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Wratten filter gels


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#1 Edgar Nyari

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Posted 07 August 2015 - 05:22 AM

Hi,

 

I have this old Kodak Wratten filter lying around, and I'm not sure if I can put it to good use. I have a mattebox with metal trays, and I was wondering if the filter can be placed on the mattebox like a glass filter. The filter is 100mmx100mm, which slightly smaller than 4x4, so I guess I'd need something to hold it. Is it possible to make a cardboard frames for it, and sandwitch the gel in between two such frames, so that it's sturdy enough to be held in the tray.

 

Sorry for the beginner's question.

 

thanks

 

Edgar


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#2 aapo lettinen

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Posted 07 August 2015 - 08:37 AM

you would need a holder so that the gel does not warp in the filter frame. I don't use wratten gels but I use normal light filters for special fx and have Lee plastic 4x4 holders for that purpose, they seem to work OK for this. 

Gels damage very easily so if you could get two thin 4x4 glass plates you could sandwich the gel between them 


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#3 Gregg MacPherson

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Posted 07 August 2015 - 05:06 PM

What is the filter? What camera do you want to use the filter for?  Cameras like the Bolex and the Eclair ACL had small behind the lens filter slides for this gel filter.  I remember taping some in place in the lens port of a Beaulieu R16.  It's really convenient for the color correction.  I don't think the gel sits flat in those holders and I don't think it ever mattered,  but they are well protected from stray light back there.  Lens collimation of wide angle lenses was in theory affected by the behind the lens gel but I think some people got away with that.


Edited by Gregg MacPherson, 07 August 2015 - 05:08 PM.

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#4 Edgar Nyari

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Posted 07 August 2015 - 08:54 PM

Hi and thanks for your replies,

 

to answer your questions Gregg: The filter is 85B and the camera (Arri 35-III) doesn't have the behind-the-lens option.

 

I actually managed to use it without problems today. What I did was cut two black cardboard frames, and sandwiched the gel in between. It works just fine. Though I can already tell it's not such a good idea on a windy day.

 

Edgar


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#5 Gregg MacPherson

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Posted 07 August 2015 - 09:05 PM

... two black cardboard frames, and sandwiched the gel in between. It works just fine. Though I can already tell it's not such a good idea on a windy day.

 

 

Well thought (some sort of smiley face)


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#6 Gregg MacPherson

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Posted 07 August 2015 - 09:18 PM

Edgar,

I gather that this is for personal stuff that you are shooting and you would save bucks if you can? Do you have a 4x5.65 (PV size) box?  If you can get or customize a 4x5.65 tray that accepts 4.5" rounds then you can access lots of cheaper filters on ebay.  If you need some 85ND 4-1/2 rounds I have some here,  may cover the set,  cheap. 

 

Just make sure that we can cover image circle of the lenses you are using.  If you have a 4-1/2 round,  tape it into a tray somehow and try it.  Or just use a rectangle of black card with a circle cut out.  This will show any vignette.


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#7 Edgar Nyari

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Posted 08 August 2015 - 09:05 AM

Hi, yes, I was planning on buy some glass filters, but wanted to see if I can make use of this gel at least temporarily. As you suspected, the price is a major consideration because this is my personal stuff. And yes, I do have a 4x5.65 tray in my matte-box set. I also have a 4x6 tray, Thanks for the tip. I'd much rather find a rectangular one of the correct size, because once I get it it's a permanent solution. For now I'll use the gel.


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#8 Stuart Brereton

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Posted 09 August 2015 - 12:56 AM

Just make sure that we can cover image circle of the lenses you are using. 

Image Circle is a term which refers to the light transmitted by a lens onto a sensor or film negative. I think you are referring to the front element of a lens, which is different. 


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#9 Gregg MacPherson

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Posted 09 August 2015 - 01:29 AM

Hey,  Stuart,
maybe I got lazy or had a brain fart there...Lets see. If we mask the front of a lens with a circular element that is too small, let's say a 4-1/2" round,  which might reduce (or could we say, reduce, or crop) the image circle of the lens,  the circular projected image at the film plane,  we might legitimately worry whether that filter,  it's diameter,  can allow the image circle or not.  Can it cover the image circle.

 

To say "cover the image circle" ?.  Perhaps its a bit wingy.  Nah,  not really,  but maybe...

Are we clear?

 

I thought that the writers, dreamers and philosphers were the pedantic ones,  not the cinematographers.


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#10 Stuart Brereton

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Posted 09 August 2015 - 10:10 AM

You call it pedantic. I call it accurate. To say that something is cutting into the image circle would imply that it was happening behind the lens.

 

The term you want is Field of View.


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#11 David Mullen ASC

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Posted 09 August 2015 - 10:23 AM

Generally if a front filter is too small and cuts into the picture area, we call that vignetting, though I guess a vignette could happen behind the lens too.


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#12 Gregg MacPherson

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Posted 09 August 2015 - 01:27 PM

...I guess a vignette could happen behind the lens too.

 

Stuart might not agree with that.

But I promise him that I will choose my words more carefully next time (some sort of round yellow laughing emotidoodle). 

 

Having an acurate,  common, pragmatic language to discuss lenses is good.  After all,  there's not much poetry in there eh (the I just couldn't help myself emoticon).


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#13 Stuart Brereton

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Posted 09 August 2015 - 03:34 PM

 

Stuart might not agree with that.

But I promise him that I will choose my words more carefully next time (some sort of round yellow laughing emotidoodle). 

 

Having an acurate,  common, pragmatic language to discuss lenses is good.  After all,  there's not much poetry in there eh (the I just couldn't help myself emoticon).

Why would I not agree with that? Vignettes behind the lens can happen. they're just not caused by things in front of the lens.

 

Using the correct terminology might not mean much to you, but I find that accuracy in technical conversations usually helps to avoid confusion.


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#14 Gregg MacPherson

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Posted 09 August 2015 - 05:55 PM

Why would I not agree with that? Vignettes behind the lens can happen. they're just not caused by things in front of the lens.

 

Using the correct terminology might not mean much to you, but I find that accuracy in technical conversations usually helps to avoid confusion.

 

If I have to explain my jokes I will feel sad.  It would be easier if you cultivated a sense of humour.

 

Vignetting,  I thought,  commonly refered to something happening at the edges of an image.  An image,  not the front of a lens.  It's softer or darker there (in the image),  or completely matted.  So,  I thought that this was the common technical meaning.  But DoP or camera crew,  needing a shorthand, a fast language,  when using the word "vignette" have their attention understandably looking at the front of the lens.  So we say that this round filter or diopter etc, is vignetting.  So they are thinking of what caused the vignette,  not the vignette itself.

 

Language belongs to those who use it.  But any respectful person will allow for the history,  the place that the words came from.  And some logical readjustments.

A sense of humour helps.

Stuart,  if you aren't laughing by now,  well I just don't know what I can do.

Gregg.


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#15 Stuart Brereton

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Posted 09 August 2015 - 11:22 PM

Doesn't change the fact that what you are talking about is whether a filter will cover the field of view of a given lens, not the image circle. I'm sorry if using correct terminology is difficult for you.

 

"A sense of humor helps". Well apparently, I have no sense of humor. I also don't suffer fools. Make of that what you will.


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#16 Gregg MacPherson

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Posted 10 August 2015 - 12:22 AM

Doesn't change the fact that what you are talking about is whether a filter will cover the field of view of a given lens, not the image circle. I'm sorry if using correct terminology is difficult for you.

 

"A sense of humor helps". Well apparently, I have no sense of humor. I also don't suffer fools. Make of that what you will.

 

I don't think me straying into ambiguous language is enough excuse for this bad humour.  Meaning,  the reverse of good humour.  To make fun of your "I don't suffer fools" phrase,  I think you would have suffered less if I was a fool.  So well done there,  some precise language.

 

No one likes to be thought of as a humourless twep,  but all that dissapears as soon as we laugh,  especially at ourselves.  Give it a try.


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#17 Stuart Brereton

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Posted 10 August 2015 - 03:56 AM

 

 Give it a try.

I will. As soon as I 'cultivate a sense of humor', I'll be happy to laugh at you.


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#18 Gregg MacPherson

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Posted 10 August 2015 - 06:04 AM

 As soon as I 'cultivate a sense of humor', I'll be happy to laugh at you.

 

You do have some challenges there,  but I have been trying to help.


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