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Making Gel Filters For A Krasnokorsk-3
Published : 12th April 2005
Hello, my name is Sean and I am a film student. I have recently acquired a Krasnokorsk-3 16mm camera and have found that my sample book of Lee gels are big enough to cut out and mount between the lens and the screw-on lens hood. I made myself a full CTO and full CTB gel which fit quite nicely, but I am not sure whether I still follow the same rules as glass filters.
>Does the CTB (gel) cut light by 2+2/3 of a stop and the CTO (gel) cut 2/3 of a stop? I've tried figuring this out with a Sekonic L-398 light meter but I am not sure whether using the "dome" under the gel will render an accurate reading (because it reads side-light as well). The internal light meter on the K-3 does not seem to be working either so I'm kinda stuck...
Probably the transmission is about the same but I'm not so sure about the optical quality of those gels.
>P.S. You should be able to take reflected readings through those gels with your meter, there's a grid disc for reflected, no?
>If you are using the supplied Meteor lens, then you are already at a disadvantage.
>Shell the money out for glass filters. You can find reasonably priced ones at photo shows fairly easily.
>Additional to the, I would suspect, poor optical performance of the gel filters - why make a filter that is meant to have hot lights shown through them optically clear, when the heat will distort the gel quickly anyway. You would also have to worry about the flatness of the gel in front of the lens, and about cleaning it, which I would imagine to be quite difficult to do without scratching it.
>Get yourself the following.
>Circular polarizer, and a wratten 85 to start with. Then start adding a Clear (or many people use a SKY 1A uv filter). A set of ND filters and/or 85 ND combos, and start looking for diffusion filtration that you like.
>You might consider getting some lens step up rings from your lens to series 9. Although the glass will be more expensive than filters sized for the front of the Krasnokorsk 3 lens, having the Series 9 size will allow you more flexibility later. I've also found that at still photo shows series 9 filters sometimes get a pretty nice discount, and there are a bunch of wacky ones worth picking up. (I picked up a five image multiplier for $40.00 once)
CML East Coast List Administrator
I did use a Nikon gel filter holder at one time, but that's with the Kodak gel filters which are specifically photographic filters.
>They are "cheaper" but Steven is right, glass is best, and durable - probably cost you less in the long or even short term anyway.
>(I use the Kodak gels behind the lens with a Bolex camera and replace them all the time, they bend don't stay flat etc. Don't like humidity which contradicts my use of a Bolex as jungle camera.....
If you want to use cheap filters then get a Cokin adapter and use those, if the lens is smaller than series 9 then you don't even need the Pro size, and they're very cheap anyway!
Geoff Boyle FBKS
Director of Photography
>Geoff Boyle writes :
class="Paragraph">>If you want to use cheap filters then get a Cokin adapter and use those
>I've used Cokin grads a lot for Mini-DV docco work. They're a great compromise between gels and glass filters. For standard-def video and 16mm film you won't be able to see a difference between Cokin's and glass. And if you drop one on its edge it won't crack. But make sure you clean them gently -- avoid scratches. Dish detergent and warm water is better than dry rubbing, to get fingerprints off.
>If you want to build yourself a homebrew mattebox, the Cokin filter holders are a good item to start with. Just make sure you close the tops of any empty filter slots with gaffer tape to prevent stray light from striking any dust on the filter surfaces. And make sure the filter holder doesn't intrude into wide-angle shots (I had to slice my holder thinner in order to use it with a Century WA adaptor for a PD150).
In addition to the Cokin system, there is another system made by Lee and sold by various people (including Calumet Photo in Chicago & LA and B&H Photo supply.
It is called the Compendium system (I believe) and it consists of a system of 4x4 mattebox and filter holder which attach themselves to special threaded lens adaptors - thread the adaptor onto the lens and clip the filter holder and/or matte box to it. I use this extensively when shooting miniatures and things like that where there is not room for a full mattebox and a lot when shooting stills.
The system is designed to take 4x4 gels or glass (or resin) filters like the Cokin, you can slide grads in the holder.
This system is not cheap, but may be more flexible than the Cokin system long-term, as you can by 4x4, 4x5, 4x6 filters that you can use later with a real mattebox.
When using gels, you can buy the gelatin filters and put them in the fancy little Kodak 4x4 gel holder which then slides into the filter slot.
>There is a definite advantage to the gelatin filters over lighting filters, as they are optically a lot better, and because they are very thin and not of a really high refractive index, a very slight lack of flatness won't totally ruin your day...the filter holder should do the trick for you.
>DO NOT GET GELATIN FILTERS WET...THEY REALLY ARE MADE WITH GELATIN AND THEY WILL MELT
Yesâ€¦they are NOT flavoured the way you would think from the colors, either.
Warning # 2 If you use this system with glass filters and put a 4x6 grad in the slots and start sliding it up and down to set up your shot and forget to put a piece of tape on it to keep it from sliding out the bottom...you WILL be cleaning up broken glass.
>You can ask me how I know
>Just a thought.
>In addition to the Cokin system, there is another system made by Lee
>Yeah, it's great, I use it on my Polaroid and digital stills cameras so that I can use the same filters that I use on the "real" cameraâ€
>I didn't mention it because it's considerably more expensive than the Cokin system.
Geoff Boyle FBKS
Director of Photography