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Dodgy Circular Polariser?
Posted:
Fri Jan 06, 2006 3:32 pmby Zeeke
Ive been playing with my sigma 70-200 this afternoon because i think there is something wrong with it.. but.. it may not be the lens at all.. i think its possibly the filter... i used the filter on Oneputt's 80-400 and took 5 or 6 photos with it on.. and the images came out slightly blurry but i didnt take much notice of it.. i havent used the filter on his lens since then but now im back to the 70-200... i think the circular polariser is causing the image to blur.. has anyone else had the same problem with a CPL or any other lens?
Tim
Re: Dodgy Circular Polariser?
Posted:
Fri Jan 06, 2006 3:44 pmby birddog114
Zeeke wrote:Ive been playing with my sigma 70-200 this afternoon because i think there is something wrong with it.. but.. it may not be the lens at all.. i think its possibly the filter... i used the filter on Oneputt's 80-400 and took 5 or 6 photos with it on.. and the images came out slightly blurry but i didnt take much notice of it.. i havent used the filter on his lens since then but now im back to the 70-200... i think the circular polariser is causing the image to blur.. has anyone else had the same problem with a CPL or any other lens?
Tim
No, how can the CPL make the photo blurred?
Posted:
Fri Jan 06, 2006 3:51 pmby sirhc55
A faulty CPL can be caused through the construction of the filter not being up to standard
Edit: a simple test is to take some pics with the 70-200 without the filter!
Posted:
Fri Jan 06, 2006 3:52 pmby Zeeke
Wish i knew but it is.. heres samples.. 100% crop
I set the camera on the tripod, manual settings.. its shooting at f11.. camera was focused on the crack, then set the lens to manual focus so it wouldnt change.. took a shot then fitted the CPL.. and took another shot
Tim
Original... Focused and without CPL
With CPL and Previous Images focusing
Posted:
Fri Jan 06, 2006 3:54 pmby Zeeke
BTW... its a Fotar CPL
Tim
Posted:
Fri Jan 06, 2006 3:56 pmby big pix
this might sound stupid but do you know that you loose 1 1/2 to 2 stops of speed using a polorizer which means if shooting at a 200th without the filter then you will be shooting at 50th with the filter using the same f stop.......
Posted:
Fri Jan 06, 2006 3:58 pmby birddog114
big pix wrote:this might sound stupid but do you know that you loose 1 1/2 to 2 stops of speed using a polorizer which means if shooting at a 200th without the filter then you will be shooting at 50th with the filter using the same f stop.......
Tim,
Does this post from big pix make sense?
Posted:
Fri Jan 06, 2006 3:59 pmby sirhc55
Tim was using a tripod so it should be OK even if the speed drops
Posted:
Fri Jan 06, 2006 4:03 pmby Michael
Tim, I think your prognosis is on the money and since you are no stranger to cameras I think you should go with your gut instinct.
and find another CPL.
Posted:
Fri Jan 06, 2006 4:04 pmby Zeeke
The only difference between the 2 images is that one was fitted with the CPL.. all the settings were the same... the CPL is causing the lens to give soft focusing... and yes... the camera was fitted on a tripod.. so slower shutter speed shouldnt effect the image as much as it did with the images i posted.... i guess i got a faulty CPL.. not a faulty lens
Tim
Posted:
Fri Jan 06, 2006 4:07 pmby stubbsy
Is it definitely a CIRCULAR polariser. If it's a linear polariser that can stuff up a digital camera's auto focus and metering. If it weren't for the fact you did this manual it would be my first guess. Just posting on the off chance
Posted:
Fri Jan 06, 2006 4:10 pmby Zeeke
Unless they stuffed up with the stamping on the side.. id say yes is deffinantly a CPL.. it has on the side
"FOTAR 77mm C-P.L Japan"
Tim
Posted:
Fri Jan 06, 2006 4:13 pmby stubbsy
Well it WAS a long shot. I'm guessing you've checked the filter is clean and not smeared with vaseline
And now I'm out of useless ideas. Sorry couldn't help Tim.
Posted:
Fri Jan 06, 2006 4:35 pmby Zeeke
Yerh its clean... i try and keep my camera gear spotless... like my fishing gear... .. easier fix i think if its just the CPL and not the lens...
Tim
Posted:
Fri Jan 06, 2006 5:51 pmby birddog114
Zeeke wrote:Yerh its clean... i try and keep my camera gear spotless... like my fishing gear... .. easier fix i think if its just the CPL and not the lens...
Tim
Maybe Sigma doesn't like FOTAR C-P.L Japan and Nikkor does
Posted:
Fri Jan 06, 2006 6:03 pmby Zeeke
maybe Nikkor doesnt either.... because as i said in my first post, the first time i used Oneputts 80-400 i took a few photos and the images came out blurry, i think there is something wrong with the filter and not the lenses...
Tim
Posted:
Fri Jan 06, 2006 6:17 pmby birddog114
Zeeke wrote:maybe Nikkor doesnt either.... because as i said in my first post, the first time i used Oneputts 80-400 i took a few photos and the images came out blurry, i think there is something wrong with the filter and not the lenses...
Tim
Why should Oneputt left the CPL on his 80-400 for? A trick for you to find?
Posted:
Fri Jan 06, 2006 6:49 pmby Zeeke
I used my 77mm CPL on Oneputt's 80-400 and it caused the same blurry images as it did on my 70-200...
Tim
Posted:
Fri Jan 06, 2006 7:56 pmby big pix
Birddog114 wrote:big pix wrote:this might sound stupid but do you know that you loose 1 1/2 to 2 stops of speed using a polorizer which means if shooting at a 200th without the filter then you will be shooting at 50th with the filter using the same f stop.......
Tim,
Does this post from big pix make sense?
The basic understanding of exposure and f stop using speed, f stop and iso...........
Posted:
Fri Jan 06, 2006 8:21 pmby mudder
If both those shots are using the same focus and the increased exposure time hasn't contributed to the blurring (I assume not as it's of a static object) then the CPL does look dodgy... Especially if it's occured on more than one lens...
Posted:
Fri Jan 06, 2006 10:04 pmby Zeeke
I'm leaning on the polariser being dodgy... when i can ill try another polariser on it to double check its not a once off..
Tim
Posted:
Fri Jan 06, 2006 10:50 pmby Dug
