To CPL or not to CPL?

[jedirunner]

Heya guys and gals with far more experience than me... I've shot a few times with a CPL filter on -- mostly when I've been intentionally testing it to see the difference it makes -- and I've been impressed at the difference I've seen in my intentional tests (mostly testing to see how it removed glares and reflections).

So here are my questions:
When do you all shoot with a CPL?
Do you always have one in your bag?
What sorts of situations do you use it in?
Is it always on the back of your mind as another tool in your bag of tricks?
Or is it for you a rare (or never) used item?

Most of my local friends at their varying levels of expertise (all have been shooting longer than me, so I ask them lots of questions) don't even have CPL filters at all.

Thanks much for any advice you can give me on CPL usage,

Kevin

 

[Overread]

It really depends a little what you shoot, how you shoot and what you like shooting. That said a circular polarizer is one of those accessories that is worth carrying around if you have one or a few and the space to do so.


Myself if I'm going to the zoo or near watery areas I'll certainly pack mine in the bag for the ability to remove reflections from glass and water. If I were interested in cars and such I'd likely take one along to that as well (note it won't work on removing reflections from metal surfaces, but windshields will be safe at least).

Another time to consider using one isn't for its reflection removing properties, but to let you have a slightly slower shutter speed due it its 1 to 2 stop removal of light (varies a little depending on the polarizer you have; some block more than others). This can be great it you want to blur details, for example going for a blurry water effect. The 1 to 2 stop difference won't be masses, but when the light is already fading it can give you that edge you need just to push it enough into blur for your desires.

 

[MK3Brent]

I like using them, but most if not all the time my lens hood is in the way, so i cant reach it.

 

[David444]

.

 

[cynicaster]

They also increase color saturation.

This is my favorite use for the CPL; it makes blue skies a deeper and more interesting blue, and can also add a touch of drama to clouds.

This effect is strongest when the sun is either at your left or right, and diminishes down to nothing as the sun moves directly in front of or behind you.

Like somebody already mentioned, using a polarizer will cost you 1-2 stops of light at your sensor, meaning that if you’re already at the limit of hand-holding light, then the polarizer will push you over into the tripod zone if you want to prevent photos ruined by camera shake.

Another thing you have to watch out for is an unnatural blue “wave” in the sky that is caused by the fact that light is approaching from all directions and is therefore affected by the filter differently depending on where it’s coming from. This gets more and more noticeable as your view angle gets wider (i.e. smaller focal length).

 

[jedirunner]

Thanks everyone for the comments. I think the take-away here is that I should do some more experimentation to see the results, and keep it with me in the pack so that it's handy when it is needed.

Thanks again,

Kevin

 

[Majeed Badizadegan]

I consider the CPL optical qualities to be basically "magic".

What it does for you, if you know how to use it properly, cannot be duplicated in Photoshop no matter how skilled you are.

For a serious landscape photographer, it is used frequently. It can be used in other types of photography as well.

If it's not on the front of my camera, I keep the CPL with me at all times.

 

[480sparky]

This is my favorite use for the CPL; it makes blue skies a deeper and more interesting blue, and can also add a touch of drama to clouds.

This effect is strongest when the sun is either at your left or right, and diminishes down to nothing as the sun moves directly in front of or behind you.

Like somebody already mentioned, using a polarizer will cost you 1-2 stops of light at your sensor, meaning that if you’re already at the limit of hand-holding light, then the polarizer will push you over into the tripod zone if you want to prevent photos ruined by camera shake.

Another thing you have to watch out for is an unnatural blue “wave” in the sky that is caused by the fact that light is approaching from all directions and is therefore affected by the filter differently depending on where it’s coming from. This gets more and more noticeable as your view angle gets wider (i.e. smaller focal length).

Using a 10mm, looking north at about 2:45 PM:

Without CPL:

With CPL:

 

[Tony S]

It's really easy to see if the CPL is going to work for you.. Take it out of it's case and look through it, then turn it to see what result you get. It does not have to be on the lens to see what the effect is.

 

[pgriz]

Any reflection off a smooth, non-metallic surface will have some polarization of light. That surface can be water, wax, glass, plastic, polished wood, even tight skin. When used with foilage, it increases the saturation by reducing the surface glare off the leaves. When used to photograph objects, it can be used to eliminate a pesky reflection. When used while shooting through glass, it can reduce (or eliminate) the glass reflections. On water, you can see the fish under the surface. Lots and lots of uses, once we learn to recognize the situations where light becomes polarized.

 

[jedirunner]

Any reflection off a smooth, non-metallic surface will have some polarization of light. That surface can be water, wax, glass, plastic, polished wood, even tight skin. When used with foilage, it increases the saturation by reducing the surface glare off the leaves. When used to photograph objects, it can be used to eliminate a pesky reflection. When used while shooting through glass, it can reduce (or eliminate) the glass reflections. On water, you can see the fish under the surface. Lots and lots of uses, once we learn to recognize the situations where light becomes polarized.

Thanks for those comments. It makes sense, of course, but it isn't something occurred to me before it was simply stated like that. As of yesterday, the CPLs for both of my lenses are now in my camera bag to pack around with me.

Kevin

 

[TCampbell]

So here are my questions:
When do you all shoot with a CPL?

If I'm outside, there's a good chance I might be using my CPL. If I'm shooting anything with reflections, there's a good chance I'm using the CPL.

The CPL works by blocking light which doesn't match the polarization tuning of the filter. Reflections that come from the sides get the most dramatic reduction (if the sun is at your back and you're getting reflections you'll notice the CPL wont work as well.)

Because of the way it works, it has the side-effect of "saturating" colors. Technically what it's _really_ doing is remove the glare from the color that was already there. Regardless of why it works... the effect is that blue skies look richer, plant foliage looks greener, etc.

I don't use it with a wide-angle lens (and I think others have already provided excellent examples of what happens when you try to use it with a wide-angle lens.) Imagine you had a 180º fish-eye... keep in mind that a CPL has to be "tuned" to the polarization angle of the the wavelengths that get to pass. The reflections which appear straight-ahead (relative to where you're pointing the lens) will not have the same angle of polarization as compared to light coming from the sides -- we're referring to reflections from the same light source... such as the sun. This means it's not possible to tune the CPL to any position that works for the entire field of view. The wider the field of view, the more you'll see that banding effect.

Do you always have one in your bag?

Yes - always.

Last summer I did a short weekend getaway, went out shooting, reached for my CPL ... and it wasn't there. I had to go to four of five different camera stores to find a decent CPL (they either didn't have them, had junk (I wont use a poor quality CPL... I may as well not have one), or if they had them, they didn't have them in my size (77mm... which actually surprised me since this is one of the most commonly used sizes.)

If you own lenses with more than than one filter size, buy "step up rings" to use the CPL on smaller lenses. My 24-70 & 70-200mm lenses use 77mm threads, but I have a macro lens that uses 67mm threads. My CPL costs $150, so I didn't want to buy a 67mm version just for one lens. Instead I invested about $10 for a 67 to 77mm step-up-ring (it's an adapter).

What sorts of situations do you use it in?

Glass surfaces are obvious for reflections, but even if I'm shooting something with some shine to it -- think... furniture for example, or anything with a luster.

I recall shooting some close-ups of blooms with a macro lens ... but no CPL (I didn't think I'd need one). Got back to my computer, unloaded the images, and then kicked myself for not using the CPL.

Is it always on the back of your mind as another tool in your bag of tricks?
Or is it for you a rare (or never) used item?

Yes - always. I don't use it _every_ time I'm outside... but I DO ask myself the question "would this scene benefit from a CPL?" and if the answer to that is "yes", then I put it on.

One thing I will say... I _very_ good CPL can remove almost all of the reflection. If I'm shooting glass, sometimes I'll tune the CPL, then just slightly de-tune it to add back in just a tiny bit of reflection to make the image a bit more natural.

Most of my local friends at their varying levels of expertise (all have been shooting longer than me, so I ask them lots of questions) don't even have CPL filters at all.

That's too bad. Every photographer should own one.

In the days of "film", we used to carry several effects filters. Misty / spot-diffusion, starlight, etc. etc. Today, there are a lot of "effects" that can be applied in software (although I find that for some of these you'll get a better version of the effect if you use a physical filter.)

But there are filters that you CANNOT do in software... one is polarization. Yes, I KNOW there's a "polarization" effect in Photoshop, it's not the same and doesn't really work. Think of it this way. Suppose I'm taking a photo of a "green" leaf, but it has a reflection -- probably due to the waxy coating that so many leaves have. In any case, with no CPL, the camera registers a pixel on that leaf as some near-white color. It's not like the pixel records that the leaf is really "green" with a "near white" reflection on top of it... what should have been green is now near-white. That's "data" which is lost forever. If you use a CPL, it filters out the undesirable light wavelengths and leaves me seeing the true green color that was behind the reflection.

The other filter is a neutral density. I've seen people mistakenly believe that the job of an ND filter is to "tint" the image... a good ND wont tint anything... it changes your shooting circumstances so that you can shoot with different settings. In the end you're getting the same exposure, but since you can use different settings you can use longer shutter times or wider apertures that you'd otherwise have been able to use.

If you only buy two filters, they should be:
1) A CPL (preferably a good quality CPL because there are a lot of junk CPLs on the market. You can find lots of YouTube videos that demonstrate the difference.
2) An ND filter. These come in LOTS of strengths (I own a 2 stop, 3 stop, and 10 stop ND). If you only buy ONE, then get a 3-stop. This is because a CPL will tend to cut "about" 2 stops of light (keep in mind these are tunable so this can vary mildly). That means you could stack a 3 stop ND with a CPL and get roughly 5 stops of light reduction.