# General > Member's Lounge > Photography >  Polarizing filter for aquarium photography?

## trident

Hi all Shifu,
Do we need a Polarizer filter when taking photos of fish tank?
I was reading something about using the Polarizer filter when taking photo of fish tank cause it will cut down the glare. 
And then there is Circular Polarizer and Linear Polarizer, now very blur. Please can someone help to explain.
Thanks.

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## Shadow

yeah me too blur, thinking of buying polarizer to take scenary photo.

I was reading somewhere that polarizer can eliminate the reflection on the glass. Will it eliminate flash reflection on the glass?

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## Simon

read this URL
http://www.mat.uc.pt/~rps/photos/filters_uv_pol/

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## hwchoy

and do not forget polarisers cut down almost two-stops of light.

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## Shadow

I've been reading review and people keep saying "two stop", 3 f-stop, etc. What does it means. Sorry Richard out of topic question  :Opps:

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## hwchoy

one-stop is half, two-stop is quarter.

so if we say your lens is one-stop slower than another, that means it collects half as much light as the other. and two-stops mean it collect half of (one-stop) = &#189; &#215; &#189; = &#188;.

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## trident

Robert,
Interesting question actually, if nobody asked them, nobody will learn.

Simon, Thanks for the very informative website.

Choy, so can I conclusively say that, when you lose two-stops of light, it mean you lose a quarter of the original amount of light?

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## benny

I never used it for aquarium photography. Don't think it's of much help.

Cheers,

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## CK Yeo

You do not need a CPL filter to take tank photo but

1) Tank must be brighter than environment. Can be accomplished through remote flash INTO the tank. (not on board flash).

2) If you do not use flash, you can set long exposure. However, fish will become blur lines especially if you have reflective things like cardinal tetra swimming around.

ck

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## hwchoy

> Choy, so can I conclusively say that, when you lose two-stops of light, it mean you lose a quarter of the original amount of light?


no lah! one stop lose half. two stop lose another half. so you are LEFT WITH ONE QUARTER of the original.

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## Shadow

how does this translate to the camera setting to compensate it?

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## hwchoy

doubling ISO compensates for one-stop, so up your ISO four times to compensate for 2-stops of lost.

if you have a DSLR, put it into manual mode and try it, check it by looking at your built-in light meter.

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## Shadow

I didn't know there is build in light meter  :Embarassed:  sorry newbie

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## hwchoy

on a Canon DSLR, in your viewfinder or LCD there will be a row with a pointer thing, that is the light meter or exposure indicator. the light meter will tell you what is the expected exposure in manual mode, so you have to adjust shutter speed and aperture so that the pointer goes to "0". but this may nor may not be the right exposure, you have to test shoot as some scenes may be too complicated for the camera to meter properly e.g. a sihouette.

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## aquaturbo

If taking pictures of aquatic plants in the aqurium, polarizer will be very helpful to cut down reflection. Similar concept to landscape photo using polarizer.

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## juggler

> Hi all Shifu,
> Do we need a Polarizer filter when taking photos of fish tank?
> I was reading something about using the Polarizer filter when taking photo of fish tank cause it will cut down the glare. 
> And then there is Circular Polarizer and Linear Polarizer, now very blur. Please can someone help to explain.
> Thanks.


Current DSLRs and auto film SLRs from the 1990s onwards should be using Circular Polarisers. Linear Polarisers are for the older manual-only cameras. Can read up more if you google.

Taking tank pics not necessary to use these filters. We can take the tank pics when the surrounding is dark at night.
The filters are useful to cut down glare and reflection when outdoors. eg. reflection off the water surface, glass, shiny wax on leaves etc.

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## valice

> If taking pictures of aquatic plants in the aqurium, polarizer will be very helpful to cut down reflection. Similar concept to landscape photo using polarizer.


Reflections for aquatic photography happens when the amount of light outside of the tank is more than the amount of light inside the tank.
Therefore, there is the saying of switching off all the lights around your tank when you shoot your tank.

But always remember that the light from your tank will hit you and as a result illuminate yourself and you see yourself in the picture. So at times having a long lens allows you to shoot at a future distance.

All of us who has been shooting fishes don't use polarisers. Already we having problem with lights, why give ourselves more problems cutting down the amount of light enter the lenses by adding an addition 2-stop problem?

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## luenny

Wow! The response over here is incredible. Looks like more people are into photography than I thought. How about a shooting session then?

Anyway, if you're going to get a polarizer for fish shooting, then my advise don't. Like what the others suggested, there are other ways to do it. But if you want it for landscape and scenery as well, then it may worth the investment. It changes the landscape quite a bit with the polarizer at the right time. Of course, it also comes with some learning curve and some trial and error to find out when you should put on your polarizer and when not to.

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## trident

Luenny,
Agreed, respond is fantastic, Thanks to all shifus here.
Can save on the polarizer filter and buy something more useful since these polarizer filter is not cheap.
You have been itching to shoot, why don't you come over to my place this sunday and shoot my multiple biotope setup?

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## luenny

Richard,
I'm still down with multiple throat infection - got another one just when I was recovering from the first one. I'll see how I feel this Sunday but chances are I'll be down - if the fever doesn't get me the sore throat will.

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## Shadow

I need to buy polarisor, otherwise can't take picture of snow? By the what is those Neutral Desity filter?

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## trident

Luenny,
Better take a long rest, CNY just round the corner, don't want to spoil it.
Take care.




> Richard,
> I'm still down with multiple throat infection - got another one just when I was recovering from the first one. I'll see how I feel this Sunday but chances are I'll be down - if the fever doesn't get me the sore throat will.

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## Simon

more things to read, Neutral density filters
http://www.cs.mtu.edu/~shene/DigiCam...filter-ND.html

one good way to save on buying multi filters with different size is getting a common filter size then using step down filter rings for smaller lens.

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## valice

One thing to remember about buying filters is that different lenses are of different filter size. So to keep down the cost, try to get lenses of the same filter size and then you can use the same filter across the different lenses.

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