Diff between Linear & circular polariser


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enyu

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What is the difference between linear & circular polariser ??:embrass: I have a CPL, I used it when I took portrait, realised the skin tone turned out to be a little "bluish", my WB was set to auto. is this normal ?? or I shouldn't even be using CPL for portrait in the 1st place:cry: :cry: I eventually I have to use PS to re-gain back the skin tone.
 

justarius

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#2
You can't use a linear polariser on modern AF cameras.... they will screw up the autofocus. Use a circular polariser instead, unless you are using a manual camera and couldn't care less about autofocus, cos linear polarisers are cheaper.

The blue tint might be a result of your polariser, if you are using a cheap version where the glass is non-neutral, but I suspect a more likely culprit is your WB. You shooting under artificial (florescent/tungsten) light?
 

Artosoft

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#3
justarius said:
You can't use a linear polariser on modern AF cameras.... they will screw up the autofocus. Use a circular polariser instead, unless you are using a manual camera and couldn't care less about autofocus, cos linear polarisers are cheaper.

The blue tint might be a result of your polariser, if you are using a cheap version where the glass is non-neutral, but I suspect a more likely culprit is your WB. You shooting under artificial (florescent/tungsten) light?
AFAIK, the blue tint is characteristic of Cir-Pol. Even the expensive one have that.

Regards,
Arto.
 

enyu

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thks.... luckily i got myself a CPL:)
 

Klose

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justarius said:
The blue tint might be a result of your polariser, if you are using a cheap version where the glass is non-neutral, but I suspect a more likely culprit is your WB. You shooting under artificial (florescent/tungsten) light?
Wrong :nono:. CP "cools" the image down thus giving the blue tint. :)
 

zcwnfx

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#6
i normally use my CPL when i shooting outside, to make the sky, water and greenery look more vivid and better
 

justarius

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#7
Klose said:
Wrong :nono:. CP "cools" the image down thus giving the blue tint. :)
Is it? I've never noticed that before though, in the few occasions where I use a CP. How does a CP cool the image down? I thought a CP primary purpose is saturation of colour and control of reflections....
 

enyu

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#8
I replaced my UV with CPL to minimise the vignette. :angel:
 

nyxx88

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enyu said:
I replaced my UV with CPL to minimise the vignette. :angel:
How would CPL reduce vignetting? :dunno:
 

Artosoft

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nyxx88 said:
How would CPL reduce vignetting? :dunno:
He means if UV and CPL are stack together, it will be vignetting. So only use CPL to avoid vignetting.

Regards,
Arto.
 

Artosoft

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#12
esmondng said:
Y wld u use a CPL on portraits in the first place?
The only reason is unless u are taking the person thru glass or windows.
CPL sometimes useful when the environment is too bright and you want to use bigger aperture. ASA already lowest, shutter speed the highest, but you still get f/8. CPL can act like ND4. Using CPL you might can get f/4. Ok, it will cool down the photo (bluish tint), but you can always play with WB to warm the photo.

Regards,
Arto.
 

enyu

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#13
Artosoft was right... i stacked my uv & cpl and i noticed vignetting when using 28mm, thats why i thot of removing uv and just use cpl will help. can i do this ???:embrass: :embrass:
 

enyu

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#14
is vignetting the effect of a "No Good" lens ?? by the way I also noticed portrait turned out to be slightly bluish when using cpl.
 

esmondng

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#15
Artosoft said:
CPL sometimes useful when the environment is too bright and you want to use bigger aperture. ASA already lowest, shutter speed the highest, but you still get f/8. CPL can act like ND4. Using CPL you might can get f/4. Ok, it will cool down the photo (bluish tint), but you can always play with WB to warm the photo.

Regards,
Arto.
Oh yah. haha tks arto! Now tat u mentioned it....:bsmilie:
but i nv get the chance to try it out yet. :dunno: but i'd probably use the ND anyways.
 

Artosoft

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#16
enyu said:
is vignetting the effect of a "No Good" lens ?? by the way I also noticed portrait turned out to be slightly bluish when using cpl.
Use your camera's WB to warm it up. Or shoot RAW, adjust later.

Regards,
Arto.
 

Artosoft

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#17
esmondng said:
Oh yah. haha tks arto! Now tat u mentioned it....:bsmilie:
but i nv get the chance to try it out yet. :dunno: but i'd probably use the ND anyways.
You are welcome.

In the beach, if you are using CPL, you also can make the sky more blue. But, take a note, it is good to use CPL when the sun is behind you, the effect of CPL is more strong. Meaning in the morning or afternoon, not in 12 o'clock time, where the sun is on top of you.

Regards,
Arto.
 

enyu

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#18
tks Atrosoft for e advice.:thumbsup:
 

Artosoft

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#19
enyu said:
tks Atrosoft for e advice.:thumbsup:
You are welcome.

One thing about vignetting, it is not because the bad design of lens. It is because too many filter stack on it, so it will block the area (corners) that should be fully captured by camera's sensor. It is most happend on Wide Angle (lenses). It is similar like you put Tele's lens hood to Wide Angle lens.

Regards,
Arto.
 

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