When to take off the polarizer, if to take it off at all?

[taon]

Hi Everybody!

I've started my adventure not so long ago and still need a lot of help. After few month of shooting in and sometimes outside the city I've decided to get a polarizer. I think I know how to use it (best result when being at 90 degrees) basically. But guy in the shop told me he never takes off his polarizer. So....

What I do is, I go out once a week to some remote location, sightsee and take lots of photos. I do not go to a preset locations on a specific time of the day to get the right light in this case (but I do go sometimes). I shoot city streets and noticed my pictures to be sharper and clearer even there was no direct sunshine to utilize the polarizer to its full potential (rotating the polarizer ring hardly saturates any colors). But still the pictures appear to me somehow better. Is it only me? Please, help me! Am I going mad? I know sometimes if I don't pay attention to this at all, some of the pics have half of the skyline gray and the other more blue. Should I keep it on my lens all the time and learn how to go with it or if I want to learn photography I should take it off and use only in specific situations (like removing reflections etc.)?

Thank You.

[pwnage101]

Keep in mind that polarizing filters also have the effect of minimizing reflections; you don't necessarily need sun to see how a polarizing filter affects an image.

[Dave Humphries]

I shoot city streets and noticed my pictures to be sharper and clearer even there was no direct sunshine to utilize the polarizer to its full potential (rotating the polarizer ring hardly saturates any colors). But still the pictures appear to me somehow better. Is it only me? Please, help me! Am I going mad? I know sometimes if I don't pay attention to this at all, some of the pics have half of the skyline gray and the other more blue. Should I keep it on my lens all the time and learn how to go with it or if I want to learn photography I should take it off and use only in specific situations (like removing reflections etc.)?

Thank You.

HI there,

Leaving it on all the time is a waste of almost 2 stops of light, meaning you are either running at a higher ISO, shooting with less DoF, or risking camera shake, because of it - and maybe a combination of all three.

I think you're going to have to post an example or two before we can advise on the "some of the pics have half of the skyline gray and the other more blue" problem, I suspect they will be wide angle ones and this is a known problem with CPL on an image whose angle of view approaches or exceeds 90 degrees.

Cheers,

[Colin Southern]

But guy in the shop told me he never takes off his polarizer.

Was that before or after you bought it?

Seriously, a CPL is just like any other camera tool/accessory - there are times to use it, and times where it's not appropriate. eg ...

- If you're using an UWA (Ultra Wide Angle) lens, a polariser will give you very uneven sky tones due to the wide range of angle that the suns rays are arriving over,

- If the light is fading and you need ISO 800 to make the shot (without a polariser) than you'll need ISO 3200 (with it's associated noise) to make the same shot with a CPL fitted.

PS: Just saw that Dave has mentioned the same thing.

[taon]

17-40 mm is all I've got. So right. It is a problem to use a CPL on a wide angle lens like this. Stupid me didn't pay attention hard enough. But camera has 1.6 crop factor thus reducing the pain a bit. If I zoom in it is like 64 mm. Checked it now and problem appears mainly on the landscape positioned shots.

Yes, I loose two stops of light. But on a sunny day (not many of them nowadays) I think I can still afford it. The question is if I turn the CPL and cannot see any difference in saturation in the viewfinder (lets say I have the sun right behind me) will it actually produce better image (in terms of sharpness or anything else) as only polarized light 'goes through'. Let's forget the reflections factor in this case. If I want to take a picture of a building and cannot position myself in better place to use CPL more effectively what shall I do? I find it difficult to make a decision.

P.S. Always attempt to shoot at low ISO (100), keeping an eye on the speed I am shooting at to minimize the possibility of camera shake. But Dave gave me something to think about. DoF. I've noticed that almost all my images been shot with low f-number. I use Av and higher f-numbers only shooting from tripod.
Thank You again.

[Colin Southern]

... if I turn the CPL and cannot see any difference in saturation in the viewfinder (lets say I have the sun right behind me) will it actually produce better image (in terms of sharpness or anything else)

Probably not.

If I want to take a picture of a building and cannot position myself in better place to use CPL more effectively what shall I do? I find it difficult to make a decision.

If camera shake isn't an issue due to lowered shutterspeeds then there's no real downside to leaving it on (assuming it's not adversely affecting any sky). If you're shooting with a tripod and subject movement isn't an issue then it's really up to you. Try both

[Dave Humphries]

If you're shooting with a tripod and subject movement isn't an issue then it's really up to you. Try both

This is a very good idea, which I'd like to hijack with a couple of suggestions
With camera on tripod and CPL in place, shoot a static, correctly exposed 'sun directly behind you' scene at;
1) ISO 400, CPL fitted
2) ISO 400, no CPL, correct the exposure (for lack of CPL) by stopping down 2 stops
3) ISO 400, no CPL, open aperture by 2 stops and increase shutter speed by 2 stops
4) ISO 100, no CPL, decrease shutter speed by 2 stops

The shutter speed and aperture should be same for 1) and 4).
Shoot manual, shoot RAW (if you can), or jpg if you don't normally use RAW.
Make sure any PP is minimal, say ONLY capture sharpening and applied equally to all 4 shots.

Now compare the resultant images,
Optionally, please start an album here and post them so we can see too.

If any other member has some time and wants to have a crack at this comparison, be my guest

Thanks,

[Keith]

If any other member has some time and wants to have a crack at this comparison, be my guest
Thanks,

Ah yes, 'time', I remember I used to have some of that. lol