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Strange Fogging On K3?


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#1 Ian Cooper

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Posted 17 March 2008 - 03:33 AM

Hi,

I've been a 'lurker' for a couple of years, reading and absorbing information. I previously used Super-8 a bit, but around Christmas bought myself a K3 to experiment with 16mm.

My first task was to strip it down, loose the loop formers, clean & lubricate, free off a couple of seized rollers and fit new light trap foam.

I've been pleased (and pleasantly surprised) with the quality of the images I've obtained from the camera, but I seem to be experiencing a strange fogging issue. I routinely tape up the film chamber door to prevent it falling off and reduce light leaks.

I get the obvious flash-frame where the film sits stationary in the gate when it is not running, but I also seem to get a red fog 19 frames either side of the flash frame. It doesn't always appear, but does more often than not. It can range from one frame gaining a slight colour shift, through to two or three frames affected building up to one very red frame at the centre. The film has been Kodak 7201, so pretty low speed.

I've taken a scrap length of film, marked the 'flash' frame, then marked the 19th frame in either direction. With the 'flash' frame located in the gate I've been able to see where the 19th is sitting. Unfortunately it appears to be on the film spools! Certainly on the take-up side at the beginning of the film the 19th frame will be deep within the walls of the spool, and possibly even wrapped around the centre.

I'm at a bit of a loss. The fact that this problem is situated either side of the flash frame seemed to suggest to me that it occurs when the film is stationary with the camera stopped, but I can't see any obvious (or not so obvious) way light could reach film on both 'exposed' and 'unexposed' sides of the gate at the same time.

It's not a huge problem, I can make sure the camera is running for at least 1 second before the scene I want to capture, and run an extra second at the end as well. I'd just like to solve the problem if I can, does anyone have any ideas?
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#2 Will Montgomery

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Posted 17 March 2008 - 10:31 AM

I wonder if it has to do with your eye covering and uncovering the viewfinder before and after you stop the film. I've found a fogging issue with my Scoopic in that regard sometimes, although it was more of a hazy white fog and not a red color which sounds more like what I get at the end of a roll from loading and uploading. If I had to guess that would be my first one... sounds like the film on either side of the gate in the loop is getting exposed somehow and you seem to do a good job sealing up the film compartment.

I've never had an issue with fogging from the door itself and I never tape it.

With my K3 I seemed to have a problem where it would be perfectly in focus for three or four frames then go soft. Bernie O'Doherty at Super16inc seemed to solve that problem for me although I'm 100% convinced its gone.
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#3 Ian Cooper

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Posted 17 March 2008 - 11:22 AM

I wonder if it has to do with your eye covering and uncovering the viewfinder before and after you stop the film....


I did wonder about the viewfinder, but can't see a path between the finder and the film compartment. I think there's a slot where the meter needle pokes between the finder and the mechanism behind the film chamber, but with the dividing plate screwed in place I can't see/imagine a path through.

My other thought concerned the footage (meterage I suppose?!) counter. I've put new light foam around that and it appears a good seal, also the 19th frames aren't really very close to the counter, they're more in the centre between the two spools when the mechanism is stationary.

What I can't fathom is that I'd guess a light leak positioned away from the film itself would give a general fog on an area of the film, rather than the tightly defined frame or three I'm seeing.

Thanks for the suggestion, I'll have another peer inside tonight with more attention to the viewfinder.
I'll also see if I can post a couple of frame grabs or short clip showing what it looks like etc.


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#4 Ian Cooper

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Posted 17 March 2008 - 03:47 PM

Ok, here's a bit more information.

A SHORT CLIP (245kb).

Before the end of the scene you can spot one frame with a slight red colour cast. You see the flash frame where the film was stationary, then a moment later a strong red fog across three frames.

Sometimes it's a strong fog before and after the flash-frame, other occasions it's like this one. With one side stronger.

The three frames at the start of the new scene are:

1) Posted Image

2) Posted Image

3) Posted Image
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#5 Scot McPhie

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Posted 17 March 2008 - 04:27 PM

Perhaps it's something that happens when that 19th frame moves into a certain position. ie there's osmthing wrong somewhere in the movememtn that happens almost one second after you start filming (assuming 24fps) at which time that frame is in a certain position where it can get the light. maybe youshould put it on single release and watch the path that frame takes - see if you can spot somethign unsusual happening to that frame somewhere along the way
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#6 Ian Cooper

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Posted 17 March 2008 - 05:37 PM

Mmm, good thinking...
:
:
...I've just tried running it through a couple of times on single frame, also with the governor turned to its slowest setting - I can't see anything out of the ordinary. Even at 25fps the motion appears smooth enough, the loops both stay the same size and the clatter from the camera stays consistent.

I did initially wonder if something could be happening around the gate about a second after starting, but I couldn't then explain how the fog would affect the film which had already been exposed at the end of the previous shot. The fact that the fog appears exactly the same distance either side of the gate seemed a bit more than coincidence.

I've since had another peer around the viewfinder. It's clear light entering through the eyepiece will work back to the shutter, and thus the film sitting in the gate, but I honesty can't see a path from the finder optics through to the film chamber.

Unless I can track something definitive down before hand, the next time I shoot I'm considering taping over the door latch and also across the counter window. It can't do any harm and will at least eliminate those two as possibilities. I'm guessing that as the fog is red coloured rather than white, the amount of light hitting the film must be very small indeed.


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#7 Ian Cooper

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Posted 17 May 2008 - 02:16 PM

Thought I'd give a quick update if anyone was interested. I've just had back the next 400ft of film to go through the camera, this time I taped over the door catch and the footage counter... no red fogged frames!!

I'm pretty sure there was one section where I only taped the door and not the counter, in this bit I suddenly started getting the red fogging appear again!

Problem sorted: More camera tape required!
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