Camera Maintenance: Light Seals on the Fuji GSWiii 690
For the second time this month I find myself replacing light seals on my old cameras. Previously it was my Fuji G617 very wide format camera. That exercise was successful.
I have thought I was having light leaks in mmy Fuji GSW 690 since last summer shortly after I got it from Japan. Some photos seemed to indicate a problem. Below is an example from a hike in Montana last summer. It was a bright sunny day and I had my camera out all day. The banding I suspect was due to a light seal problem at one end of the camera or the other.
So I decided to replace the seals. The problem with camera light seals is they all seem to have used the same self adhesive foam material. This foam after decades deteriorates and turns into a black tarry substance. In my case pieces had dislodged and begun to smear on the backing plate in addition to the inability to keep light out.
I start by first protecting the lens. I push a piece of cloth onto the back of the lens to keep any debris or dropped tools off of the lens to protect it.
The first problem is to remove the old muck that the original seals have left. This I did with denatured alcohol. I started using cotton swabs (cotton buds in the UK). I found that I would have gone through a lot of these as the black tar required a lot of cleaning. I switched to bamboo skewers. I cut them to a chisel tip and scraped away the bulk of the material mechanically. I then switched to bits of paper towel (kitchen roll in the UK) wrapped on the tip of the skewer soaked in alcohol and swabbed out the light trap channels.
The light seals consist of 4 pieces. Two short wide sections (7mm wide) and two long thin (3mm wide) sections. On the far end of the film back the short light seal is attached to a small metal flange that is screwed to the back. The three small screws need to the removed and the flange can be turned over to remove the wide strip of foam.
Once the old foam is removed (a long and tedious process) then I made sure to scrape away the thin layer of adhesive backing still stuck to the metal. This is somewhat tougher and I am not sure it is entirely necessary but I wanted to be sure the new foam had a firm foundation.
There are various sources of foam sheeting. I bought some a number of years ago for a project. It is a fine closed cell foam about 1mm thick. It had no adhesive backing. Some places on the web recommend getting adhesive backing on the foam sheet. I think this is a good idea. One tip is to use alcohol on the adhesive to render it ‘unsticky’ while it is being placed. The alcohol eventually evaporates and the adhesive remains.
The foam sheeting I bought did not have adhesive. For my Fuji G617 light seal project I used contact cement. This worked but was messy. For this project I tried to used some extra 3M PMA (Positionable Mount Adhesive) I use to mount photos. Essentially this is adhesive coated on wax paper. After I cut each piece of foam I press it onto the PMA and this makes the foam sheet self-adhesive.
Each piece of foam is cut to width first then to length. I used an Exacto hobby knife. The short piece next to the hinge I placed first. This then set the length for the long thin pieces.
The long thin pieces I needed to augment with some extra lengths. I cut each end with a steeply angled ‘scarf joint’. A right angle butt joint would have given an easy path for light to leak past, The scarf joint overlaps the two ends making an effective light block. The top thin piece is easiest to apply as the light trap is a single long line. The lower thin piece has two jaunts around the areas where the film roll release buttons are. Patience here will result in carefully routed light seal around these jaunts.
Once all the lights seals are in place I carefully blowout all the backhand the inside of the camera to make sure there is no stray debris left from the work.
I have thought I was having light leaks in mmy Fuji GSW 690 since last summer shortly after I got it from Japan. Some photos seemed to indicate a problem. Below is an example from a hike in Montana last summer. It was a bright sunny day and I had my camera out all day. The banding I suspect was due to a light seal problem at one end of the camera or the other.
So I decided to replace the seals. The problem with camera light seals is they all seem to have used the same self adhesive foam material. This foam after decades deteriorates and turns into a black tarry substance. In my case pieces had dislodged and begun to smear on the backing plate in addition to the inability to keep light out.
I start by first protecting the lens. I push a piece of cloth onto the back of the lens to keep any debris or dropped tools off of the lens to protect it.
The first problem is to remove the old muck that the original seals have left. This I did with denatured alcohol. I started using cotton swabs (cotton buds in the UK). I found that I would have gone through a lot of these as the black tar required a lot of cleaning. I switched to bamboo skewers. I cut them to a chisel tip and scraped away the bulk of the material mechanically. I then switched to bits of paper towel (kitchen roll in the UK) wrapped on the tip of the skewer soaked in alcohol and swabbed out the light trap channels.
Once the old foam is removed (a long and tedious process) then I made sure to scrape away the thin layer of adhesive backing still stuck to the metal. This is somewhat tougher and I am not sure it is entirely necessary but I wanted to be sure the new foam had a firm foundation.
There are various sources of foam sheeting. I bought some a number of years ago for a project. It is a fine closed cell foam about 1mm thick. It had no adhesive backing. Some places on the web recommend getting adhesive backing on the foam sheet. I think this is a good idea. One tip is to use alcohol on the adhesive to render it ‘unsticky’ while it is being placed. The alcohol eventually evaporates and the adhesive remains.
The foam sheeting I bought did not have adhesive. For my Fuji G617 light seal project I used contact cement. This worked but was messy. For this project I tried to used some extra 3M PMA (Positionable Mount Adhesive) I use to mount photos. Essentially this is adhesive coated on wax paper. After I cut each piece of foam I press it onto the PMA and this makes the foam sheet self-adhesive.
Each piece of foam is cut to width first then to length. I used an Exacto hobby knife. The short piece next to the hinge I placed first. This then set the length for the long thin pieces.
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| Detail of Scarf Joint |
Once all the lights seals are in place I carefully blowout all the backhand the inside of the camera to make sure there is no stray debris left from the work.
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