[photo-3d] Curing Infamous Realist Light Leak

["Dr. George A. Themelis" <drt-3d@xxxxxxx>]

Joseph wrote:

> Another problem I have run into is a light leak which shows up as
> a fuzzy red band running vertically on the right side of the right chip.
> This will show up is the camera is exposed to bright sun without the leather
> case bottom attached to the camera.  Keeping the camera in the case will
> solve this.

It is better to attack the problem itself than rely in the camera
case (there are a few people who like to use the camera without
the case) or taping the back, etc.  

Since this is a very common Realist problem, I am quoting 
what I have written about it in my Realist book (references
to literature and figures have been omitted)

==== BEGIN QUOTE =====

The Realist light leak is such a common occurrence that some 
people have called it a "feature" instead of a defect!  In a 
1997 world-wide survey via the Internet, 68 people reported 
data for a total of 139 Realist cameras.  An astonishing 67 
of them (48%) had a light leak. 
 
The leak manifests itself as an orange streak running vertically
(concentrated at the bottom of the image) usually in the right 
film chip.  The frequency and intensity of the problem varies 
widely, depending on the location and size of the opening that 
causes the leak and the amount of exposure to sunlight.

The most common location of the leak is the edge where the back 
meets the body on the side by the focusing knob.  While the top 
and bottom edges of the camera back are protected by a double 
light baffle, the sides have only one and this invites light 
leaks.  This is a design flaw that went unnoticed in the '50s 
with Kodachrome's very slow speed.  With today's faster films, 
more and more users are frustrated by this leak.  In the 
following paragraphs I will describe a clever method for 
detecting light leaks and ways to eliminate them.

As a result of the 1997 Internet discussions and based on an 
idea by Greg Wageman I came up with a system to check for light 
leaks, based on the light leaking out of the camera.  A small 
2.5V light bulb is attached to a pair of AAA batteries via a 
switch.  The batteries are placed inside the film canister cavity, 
the switch into one of the two film apertures and the light bulb 
by the pickup spool.  A piece of white reflector is placed around 
the pickup spool to increase reflections and make the light more 
visible (the interior of the camera is black, so without this 
reflector the bulb filament would be the only source of light, 
making it difficult to see the leak).  The room lights are then 
turned off for 5 minutes for the eyes to get adjusted to the dark.  
Then, with the room lights still off, the switch is turned on 
and the camera back is quickly closed.  The dark-adapted eyes 
are very sensitive so any light coming out of the camera can be 
easily detected as a faint glow.  This method will not only 
find the exact location of the leak but will also monitor the 
progress in eliminating it.
 
To eliminate the light leak the following methods have been used:

Use the camera case bottom and avoid direct exposure to the sun. 
Sometimes this is enough to shield the leak.  But in most cases 
the leak is higher (around the focusing knob) and is not shielded 
by the case.

After loading the film and closing the back, put black tape around 
the edge.  It works but it can be a mess and can also damage the 
camera's leather finish.

Bend the back.  I have managed to eliminate the leak in my camera 
by simply bending the back, but it is not clear how it should be 
bent.  If bent the wrong way, it can make things worse.

Reshape the latch that locks the back.  Using a pair of pliers 
work the latch to increase its curvature at the end.  This 
increases the camera-to-back tightness and it might eliminate 
the leak, but not always.

The most effective method is to place a "light gasket" to seal the
leak-inducing gap. This can be something simple, such as a piece 
of electric tape, or more fancy such as the velvet that forms a 
light trap in the opening of 35mm film cassettes.  Cut the material 
to a thin (1.5 mm or 1/16 inch) strip and attach it to the edge of 
either the camera or the back.

One of the last two methods, or a combination of them, will 
eliminate the light leak forever!  

But keep in mind that while perhaps 95% of the leaks originate 
from this location (right hand side) there are a few rare cases 
where the leak comes from other places.  For example, if you omit 
any screws when you put the camera back together, then you will 
probably get a leak from the open hole.  Also, a camera that does 
not have a leak might develop one in the future as the back gets 
loose with use or if the camera is dropped or deformed in some 
other way.

==== END QUOTE =====

George Themelis