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Using a Roscosun 85 filter in place of (recommended) Kodak Wratten filter type 85 - help desperately needed and greatly appreciated!


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#1 Eloise Maree

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Posted 05 October 2012 - 06:44 AM

Dear cimematography.com community,

I’m a fine arts student based in Sydney, Australia, and I’m shooting a short film using a Bolex (this is the only film camera my university loans out, though I do love its straightforwardness so).

As I’m shooting indoors as well as outdoors, occasionally in low light conditions, it was recommended to me that I purchase Kodak Vision 3 200T film, and so I did (I am no film stock expert, so happily took the advice of the Kodak rep I spoke to). I of course need to use an 85 filter (according to the film can) to convert my stock’s speed rating for shooting the daylight, sunlit scenes; what I was not aware of, however, is that my uni does not have any such filters (can you believe it?)!

I contacted a range of labs to see if they sold any 85 gel filters that I could use -within- the Bolex, in it’s special filter holder, however nobody seemed able to help me (everybody was selling glass lens filters, which would be impossible to cut to fit, I imagine). As a result I am quite concerned, as my shoot is in a week’s time and I don’t know what to do!

The kind people at Rosco Australia, however, gave me a sample sheet of their Roscosun 85 filter (“3401 Roscosun 85… Standard window correction to convert 5500K daylight to 3200K… optically clear”, apparently). I do believe this is meant to be used on lights, not in a Bolex filter holder, however.

Short of performing a test to see if this gel works as a filter (which I so sadly cannot afford to do), does anyone have any suggestions as to whether this might work? Might I be compromising image quality using this gel as a filter, or should everything be fine and dandy?

Any help would be -greatly- appreciated!

Thank you ever so much,

Eloise x
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#2 John Holland

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Posted 05 October 2012 - 07:12 AM

I think you will find it to thick to fit into the Bolex filter holder, plus its not optical perfect so could cause soft focus .
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#3 Adrian Sierkowski

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Posted 05 October 2012 - 07:53 AM

While it's good practice to use an 85 on 200T when shooting outside; you can just shoot a grey card and have them time out the blue in the TC.I wouldn't really wanna throw gel filters in that behind the lens bolex thing.
Another option would be seeing if you can buy a cheap screw-on stills photo filter and just taping it on the front of the lens if you need to-- though I'm sure you should be able to track down an appropriately sized screw on filter.
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#4 Eloise Maree

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Posted 05 October 2012 - 08:14 AM

Thanks for your replies John and Adrian!

John, the Roscosun sample card reads "optically clear"- what do you mean by it might not be optically perfect? I'd love any clarification you might be able to offer as I really don't know much about filters/ gels..

Also, Adrian, what do you mean by "time out the blue in the TC"? (I'm really not up with film speak, sorry!)

Also, are you able to explain to me the difference between using a gel filter behind the lens and screwing a photo filter onto the lens? :) (I'm a total novice, though super keen to know more!)
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#5 Adrian Sierkowski

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Posted 05 October 2012 - 08:27 AM

The gel filters, well they're not really designed to work in front of a camera lens-- If I am understanding what you have-- it is CTO which is a gel sheet for lighting. It can roll and bend ect, and just basically distort light-rays. Hence why you wouldn't really use it on a camera-- though the Bolex did house a filter-holder for behind the lens I don't really know of anyone who has used it or tried to.

As for timing it out in the TC, once you shoot and develop you'll need to telecine or in some way scan your negative film in order to work with it. Timing it out in post would just be correcting the blue bias in the shot. This is done very often as it is a common situation-- from something as simple as forgetting to put the 85 filter on, to having to pull it to get that extra 2/3rds of a stop exposure, or pulling it because you need more filters than you have filter trays in your matte-box, sufficient to say colorists will often seen footage with a blue hue from shooting Tungsten stock, or balance, under daylight. They will correct it while scanning it-- hopefully-- else you can do it @ home pretty simply. Programs such as Resolve and Color actually have auto-color buttons which can do a respectable job of cleaning up clue-biases.
The point of shooting a grey card would be to give the colorist what is a known value which they can correct to. They will see the grey-card is not grey, it's blue, so they'll correct to balance it back to normal.

hope that makes some sense.

Also do try to recall, film is MUCH more forgiving than digital.
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#6 Eloise Maree

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Posted 05 October 2012 - 08:51 AM

Thanks so much for that Adrian, it's so good to finally be talking to a pro (there's a definite shortage of them at my uni ;)).

I'll contact Deluxe (as they're doing my transfer) to check what sort of grade they offer!

Just quickly, though, if I were to want to shoot half my shots without a filter and half with, do you think the focus would be that much softer with the Roscosun filter?

Best,

Eloise
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#7 Adrian Sierkowski

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Posted 05 October 2012 - 08:55 AM

I honestly can't say. On the one hand, It won't be perfect, but on the other hand, as it's behind the lens, it might not be that bad all in all. Personally, I'd go either 100% one way or the other. Either embrace the filter idea, and roll with whatever effect it happens to give, or go without it.
It won't be as though the whole film will be a blob (well hopefully) but it may cause all your shots to be slightly soft-- which may or may not be a good thing.
Deluxe is fantastic, it's always one of my main choices for development and transfer here-- well since my local TC house lost the colorist I really liked.
In the end, you're still in school, go nuts, because this is one of the few times you can really play around and not have a director or client imminently pissed at you afterwards.

Let us know how it turns out.
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#8 Eloise Maree

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Posted 05 October 2012 - 09:40 AM

Haha, you're last point is certainly a good one :). I guess I'll make a decision this weekend and, if I choose to roll with the filter, I'll definitely share how it turned out! x e
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#9 John Holland

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Posted 05 October 2012 - 03:49 PM

Eloise I havent used a 85 filter to correct for to many years to remember . As Adrian said its so easy to grade/time it out . Just make sure you dont underexpose your neg. Deluxe will have no trouble with dealing with it .
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#10 Eloise Maree

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Posted 05 October 2012 - 06:29 PM

Great, thanks John!
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#11 Eloise Maree

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Posted 03 November 2012 - 05:13 AM

Hi,

Just thought I'd update anyone who's interested. I didn't end up using the Roscosun filter, as I luckily found a Lee brand Wratten filter. I used it in the Bolex filter holder, and it produced good results (see attachments; I apologise for the low quality). The gel Wratten filter (which I cut to fit) was very easily scratched when inserted correctly into the metal holder, so I ended up taping it -onto- the holder. This worked fine. Attachments are completely ungraded.

Eloise

Attached Images

  • 1M.jpg
  • 2M.jpg

Edited by Eloise Maree, 03 November 2012 - 05:15 AM.

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#12 Adrian Sierkowski

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Posted 03 November 2012 - 05:58 AM

Looks very nice-- softer than you'd get with the top of the line optics and matte-box filters; but creamy in a not all so bad way!
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#13 Gregg MacPherson

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Posted 03 November 2012 - 04:23 PM

Hey Eloise, Adrian,
If you shot a test with a Wratten gel filter behind vs a glass filter in front my assumption would be that you would have great difficulty noticing any softness in the gel filter shot. People used to use those bolex behind the lens gels all the time, Eclair ACL also. I read somewhere that you may get a tiny back focus shift that you might see on a wide lens. But the fact that the gel is not sitting perfectly flat was never an issue. One could do some tests with a digital stills camera at high resolution with gel filter behind or in front of the lens. The filter in front test could be a comparison to a glass filter. My guess is that we can't see a difference, or something close to that. Though maybe the gel filter not being flat is an issue if in front of the lens (just a guess). The origional question of lighting gell vs Wratten gel designed for the purpose. Maybe also it will be impossible or nearly impossible to tell the difference.

Cheers,
Gregg.
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#14 Eloise Maree

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Posted 09 November 2012 - 06:34 PM

Adrian: thanks!

And Gregg: interesting! I'll be sure to do some tests before I shoot next.


:) Eloise
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