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08-30-2013, 10:31 AM   #1
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ND or Polarizing filter for my two lens?

I'm planning to use both a Sigma 10-20mm (77mm lens filter diameter) and Pentax 18-135mm (62mm lens filter diameter) lens to take landscape and outdoor photos during an upcoming vacation. Due to the nature of groups tours and time limited sight seeing, a lot of the shots will be taken towards the sun or in sunny situations and some overcast situations. In order to take better photos, is it better to purchase a polarizing or ND filter for both of these lenses? Should the polarizing lens be circular or square? Is it possible/ a good idea to have one ND and/or polarizing filter and swap it between the two lens? Should these two filters ever be stacked?

08-30-2013, 10:42 AM   #2
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You can use a step-up ring and use the same filter on both lenses.
If you take group photos, it is usually a good idea to guide the group for better light, just tell them where to position themselves. A lens hood will also help a lot with flare and similar problems.
ND filters are great for landscape photos and long exposures, but they make the exposure longer (as in, slower shutter speed). This causes problems when taking photos of moving subjects (like people) or if you are hand-holding the camera (hand shake), because blur can become apparent. ND filters are usually for photos without people or animals, though some photographers use an ND filter for portraits, so they can have wide open aperture in bright light. But these portraits should be staged, doing them on the move can be difficult

A polarizer works very differently from ND. The polarizer can improve the contrast of the final image you get and reduce reflections. I would recommend this one.
Circular or linear - here is the problem. Some say that linear polarizers don't work well on digital cameras. But other users report that they have no problems using linear polarizers. So most people use a circular polarizer on digital cameras, but it might not be needed. I havent personally tried a linear one, so I cant say.
The other problem is if you get a cheap filter, it might say one thing, but actually be the other. For example, it might say its circular, but its not. Its a good idea to get a decent grade filter, because if the filter is bad, it will ruin your shots (it can add flare, tint the photo green or purple, odd things).
And here is the fun part! Some cheap variable ND filters (the type where you twist them and they get darker) are actually made out of two polarizers put on top of each other. These can be very useful because of their flexibility, but they can cause a dark X across the frame.
08-30-2013, 11:05 AM   #3
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As mentioned, they do very different things. IMHO, the only essential filter is a polarizer. I'd recommend the best quality circular polarizer you can afford for the 18-135 mm. Due to the physics of how polarizers work, they can cause poor results on extremely wide angle lenses, often making skies look blotchy. I don't bother with one for my UWAs. Remember that polarizing filters work best when shooting with the sun at 90 degrees to your shot direction (shining across the shot, not with it). As the angle of the light to lens direction decreases, the CP will have less effect. When shooting directly toward or away from the light, the CP will only act as a ND, slowing the shutter speed. A tip for using polarizing filters - look and adjust the strength before shooting. Full-strength polarized images can look quite unrealistic. Sometimes, less is more.

ND filters can be very useful when you want to slow down the shutter speed, such as for long exposures of moving water, but are more of a specialty item. I carry a couple of NDs for travel but frankly they only come out on rare occasions - waterfalls, evening surf, etc. You can certainly get wonderful travel pictures without investing in an ND filter.

One other tip for using a CP. If you like to wear polarized sunglasses, take them off when shooting with the CP. The first time you try it, you may think you are going color blind or your camera has gotten bunged up. The two polarizers (glasses and lens filter) conflict, giving some VERY strange results in the viewfinder. :-)

Last edited by abmj; 08-30-2013 at 11:14 AM.
08-30-2013, 11:17 AM   #4
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QuoteOriginally posted by Newtophotos Quote
In order to take better photos, is it better to purchase a polarizing or ND filter for both of these lenses?
The short answer is NO. Polarizers and ND filters have specific functions, use them when you need a particular effect. But they will not magically make your pictures 'better'.
QuoteOriginally posted by Newtophotos Quote
Should the polarizing lens be circular or square?
I prefer circular if you mean round screw in rather than square like a Cokin. There are also circular and linear polarizers as noted above but that is different.
QuoteOriginally posted by Newtophotos Quote
Should these two filters ever be stacked?
'Should' has nothing to do with it. If the effect you want requires them to be stacked then you stack them, if not then you don't.

A CPL reduces glare and reflections from non-metallic objects, like water. It only works well when you are pointing it at 90 degrees to the sun. So pointing it directly into the sun really has little affect.
A ND filter reduces the amount of light that goes through the lens, this is used to get really slow shutter speeds for things like dreamy misty waterfalls.

One other factor is that adding a filter (or two) to the front of the lens reduces the image quality to some degree. So only use a filter when it will do something that you need. And one of the big downsides of filters is that in some situations, like shooting into the sun, they produce ghost reflections in the image. So in general I avoid using filters when the sun or any point light source is in the frame.

And another thing is that on very wide lenses, (wider than say 20mm on APS-C) a CPL can cause weird looking skies with dark areas and light areas that looks unnatural.

My recommendation would be to make sure you have and use the hoods for your lenses and if you want get a CPL for the 18-135 but I wouldn't bother for the 10-20. Just MHO.

08-30-2013, 11:48 AM   #5
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QuoteOriginally posted by abmj Quote
One other tip for using a CP. If you like to wear polarized sunglasses, take them off when shooting with the CP. The first time you try it, you may think you are going color blind or your camera has gotten bunged up. The two polarizers (glasses and lens filter) conflict, giving some VERY strange results in the viewfinder. :-)
The very bane of my existence!

I agree, a decent CP for the 18-135 will be nice. Then go to the lake or creek and take pictures of fish.
08-30-2013, 12:05 PM   #6
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This has been posted here before and it's a great resource for choosing a CPL: Polarizing filters test - Results and summary - Lenstip.com
08-30-2013, 04:12 PM   #7
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For landscape photos, I often will use a graduated neutral density filter where half of the filter is dark and it transitions to clear. I use this if the sky is much brighter than the landscape (sunsets and sunrises especially). The cheaper filters will make the sky look purplish so these filters can get pretty expensive ($100 or more) - but it's not often I use these since they are squares and need to be held in front of the lens (there are holders you can get, I'm just too lazy to use them and on super wide lenses like your 10-20, they tend to cause vignetting). Using this kind of filter does require removing the lens hood which can leave your front element a bit more exposed to accidents.

As for polarizers, I use circular ones as needed - usually to make the sky a bit deeper blue or if I need to control reflections and or glare.
08-31-2013, 04:46 PM   #8
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QuoteOriginally posted by StevePrime Quote
This has been posted here before and it's a great resource for choosing a CPL: Polarizing filters test - Results and summary - Lenstip.com
Thanks for all the great feedback guys. The best bet at this moment seems to be to get a high quality ($100+) 72mm circular polarizing filter and get two step-up rings (52-72mm for the 18-55 WR and a 62-72mm for the 18-135 WR, in case wife has one of them). I am assuming the step-up rings will also allow a ND filter to be used on a three lens, in other words, the ND filter and CPF are the same size/work with the same ring.

Can the lens hood be used in conjunction with a step-up ring? I assume the hood will have to fit the larger dimension on the step-up ring.

Other than picking the best one I can afford from the lens tip article, is there anything else that is a must on the filter?

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