02-25-2015 10:18 AM
Do circular polarizing filters come in various strenghts or ranges of change? ARe all C-polarizing filters the same? Yes, I know how to use them. I know the 90degree angle to the sun and all that ...I feel that I should be able to rotate the filter and see through the lens excactly what the change will be...frankly I find it very difficult to see the amount of change in the blue of the sky using the filter that I have....shouldn't you be able to rotate the filter and observe the change gradations? Shouldn't they be obvious as in a ND filter? Should I ask for a "stronger" polarizing filter?
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02-25-2015 11:51 AM - edited 02-25-2015 11:51 AM
Polarizers can have different strengths. Technically they should all be similar, since theoretcially they should eliminate all waves perpendicular to the axis. But that's theoretical, and cheap polarizers might not be efficient. What brand?
It's unlikely it's a complete fake, but I wouldn't be totally surprised if you bought a cheapo somewhere. I've seen plenty of polarized sunglasses that aren't.
One thing: technically it's not 90 degrees to the sun, it's 90 degrees to a reflected surface. The reflection has become polarized, which allows the polarizer to block it. The effect on blue sky can vary, depending on how much reflection (haze) there is in the sky. The best way to check that it's working is to look at sunlight reflecting off of something, like a shiny object.
02-25-2015 12:52 PM
The polarizer that I have is a Hoya 77mm that I use on my 17-55mm f2.8 lens. Now I will say that the colors generally in the photos I have processed using this filter are richer, but my issue is with gray, overcast skies. In those situations where there is a patch of very faded blue showing through the clouds I never seem to be able to determine as I look through the lens and turn it how much I am affecting the "blueness of those patches". I thought you were supposed to be able to see those changes as you rotate the lens...but I have not found much success noting those changes using the LD display or through the lens...
02-25-2015 12:56 PM
02-25-2015 03:32 PM
Thank you for reminding me of several things in your response...yes, the lens does seem to cut water reflection and such but I still am aggravated at not being able to determine the amount of change in my view finder or on the LCD on the back of my camera...A great boon to photography would be to fix that LCD display so that you can tell "doodleysquat" when the sun is bright outside.
02-25-2015 03:35 PM
02-26-2015 11:23 AM
Polarizing filters do increase color saturation. You should be able to see it in your view finder and LCD display.
A good way to visualize how this works is to aim your pointer finger at the sun while holding your thumb straight up. Everywhere your thumb points when you rotate your hand (while still pointing it at the sun) is where the polarizer will have the strongest effect. They require the camera to be pointed at a right angle to the sun for maximal effect.
The problem is all color saturation is not equal. It can vary and not be uniform across the frame. Another is when used on a wide angle or UWA lens the effect can be less. Which can make it quite difficult to see the effect in a viewfinder or LCD screen. Cheap ones can degrade IQ.
If I missed anything maybe Tim can help me out. This is right up his alley.
02-26-2015 06:01 PM
02-26-2015 07:01 PM
e-biggs, I notice you have a Sigma lens..my husband recently purchased Sigma 150-500mm f5-6.3 lens for my Canon..due to my unhappiness with my Hoya and apparently a rarity of polarizers for the 86mm lens in question, what do you use in the way of a cpl for your Sigma and what 86mm cpl would you suggest for my Sigma named above?
02-26-2015 10:51 PM
I have that very Siggy. It is a great lens for the money and will give all but the many thousand dollar rigs a run.
I use a B+W polarizing filter but I use it on more normal lenses. One problem with the big Siggy and its ilk, is they are slow. It really can't afford any f-stop penality. And filters of any kind degrade IQ.
Now what do I do about it? Photoshop of course. In reality, the only filter that you can't duplicate in PS is the ploarizer.. But you can agive it a darn good try.
BTW, have you done any HDR? I have beeb toying around with it a little bit. Some pretty "interesting" results!