Using polarizers on wide angle lenses

[mark_pierlot]

<p>I recently bought a decent circular polarizer to improve my landscape photography, i.e., to more richly saturate skies, crisply delineate clouds, etc. I have heard that they work best at 90 degrees from the sun, and that consequently they will render uneven saturation of skies when used on wide angle lenses.</p>

<p>I'm wondering at what focal length this effect becomes pronounced. I have heard it claimed that ultrawides (lenses 20mm or wider) display it, but some have even claimed that it's a problem at 35mm. What is your experience? Should I be worried about using the polarizer at wider angles, or just shoot some images to test the effect myself? I should add that I shoot digital and film, and would rather not "waste" alot of film experimenting with this phenomenon.</p>

[nathangardner]

<p>My 17mm on an APS-C camera shows it, but its not so bad that I won't use a polarizer. You get it a lot of times even without a polarizer when the entire sky isn't a uniform blue. It is true that polarizers work best at 90 deg. angles to the sun. Go outside and look through the polarizer (you don't even have to mount it to the camera). Look at a 90 deg. angle from the sun and start to turn the ring on the filter; you'll see the sky turn darker. Now turn directly at the sun or away from it and turn the ring. You won't notice any difference. If your lens is wide, the center of the image may be at a 90 deg. angle to the sun, but the outer edges may be at 45 deg. angles, causing less of a polarizing effect, giving you the uneven sky. You could put a longer lens on, but you won't get as much of the scene, and even by stitching with a longer lens, you will eventually have to turn away from 90 deg. causing the uneven sky again. As for an actual focal length that this won't occur with, I don't know exactly. I would just pick the right lens for the job and take the photo you want. If a polarizer adds to the photo, then use it.</p>

[LenMarriott]

<p>Mark, I have experienced the disappointing results you describe with my Bronica SQ Ai and 50mm PS lens (equiv to 30mm on a 35mm full frame). As a result I now only use the polarizing filter on my normal (80mm) and tele (150mm) lenses. On my 35mm system I'll only use it on 35mm and longer lenses. It's basic physics I guess, the further away from 90 degrees you are from the sun the less the effect. If there's a 'work around' I'd dearly love to know it. Perhaps we won't (noticeably) get a poor result if we stick to subjects that don't include the sky area. (landscapes & vegetation). Digital or film, the results will be the same. Best, LM.</p>

[zml]

<p>It all depends... Here's a decent slim polarizer (Heliopan MC) on a 24-105/4 L IS @ 24 mm (EXIF intact.)<br>

Sun almost directly overhead (in El Salvador) at perhaps 105-110 degrees. You can see uneven polarization (and the lens' vignetting but that's not important here.)<br>

<img src="http://d6d2h4gfvy8t8.cloudfront.net/8515023-md.jpg" alt="" /></p>

[JDMvW]

<p>As suggested, it's not so much that it is <em>unacceptable</em> as it is whether you can tolerate the unevenness in the resulting image.</p>

<p>For anything that is called an "ultrawide" lens (10-20mm on APS-C and 12-24 sort of range on 35mm-sensors), if you want uniformly dark sky, the thing to use is a big, honking Cokin-style graduated neutral density filter rather than a polarizer.<br /> Mind, polarizers also cut reflection and thereby deepen saturation and other things that may be very helpful on even ultrawides.</p>

[arie_vandervelden1]

<p>I think uneven skies get noticeable at focal lengths wider than 28 mm. 20 mm is definitely tricky, but 35 mm you're unlikely to run into problems I say.</p>

<p>I have successfully used a polarizer at 16 mm. This was a portrait-oriented shot in Zion canyon with just a sliver of sky at the top. I managed to darken the sky. Polarizers are good at diminishing reflections off of water, wet leaves etc. which makes them useful for ultrawides (e.g. jungle waterfall). They also cut light by a few stops which helps you blur motion (e.g. rivers, waterfalls).</p>

<p>You can clearly see the effect in the viewfinder, so no surprises there, no film wasted.</p>

[david_henderson]

<p>It is the case that skies are not evenly blue regardless of polariser use. Some variation is natural . Bear in mind also that 90 deg from the sun might fall at the edge of the frame rather than the centre as shown on the example above which might make things better or worse according to your own impressions. Finally note that the extent of this tonal distortion will vary with how you set the polariser and will be worst when you set the effect to maximum, and this is not compulsory. </p>

<p>So there's no magic focal length at which this problem becomes noticeable or unacceptable, and no absolute point at which the use of a polariser becomes inadvisable.<br>

With a digital camera, nothing beats trying it to see and if you can't get it right , and a deeper sky is your objective, then switch to a ND grad.</p>

[Ian Taylor]

<p>You don't have to dial it in all the way, sometimes a touch will do.<br>

On 17mm:<br>

http://iantaylor.ca/littlebluff.jpg</p>

[martin-s]

<blockquote>

<p>"It is the case that skies are not evenly blue regardless of polariser use. Some variation is natural."</p>

</blockquote>

<p>Exactly.<br>

There are always noticeable, gradual changes across the sky. The worst case scenario is a cloudless, blue sky. However a polarizer can still be used in moderation to darken the sky without producing an unnatural effect even on a wide angle.</p>

<p>If there are evenly distributed clouds, things get even easier since the clouds break up the sky area thereby concealing the effect of the polarizer.</p>

<p>And as others have mentioned, a polarizer has other uses that aren't affected by the focal length at all, e.g. cancelling out reflections on water, foliage and other subjects.</p>

[philip_wilson]

<p>Mark - I have had it occur slightly at 35mm on full frame and noticibly with 20 - 24mm. It is really a problem once you get very wide (i.e. below 20mm) above that you can usually manage it with care and it is not too pronounced. As Nathan says it depends on you angle to the sun and how blue the sky is - strong clear blue skies are the worst (unfortunately we get them a lot here in Alberta!)</p>

[stp]

<p>While it is true that there is natural variation in the "blueness" of the sky, a polarizing filter makes the transition from light to "not as light" much more abrupt and therefore is appears (to my eye) much less natural. I trust a polarizer only on a telephoto. Depending on the angle, I can sometimes see uneven sky even using a normal lens. I also find that the effect is more pronounced on a printed or web image than what the eye can discern through a viewfinder (or by simply looking through the filter at various parts of the sky). I limit polarizers on wide angle lenses to interior forest shots where I'm wanting to cut down on vegetation glare.</p>

[dan_south]

<p>Mark, I wouldn't worry about it too much.</p>

<p>- If you're skilled at photoshop you can probably undo some of the "dark sky in the corners" effect with some editing.</p>

<p>- You can dial your polarizer to less than the full-strength effect. This will help a bit when shooting with wide-angle lenses.</p>

<p>- You can shoot the image with and without the polarizer and decide later which one looks better. If you use a tripod you might even be able to create a composite image in PS.</p>

<p>- Watch out for hazy days and high altitudes. The darkening of the sky will be more pronounced under either of these conditions.</p>

<p>- Consider buying a "thin mount" polarizer for your wide-angle lens(es). This version elimates the front threads (which you don't really need anyway, especially on a wide-angle lens).</p>

<p>Good luck!</p>

 

[brian_ellis19]

<p>When the effect is in the corners, as it usually is, it isn't too difficult to remove it or at least greatly minimize it using he gradient tool in Photoshop.</p>

 

[david_henderson]

<p>Some of these responses don't differentiate between vignetting and the uneven colour that can occur across the sky with a polariser. IMO the OP is questioning the latter, which is much harder to correct in post and not as easy to avoid by using the right polariser for your lens.</p>

[stp]

<p>If the intent in using a polarizer is to darken the sky and increase contrast between the sky and clouds, I'd much rather do this with software on a shot taken with a wide angle lens. It seems to me that the suggestions use software to correct the wide angle effects of a polarizer will require much more work with possibly a less desirable outcome.</p>

[fotograf]

<p>I doubt if any software could match what a polarizer can do.</p>