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class="style8" Steel Film

>Published : 11th February 2005

>Hello List,

>Anyone happen to know of a manufacturer of steel film. Aaton has a brass film, Arri doesn't produce it anymore, Kodak laughed at my request and every other service shop I've called either got lucky and brought out someone else and acquired it or have had the same strip for 20 years.

>The brass film isn't ideal as a magnet won't snatch it easily out of the gate.

>Any leads would be swell...

>Regards,

>Nathan Milford
Camera Tech
NYC


>I've heard that 'steel film' is the thing to use when checking the collimation of a lens.

>When I use my little pocket Richter collimator I must use the metal block from my depth gauge to 'project' the infinity target...but if I had a more reflective surface like steel film I would be able to see the image so much better.

>Is this true?

>Cheers,
Jeff Barklage, s.o.c.
US DP
www.barklage.com



I've never used steel film for lens collimation. At Abel we have a beautiful Chroziel collimator

>( http://www.chrosziel.com/KolliPL09_03.pdf )

>on which to check your lenses. I also throw the camera on the collimator with a lens on it and use it to check the screen focus and shutter/mirror flatness. I also check film focus on it by throwing a magazine loaded with film on it and making sure that everything (the lens, the screen and the film) appear sharp. After all, it can be clear as day on your fibre screen/ground glass but way out of focus when it hits the film. In a perfect world if your lens back focus is at 0, your flange is at 52mm (minus .007mm to -.014mm to accommodate for film curl) then everything should be in focus, but it's always nice to 'see' it with your eyes and not just trust the numbers.

>I use steel film to check a few things, but not collimation or film focus. I use it to check the 'shape' of the claw movement, frameline, shutter/claw timing and lateral pressure (with a tension gauge).

>I also use post-it notes a lot in the shop. Amazing tools. It's the 35-III ground glass removal tool AND the XTRProd glow guard to mirror clearance tool (two post-it notes together is conveniently the thickness of the Teflon washer behind the mirror gear).

>Sometimes I take notes on them too...

>If I can't find a supplier of steel film I'll probably throw some magnetic tape on the back of some brass film. *shrugs*

>Regards,

Nathan Milford
Camera Tech, Sometimes A Gaffer
NYC



Jeff Barklage writes :

> __ I've heard that 'steel film' is the thing to use when checking the >collimation of a lens.

>My understanding of Steel film, is that it is used to check the pull down claw (and perhaps the register pin) placement.

>I've seen it manually inched, but nothing more.

>Steven Gladstone
CML East Coast List Administrator
Gladstone Films
www.gladstonefilms.com



>I've heard that 'steel film' is the thing to use when checking the >collimation of a lens. When I use my little pocket Richter collimator I >must use the metal block from my depth gauge to >project' the infinity >target...

>You should be able to use a piece of unprocessed film stock, no?

>I wanted to add a piece of steel film (aka film gauge) to my field kit in order to check whether a piece of film stock was in spec or not, but when I queried Kodak about it, they said that they no longer made it.

>Mark Weingartner
LA based VFX super/DP



Steve Gladstone writes:

class="style9">>My understanding of Steel film, is that it is used to check the pull down >claw (and perhaps the register pin) placement.

>Steel film can be used for as many purposes as you mark it for. For instance if a frame line is scribed on it, it can be used to check if the aperture plate and the registration pin are positioned correctly in relation to each other. It can also be use to check the ground glass position and the cross hairs, if they are scribed on the steel as well.

>The advantage of the steel over the SMPTE test film is it can be reused over and over and as mentioned, can be scribed as needed for any ground glass markings.

>See Denny Clairmont's extremely informative posts about testing Super-16 conversions, especially about shooting a film test. The neg tells all.

>Brian Heller
IA 600 DP



Kodak no longer makes perforated "steel film", as it could not be dimensionally controlled, and usually ruined the perforator punch and die set used to make even a small quantity.

>Many find the thick perforated polyester leader used by processing labs is stiff enough to use for equipment alignment purposes, and the dimensions are much closer to SMPTE standard than perforated metal film could be:

>http://www.fpchollywood.com/film-leaders-lab-processing-machine-leaders-blue-polyester-leaders.html

John Pytlak
Eastman Kodak Company
http://www.kodak.com/go/motion



John P. Pytlak wrote:

class="style9">>Kodak no longer makes perforated "steel film", as it could not be >dimensionally controlled

>Me I just want a piece to go into my museum.

>If anyone has a small piece lying around.

>Steven Gladstone
CML East Coast List Administrator
Gladstone Films
www.gladstonefilms.com


>John P. Pytlak wrote :

class="style9">>Many find the thick perforated polyester leader used by processing labs >is stiff enough to use for equipment alignment purposes, and the >dimensions are much closer to SMPTE standard than perforated metal >film could be :

>Someone should make a tool akin to a splicer -- with real pins and various templates you put atop the film to scribe in different formats -- or else punch them out.

>Bet they'd sell at least 5 of them!

>Jeff "mass production" Kreines



>I also check film focus on it by throwing a magazine loaded with film on >it and making sure that everything (the lens, the screen and the film) >appear sharp

>Nathan,

>How do you do this :

>Cheers,

Jeff Barklage, s.o.c.
US DP
www.barklage.com


>Kodak no longer makes perforated "steel film", as it could not be dimensionally controlled, and usually ruined the perforator punch and die set used to make even a small quantity.

>Many find the thick perforated polyester leader used by processing labs is stiff enough to use for equipment alignment purposes, and the dimensions are much closer to SMPTE standard than perforated metal film could be:

>http://www.fpchollywood.com/film-leaders-lab-processing-machine-leaders-blue-polyester-leaders.html

>John Pytlak
Eastman Kodak Company
http://www.kodak.com/go/motion


>Jeff Barklage, s.o.c. writes :

class="style9">>How do you do this :

>Jeff

>It's usually when I final check the camera after I know all the numbers. I'll mount the camera (with a lens) on the collimator bench and I should see the objective clearly on the monitor (from the light hitting the shutter/mirror/screen). I set the lens to the long end and find infinity, zoom it to the wide end and hopefully it should stay in focus (and hopefully the zoom curve should look alright). If it isn't I adjust screen focus and go back and forth until everything is kosher.

>I then put a magazine on and inch the mirror out of the way and the objective should now be reflecting off of the film itself (you lose a bit of light so you should pump it up a bit). You can even make out little grains of film. If I can't see the film grain and the objective shows that it is plus or minus I know then that I measured flange distance on the camera or back focus on the lens incorrectly. If everything is swell I run the camera and watch for any discrepancy between the film and the screen focus. You can also see if there is any mirror flatness problem.

>The screen could be in focus at the beginning and out of focus by the end of it's turn. If that's the case it's a huge pain in the arse... I have to disassemble the camera for the most part and check the mirror with a height gauge.

>Regards,

>Nathan Milford
Camera Tech
NYC


Thanks Nathan!

Cheers,
Jeff Barklage, s.o.c.
US based DP