Polariser question

[vdzande]

Hi there all, could someone help me with this seemingly easy question?

I have been searching the forum but I couldn't find the answer to my newbie question regarding the use of a polarising filter. I know that when I use the filter, the exposure goes 2 clicks down. When I correct that by leaving my lens open for just a bit longer, I feel the effect is almost gone. Which leaves me thinking: what's the use of the filter?

What am I doing wrong? I am turning the filter to it's maximum effect position.

All suggestions are very welcome, since I am going away friday on a trip through south western europe for a month.. ;)

[Woolley]

Re: Polariser question

Hmm, curious. I use mine a lot and can't think what phemomenum you're experiencing. Lengthening the exposre time only changes the amount of light - back to the level without the filter - while the filter changes the direction and quality of light. Any chance you could post an example shot to see what the result is and maybe identify what's happening?

[SamFisher]

Re: Polariser question

If you are using one of the Auto modes ie Av Tv P the camera will have compensated for the 2 stop loss by altering the exposure.
By opening up the 2 stops you are in effect overexposing the image by that amount.

Mike

[vdzande]

Re: Polariser question

Thanks for your suggestions my friends.
@Sam: I use manual almost all the time.

Does the white balance have to fixed also? Could that self-compensate the effect? That one is on auto a lot when I'm taking pictures..

I'll make two sample shots today and post the exif data with it. Thanks for helping.

Another question: is there a pol.filter available that I don't have to turn in the right position, but always has the same 'effect'?

Rutger

[SamFisher]

Re: Polariser question

Are you manual metering with the filter in place?
If you are then I would imagine that you are already compensating for the 2 stop loss and by opening up you are overexposing.
If you meter without the filter and add the filter after taking the reading then you would add 2 stops.

Mike

[vdzande]

Re: Polariser question

Are you manual metering with the filter in place?
If you are then I would imagine that you are already compensating for the 2 stop loss and by opening up you are overexposing.
If you meter without the filter and add the filter after taking the reading then you would add 2 stops.

Mike

Thanks Mike. i always add stops (2 or 3) untill the lightmeter is at my favourable position again.

Btw: I tried to make two pictures today but I messed up :-/ I'll give it a go tomorrow.

Thanks in advance!
Rutger

[Woolley]

Re: Polariser question

If you're metering with the filter in place, then just meter on what you can see. If you're metering and then fitting, 2 stops may be too much - I think mine loses about 1 1/3rd stops. Compare your own settings with the AV choice and I suspect you'll find a difference. I often find it better to under-expose by ½ a stop with the filter on anyway, so 1 stop will probably be enough compensation.

You need one that turns for two reasons. According to the direction of light, reflections, time of day and what you're taking you often don't want maximum effect. If I have lots of blue sky at mid-day, for instance, I'll only want about half a turn. Trees and grass around a pond then I want all of it. Secondly if you turn your camera through 90deg you'll need to do the same with the polariser.

[vdzande]

Re: Polariser question

If I have lots of blue sky at mid-day, for instance, I'll only want about half a turn. Trees and grass around a pond then I want all of it.

Woolley,

Isn't the clear blue sky the moment where you want the full effect in so that the sky is actually nice and blue? This where I expects the filter to cause it's effect. And why would you have tha maxamise the effect at the pond with trees and grass?

More and more I get the feeling there is little wrong with my filter, but more with when I use it and the results I expect from it. :-/

BTW: today here in Amsterdam is all rain and thunderstorms, after a couple of very hot days. So no filter usage here ;)

Last question: there's no way to check the filter's effect physically, by the way it is positionned on the lens, is there? You always have to see the effect through the camera right?


My god, what a newbie questions.. I feel like restarting photography again.. Hope I can count on your patience :-/

[MartinR]

Re: Polariser question

"Last question: there's no way to check the filter's effect physically, by the way it is positionned on the lens, is there? You always have to see the effect through the camera right?"

Try holding the filter in front of either a TV screen or a computer monitor - you will see how it affects what you see. I mark the rim with a dab of paint to indicate how to position it for max / min effect.

Martin

[Woolley]

Re: Polariser question

Isn't the clear blue sky the moment where you want the full effect in so that the sky is actually nice and blue? This where I expects the filter to cause it's effect.

Not necessarily. If you're 90deg to the sun and using an averagely wide lens then that's fine, but if you're at an angle or using very wide you'll get part of the sky noticeably darker than the rest. This is where you may want to reduce the effect for a more balanced image.

And why would you have tha maxamise the effect at the pond with trees and grass?/

Polarizer cuts out scattered (reflected) light and there's a surprising amount of that comes off green plants. Turning the filter to maximum cuts out all this scatter and gives clearer, more saturated colours. It's the same reason clouds suddenly look almost 3D. Works well on pale buildings and slate roofs as well.

[vdzande]

Re: Polariser question

Wow, those are some excellent tips. Thanks Woolley, Sam & Martin (I will be using a marker to indicate the 'max' position).
Thanks for your patience. Last few days have been a steep learning curve :)

Enthousiastic as I've become I will try to experiment a bit today, but we're leaving on our trip tomorrow.
So in case I can't manage to take and share the sample shots before I leave: thanks so much! You've been a great help and this will improve my pictures of the Italian Lakes, Venice, boat trip to Greece, Greece itsself, Bulgaria and Vienna :))

Rutge

[Woolley]

Re: Polariser question

Enjoy. I my opinion a polarizer is the easiest way to make a huge improvement to your pictures. The great thing about learning it on digital is you can take several shots at different strengths then choose the version you like best afterwards.

Envious of your trip. Could do with a bit of sunshine and mediterranean lifestyle.