
Share on other sites

TTL stands for through-the-lens, as opposed to metering designs that had a light meter mounted to the camera but would take a reading through its own prism somewhere on the face of the camera body (these disappeared from major camera manufacturers' models prior to 1970). The need for a circular polarizer is a concern for only the autofocusing system, which is rendered ineffective by a linear polarizer's effect on the incoming light. So in the case of your N70, no matter what was on the front of the camera lens, the light that makes it to the film plane is what the meter measures, end of that story. My first guess is your lens has a sticky iris. The camera leaves the aperture (iris) wide open for optimal viewing and focusing, metering when the shutter button is in half trip position (for exposure/focus lock) or at the last moment before exposure (in auto modes). Right before the shutter trips, the camera stops the aperture down to the setting the metering system has calculated. The iris is a spring loaded mechanism and will stay wide open until a lever on the bayonet ring is moved. This mechanism has lubricants that can get gummed up from rapidly changing temperatures, extreme cold, foreign matter, etc. To check it, take the lens off the camera, and wiggle the little bar sticking out of the back of the lens while looking thru the lens, you should see the aperture open and close. If this is a very new lens it will just have a set of contacts and a small motor or solenoid inside the lens actuates the iris. You can still check if that is the problem, tho- the camera should expose properly in aperture priority mode set at max (lowest number) aperture. After that, check your exposure compensation setting, the DX reader pins inside the camera are clean, the same film/camera/lens/filter/processor combo works or not, if all that fails, take it to a reputable shop (Phototronics on Dexter is one). Long shots are incorrect DX coding, processing errors, or a meter error. Nikons have very reliable metering systems and are shock and temp resistant. Those problems tend to be expensive fixes, but are very unusual, and should be covered by your warranty. First and foremost, test the camera again with different lenses, filters, film speeds, exposure modes and processing before you make any expensive assumptions. Chances are it was a fluke.

[ 03-21-2002: Message edited by: joekania ]

Share this post


Link to post
Share on other sites

Good responses, I was about to leave work so I had to make it quick, but everyone pretty much covered the bases. I have an N70 and have never had a problem with a filter on it. In fact, I don't think I've ever had a improperly exposed picture except when I'm screwing around in manual mode. The computer on the N70 is great. If you were shooting slide maybe they accidently pushed your film? I'd shoot another roll and see how it comes out, like someone said it could be a fluke, you could have been the DX, or bracketing. Just so you know camera repairs can be pretty expensive.

Share this post


Link to post
Share on other sites

What ASA film were you using? What type of camera? Were you shooting with a bright background? Did you bracket +2?

The only time I've had a problem such as yours was when I shot Kodak 64 slides once (instead of Fuji50) in my old camera, and didn't realize my auto DX did not read ASA 64 and automatically defaulted to 400!

I bought a Nikon N80 last year and have had NO exposure problems with or without filters. This camera is "way smarter than me". I love it!

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

Sign in to follow this  

×