OT: Linear polarizer vs circular polarizer

[MrKnobs]

I've seen the evidence that some of you SSS guys are pretty accomplished photographers, so I thought I'd ask this question here:

 

I know that circular polarizers are supposedly necessary for autofocus TTL cameras to focus properly. Seems to me that linear polarizers work better, though, and the camera can always be set to manual focus, especially for landscapes.

 

What do you guys use and why?

 

Terry D.

[Anderton]

I use a tripod, point at what I'm shooting, push the little button, and hope I don't push on the camera while pushing the little button.

 

Hopefully Ken Lee, four-time winner of the prestigious SSS Excellence in Photo-Journalism award, will see this thread and be able to give you a more meaningful answer.

[Huh?]

 

I know that circular polarizers are supposedly necessary for autofocus TTL cameras to focus properly.

 

 

The wording here is somewhat ambiguous maybe? I am assuming you know what a pola does and just meant that one type works best with camera's that do not have autofocus, the other meant for camera's that do?

 

Because, the polarizer is not about focus itself.

 

These filters control reflections in water and on glass etc, they darken sky and also manipulate color saturation. A very necessary filter in one's kit, along with a nice fully coated UV filter.

 

I have wanted a very nice pola for a long time now for my Canon SLR. I looked at one yesterday, a 72mm Hoya that was over $150.

 

I own a much smaller one, a Hoya, and use it with my Mini DV camcorders. I just bought a lens adaptor kit so I can use it on my Contour HD 1080P which is a wearable action/sport dealio with a 135

[JeffLearman]

 

I use a tripod, point at what I'm shooting, push the little button, and hope I don't push on the camera while pushing the little button. Hopefully Ken Lee, four-time winner of the prestigious SSS Excellence in Photo-Journalism award, will see this thread and be able to give you a more meaningful answer.

Aha, so THAT's who she's singing about here?

[video=youtube;FQt-h753jHI]

I always wondered!

 

(Sorry, just couldn't resist.)

[rjt]

A circular polarizer will not only permit auto-focus but it will not mess with the metering or white balance on newer cameras. It is a very helpful filter and one of the few I own, but a good one gets expensive fast. The CPs are best on outdoor, brightly lit, days.... to cut glare and saturate colors. Inside, in low light, when facing the wrong way etc. they don't do much. Here is a pretty good link to the advantages and disadvantages of a CP.

 

http://www.great-landscape-photography.com/polarizing-filter.html

[MrKnobs]

Thanks to everyone who answered so far. Let me clarify my question a bit.

 

I've used polarizers for many years, I'm pretty clear on what they do including things besides making the sky a deeper blue at right angles to the sun.

 

What I'm asking is a question about circular vs linear polarizers. I know autofocus cameras will sometimes not focus correctly through a linear polarizer, and I understand why. What I've observed, though, is that my circular polarizer gives less of an effect than a linear polarizer with all else being equal (i.e. same shutter speed, f stop, white balance, etc). This has led me to abandoning my circular polarizer in favor of the linear with the small nuisance of having to use manual focus.

 

I was just wondering if any of you experienced photo folk have come to the same conclusion.

 

 

Terry D.

[Don Solaris]

 

I use a tripod, point at what I'm shooting, push the little button, and hope I don't push on the camera while pushing the little button.

 

 

Just use the timer and you no longer have to worry about this anymore.

[Don Solaris]

I was just wondering if any of you experienced photo folk have come to the same conclusion.

Don't know about the autofocus problems with linear polarizers, but just looking at the physics itself, given the pixel size of the sensor vs. size of the polarizer's transmission line, i'd say at certain angles you would have interference on some of the sensors - thus colors would go wrong or even the image itself might look weird. Again, this depends on the CCD/CMOS pixel size and the prism system. One some cameras it shouldn't be an issue.

 

Anyway, if you ever get a chance, try the German firm called B+W and their polarizers. Standard ones already kick ass (better than anything), but their Kaesemann version - boy this is the best thing i've ever tried. Plus, it's circular so no worries about the colors shift. Bonus, they even have the slim version, if you're one of the wide-angle aficionados.

[rjt]

Sorry to have misread the original question. Well my answer is this, I have not used a linear polarizer much so can't answer that part. What do I use and why? Well, back in the day of film, I used a circular polarizer as it was "the thing" and did a good job. Today, I still use a circular polarizer...... because I don't have much experience with linear polarizers. However, I don't use the CP nearly as much as I did back in the day. With film, and no home processing, the image capture was everything. Today, given you can do so much more with (tasteful) post processing (including selective saturation etc.) I usually only use a CP to reduce glare. Otherwise, I shoot the pic pretty straight and use post processing. I used to take two shots (with and without CP) but found I liked the "without" which had been post processed better. So, that's my take on it.

[UstadKhanAli]

I haven't used a linear polarizer, and can't comment on it.

 

I have a Tiffen circular polarizer, which I believe is probably considered a really good (but perhaps not fantastic) circular polarizer. There are others, perhaps like the one rjt mentioned, that are better. I also use a CP to reduce glare and punch up the blues in the sky upon occasion.

 

The only other filter I use on my lens are ND filters, which are also Tiffen. Well, okay, that and your standard clear UV filter.

[UstadKhanAli]

I use a tripod, point at what I'm shooting, push the little button, and hope I don't push on the camera while pushing the little button. Hopefully Ken Lee, four-time winner of the prestigious SSS Excellence in Photo-Journalism award, will see this thread and be able to give you a more meaningful answer.

 

I have all the trophies in my living room!!!!

 

And the fact that you use a tripod probably puts you ahead of most people toting a camera as it is.

 

And yes, learjeff, she is singing to me. This is very sweet of her and I'm flattered.

[UstadKhanAli]

http://www.bobatkins.com/photography/technical/polarizers.html

 

I thought I'd look this up just to learn a little myself and post something that was more specific.

 

 

Now for circular polarizers. If a linear polarizer blocks or allows the passage of linear (or plane) polarized light, you might justifiably think that a circular polarizer should do the same thing for circularly polarized light - and it does, but it is also sensitive to linear polarization . This is just as well, since the phenomena we have just looked at, such as reflection of randomly polarized light from a partially reflecting surface, result in linear, not circular polarization. A polarizer which accepted only left or right handed circularly polarized light would be of no use in suppressing reflections - in fact it would mainly act as a rather expensive neutral density filter!

 

 

 

Older SLRs used fully reflecting mirrors , which reflect all polarizations with equal intensity. Newer SLRs, and particularly autofocus SLRs, often use partially reflecting mirrors. The reflected light goes to the viewfinder and metering systems, while the transmitted light goes on to the auto focus sensors. If a linear polarizer was used on such an SLR, the intensity of light sent to the metering system would depend not only on the intensity of the light, but also it's polarization angle. However, when a picture is taken the mirror is out of the light path and the film is only sensitive to the intensity of the light, not its polarization. Thus metering errors can (and do) occur when a linear polarizer is used with an SLR which has a partially reflecting main mirror.

 

 

 

So, do you need a circular polarizer? If you have a modern AF SLR the answer is almost certainly "yes". yes. Check your instruction manual. Some older manual focus SLRs also require circular polarizers. The camera manufacturers should be able to tell you if you don't have an instruction manual, or the manual doesn't say. What happens if you use a linear polarizer on a camera that really needs a circular polarizer? Basically you run the risk of exposure errors ( +/- 1 stop might be typical). This may not be a problem for print film, but can be a disaster for slide film. Not all exposures may be wrong, but some will be. There can also be small autofocus errors in some cases if any of the lenses in the AF system are birefringent (polarization sensitive), which can happen if plastic lenses are used and they are under some stress. If you care about your pictures and your camera needs one, spend the few extra dollars and get a circular polarizer. If you have an older camera and you are unsure, there is an easy test which can often indicate whether or not a camera needs a circular polarizer. Attach a linear polarizer to the camera and take a TTL meter reading off a blank wall illuminated by indoor (tungsten) lighting. Don't use any kind of shiny (reflective) surface. A carpet might also make a good target. Rotate the polarizer and see if the indicated exposure changes. If it does, you need a circular polarizer. The only problem with this test is that some cameras read out exposure only in full stop increments, which may not be enough to detect the effect of the polarizer on exposure. Though the camera may actually be changing it's exposure settings by almost a full f stop, the readout might not show it. Cameras with 1/2 or 1/3 stop readouts should clearly show BTW if your canera doesn't need a circular polarizer, you can still use one and it will act just like a linear polarizer. Any camera can use a circular polarizer. The only downside to using a circular polarizer where only a linear polarizer is needed is that circular polarizers are a little more expensive than the linear variety.

 

[MikeRivers]

So how come we don't have a circular polarizer plug-in for Pro Tools? Just the name itself should make it sell big.

[UstadKhanAli]

You could put a circular polarizer over your monitor, Mike.

 

Aren't you glad you asked?

[rjt]

Kind of like Ken, the only other filter I use (aside from a UV to protect the lens) is an ND. As I said, today, with tasteful processing, I don't use a CP all that often.