Saturday, 27 September 2008

Bessa - film slack is bad

Soon after I started using my Bessa I had some annoying problems occurring like in this image:


All the opinions I've had on this indicate that its light leaking along the edge of the film when changing the film (taking out the old, and putting in the new).

For those who are not familiar with 120 film this may seem a strange thing, but the fact is that 120 film is just wound onto spools (like in the above wikipedia link) with a light proof paper backing. This effectively sandwiches the film between two layers of light proof coated paper. It depends however on being tightly wound or else light can leak in at the edges of the paper and spool at the top.

There is a pinch spring arrangement which is designed to keep the film tight on both the takeup spool and the film supply spool.

It looks like this (I'll get to the foam in a minute)

Many people have suggested that this needs to be bent in a little more to keep the film from becoming unspooled with movement in the camera.

I tried this, but well .. its spring steel, thin and flimsy. So I was less than confident that this was going to work.

Well sure enough every film I took out of the camera needed a final "wind" in my fingers to "tighten it up on the spool".

I thought that what it needed was some 'friction' and something to 'grab' it to prevent it becoming slack. Sure the take up spool can't move backwards, but nothing is holding the supply spool.

I thought I'd add a little window sealing foam tape to the holders of the spools to ensure that it was firmly held and didn't unwind.

I put a little of it to go around the edges of the holders like in this picture. Even with no film on the spool you can see that it holds it nicely against the spring clip.

Its important to not use much tape either, as you only want to make the slightest effect. The tape here bends around over the spool holder so that the paper flow will not then snag on the foam and then drag it into the holder and cause any jam.

The tape is at both ends to keep the roll tensioned evenly as in the image below.

It then neatly drags the paper backing and the self adhesive tape has enough space on the other side so that it attaches well and can't be then dragged under and jam mid roll (this btw is what happened on my first attempt).

There is slightly more resistance on the uptake now when I advance the film, but since then 100% of my images have been perfect and film is wound on as tightly on the uptake spool as it was on the supply spool when I got it from the packet.

fantastic :-)

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