I've been looking into whether to use a regular UV or polarizing filter for a 16mm wide-angle lens and have found that a large number of people believe that you should never use a polarizer with a wide-angle lens. The reasoning seems to be that because of the sheer width of the image frame, the angle away from the sun can vary by such a large degree across the width of the frame that your picture will likely exhibit clear changes in saturation and brightness from one edge to the other. I can see why this might be the case and that for the most part that it might be undesirable, but is it really that much of a problem? Are there any examples of situations where this effect can be used to your advantage?
It's something to be aware of, but as long as you're aware of it, you can often still use a polarizer.
I've a 10-22mm UWA and I'm quite happy that I spent the money to get a polarizer for it. A couple of suggestions for you:
- You can often hide the variation across the image by e.g. including clouds in skies for example
- When you've rotated your polarizer to get maximum effect, rotate it back slightly to back off the effect, and you can still get some of the benefit of a polarizer.
- Shoot portrait instead of landscape.
Couple of examples:
This question already has nice answers. I'll just address one sub-question inside your question. Namely:
I can see why this might be the case and that for the most part that it might be undesirable, but is it really that much of a problem?
Yes, it can be a problem. Painfully obvious in this photo of mine:
Here the reason is not only the wide angle of the lens. The direction I am shooting at is roughly at 90 degrees angle from the sun. That makes for pretty strong polarizing effect, and as the lens is a wide angle (18 mm on a crop sensor body) it means the angle of light is 90 degrees only in the middle of the view.
The angle of sunlight is far from the optimal 90 degrees on the sides of field of view and polarizing effect a lot weaker.
The question seems to answer itself :)
If you use a polarizer on a wide-angle lens you will most likely have an image which looks unnatural, except in circumstances where the polarizer has no effect of-course. This may occur when it is extremely overcast for example.
Once you know this, it is up to you to decide whether you want to create images that have that effect. Photography is art after all.
You've basically answered your own question. ;-)
At wide angles, the greatly varying angle from the light source does indeed cause problems. Usually, you will see a large, darkening "spot" where you have the polarizer angled. This is due to the widely varying angles of polarized light reaching the lens.
An excellent article that superbly demonstrates this nasty effect can be found at Cambridge in Color:
However, polarizing filters should be used with caution because they may adversely affect the photo. Polarizers dramatically reduce the amount of light reaching the camera's sensor—often by 2-3 f-stops (1/4 to 1/8 the amount of light). This means that the risk of a blurred handheld image goes up dramatically, and may make some action shots prohibitive.
Additionally, using a polarizer on a wide angle lens can produce an uneven or unrealistic looking sky which visibly darkens. In the example to the left, the sky could be considered unusually uneven and too dark at the top.
- C in C
The effect you mention is real, but
- You can work around it or work with it, as demonstrated by Conor Boyd's answer.
- Removing haze from the sky isn't the only thing polarizing filters do.
Any reflection of a dielectric at the right angle will be polarized. Even leaves on a forest floor will look different with a polarizer at opposite orientation. Car windshields, puddles, glint off of some painted object, etc, are all common examples.
Many of these things won't extend all the way across a picture. You can therefore adjust the polarizer to make that object look the way you want, and the rest comes out the way it comes out.