blurry pictures with CPL

[mrjames]

Hi, I purchased some of the fire sale jacobs filters, and I was very happy with my 77mm CPL on my 17-40

I went out in the snow last week and my gear got soaked (not to worry as it's a 1 series camera and sealed lens)

but I was shooting with my 70-200 yesterday and I could not get a sharp shot with the polariser on- even with live view when manual focussing there was a 'haze' over the image.

I put the filter back on my 17-40 and there's no, or very little difference, only on the 70-200 (and more so at the 200mm end) do I see a real drop in IQ

is this just an issue of using a crappy filter with a telephoto lens which exaggerates the filter flaws more than a wide angle lens?
or does it have something to do with it getting wet- moisture between the 2 inner surfaces?


I have heard the way to check filter quality is to look through it with binoculars- so I guess that points to the fact that telephoto lenses are more demanding on filters? I will have to do more tests

 

[BacktotheFuji]

The 70-200mm is known for having issues with CPL filters I believe, give it a Google.

 

[HoppyUK]

Hi, I purchased some of the fire sale jacobs filters, and I was very happy with my 77mm CPL on my 17-40

I went out in the snow last week and my gear got soaked (not to worry as it's a 1 series camera and sealed lens)

but I was shooting with my 70-200 yesterday and I could not get a sharp shot with the polariser on- even with live view when manual focussing there was a 'haze' over the image.

I put the filter back on my 17-40 and there's no, or very little difference, only on the 70-200 (and more so at the 200mm end) do I see a real drop in IQ

is this just an issue of using a crappy filter with a telephoto lens which exaggerates the filter flaws more than a wide angle lens?or does it have something to do with it getting wet- moisture between the 2 inner surfaces?


I have heard the way to check filter quality is to look through it with binoculars- so I guess that points to the fact that telephoto lenses are more demanding on filters? I will have to do more tests

Exactly that. The longer the lens, the worse it gets.

Basically longer lenses only look through a small portion of the filter in the middle. Therefore small imperfections become greatly magnified and have a much bigger impact on sharpness.

 

[mrjames]

The 70-200mm is known for having issues with CPL filters I believe, give it a Google.

i've googled it and I can't see anything specific to the 70-200, only people complaining about cheapo CPL's, so I might try a b&w and see if it fixes the problem

I might try and see if it's a problem with my 50mm hand held, or with the 40mm end of the 17-40
I only really use it for wide angle at 17mm

 

[mrjames]

Exactly that. The longer the lens, the worse it gets.

Basically longer lenses only look through a small portion of the filter in the middle. Therefore small imperfections become greatly magnified and have a much bigger impact on sharpness.

thanks, I get that- but it's as if the lens was smeared with vaseline.

should it be this bad?
it's a jacobs own brand filter- and many of the people buying these filters will be people with 55-250 lenses, so do they just assume that people will only use them for wide angle shooting?

no filter

filter

same shutter speed and apperture

 

[hoolio]

Same shutter speed and aperture, that's not right unless ISO is changing?

 

[HoppyUK]

thanks, I get that- but it's as if the lens was smeared with vaseline.

should it be this bad?
it's a jacobs own brand filter- and many of the people buying these filters will be people with 55-250 lenses, so do they just assume that people will only use them for wide angle shooting?

no filter

filter

same shutter speed and apperture

That's terrible, but you've also got a lot of camera-shake there. You can tell by the downwards direction of the blur pattern. And yes I know it was taken at 1/250sec - it's still mostly camera shake.

And some back-focus too I think. It's not uncommon for poor grade filters to shift focus.

 

[BacktotheFuji]

What happens if you manually focus?

I'm sure one of the sellers of these filters on ebay added a note to say that it wasn't compatible with the 70-200mm lenses from Canon.

 

[Maggie52]

Strangely enough I bought a cpl from Jacobs and found the same thing on my 70-300. Looked like a haze or smear on the lens I kept cleaning it thinking it was something I had done. Took it off in the end and gave up.

 

[BacktotheFuji]

I should add, that my 6D struggles to focus at infinity when using the black Jacobs CPL on my Tamron 28-75/2.8 at infinity. When it locks (or is focused manually), the quality is very good however...I can't see a difference between the Jacobs filter and my Marumi DHG CPL other than a warmer colour cast.

 

[Riz_Guru]

It looks like it's the filter.

I've ordered some HOYA Pro-1 UV Digital filters for my lenses, hope they work.

Riz

 

[PitaDaVespa]

mrjames,

Did the filter also got wet?
I believe all CPL filters have two glass elements. In that case, you filter may have "water inside", creating that unwanted effect.

 

[ecoleman]

This is an issue with the Jacobs filters and the 70-200 lens. I also bought some and even got the cpl replaced, but the replacement was exactly the same. Seller gave me a refund and also said he had other complaints of blurred images with the 70-200 lens.

 

[mrjames]

Same shutter speed and aperture, that's not right unless ISO is changing?

the picture is lit completely with flash
so it's just the flash output that varies

That's terrible, but you've also got a lot of camera-shake there. You can tell by the downwards direction of the blur pattern. And yes I know it was taken at 1/250sec - it's still mostly camera shake.

And some back-focus too I think. It's not uncommon for poor grade filters to shift focus.

there might be some focus shift- but even manual focus, on live view it looks this bad throughout the whole focus range

you mention camera shake but every shot is this bad, so it's 100% the filter

What happens if you manually focus?

I'm sure one of the sellers of these filters on ebay added a note to say that it wasn't compatible with the 70-200mm lenses from Canon.[/QUOTE
manual focus is just as bad- so it's not an AF issue
so either it's incompatibility with the 70-200 or it's just a general cheap filter with tele lens issue- if I had a 300mm prime to test it out on I could isolate the issue

Strangely enough I bought a cpl from Jacobs and found the same thing on my 70-300. Looked like a haze or smear on the lens I kept cleaning it thinking it was something I had done. Took it off in the end and gave up.

this makes me think it's more that the filter is junk, rather than a specific issue with 70-200 lenses

mrjames,

Did the filter also got wet?
I believe all CPL filters have two glass elements. In that case, you filter may have "water inside", creating that unwanted effect.

the filter possibly did get wet- but it's been about a week since then, and to look through the filter I can see no smearing or anything

This is an issue with the Jacobs filters and the 70-200 lens. I also bought some and even got the cpl replaced, but the replacement was exactly the same. Seller gave me a refund and also said he had other complaints of blurred images with the 70-200 lens.

hmm, other than the 70-200 what other popular tele lenses are 77mm? So maybe it is just an incompatibility with telephoto lenses- because I use it on my 17-40 stacked with a 3 stop ND and my images were sharp as a tack- but i'll try it again tomorrow just in case there is moisture between the glass- but when I first bought it before xmas, it was fine, but I never used it on the 70-200 until the other day

 

[ecniv]

Silly point probably, but surely the filter will reduce light getting in, so will need a slower shutter or higher iso to compensate..?

I have a Zeikos cpl 77mm for the Tokina and when shooting over the weekend (practice) it required a forced under exposure of -1. Somehow it was being fooled by the amount of light entering. Handheld in sunlight. I haven't processed the pics yet.

Thought it might be that...
My 2p

 

[PitaDaVespa]

hmm, other than the 70-200 what other popular tele lenses are 77mm? So maybe it is just an incompatibility with telephoto lenses- because I use it on my 17-40 stacked with a 3 stop ND and my images were sharp as a tack- but i'll try it again tomorrow just in case there is moisture between the glass- but when I first bought it before xmas, it was fine, but I never used it on the 70-200 until the other day

Well, in that case, and if with other lenses it's ok, maybe the 70-200 doesn't like that filter. :shrug: