apgfine

Just bought a circular polarizer for use with my Nikon D90. If I use the polarizer to cut glare and then use autofocus the lens rotates somewhat, thus negating the effect of the polarizer. I'm assuming I should autofocus first and then rotate the polarizer to achieve the desired effect. Am I correct in my assumption or am I missing something?

SX2002 Loc: Adelaide, South Australia

If your lens rotates when in auto focus, shoot with manual focus so the lens doesn't rotate...
What lens are you using...?

apgfine

Using Nikon 18-55 mm, or 55-200mm. So it seems O'm correct in assuming that there's no way to use the circular polarized other than with autofocus.

SX2002 Loc: Adelaide, South Australia

You mean other than manual focus...?
If it rotates too much in Auto, just give it a tweak after you have composed your shot before you shoot...

apgfine

Right, I meant manual focus; thanks for the catch.

mcveed Loc: Kelowna, British Columbia (between trips)

Of course the lens rotates when you use manual focus. How else do you focus the lens?

mcveed Loc: Kelowna, British Columbia (between trips)

Yes, you are right. Focus first then adjust the polarizer. If your lens rotates with auto focus it will rotate with manual focus. Many lenses have internal focusing and the lens does not rotate when it focuses. These are much easier to use a polarizer with.

dooragdragon Loc: Alma , Arkansas

A polarizing filter or polarising filter is often placed in front of the camera lens in photography in order to darken skies, manage reflections, or suppress glare from the surface of lakes or sea. Since reflections (and sky-light) tend to be at least partially linearly-polarized, a linear polarizer can be used to change the balance of the light in the photograph. The rotational orientation of the filter is adjusted for the preferred artistic effect. For modern cameras, a circular polarizer is typically used, this comprises firstly a linear polarizer which performs the artistic function just described, followed by a quarter-wave plate which converts the now-linearly polarized light into circularly-polarised light before entering the camera. The additional step of converting the light to circular polarization avoids problems with auto-focus and light-metering sensors within some cameras, which otherwise may not function reliably with a simple linear polariser.

Polarizing filters can be rotated to maximise or minimise admission of polarised light. They are mounted in a rotating collar for this purpose - You need not screw or unscrew the filter to adjust the effect. Rotating the polarizing filter will make rainbows, reflections, and other polarized light stand out or nearly disappear depending on how much of the light is polarized and the angle of polarization.
There are two types of polarizing filters readily available, linear and "circular", which have exactly the same effect photographically. But the metering and auto-focus sensors in certain cameras, including virtually all auto-focus SLRs, will not work properly with linear polarizers because the beam splitters used to split off the light for focusing and metering are polarization-dependent. Linearly-polarized light may also defeat the action of the Anti-aliasing filter (Low-pass filter) on the imaging sensor.

"Circular" polarizing photographic filters consist of a linear polarizer on the front, with a quarter-wave plate on the back. The quarter-wave plate converts the selected polarization to circularly polarized light inside the camera. This works with all types of cameras, because mirrors and beam-splitters split circularly polarized light the same way they split unpolarized light.[6]

Linear polarizing filters can be easily distinguished from circular polarizers. In linear polarizing filters, the polarizing effect works (rotate to see differences) regardless of which side of the filter the scene is viewed from. In "circular" polarizing filters, the polarizing effect works when the scene is viewed from the male threaded (back) side of the filter, but does not work when looking through it backwards.

Polarizing filters reduce the light passed through to the film or sensor by about one to three stops (2-8x) depending on how much of the light is polarized at the filter angle selected. Auto-exposure cameras will adjust for this by widening the aperture, lengthening the shutter, and/or increasing the ASA/ISO speed of the camera. Polarizing filters can be used deliberately to reduce available light and allow use of wider apertures to shorten depth of field for certain focus effects.

Some companies make adjustable neutral density filters by having two linear polarising layers. When they are at 90° to each other, they let almost zero light in, admitting more as the angle decreases.

dooragdragon Loc: Alma , Arkansas

Checklist: Using polarizing filters

1: Buy a circular polarizing filter which matches the thread on your lens; check the end of the barrel to find out the correct size. Canon’s 18-55mm and the Olympus 14-42mm kit lenses have a filter thread of 58mm. The Nikkor and Pentax 18-55mm kit lenses have a filter thread of 52mm. Sony’s 18-70mm kit lens has a 55mm thread.

2: With the polarizer screwed onto the end of your lens, turn the outer section to see the polarizing effect. As you turn it, the effect will increase and decrease, then repeat. Simply stop when it looks best to you. The strength of the effect also varies depending on your angle to the Sun.

3: To prevent your DSLR from counteracting the polarizing effect, set the White Balance to Daylight and consider applying negative Exposure Compensation of, say, -2/3 or -1 EV.

4: After taking your photo, remember to set the White Balance back to Auto and the Exposure Compensation back to zero. Unless it’s a bright sunny day, remove the polarizer and return it to its case.


Watch out!

Polarizing filters reduce the amount of light entering your camera, forcing you to use longer exposures. This in turn increases the risk of camera-shake, so when using polarizing filters, always take care to keep your camera steady.

Polarizing filters will only have the effect shown here on bright sunny days. If it’s overcast or cloudy, they’ll have little or no effect, so it’s best to remove them. Likewise indoors or at night.

Sometimes polarizing filters can make the sky an unrealistic colour. To avoid this, adjust the outer ring for a lesser effect, and also consider taking two shots, one with the polarizer and one without in case you end up preferring the latter.

Cheaper kit lenses rotate their barrels when auto-focusing, which will also turn a polarizing filter, changing its effect. If you have this kind of lens, half press the shutter release first to autofocus before turning the polarizer. When subsequently turning the filter, you may knock the focus very slightly, so once the polarizer is in the right position, half-press the shutter again to get the focus spot-on.


Equipment tip

Polarizers come in two main types: Linear and Circular. Circular polarizers, or CPLs for short, are designed to not confuse the autofocus or metering systems on modern cameras, so this is the type you’ll need to buy for your DSLR.

Terra Australis Loc: Australia

Why not just post a link to things you find with Google rather than cut and paste whole articles?
The article does not address the OP's concerns anyhow.

dooragdragon Loc: Alma , Arkansas

These were taken from a much larger article concerning polarizing filters and the last one may have been of intrest to anyone considering buying filters.
As for not posting the link , I was trying to be nice and not make anyone have to read thru the entire article to see these area's of discussion, is that a good enough reason?
Or they could have done as I did and do a google search on Circular Polarizing filters and read thru 2-3 to find the imformation.

Terra Australis Loc: Australia

No. Showing you can use Google to cut and paste articles that have nothing to do with the OP question is not a good enough reason.
The OP was querying the best way to use a filter with a lens that rotated the filter when focusing. Trying to make the OP look less intelligent than you helps no-one.

dooragdragon Loc: Alma , Arkansas

Well sorry the article was to in depth for you, maybe you should have just skipped over it as your reponses have nothing to do with his question what so ever only to nit pick at my reponse that I felt might happen to be informative to not only the OP but any one else that might read the response that had questions regarding CP filters.
And there was no intent to make anyone look unintelligent, quit trying to read more into the post then was intended , so far your the only one with your panties in a wad over my answer.

Terra Australis Loc: Australia

But it wasn't your answer was it?. You just cut and pasted some other person's work and presented it as your own, under your name.

dooragdragon Loc: Alma , Arkansas

http://en.wikipedia.org/wiki/Polarizing_filter_(photography) there are you happy now?
Time for you to put on your big girl panties and get over it. .