uv and polarizer?

Marcus Marchesseault · September 8th, 2007, 04:28 AM

The V1 doesn't seem to need a polarizer. I don't think polarized light is used for AF and AE anymore.

The polarizer must rotate in order for it's filtration to line up with the polarized waves of light. The visual analogy I use is that the polarized light that bounces off a shiny surface must be blocked with a "shield" that is perpendicular to it's orientation. Depending on the angle of the sun to your shiny surface, the angle of the light you want to filter will change. Without finding the correct alignment, the filter will not have a desirable effect.

Polarized light is light moving in waves of the same orientation. For example, the ocean has all of it's waves moving up and down. Since light can orient in any 3D wave pattern, it can have side-to-side, diagonal, or any orientation. A polarizer blocks waves coming in at one orientation but lets the others pass. Since light reflected off a shiny surface acquires polarization, it can be singled out for filtration. This is what allow a camera with a polarizer to "see" through the shine on water or leaves. The net result is that the color underneath the shiny highlights can be seen as long as you have rotated the filter to align with the polarized highlights.

Piotr Wozniacki · September 8th, 2007, 04:35 AM

Quote:

Originally Posted by Marcus Marchesseault

The V1 doesn't seem to need a polarizer. I don't think polarized light is used for AF and AE anymore.

You got me lost here Markus - do you mean it doesn't need a *circular* polarizer? That's exactly what I heard (only it was so long ago I confused it with HD cameras being ok with linear pols; it's of course about their AF and AE systems).

If a linear is OK, and better still - could fit under the lens hood, where to search for one?

Leslie Wand · September 8th, 2007, 05:07 AM

[QUOTE=If a linear is OK, and better still - could fit under the lens hood, where to search for one?[/QUOTE]

ah - back to square one - especially so with the kit wa. and hood - nothing fits under it, and even if it did, how would you rotate it?

leslie

Piotr Wozniacki · September 8th, 2007, 05:25 AM

Fair enough, Leslie. So much for a cheap, low-profile sky-puncher:)

Bob Grant · September 8th, 2007, 06:00 AM

I have a Cokin filter system I bought 30 years ago for my OM-1. It's a good system for the money however for video / film use there's drawbacks.

The seriously expensive matte boxes load the filters into a carrier and this isn't just to justify the high prices associated with all that precision machining. When the filters and the carriers are in the matte box light can only get in one way, the Cokin system lets light into the top of the filters. Standing in the bright Australian sun with light coming in the top of the filters I think you'd have a problem. One could address this issue in some ways (gaffe tape?) but loose a lot of the functionality.
Another issue to consider, not all the light that hits a filter goes through the filter, same goes for a lens. Light can bounce around between two filters or a filter and a lens. Careful design is needed both of the filters and the matte box to minimise this. Using the smallest possible number of filters also probably helps. Another issue is the quality of the filters. Some ND filters don't block IR, that can cause color shifts (CCDs are very sensitive to IR) and might throw auto focus and AE systems out of whack.

Leslie Wand · September 8th, 2007, 06:58 AM

evening bob, like rust, you never sleep ;-)

you're obviously quite right in your observations - that's why i liked the formatt matte box with the little flap over the filter slots, one of which is rotatable. it looks like this is going to be my final solution - it's about as 'cheap' a box as i can get, without resorting to the indian line from ebay - which look appealing though i'm loathed to buy before i know a great deal more about them. unfortunately, i've sent a good many emails recently to various people there and have got 'this is most suitable for your camera' replies from all of them, but no answers to any of the technical questions i asked...

my problem now is finding the best 'cheap' polarising 4 x 4 filter. cavision make one for $55us,

http://cavpol.notlong.com

followed by most others at around $150us, then jumping to $250us. i'm left wondering what $55 get's me compared to the $150

http://tifpol.notlong.com

after all, i'm not shooting for bertolucchi, just bloody horses and landscapes, so i'm not after perfection, just as close to it as possible for as little as possible....

good night one and all, it's almost 11 and though i no longer need my beauty sleep, my brain needs to rest those few active cells left functioning.

leslie

Marcus Marchesseault · September 8th, 2007, 07:49 AM

You might want to try cinevate.com for a $530US matte box that has two rotating filter stages. It also has a french flag and side flags (possibly optional).

You might also want to consider that a matte box probably requires a rail system which adds quite a bit to the cost and bulk of the camera.

Nevermind, I see that the Formatt screws onto the filter threads instead of mounting to rails.

Leslie Wand · September 8th, 2007, 11:41 PM

[QUOTE=Nevermind, I see that the Formatt screws onto the filter threads instead of mounting to rails.[/QUOTE]

thanks marcus,

yes, that's why i'm leaning towards the formatt, and the fact that bob showed me his - which was reasonably well made, light, and would seem to fit the bill. the other alternative was the cavision, but it's more money and a bit more sophisticated - but what i'm after is plain and simple and cost effective, after all, what i really what is a glorified sunshade and somewhere to rotate a polarizer...

again, thanks everyone for your constructive thoughts...

leslie

Leslie Wand · September 22nd, 2007, 02:20 AM

okay - finally settled and received this one from india - ebay item 120082040810

almost immediate delivery.

pro's: cheap, reasonably well made, does the job i want. it doesn't have a rotating filter stage, but works with either 4x4 or (i have yet to get one) circular filter. don't workwith grads so not a problem. truth is, my sunglasses dont rotate either and they work well enough ;-)

con's: dont make a 86mm t0 95mm adaptor. however, cheapskate that i am - a plastic down pipe box for guttering has the cicular bit, ready for it - 90mm internal, 94.5mm external. one wrap of gaffer tape and i now have a rock solid hood on my sony kit wide angle.

would i do otherwise knowing what i know now? probably not. i appreciate the engineering that goes into proper matte boxes (i used to have one on my 400sp rig), but for what i want, and can afford in retirement, they're out of my league.

my home made improvisation is as good as it gets.

so far, don't see the need (literally) for rotating stage. i generally set up my shots with teh sun in optimum position, so the polarizer by default works at it's best (yes took it off and turned it to check).

cost (aus$) box 175, cavision pol. 85, down pipe 2.50. so, for around 275 i have what i needed, and as an added bonus, the rig now looks more pro than ever - not that that matters to me, but the clients are impressed enough to NOT quibble with my fees...

leslie

September 8th, 2007, 05:25 AM	#19
Piotr Wozniacki Inner Circle Join Date: Aug 2006 Location: Poland Posts: 4,086	Fair enough, Leslie. So much for a cheap, low-profile sky-puncher:) __________________ Sony PXW-FS7 \| DaVinci Resolve Studio; Magix Vegas Pro; i7-5960X CPU; 64 GB RAM; 2x GTX 1080 8GB GPU; Decklink 4K Extreme 12G; 4x 3TB WD Black in RAID 0; 1TB M.2 NVMe cache drive

September 8th, 2007, 04:28 AM	#16
Marcus Marchesseault Trustee Join Date: Nov 2005 Location: Honolulu, HI Posts: 1,961	The V1 doesn't seem to need a polarizer. I don't think polarized light is used for AF and AE anymore. The polarizer must rotate in order for it's filtration to line up with the polarized waves of light. The visual analogy I use is that the polarized light that bounces off a shiny surface must be blocked with a "shield" that is perpendicular to it's orientation. Depending on the angle of the sun to your shiny surface, the angle of the light you want to filter will change. Without finding the correct alignment, the filter will not have a desirable effect. Polarized light is light moving in waves of the same orientation. For example, the ocean has all of it's waves moving up and down. Since light can orient in any 3D wave pattern, it can have side-to-side, diagonal, or any orientation. A polarizer blocks waves coming in at one orientation but lets the others pass. Since light reflected off a shiny surface acquires polarization, it can be singled out for filtration. This is what allow a camera with a polarizer to "see" through the shine on water or leaves. The net result is that the color underneath the shiny highlights can be seen as long as you have rotated the filter to align with the polarized highlights.

September 8th, 2007, 05:07 AM	#18
Leslie Wand Trustee Join Date: Mar 2004 Location: upper hunter, australia Posts: 1,410	[QUOTE=If a linear is OK, and better still - could fit under the lens hood, where to search for one?[/QUOTE] ah - back to square one - especially so with the kit wa. and hood - nothing fits under it, and even if it did, how would you rotate it? leslie

September 8th, 2007, 06:00 AM	#20
Bob Grant Trustee Join Date: Nov 2005 Location: Sydney Australia Posts: 1,570	I have a Cokin filter system I bought 30 years ago for my OM-1. It's a good system for the money however for video / film use there's drawbacks. The seriously expensive matte boxes load the filters into a carrier and this isn't just to justify the high prices associated with all that precision machining. When the filters and the carriers are in the matte box light can only get in one way, the Cokin system lets light into the top of the filters. Standing in the bright Australian sun with light coming in the top of the filters I think you'd have a problem. One could address this issue in some ways (gaffe tape?) but loose a lot of the functionality. Another issue to consider, not all the light that hits a filter goes through the filter, same goes for a lens. Light can bounce around between two filters or a filter and a lens. Careful design is needed both of the filters and the matte box to minimise this. Using the smallest possible number of filters also probably helps. Another issue is the quality of the filters. Some ND filters don't block IR, that can cause color shifts (CCDs are very sensitive to IR) and might throw auto focus and AE systems out of whack.

September 8th, 2007, 06:58 AM	#21
Leslie Wand Trustee Join Date: Mar 2004 Location: upper hunter, australia Posts: 1,410	evening bob, like rust, you never sleep ;-) you're obviously quite right in your observations - that's why i liked the formatt matte box with the little flap over the filter slots, one of which is rotatable. it looks like this is going to be my final solution - it's about as 'cheap' a box as i can get, without resorting to the indian line from ebay - which look appealing though i'm loathed to buy before i know a great deal more about them. unfortunately, i've sent a good many emails recently to various people there and have got 'this is most suitable for your camera' replies from all of them, but no answers to any of the technical questions i asked... my problem now is finding the best 'cheap' polarising 4 x 4 filter. cavision make one for $55us, http://cavpol.notlong.com followed by most others at around $150us, then jumping to $250us. i'm left wondering what $55 get's me compared to the $150 http://tifpol.notlong.com after all, i'm not shooting for bertolucchi, just bloody horses and landscapes, so i'm not after perfection, just as close to it as possible for as little as possible.... good night one and all, it's almost 11 and though i no longer need my beauty sleep, my brain needs to rest those few active cells left functioning. leslie

September 8th, 2007, 07:49 AM	#22
Marcus Marchesseault Trustee Join Date: Nov 2005 Location: Honolulu, HI Posts: 1,961	You might want to try cinevate.com for a $530US matte box that has two rotating filter stages. It also has a french flag and side flags (possibly optional). You might also want to consider that a matte box probably requires a rail system which adds quite a bit to the cost and bulk of the camera. Nevermind, I see that the Formatt screws onto the filter threads instead of mounting to rails.

September 8th, 2007, 11:41 PM	#23
Leslie Wand Trustee Join Date: Mar 2004 Location: upper hunter, australia Posts: 1,410	[QUOTE=Nevermind, I see that the Formatt screws onto the filter threads instead of mounting to rails.[/QUOTE] thanks marcus, yes, that's why i'm leaning towards the formatt, and the fact that bob showed me his - which was reasonably well made, light, and would seem to fit the bill. the other alternative was the cavision, but it's more money and a bit more sophisticated - but what i'm after is plain and simple and cost effective, after all, what i really what is a glorified sunshade and somewhere to rotate a polarizer... again, thanks everyone for your constructive thoughts... leslie

September 22nd, 2007, 02:20 AM	#24
Leslie Wand Trustee Join Date: Mar 2004 Location: upper hunter, australia Posts: 1,410	okay - finally settled and received this one from india - ebay item 120082040810 almost immediate delivery. pro's: cheap, reasonably well made, does the job i want. it doesn't have a rotating filter stage, but works with either 4x4 or (i have yet to get one) circular filter. don't workwith grads so not a problem. truth is, my sunglasses dont rotate either and they work well enough ;-) con's: dont make a 86mm t0 95mm adaptor. however, cheapskate that i am - a plastic down pipe box for guttering has the cicular bit, ready for it - 90mm internal, 94.5mm external. one wrap of gaffer tape and i now have a rock solid hood on my sony kit wide angle. would i do otherwise knowing what i know now? probably not. i appreciate the engineering that goes into proper matte boxes (i used to have one on my 400sp rig), but for what i want, and can afford in retirement, they're out of my league. my home made improvisation is as good as it gets. so far, don't see the need (literally) for rotating stage. i generally set up my shots with teh sun in optimum position, so the polarizer by default works at it's best (yes took it off and turned it to check). cost (aus$) box 175, cavision pol. 85, down pipe 2.50. so, for around 275 i have what i needed, and as an added bonus, the rig now looks more pro than ever - not that that matters to me, but the clients are impressed enough to NOT quibble with my fees... leslie