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La caméra maison de John Gerndt |
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02-07-2005 |
Une caméra artisanale 12x20 à faible coût dont le concept peut amener des gens à s'intéresser à l'UGF et aux tirages contact. Les châsssis porte-négatifs sont également faits à la main
ULF on a tight budget
by John Gerndt
OK, so I am not entirely altruistic in sending out these plans
for a 12x20 ULF camera. I am first motivated by the desire for those large luscious
contact prints as I hope you are too. I want this form of photography to continue
to exist and therefore it must be available to more people, like me, and you!
So, how to avoid the $3000 to $6000 dollars to have such a beast?
Compromise
is the answer. I picked the one thing I love most to preserve and put every
decision to its service. I wanted a beautiful, sharp full range negative for
contact printing, big enough to imitate a small bathroom window. I wanted that
portal on the world. I wanted it for a few hundred dollars.
Like that famous
industrialist I determined what I needed to do the last step first. I needed
to contact print the negative. I heard a call to buy up some AZO or it might
disappear (a call you all are sure to hear again). I bought the paper. Like
Michael and Paula I decided it was a good use of the credit afforded me. OK,
so I am well over a few hundred dollars already but this paper is known to outlast
many a mortal so if I use it sparingly…
Film is tougher; it does expire. I put
it on hold and spent my free time researching it on the web.
A lens would be
good too. I am always surfing around ebay. I found two barrel lenses from Kodak
for cheap that cover the format: 18 inch f-16, Wide Field Copying Ektanon and
a much more common 21 and a half inch f 11. (I fixated on the wide angle and would
have had a much easier time with the 21 and a half, still slightly wide for 12x20.)
Now, the film holder... This was the toughest thing to deal with. I got lost
here for some time. I asked for advice on materials and decided against it for
its cost. I ended up spending more on this route as I came to a few dead-ends.
Just buy the Phenolic plastic. If you want to do a prototype in cheap hardware
store stuff that makes sense but in the end you’ll like the better material.
Mail order is fine. Consider paying to have it precision cut. The recommended
source for this is www.mcmaster.com.
I used basswood for the structure, as I
could not find out enough about balsa. Basswood is light and strong and machines
nicely.
Beyond materials is the precision needed to make two, three or four
holder all the same. Again prototyping is a good idea. Later, when it comes
then to making multiples you can leave your saw set the same way and start running
multiple pieces. I also decided to make the GG back at the same time as it is
the coordination of the film holders and the GG back that is the critical element
in getting good results, that and the alignment of lens to film, but more on
that later.
The film holder has two jobs it needs to repeat without flaw: hold
the film flat and don’t let the light strike the film until and exactly where
the photographer wishes.
Now I am pretty good with a table saw, but taking apart
a couple of film holders humbled me. This construction is not table saw work
to these eyes. I don’t know how the independents make theirs (chime in here
if you want to, you better craftsmen) but I needed a design I could handle.
Think simple. I got a tip from a member of the LF group at photo.net (many thanks!)
about the manner of keeping the flatness on a Lotus 20x24 holder. Nice and simple:
use wedges to pull and keep the film taught. Some experimentation determined
that a slightly tapered cleat in conjunction with a piece of _” aluminum angle
stock did the trick. So now the holder is simple in design and execution. (By
the way, I tried a double holder but it saved very little space and greatly
complicated the build.)
My film holder is a shallow box with cleats on two sides.
A slight buckle to get the film to drop under the cleats and push the angle
aluminum in, from inboard to outboard and the film is taught. The making of
the light seal was again a matter of finding the right materials.
I tried windshield
wiper blades. For years I thought this would be a great idea. It did work but
it worked to tightly. The blades really wanted to hold/grip the dark slide and
created a jump/bump to get them to change directions from slide-in to slide-out.
I thought about imitating the metal spring blade covered in black felt as in
a Graflex holder, but spring steel is temperamental stuff. The scale changes
its abilities to cope with the task too.
I mention these mistakes to keep those
of you who are inventive from trying what I did and getting you right to making
pictures. Experiment away, you may come up with something far better than me.
I hoped for this very article I am writing now to appear on the net to guide
me. All I can do is put it out there in retrospect. I hope it does some good.
I ended up using a very thin vinyl material from painting guide strips. These
were yellow (I painted mine) plastic straight edges used by armatures to paint
straight lines especially in corners and the like. The requirement was for material
that gives and springs back with only _” of material to work with. I went with
two blades pointing down ad two up. I made them extra wide/long, wider than
the dark slide slot, to keep out the light when the dark slide was removed.
My film holders are made from 1/2 x 1&1/4 basswood so there is room for this kind
of manipulation. The dark slides are made from 1/8” birch plywood. I used 1/8”
Masonite for the bed the film lies on. It is very smooth and flat though a bit
heavy. Aluminum is far worse; I tried that. These holders are NOT ideal, they
are, however, easy enough to make well. I will only take three on a trek. For
further detail I hope to include some drawings.
I have at this point, the end
product paper (AZO) and film holders (no film). I made my ground glass back
(GG) as per an article in Photo Techniques, May/June, 2003 by Dick Dokas. The
whole back is removed and replaced by the film holder. This precludes the huge
springs and large forces a standard arrangement would entail.
I made the film
holders and GG with a lip so that one edge locks into the rear “standard”. I
developed spring clamps to hold the other end but a bungee chord would do just
as well. I attached a very crude, black denim dark cloth all the way around
the GG back. It makes it more difficult to attach the GG to the camera but once
on there is not fussing around with light leaks and it wraps around the back
for protection. I used and old shirt for the bottom of the cloth allowing me
to use the arm holes inside the dark-cloth-compartment. I made a flap to hang
down from the GG back and block the light that comes through this thin shirt.
The thin shirt allows for some air transfer. The hanging flap can be brought
up to make things really, really dark.
Finally to the camera...
I decided that
I would forgo camera movements. WHAT! This sacrifice was in the interest of
rigidity, balance and a very good (fixed) alignment between the lens and film.
This was a compromise I needed to make in order to keep down weight, cost and
error. In theory some scheimflug movements could be possible with the design
I came up with but would necessitate creating a Zero position to come back to.
The bit of engineering escapes me. I decided on a rigid box (with two internal
light baffles which add strength), which also allows for a so-simple method
for focusing from behind the camera. The lens stage is hung from a sliding pole
and connected to the box camera by a bag bellows (twelve pieces of vinyl easy
to sew). I also use that sliding pole to hang the dark cloth from keeping it
off my head and allowing a better view of the GG.
Getting this big box off the
ground and firmly rooting it to the ground is a daunting task. Some very “creative”
ideas were needed to keep down cost having spent my first year’s budget on AZO
and building materials.
For the purists out there, my solution is going to be
harder to swallow than the box-camera-without-movements. I made my own very
large diameter ball-head: I made it out of a large stainless steel mixing bowl
and a bucket and I mounted the whole to a cheap aluminum step ladder.
The mixing
bowl is about 16 inches in diameter (6 inches deep) and the bucket is a standard
3 1/2 gallon Home Depot model (the 5 gallon being too tall in the end). The head
is assembled on top of a 4’ stepladder (with a plastic head). The camera is
held to the ladder by ropes and hooks in tension provided by those ratcheting
Cord Cuffs also from the ‘ol home despot. Total cost is about $40.00. The total
weight is less than my Bogen 3051 with its 3047 head and it is more stable,
especially as I can stand on this support to keep the wind from buffeting this
very large (but quite rigid) structure. I can pick up and move the assembled
rig without trepidation, it is quite solid until the tension is released from
the ratchets. Getting everything assembled and tensioned is a bit of a balancing
act but I imagine it is a bit of a trick for any camera of this size. This whole
article is for the handy-guy (girl?) anyway.
Attach the mixing bowl to the stepladder
with a threaded rod, washer and wing nuts. Attach the bucket to the bottom of
the camera any way you want (tape or screw…).
Put eye screws in the four corners
of the box and in the four legs of the stepladder. I put two of the cord cuffs
in each cord to allow for the various lengths needed to take advantage of the
ball and socket movements. I do not plan to use that much of the available motion
as the whole rig gets unstable after 5-10 degrees off perpendicular. Using one
cuff per chord would save you $6.00 (grin). One end of each cord is an “S” hook
and the other a carabineer.
I attach the bucket to the bottom of the camera
via standard 1/2 / 20 threaded insert in a reinforcing strut I put in the bottom
of the camera body. I use a cap screw with washer. This joint only has to prevent
too much shifting of the bucket from under the camera/box. The strength of the
rig is from connecting the camera/box to the stepladder. The camera and bucket
must be balanced on the bowl while the cords hanging from the bottom of the
camera are attached to the stepladder. That is the only vulnerable time for
a mishap in balance. I find it is best accomplished with no lens or back on
the camera. This is not a hurry-up kind of endeavor eh?
The hanging lens board
attaches to the bag-bellows and the bag-bellows to the camera with hooks and
screw, simple and cheap.
Now about that lens board…
The boxing-in of the board
allows for some protection of the lens and makes for a good and rigid frame.
Between the actual lens board and the back of the box are springs pushing the
two planes apart. Three screws keep the two surfaces from flying apart and allow
for making the lens board parallel to the film plane (I was embarrassingly off
that mark with that alignment of the superstructure, the adjustment ended up
being more than I ever thought). That measurement is done with a laser level
or a standard enlarger alignment laser device. I made my own out of a laser
pointer but that is another story.
The whole finished product required only
one sheet of 1/8” birch plywood, a sheet of Masonite, 25 board feet of basswood
(I had 6/4 stock milled to 1 1/4” and ripped it from there), one yard of vinyl,
one aluminum pole, fasteners, wire, hooks, etc. I could and would do it better
if I tried it again but I am much more interested in making photographs and
maybe reading YOUR article on how your homebuilt camera worked out.
EPILOGUE:
THINGS THAT WENT WRONG AND HOW TO FIX THEM…
First, the most obvious is that you need a consistent shutter. I thought I could
move all my exposures into the 4 seconds and greater zone for using a lens cap
for a shutter and really I couldn’t. I suppose one could if you could get some
very slow film but choices are limited in 12x20. I compounded my mistake by
then buying a new Packard shutter as I believed I could not find one as large
as needed (4 inch opening) on the net; I found a couple for half what I paid
for the new one after I ordered the new. Note: one must time the shutter. Even
my brand new #6 with the “instant” setting advertised as being a 1/25th of a
second turned out (in a 4 inch opening) to be a 1/10th.
A more serious oversight was the consideration of tolerances
for the cleat and angle aluminum used in the film holders. When loading my first
round of holders I found that I could not get the angle aluminum to slide into
position and hold the film taught. Too loose was easy to fix: put some tape
on the angle aluminum to make it larger. Too tight: one has to sand down something.
I tried to sand down both the angle aluminum and the cleat. The cleat was easier,
but still a pain. I would choose to use a different material on the cleat next
time, affix it with screws in oval slots to that this adjustment would be easier.
Also, a finger divot to get a fingernail under the edge of the film for removal
is quit a good idea. I got it done without the divot but NOT without some difficulty.
Finally, my design calls for much assembly to take place at the sight. I would
like to carry the camera and lens together and yet not have the long focus bar
sticking out perpendicular to the camera body as it makes the whole thing gangly
and prone to a bend in the pole should it suffer a jostle. The easy fix would
be to have the lens board able to clamp to the body without the aid of the pole
or (this is where I must go having not considered a design to allow for a clamp)
use a short pole to hold them in conjunction and then swap out the short for
long at the site. That said, I am quite happy with the pole focusing system.
The only improvement might be to find a better source for a pole (my hardware
store item is not truly round) and to find a bushing to aide the sliding action.
Waxed wood works pretty good but a plastic would be better.
Plans for the project :
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Dernière mise à jour : ( 18-11-2005 )
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