Circular Polorizer - will it degrade my pictures

PeterM69

PeterM69

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Pete
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I need some advice on using a Cir-PL with my Contax Distagon/Planar lenses. I'm off to a classic car event at the end of March and thought about purchasing one to reduce/eliminate reflections but am worried the filter could degrade the image I've come to love from these lenses.

Any advice appreciated.

Pete
 
Buy cheap and yes, but buy a decent Hoya or similar and you won't see anything other than the effect it's supposed to give.
 
I used mostly Hoya UV filters and was very disappointed with the image degradation so I don't use UV filters any more. Not that I'm saying Hoya UV filters are bad, just that they didn't work for me. I have got a Hoya Pro1 CPL which doesn't seem to degrade the image anywhere near the amount of the UV filters though. On the few occasions I've used the CPL I've got better with it and I can definitely see an improvement.
 
I've used a few different types over the years but am now using Sigma CPLs and they are excellent but a bit on the costly size.
 
gnirtS said:
Cheapest ive seen a Hoya HD CPL for is about £70. Most expensive £168 - £200. The variation is ridiculous. There are quite a few fakes on ebay as well so beware very cheap off there.
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I got mine from Amazon with free next day delivery with use of their free one month Prime trial :)
 
modchild said:
I used mostly Hoya UV filters and was very disappointed with the image degradation so I don't use UV filters any more. Not that I'm saying Hoya UV filters are bad, just that they didn't work for me. I have got a Hoya Pro1 CPL which doesn't seem to degrade the image anywhere near the amount of the UV filters though. On the few occasions I've used the CPL I've got better with it and I can definitely see an improvement.
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So, a single, essentially clear, piece of glass degrades your images so badly that you've given up on it. And yet two pieces of glass with much heavier coatings and an extra air-gap between them...don't! :thinking: Any idea how this could happen?
 
jon ryan said:
So, a single, essentially clear, piece of glass degrades your images so badly that you've given up on it. And yet two pieces of glass with much heavier coatings and an extra air-gap between them...don't! :thinking: Any idea how this could happen?
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You're not understanding the issues, and a polariser is only one piece, no gaps, and the more coatings the better.
 
HoppyUK said:
You're not understanding the issues, and a polariser is only one piece, no gaps, and the more coatings the better.
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Not for the first time!

So there is only one element to a circular polarizing filter? Not, as I have always believed (this belief strengthened by having just looked at mine, and noted that all of them appear to consist of two plates of glass-like material contained in a casing and which can rotate in respect to each other? If there was no gap, how could they rotate?

Perhaps you could explain the issues? Particularly my total lack of understanding about how a uv filter will seriously degrade an image, but a cpl will not.
 
jon ryan said:
Not for the first time!

So there is only one element to a circular polarizing filter? Not, as I have always believed (this belief strengthened by having just looked at mine, and noted that all of them appear to consist of two plates of glass-like material contained in a casing and which can rotate in respect to each other? If there was no gap, how could they rotate?

Perhaps you could explain the issues? Particularly my total lack of understanding about how a uv filter will seriously degrade an image, but a cpl will not.
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You may want to have another look at your polariser Jon ;) ... mine are only one piece of glass.

Reports of UV filters causing issues with images are not unusual on the internet, tends to be with longer focal length glass, but it does happen ... why I do not know and neither do I care as I never use them, but I have seen the with and without images, and the problem exists.
 
Are yours circular or linear, Martyn? If circular, what is rotating around what?
 
my CPL has two halves - one mounts onto the lens and is just a ring, the second part is a ring which rotates around the first and a piece of glass
 
jon ryan said:
Are yours circular or linear, Martyn? If circular, what is rotating around what?
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They are circular (for digital) ... I have an old linear one with my film kit, if I can lay my hands on it I shall have a look later.

Simple way to check is just stick a bit of tape or post it note on the rear face and rotate it, you will see the tape moving.

As to what rotates around what ... :shrug: ... it works and that is all that matters to me :D
 
Just to clarify Jon ... one piece of glass (the filter) and two pieces of metal (the rotating framework).
 
Martyn... said:
They are circular (for digital) ... I have an old linear one with my film kit, if I can lay my hands on it I shall have a look later.

Simple way to check is just stick a bit of tape or post it note on the rear face and rotate it, you will see the tape moving.

As to what rotates around what ... :shrug: ... it works and that is all that matters to me :D
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Precisely! My point is that a CPL is made of two distinct elements and and for them to be able to rotate about each other there needs to be a gap between them. A small gap will do, but there needs to be a gap.

But I may be wrong...:thinking:
 
Martyn... said:
Just to clarify Jon ... one piece of glass (the filter) and two pieces of metal (the rotating framework).
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Cross-posted. I thought a cpl was made up of a linear polarizing filter and a quarter-wave plate which disrupts the amplitude of the light crossing it?

But...:thinking:
 
Apologies all round- it is just a single plate. For years I believed it was two, and had never properly checked before.

Which just goes to shot there is always something to learn. (And I still don't understand how one works - any offers?)

Mea maxima culpa. :schtum:
 
jon ryan said:
Precisely! My point is that a CPL is made of two distinct elements and and for them to be able to rotate about each other there needs to be a gap between them. A small gap will do, but there needs to be a gap.

But I may be wrong...:thinking:
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jon ryan said:
Cross-posted. I thought a cpl was made up of a linear polarizing filter and a quarter-wave plate which disrupts the amplitude of the light crossing it?

But...:thinking:
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Have just checked my 1970's polarising filter .... one piece of glass and the rotating metal frame.
 
jon ryan said:
Apologies all round- it is just a single plate. For years I believed it was two, and had never properly checked before.
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So did I ... but when Hoppy said it was only one piece of glass, rather than dive in and tell him he was wrong I checked my own. :D

I would not normally exercise such caution but I read a few days ago he had recently tested about twelve PL filters for a magazine, so assumed on this occasion he may actually know what he is talking about :D
 
Martyn... said:
So did I ... but when Hoppy said it was only one piece of glass, rather than dive in and tell him he was wrong I checked my own. :D

I would not normally exercise such caution but I read a few days ago he had recently tested about twelve PL filters for a magazine, so assumed on this occasion he may actually know what he is talking about :D
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Exactly what I should have done! Just goes to show...:bonk:
 
jon ryan said:
Cross-posted. I thought a cpl was made up of a linear polarizing filter and a quarter-wave plate which disrupts the amplitude of the light crossing it?
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It is - though the purpose of the quarter-wave plate is to effectively "depolarise" the light (so the autofocus still works)... the polarising plane having already done it's job.
 
jon ryan said:
Would you say it degrades you images more or less than a uv?
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All filters have the potential to degrade images, even the best. The difference with a polariser over a UV is the polariser actually does something useful, very useful, whereas a UV does absolutely nothing.

High quality multi-coated filters are best, but they can all cause problems:

a) Ghosting. A big problem with bright lights against a dark background, eg sunsets, street lights, neons, car headlights etc. Light bounces off the shiny surface of the sensor, then back again off the rear of the filter to form a mirror image ghost. You can't see it through the viewfinder so can catch you unawares. Very visible in live view though.

b) Flare, where bright light sources are made bigger.

c) Veiling glare, where residual light reflected from the filter surfaces bounces around inside the lens and ends up putting a slight fog over the whole image. Rarely a problem, but it's there if you look for it in the certain circumstances.

d) Poor sharpness. This only happens with a low grade filter used on a long lens. The focal length greatly magnifies imperfections. Can be just a slight blurring, or look a bit like camera shake, and can also create unusual patterns in out of focus areas.
 
whatever you do, don't by a cheap polorizer - this is what I got last weekend, won't be using that again!

IMG_3940_Polorizer-800.jpg


:lol::lol::lol::lol::lol::lol::lol::lol::lol:
 
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