Polariser Reviews

Messages
4,608
Name
Kris
Edit My Images
No
Someone posted a link recently for a review on all the top Polarisers but i can't find it for the life of me....
 
A ha, that's the one, thank you,Kris

I've been looking for the best price for a Marumi 72mm DHG
[cannot afford a Super DHG]
Clifton Cameras seem to have the best at £51

should you find better prices in your searches - pls let me know

Camera King offer good prices through eBay but I'm of the mind..
"if it's too good to be true...etc"
 
Just get a Hoya HD - there's nothing better :thumbs:
 
Just get a Hoya HD - there's nothing better :thumbs:

re Polarizing --
Actually the Marumi DHG and Super DHG both scored better than the Hoya Pro-1 Digital MC.--- although a Hoya HD wasn't tested

however a 72mm Hoya HD Digital C-PL at Clifton Cameras lists at £162 !

The Marumi DHG scored well [4th] at cost £51
 
Just get a Hoya HD - there's nothing better :thumbs:

B+W Linear Kaesemann or Singhray LB polarizer? ;)

(I'm still dreaming that one day I may be able to afford the latter ...)

For OP: don't discount the linear polarizers - a second hand B+W Linear Kaesemann one will cost you around 60 quid (I got a second one precisely for this amount from eBay recently) and that is the best glass there is.
 
Well I have the No.1 on that list B+W Slim KSM C-POL MRC 72 mm and was very worried at first that I had a fake as the effect is far far more subtle than on the cheap Hoya I had before.

I would never recommend but one to someone else, I just say go for a top of the line Hoya and save some money.
 
,,,,,,,, I just say go for a top of the line Hoya and save some money.

no offense - but cannot see how you "save money"...?..:shrug:

forgetting the HD at £162
and using the lenstip report, and Clifton, and 72mm, for sake of discussion

joint 1st = Marumi Super at £92
4th = Marumi DHG = £51
7th = Hoya Pro-1 Digital MC [their best] = £114

Nothing against Hoya - they came out at the top in the UV testing

FWIW - at 52mm I have the Hoya Pro-1 Digital MC C-PL and the Hoya HD Protector - both excellent
but for my new Sigma 17-70 I will switch to Marumi - each to his own...:cool:
 
Well I have the No.1 on that list B+W Slim KSM C-POL MRC 72 mm and was very worried at first that I had a fake as the effect is far far more subtle than on the cheap Hoya I had before.

I would never recommend but one to someone else, I just say go for a top of the line Hoya and save some money.

The circular polarisers do have less effect than linear ones so if you want better effect you may need to look at LPs. Also cheaper glass may have some problem with neutrality - are you sure you are not confusing polarisation effect with bluish cast? My Kenko CPL filters although are very good do give slight overall cast and B+W seems to be pretty neutral.
 
no offense - but cannot see how you "save money"...?..:shrug:

forgetting the HD at £162
and using the lenstip report, and Clifton, and 72mm, for sake of discussion

joint 1st = Marumi Super at £92
4th = Marumi DHG = £51
7th = Hoya Pro-1 Digital MC [their best] = £114

Nothing against Hoya - they came out at the top in the UV testing

FWIW - at 52mm I have the Hoya Pro-1 Digital MC C-PL and the Hoya HD Protector - both excellent
but for my new Sigma 17-70 I will switch to Marumi - each to his own...:cool:

£162 for a Hoya HD CPL? :eek: I bought mine for £78 off Amazon - swapped a Pro-1 for it.

HD is the top of the range Hoya, and I think it is the best you can get because it not only has all the high optical quality of the best German filters - including hardened glass and easy-clean multi-coating, it only reduces the light by 1.2 stops as opposed to 1.7-2.0 stops. And it's cheaper.

As a result, it stays almost permanently fitted to my super-wide.

Linear polarisers are not suitable for DSLRs.
 
£162 for a Hoya HD CPL? :eek: I bought mine for £78 off Amazon - swapped a Pro-1 for it.

HD is the top of the range Hoya, and I think it is the best you can get because it not only has all the high optical quality of the best German filters - including hardened glass and easy-clean multi-coating, it only reduces the light by 1.2 stops as opposed to 1.7-2.0 stops. And it's cheaper.

As a result, it stays almost permanently fitted to my super-wide.

Linear polarisers are not suitable for DSLRs.

i didn't want to get into a "I can get it cheaper discussion" - I just used Clifton Cameras as "my" choice as I personally dont like from Amazon - just me

Agreed - HD is indeed "top-class" but we were discussing C-PL, and both the DHG Marumis scored better than the Hoya Pro-1. [I did say the HD wasn't included]

Agreed - Circ-PL for Digital - i read somewhere the light through a Linear confuses the metering, or was it the focusing...:shrug:

(as i said above, I have 52mm Hoyas for my 55-200VR - and wont be changing as they are excellent)
 
Linear polarisers are not suitable for DSLRs.

Oh yes they are ;)

I know all the theory - in practice though I have yet to see any AF or metering problems. I specifically tried it with extreme angles and polarisation effects - both AF and metering on my D200 were still working. True the occasional issues with AF still may be there (though some say that recent cameras are less affected) but the benefits (less flare, stronger polarization effect) do outweight the problems (at least for me they do).
 
Oh yes they are ;)....

damn - just sold my 2 Hoya PL for £5 each ---should have asked more...:lol:

pity they're both posted - never thought to try them out

though that's impossible - it's p***ing down snow ATM......:razz:
 
damn - just sold my 2 Hoya PL for £5 each ---should have asked more...:lol:

pity they're both posted - never thought to try them out

though that's impossible - it's p***ing down snow ATM......:razz:

It's weird how firmly this belief is established. But from the very beginning the LPs were not unusable - they just had certain conditions where the AF and metering could be affected on certain cameras. I actually never thought of that until some time ago a few threads on Dpreview talked about that and people shared their experiences with LPs.

If you think about it, the CPL construction is a bit more convoluted - it has another layer in the filter sandwich (glass, foil, quarter wave plate, glass) so more layers in the overall optical path hence more chances for flare (not the large one but the one that spoils overall contrast). Of course that may not be something everybody cares about (I do personally).

Also there must be a reason why the Singhray (the ultimate in filter quality in my view and looking by their prices ;)) do not even do CPLs only LPs.

This quote from another old forum conversation does explain some differences in quality, prices and polariser types quite well imo (bear in mind it is quite old):

If your camera utilizes a beam splitter in the optical path to adjust focus or to meter or if your camera has a polarized display then you need a circular polarizer for the functions of the meter/focus/finder to work properly under all condition.

If your camera does not have any of the above then a linear will work properly.

Or, in simpler terms, a circular polarizer will work properly under all lighting condition and on any camera.

A linear will work properly only if the camera does not have a beam splitter and/or a polarized viewfinder display.

There are all different grades of polarizing foils that can be used by filter manufacturers to make a polarizing filter. The better grades are more neutral and have less effect on color then cheaper ones. They also are optically better to have less effect on image sharpness then cheaper ones. The glass used to sandwich the polarizing foil is also available in different grads as is the adhesive used to cement the foil between the glass plates. There is a also a manufacturing technique for polarizers
called Kaesemann which stretches the foil to hold it flatter between the glasses and the glasses are rim sealed. This also makes the foil immune to moisture and fungus damage so it is a superior performer, especially in tropical areas.

The glasses used on a polarizer may be uncoated, coated (both sides or multi coated. Some multi coating like the Heliopan SH-PMC have a top coat on each side that repels dust and moisture. The better the coating the less flare and the better contrast and color saturation the filter will deliver.

Lastly there is the matter of the mount. Some filters are mounted in plastic or aluminum mounts. These are fairly easy to cross thread and may be difficult to screw-in or remove from lens mounts made of the same materials. Best filters are in brass mounts.
 
It's weird how firmly this belief is established. But from the very beginning the LPs were not unusable - they just had certain conditions where the AF and metering could be affected on certain cameras. I actually never thought of that until some time ago a few threads on Dpreview talked about that and people shared their experiences with LPs.

If you think about it, the CPL construction is a bit more convoluted - it has another layer in the filter sandwich (glass, foil, quarter wave plate, glass) so more layers in the overall optical path hence more chances for flare (not the large one but the one that spoils overall contrast). Of course that may not be something everybody cares about (I do personally).

Also there must be a reason why the Singhray (the ultimate in filter quality in my view and looking by their prices ;)) do not even do CPLs only LPs.

This quote from another old forum conversation does explain some differences in quality, prices and polariser types quite well imo (bear in mind it is quite old):

Interesting post and quotes Alexey :)

I've just spent the last hour comparing linear and circular polarisers on my 5D2 and 24-105L - a Hoya HD and a Cokin linear.

The theory is as quoted in your full post above, in practise I found that if I pushed the AF to the point where it would only just focus by selecting a very difficult target, if I turned the linear polariser 90 degrees it would no longer AF. With the circular polariser, it would AF in all positions. It has to be said that I chose a very difficult low-contrast target in low light that TBH I didn't think the camera would AF anyway, but it did, and the difference was there.

Perhaps more significantly, it would fool the metering system and under-expose by one third of a stop depending on the degree of rotation, regardless of conditions. The circular polariser did not do this.

I don't think this is in anyway surprising, given the theory, and I'm a little surprised folks really question it. It's there, fact. Whether you think it's significant is another matter but I don't see why manufacturers would bother to make circular polarisers if the plain linear ones were better (or even as good). Also, it's kind of a moot point anyway as trying to buy a decent linear polariser is actually quite difficult - they are never a regular stock line.

I'm less convinced of the downsides of using circular polarisers, the arguments about increased flare and reduction in contrast, plus a reduced polarising effect. I've tried hard and failed to detect either.

On the flare and contrast issue, whatever the effect is, I cannot see it, and if it does exist, it is certainly insignificant compared to the general impact on image quality that fitting any filter has - which can be dramatic, depending on circumstances.

The other thing I've tried hard to detect is the increased polarising effect of the linear type. On both bright blue skies and reflections, I've been unable to see any difference. Perhaps it's there, but I can't tell. Again, compared to all the other upsides and downsides of using a filter, whatever the effect is, it's not significant in my view.

I've tried a lot of polarisers over the years and in terms of polarising effect and colour, I've never noticed much difference between them. The big difference has always been flare from uncoated filters, and less flare from coated and multi-coated filters. Apart from that, the reason I like the Hoya HD is because it has all the advantages of every other polariser that I'm aware of, plus it is about 2/3rds of a stop brighter - for no penalty. You can just leave it on, get a brigher viewfinder image and a higher shutter speed. Those are real, significant benefits.

IMHO Singhray sell snake oil - and expensive snake oil at that ;)
 
The theory is as quoted in your full post above, in practise I found that if I pushed the AF to the point where it would only just focus by selecting a very difficult target, if I turned the linear polariser 90 degrees it would no longer AF. With the circular polariser, it would AF in all positions. It has to be said that I chose a very difficult low-contrast target in low light that TBH I didn't think the camera would AF anyway, but it did, and the difference was there.

When I got mine, I did similar tests on my D200 and it did fine. I have not tried the low-contrast targets but my D200 has troubles focusing in low light and low-contrast cases anyway (may need to somehow clean those AF sensors after years of abuse).

I don't think this is in anyway surprising, given the theory, and I'm a little surprised folks really question it. It's there, fact.

I may said it in a wrong way but it's not the theory that is questioned - that is correct of course. It is that now established belief that LP won't work on SLRs full stop. I would say it needs to be tested. Different cameras has differently built mirror chambers and not all of them affected by polarised light. Plus those LP proponents argue their cause in most of the cases that it largely depends on the usage - for landscapes the AF is (arguably) not needed very often and metering should be carefully done before turning LP to the maximum effect.

...but I don't see why manufacturers would bother to make circular polarisers if the plain linear ones were better (or even as good).

I do - they can charge a lot more under the pretence of more difficult manufacturing ;) Seriously though, the difference in prices can be staggering and all of that is what - adding quarter wave plate to the optical sandwich...

Also, it's kind of a moot point anyway as trying to buy a decent linear polariser is actually quite difficult - they are never a regular stock line.

The cheaper and popular ones (Marumi, Kenko) do not - but big names like Singhray, B+W even Hoya all produce them.

I'm less convinced of the downsides of using circular polarisers, the arguments about increased flare and reduction in contrast, plus a reduced polarising effect. I've tried hard and failed to detect either.

On the flare and contrast issue, whatever the effect is, I cannot see it, and if it does exist, it is certainly insignificant compared to the general impact on image quality that fitting any filter has - which can be dramatic, depending on circumstances.

This I cannot fully answer yet (I am still learning to get the best of my RAWs), but there is a photographer on Dpreview - Iliah Borg, that often comments on that. My understanding is that the effects though subtle still are there but using standard RAW converters like ACR, LR or Bibble won't show much of a difference. Using the floating point converters that extract the maximum details from RAWs (like RPP or RawMagick) will make it more obvious. But for the details, I'd refer you to check with Iliah (incidentally he is the author of the RawMagick and co-author of the RPP as well as raw processing library).

The other thing I've tried hard to detect is the increased polarising effect of the linear type. On both bright blue skies and reflections, I've been unable to see any difference. Perhaps it's there, but I can't tell. Again, compared to all the other upsides and downsides of using a filter, whatever the effect is, it's not significant in my view.

Though Iliah commented on this as well on Dpreview, I did see the significantly better effect on my B+W LP as opposed to the Kenko UW Pro 1 D. Can now turn the sky nearly black (have not managed it before with Kenko) - not that it is something I do usually ;)

I am not pretending to understand why this is so yet but will try to dig some information up.

I've tried a lot of polarisers over the years and in terms of polarising effect and colour, I've never noticed much difference between them. The big difference has always been flare from uncoated filters, and less flare from coated and multi-coated filters. Apart from that, the reason I like the Hoya HD is because it has all the advantages of every other polariser that I'm aware of, plus it is about 2/3rds of a stop brighter - for no penalty. You can just leave it on, get a brigher viewfinder image and a higher shutter speed. Those are real, significant benefits.

My CPL (Kenko one) does have a funny blue cast - not too much yet noticable comparing to the B+W LP. Before I thought and attributed that to the polarising effect.

IMHO Singhray sell snake oil - and expensive snake oil at that ;)
It is the best I have tried - can't afford it though. It is also very bright as that Hoya HD.
 
When I got mine, I did similar tests on my D200 and it did fine. I have not tried the low-contrast targets but my D200 has troubles focusing in low light and low-contrast cases anyway (may need to somehow clean those AF sensors after years of abuse).



I may said it in a wrong way but it's not the theory that is questioned - that is correct of course. It is that now established belief that LP won't work on SLRs full stop. I would say it needs to be tested. Different cameras has differently built mirror chambers and not all of them affected by polarised light. Plus those LP proponents argue their cause in most of the cases that it largely depends on the usage - for landscapes the AF is (arguably) not needed very often and metering should be carefully done before turning LP to the maximum effect.



I do - they can charge a lot more under the pretence of more difficult manufacturing ;) Seriously though, the difference in prices can be staggering and all of that is what - adding quarter wave plate to the optical sandwich...



The cheaper and popular ones (Marumi, Kenko) do not - but big names like Singhray, B+W even Hoya all produce them.



This I cannot fully answer yet (I am still learning to get the best of my RAWs), but there is a photographer on Dpreview - Iliah Borg, that often comments on that. My understanding is that the effects though subtle still are there but using standard RAW converters like ACR, LR or Bibble won't show much of a difference. Using the floating point converters that extract the maximum details from RAWs (like RPP or RawMagick) will make it more obvious. But for the details, I'd refer you to check with Iliah (incidentally he is the author of the RawMagick and co-author of the RPP as well as raw processing library).



Though Iliah commented on this as well on Dpreview, I did see the significantly better effect on my B+W LP as opposed to the Kenko UW Pro 1 D. Can now turn the sky nearly black (have not managed it before with Kenko) - not that it is something I do usually ;)
I am not pretending to understand why this is so yet but will try to dig some information up.



My CPL (Kenko one) does have a funny blue cast - not too much yet noticable comparing to the B+W LP. Before I thought and attributed that to the polarising effect.


It is the best I have tried - can't afford it though. It is also very bright as that Hoya HD.

I'm not convinced by any of your points Alexey ;) Got to rush out now, but if you want black skies with a circular polariser, here's one.

It also demonstrates that you don't always get patchy skies with a wide-angle and a polariser. You sometimes do, but that has got to do with the angle of the sun, not the lens or the filter. In this shot, the sun is almost directly overhead and the dark 'patch' runs evenly across the top of the frame.

Canon 10-22 at 10mm, Hoya Pro-1 CPL
EPV0118.jpg
 
I'm not convinced by any of your points Alexey ;)

I was not trying to convince you Richard - I still am trying to make sense of this all myself and only say what I saw or read. A few references to Iliah (sometimes cryptic) replies:

This thread

This reply as well

Yet a long time ago in 2004 he said this and this.


Got to rush out now, but if you want black skies with a circular polariser, here's one.

Well I said I could never achieve this on my Kenko - so may be it has to do with cheaper quality make.

Great image btw...
 
I was not trying to convince you Richard - I still am trying to make sense of this all myself and only say what I saw or read. A few references to Iliah (sometimes cryptic) replies:

This thread

This reply as well

Yet a long time ago in 2004 he said this and this.




Well I said I could never achieve this on my Kenko - so may be it has to do with cheaper quality make.

Great image btw...

Thanks for those links Alexey. I do appreciate your time and input with this stuff. It might not be earth shatteringly important, but I think it's interesting nonetheless ;)

But it has to be said that this Eliah guy that you have quoted a) says quite clearly that linear polarisers affect both AF and metering systems in the last link, and b) when asked specifically to explain his apparently contradictory comments, particularly in support of Singh-Ray filters, his replies are rather less cryptic and more simply evasive.

I have to say that reflects the general impression I get of Singh-Ray - gimmicky, and prone to marketing speak and hyperbole. That is a polite way of saying (expensive) bullcrap. On another subject, I have also read Singh-Ray's explanation of why their dark ND filter produces a colour cast, claiming IR interference at the sensor - that's not even bullcrap, just a rubbish filter made worse by (rare) IR issues. That's all BTW, but it just builds a bad impression :)

What this boils down to for me, is that there are real problems using a linear polarising filter on a DSLR. Metering is the major concern, and while I didn't get much of an exposure shift in the tests I did earlier today (under-exposing by 1/3rd stop) they were done indoors with zero polarised light around. I strongly suspect that if I repeated the test under a bright blue sky, things would be much worse. I'll give it a try if the sun ever shines again this week but whatever the outcome the effect is there and is significant.

On the AF test, yes I could get the linear polariser to make the camera under perform, but I really did have to try very hard to do it. On the basis of that test, I would say it's a non-issue.

It would be interesting to see how other cameras behave under the same conditions, but I only have a 5D2 to hand. TBH, all DSLRs are so similar with their metering and AF systems that I'd be surprised if there was much to choose between them.

On the other issues:
Increased flare due to the addition of a quarter-wave plate in a circular polariser, and reduced sharpness: I have looked hard, with the best lenses and filters on the just about the sharpest camera you can get, and been unable to detect anything. If there is a detrimental effect, and you need to go to the lengths you have suggested above to find it, I'm just not going to worry. Certainly compared to the image degradation that you can potentially get by sticking any piece of glass in front of the lens, it's insignificant.
Reduced polarising effect with a CPL - I've done a few tests on this in the past, and have noted zero difference.
Linear polarisers are cheaper - well they might be cheaper to make in theory, but the reality is that they are both hard to come by and quality ones are actually just as expensive.

Sorry, I know I go on a bit, but I've leaned something doing those tests today and thought I'd share it :)

Thanks for your kind comments on the pic. I actually prefered another one I did without the polariser - wish the door was red though :D
 
But it has to be said that this Eliah guy that you have quoted a) says quite clearly that linear polarisers affect both AF and metering systems in the last link, and b) when asked specifically to explain his apparently contradictory comments, particularly in support of Singh-Ray filters, his replies are rather less cryptic and more simply evasive.

He is wrong - I have a Linear Pol and it works identically to a C-Pol right down to AF and metering (I can't see how a Pol could affect TTL metering anyhow)

The AF issue I believed until I tried it myself - tested across several Sony and Nikon bodies - it just "works".
 
But it has to be said that this Eliah guy that you have quoted a) says quite clearly that linear polarisers affect both AF and metering systems in the last link

puddleduck said:
He is wrong - I have a Linear Pol and it works identically to a C-Pol right down to AF and metering

As I said - those two later quotes are from 2004. It seems he since changed his mind and now using LPs only.

b) when asked specifically to explain his apparently contradictory comments, particularly in support of Singh-Ray filters, his replies are rather less cryptic and more simply evasive.

That is in Iliah nature to reply like this and he explained why in one of his posts (can't now find it easily using that darned DPR search) as the purpose is not to let people know something but to arrive to their own conclusion. For Singhray he stated somewhere that they (Singhray) are actually quite good answering technical questions about their filters.

What this boils down to for me, is that there are real problems using a linear polarising filter on a DSLR. Metering is the major concern, and while I didn't get much of an exposure shift in the tests I did earlier today (under-exposing by 1/3rd stop) they were done indoors with zero polarised light around. I strongly suspect that if I repeated the test under a bright blue sky, things would be much worse. I'll give it a try if the sun ever shines again this week but whatever the outcome the effect is there and is significant.

On the AF test, yes I could get the linear polariser to make the camera under perform, but I really did have to try very hard to do it. On the basis of that test, I would say it's a non-issue.

It would be interesting to see how other cameras behave under the same conditions, but I only have a 5D2 to hand. TBH, all DSLRs are so similar with their metering and AF systems that I'd be surprised if there was much to choose between them.


I still would say that it really needs to be tested on the camera. This is simply because my observation on my camera are different from yours. And having recently tried it on D700 (albeit very briefly for about half an hour) I didn't have any problems there either.

On the other issues:
Increased flare due to the addition of a quarter-wave plate in a circular polariser, and reduced sharpness: I have looked hard, with the best lenses and filters on the just about the sharpest camera you can get, and been unable to detect anything. If there is a detrimental effect, and you need to go to the lengths you have suggested above to find it, I'm just not going to worry. Certainly compared to the image degradation that you can potentially get by sticking any piece of glass in front of the lens, it's insignificant.
Reduced polarising effect with a CPL - I've done a few tests on this in the past, and have noted zero difference.

As I said I am still learning about all this and its a slow process. I do like to experiment using RPP (Raw Photo Processor) and LibRaw (directly with RAW data) so I am trying to discover all those things Iliah is talking about but it does take time. Having though tried using CC30M and UniWB on my Nikon it does indeed improve shadows (Iliah again talked about that a few times on DPR) so I tend to take info he provides with interest.

Sorry, I know I go on a bit, but I've leaned something doing those tests today and thought I'd share it :)

I enjoy it - it is always interesting to have conversations with you especially since you do "go on a bit" on various subjects which makes it more interesting (at least for me it does).
 
<snip>

I enjoy it - it is always interesting to have conversations with you especially since you do "go on a bit" on various subjects which makes it more interesting (at least for me it does).

Cheers Alexey. Good banter :)
 
I've been looking for the best price for a Marumi 72mm DHG
[cannot afford a Super DHG]
Clifton Cameras seem to have the best at £51

should you find better prices in your searches - pls let me know

Camera King offer good prices through eBay but I'm of the mind..
"if it's too good to be true...etc"

John

Just got the Marumi DHG 72mm CPL from Camera King through Amazon for about £43 inc postage. first class service and it works a treat. :)

Cheers

Dougie
 
John
Just got the Marumi DHG 72mm CPL from Camera King through Amazon for about £43 inc postage. first class service and it works a treat. :)
Cheers....Dougie

thanks for the info........:thumbs:
 
Hold that last one John.....! I'm getting confused now! I got the CPL from Microglobe (I got the Hoya UV pro from Camera King)
Sorry! :bonk:....Dougie

wondered cos I couldn't find it..:shake:

so, MicroGlobe delivery was OK?
 
I've done a few more tests on polarisers, if anybody's interested ;) Summary: yes, there is a difference between circular and linear polarisers, on both auto-focus and metering in DSLRs, but it's maybe not worth worrying about. And don't buy a cheap polariser!

Circular vs Linear polarisers - affect on exposure metering. The sun shone briefly this morning, so I thought I'd see what difference a bit of blue sky, ie polarised light, had on the 1/3rd of a stop under-exposure I reckoned I had got previously with the linear polariser (see post above). The new outdoor test was inconclusive - it didn't appear to be any worse than the previous indoor tests but since the exposure was varying quite widely anyway due to the large amount of polarised light about and the rotation angle of the filter, I had to conclude that the affect was not worth worrying about so didn't pursue it any further. No doubt it is there, but pretty insignificant overall given that there is usually a bit of chimping and tweaking of exposure anyway when using a polariser.

Still intrigued, I thought I'd repeat my earlier tests with a subject containing zero polarised light, a bit more carefully and controlled this time, so that absolutely the only difference was the effect of the filter on the exposure metering system. I used artificial light on a matt 18% grey card, with no reflections to upset anything. Despite taking even more care, the result was the same.

With the linear polariser, rotating the filter reduced the indicated exposure (incorrectly) by between zero and 1/2 a stop and maybe 2/3rds, depending on the angle of rotation, as best I could estimate. To double check, I did the same test in live view, which of course by-passes the viewfinder metering which is the problem here - indicated exposure was exactly consistent, regardless of the rotation of the linear polariser, as you would expect. Switching to the circular polariser, there was no shift in the indicated exposure, in any mode, again as you would expect.

So, at least with my 5D2, using a linear polarising filter does indeed upset the metering, leading to up to 2/3rds of a stop under-exposure. Not sure how much of an issue that really is in practise, but it's there and I guess is one more variable that we can do without. Other cameras may be better or worse, but I would expect most models to be broadly similar as they all use the same basic technology.

I also did some sharpness tests, to see if I could detect any difference there between the linear and circular polarisers - the theory being that the quarter-wave plate in the ciruclar polariser reduces sharpness. I actually tried a range of filters, by way of a control. I used a 70-200L zoom plus 1.4x telecon, effectively 280mm, as sharpness issues are magnified by focal length.

The worst result by far was from the linear polariser! But hold on, the reason for that is because it is a cheapy Cokin, an old screw-in jobbie I bought secondhand. It was really quite bad, smearing fine detail that looked a little like camera shake or mirror slap, so I repeated it a few times, with mirror-lock up on the tripod. Same result every time - not good.

Results from all the other filters - Hoya Pro-1 UV, Hoya HD CPL, 7DayShop cheapy grad, posh Tiffen HT 4-stops ND, B+W 10 stops ND - were pretty even, and all very good TBH. I could just detect a very slight softening with the 10-stops B+W and also the cheapy 7DayShop grad - they are both a bit thicker than the others - but in terms of sharpness alone I wouldn't hesitate to use any of them. We're talking a very high level of sharpness here, 70-200L 4 IS, at f/8, on 5D2, and no worries.

What I think is happening here with the naff linear polariser, and I've seen it before with cheap polarisers with problems magnified by focal length, is actually the effect of the polarising foil layer in the glass sandwich, which is not perfectly flat and even. So this is a filter manufacturing quality issue, not a polarising filter problem - either linear or circular. Don't buy a cheapy, of either flavour.

I've also done some comparsion flare tests which I think are quite interesting - I posted the images here http://www.talkphotography.co.uk/forums/showthread.php?t=212297 So save you looking, just buy a multi-coated filter, whatever the type. I also think that multi-coating might also be a reasonable indicator of other optical qualities as it's quite expensive to do, based on the theory that nobody would bother to multi-coat a rubbish filter. It's a thought anyway :)
 
Wow, i did get out the can opener out lol.

I ended up ordering a 77mm Hoya HD for the reason Richard makes about the 1.2 stops etc. I was really going to go for the Kaseman but at £130ish from Robert Whites against £84 delivered from HK via fleabay it was a no brainer. I've got an MRC 67mm C-POL plus the cheap green Hoya and to be honest there's not much noticeable difference other than flare as the Hoya isn't coated.

Not in too much of a rush should get it within 10-20 days. Amazon worked out just over £100 so saved around another £20 :thumbs:
 
Wow, i did get out the can opener out lol.

I ended up ordering a 77mm Hoya HD for the reason Richard makes about the 1.2 stops etc. I was really going to go for the Kaseman but at £130ish from Robert Whites against £84 delivered from HK via fleabay it was a no brainer. I've got an MRC 67mm C-POL plus the cheap green Hoya and to be honest there's not much noticeable difference other than flare as the Hoya isn't coated.

Not in too much of a rush should get it within 10-20 days. Amazon worked out just over £100 so saved around another £20 :thumbs:

I reckon it's less than 1.2 stops actually. Camera says nearer 1.0 and using a light meter accurate to 1/10th says 1.1 stops :D
 
Back
Top