Hoya PL/Cir Filter


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stl

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#1
i have this PL/Cir filter and understand that there is a ring that you can turn. But what the effect? i also dunno where to turn to, there's no indication like 1,2,3,4 or +/-...
 

Ian

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Feb 20, 2002
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#4
Go outside when the sun is shining and stand at right angles to the sun and rotate the filter when it's attached to the camera while looking at the sky.

You'll see it's effect then.
 

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Midnight

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#5
Originally posted by stl
can see the effect through the viewfinder meh?
If you are using an SLR camera, the answer is definitely yes. However, if it's a compact camera, you will of course not see the effect of the polarising filter through the optical viewfinder. The good news is that if you are using a digital compact camera, you can still get the through-the-lens (TTL) view of the polariser effect using the LCD preview screen and your electronic viewfinder, if available.

To add another tip, I find that polarising filters are also very useful for reducing specular reflections off non-metallic surfaces, eg. water, glass and foilage. In most cases, you can achieve this by turning the polariser so that its blocking axis is parallel to the reflecting surface, although it also depends on where your lens is pointing relative to the reflecting surface.
 

jimtong

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#6
Try on the SLR cam. then point towards a LCD screen (if you have a laptop) . By viewing thru the view finder, try turning the filter, you will see the effect...... the whole LCD screen will appear to be black out!!!
 

stl

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Originally posted by jimtong
Try on the SLR cam. then point towards a LCD screen (if you have a laptop) . By viewing thru the view finder, try turning the filter, you will see the effect...... the whole LCD screen will appear to be black out!!!
it works... but why does it works on LCD only? my CRT monitor cannot leh... i also tried on some HDB windows... those that i point towards has got no effect. But for those about 90 degree from my direction, it has got the changes when i turn the filter. Normally, does the filter works if i has to shoot through glasses/windows?
 

jimtong

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#8
Originally posted by stl


it works... but why does it works on LCD only? my CRT monitor cannot leh... i also tried on some HDB windows... those that i point towards has got no effect. But for those about 90 degree from my direction, it has got the changes when i turn the filter. Normally, does the filter works if i has to shoot through glasses/windows?


It works on LCD bcos LCD itself is made of Linear Polariser (means that the light from the LCD is already polarised!). And linear polariser confines light to a single plane, juz imagine that the light travel almost straight towards one direction. that is why sometime you cannot see clearly from the side of the LCD screen, unless you are in front of it. This is to suppress reflections and to eliminate glare.

A polarising filter works by only allowing light waves oscillating in a certain direction to pass though the filter.

When we rotate a circular polariser in front of the LCD, we are actually controling the light from a certain direction to pass thru the pl filter, and at certain point of the rotation, the ligth coming straigth towards the filter will be block or reduced, that is why you cannot see the light from the LCD since the light from the LCD is travelling straigth towards the filter.

We know that the light reflected from any surfaces is about 45 degree, that including glasses, window or a water surface. If you were to stand at 90 degree from the window reflection, you can actually see the reflected light and this will prevent you from seeing thru the window. Inorder to see thru, you need to block the reflection rite? so you need to use a polariser filter to block the light travelling from that direction.

That it! Enough of physic. Hope the explaination will help you understand more on PL filter. My explaination may not be clear but to understand in dept, you need to understand how light work at the molecular and photon level which I think will be quite boring :) very chim lah..

If you still dun understand the theory, like ckiang has said...
turn until you like the effect!! that simple...

***Please take note that if you are using PL filter, you need to compensate for the lose of light by increasing the explosure by 1.5 to 2-stop

you can check out these sites for more info on polariser filter, it will give a better explanation to your questions.
http://photographytips.com/page.cfm/34
http://www.colorado.edu/physics/2000/polarization/index.html
 

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Midnight

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#9
Originally posted by jimtong

***Please take note that if you are using PL filter, you need to compensate for the lose of light by increasing the explosure by 1.5 to 2-stop
Just to clarify things a little for the original poster, this tip above will normally only apply if you are using manual exposure settings. The camera will, of course, automatically attempt to compensate for the light loss by itself if you are using auto-exposure. I used to get confused by things like this when I first started learning photography. :)
 

jimtong

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#10
Originally posted by Midnight


Just to clarify things a little for the original poster, this tip above will normally only apply if you are using manual exposure settings. The camera will, of course, automatically attempt to compensate for the light loss by itself if you are using auto-exposure. I used to get confused by things like this when I first started learning photography. :)
Oh yes, but kodak photography guide actually suggest to increase the explosure only if you are reducing the reflection from the water or window, but for the normal scene, i guess you may be rite. correct me if i am wrong.

I was actually experiment it sometime ago, but the ended result was mostly disappointing. It need practice to get things you expected rite. Maybe anyone can share a real life tips on that? :)
 

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