Clamp to hold film back shut while moving dark slide?

[Ken Lee]

It's a fairly common problem: while removing or inserting the dark slide, the film holder moves, and briefly breaks the light seal. All it takes is a fraction of a second and the slightest gap, and we get fogging in a corner of the image.

(It's helpful to make sure that the dark slide moves as smoothly as possible. To this end, I have been waxing my dark slides lately, since all my film holders are rather old.)

Some cameras have a bail back, or a levered back. This allows for the spring to be stronger, and therefore press the film holder with greater force. Even with that, one can still experience the problem.

Is there some kind of simple clamp that we could use ? Once the film is in the camera, lock the clamp. Then remove the dark slide, shoot, and replace the dark slide. Then unlock the clamp and remove the film holder.

Such a clamp has to be lightweight but strong. On wooden cameras, it can't damage the wood. And it has to be affordable and readily available.

Any suggestions ?

[Gem Singer]

I've never seen a clamp made specifically,or one that could possibly be utilized, for that purpose.

Being right handed, I've always been taught to pinch the spring back and the body of the camera between the thumb and index finger of my left hand while removing the dark slide with my right hand.

I also tend to keep a dark cloth draped over the back of the camera.

[Curt]

I've never seen a clamp made specifically,or one that could possibly be utilized, for that purpose.

Being right handed, I've always been taught to pinch the spring back and the body of the camera between the thumb and index finger of my left hand while removing the dark slide with my right hand.

I also tend to keep a dark cloth draped over the back of the camera.

Same here.

[Ken Lee]

I should have mentioned that (being right-handed) I always use my left thumb to hold the camera back against the film holder - but even so, it would be nice to solve the problem once and for all. Especially for those lefties out there ;)

[Gem Singer]

Right or left handed operation is not a concern for me. The backs of my Canham MQC and Toyo monorail are able to be set for right handed, left handed, top, or bottom insertion of film holders.

[Jason Greenberg Motamedi]

Not what you asked, but one can lock Graphmatics to a Graflock back using the sliders.

[Ken Lee]

It's revealing nevertheless. I presume those old-time press photographers wanted to be able to concentrate on the task at hand, and not worry about fogging every shot.

Sliders... hmm. Could you provide a photo ? A clamp isn't really necessary, if there is a lock of sorts instead.

[Jason Greenberg Motamedi]

Sliders... hmm. Could you provide a photo ? A clamp isn't really necessary, if there is a lock of sorts instead.

I don't have a camera with a graflock back, perhaps someone else?

[Keith Pitman]

You could have a bail installed. A bit pricey, though. I use the Gem Singer method, also.

[TheDeardorffGuy]

I load film holders from the right. I hold the camera frame and GG frame in my left hand (my personal Clamp) and pull the slide. I also use lemon pledge on my darkslides. That makes a great deal of difference in the pull force.

[Jay DeFehr]

I have a solution. I've been working on it for a while now. It's not an addition to standard backs, but a replacement for them. I call it the MagnaBack System. What the name lacks in creativity it makes up for in descriptiveness. The MagnaBack system uses no springs or clamps of any kind and relies solely on the power of rare Earth magnets to locate and secure the back, ground glass, and film holder. Once located, the film holder simply doesn't move until the magnetic bond is broken by a simple cam mechanism.

In practice, the back is located in the chosen orientation. The GG is located on the back for focus and composition. When it's time to expose, the GG is removed and attached to the film holder, and the film holder is attached to the back. Attaching the GG to the film holder is simply a convenience, and plays no part in securing the film holder to the back.

Advantages:

Less hardware- Since magnets do all the work, there are no springs, pins, tabs, bails, screws, brackets, or even a GG frame. This makes for a very clean and simple design.

More secure- Film holders placed stay placed much more securely than with spring backs, and there is no "slop" on any axis.

Easier placement/removal- Since there is no spring back, there's no need to slide the film holder under it to place it or remove it, thereby eliminating much potential for camera movement. The magnetic bond is very strong when in intimate contact, but dissipates quickly with distance between magnets, so despite the strong magnetic bond that holds the film holder securely, the holder is easily and gently removed by the use of a simple cam.

More permanent- Unlike springs, magnets won't take a "set", or weaken with time and use.

More precise- Since there is no GG frame, there is nothing to warp, swell, or shim. The thickness of the magnets precisely match the T-distance of the film holder, and the GG surface placement is as flat and true as the glass itself.

More economical- The simplified design reduces the time and materials required to build a comparable spring back design.

More beautiful- This is a matter of taste, but the absence of springs and hardware make for elegantly clean fit and finish.

Disadvantages:

Removing the GG for every exposure takes getting used to. I prefer the MagnaBack to other designs in which the GG is removed, like the *Argentum cameras, because it's very convenient to simply place the GG on the film holder, and with familiarity, it becomes second nature.

Film holders must be modified. Wooden film holders can be modified for use with the MagnaBack without affecting their use with spring backs. I haven't yet adapted metal or plastic holders.

* Several months ago I emailed Argentum Cameras about this idea, but they didn't respond.

This is just one of many projects I'm developing, and a work in progress, but It's definitely the most fun. I'm not sure how much appeal it will have for users of existing cameras- that will depend on how much they're bothered by spring backs, but it should be very appealing to camera designers and builders, and to users of MagnaBack cameras.

If anyone is interested in converting their camera to a MagnaBack, email me:

jdefehr@gmail.com

[Leigh]

The clamp attached to your left hand (a.k.a. 'thumb') works great.

- Leigh

[leighmarrin]

Not exactly a direct answer to Ken's question, but my half-arsed fix for the loose backs on my wheezy B&J view cameras also mostly fixes the brief slide-withdrawal gap problem.

I take about three feet of string or small cord and put a large clove-hitch knot in it, and drape the knot over the top of the rear standard and around part of the edge of the ground glass. Tightening the knot is quick and easy, and a clove-hitch knot holds itself tight, as long as something is underneath it.

For a vertical holder position on my B&J Saturn, I will instead use the two center-locking knobs on the side of the rear standard to put the looped string around--this puts the retaining pressure in the center of the back and film holder.

There's an easy way of making a clove-hitch with two identical side-by-side loops in a length of cord: just put the RH loop in back of the LH loop, put object(s) in the middle, and tighten, then put a simple under-over tie to firm it. Also useful for building temporary bridges & towers from sticks and binding Girl Scouts. (!)

But my fix would look really klugey on a nice Deardorff...

--Leigh M. in Santa Barbara.

[timparkin]

Disadvantages:

Removing the GG for every exposure takes getting used to. I prefer the MagnaBack to other designs in which the GG is removed, like the *Argentum cameras, because it's very convenient to simply place the GG on the film holder, and with familiarity, it becomes second nature.


Wouldn't it make sense to leave the ground glass on a hinged mechanism (so it swings away). That would certainly make it easier.

As a fan of magnets (http://www.timparkin.co.uk/blog/860165826236084689) I quite like the idea but modifying all my darkslides might put me off?

Tim

[Frank Petronio]

A big rubber band might help....

[Ken Lee]

If not a big rubber band, perhaps a strap of some kind, which can easily be opened and shut - using magnets perhaps - or better yet, a little VELCRO might do the job. Hmmmm... That might do the trick.

[BetterSense]

I have been known to jam my graflok sliders against the side of the film holders to secure them more. If you were willing to mill a groove in your film holders, you could have the graflok sliders actually lock the film holders in.

[Jay DeFehr]

Tim, the hinged GG would defeat the neat, hardware-free design, and also the way (one of the ways) reducing backs work with my system. A 5x7 reducing back for an 8x10 camera, for instance, fits in the space the 8x10 film holder occupies, and the 4x5 reducer fits in the 5x7 space, and the 3x4 fits inside the 4x5 space, and the roll back fits in the 3x4 space. This nesting system is very convenient in the studio, and very compact to carry into the field. Of course it's also possible to make any intermediate conversion by a simple adapter, if one wants to convert directly from 8x10 to a roll back, for instance, which makes for a very flexible system.

Adapting film holders is an issue, and I understand your reticence to put your holders in the mill, but adapting wood holders is very straightforward. A channel about 1.5mm deep is milled into the rails and a very strong, but thin magnet is inlaid. I've not adapted any metal or plastic holders, but I'm confident it can be done. The magnets on the holders can be thin for two reasons: 1) they're very strong 2) they mate to thicker, stronger magnets on the camera back. The adapted holders still work in standard backs exactly as before, so one doesn't need to dedicate holders to a MagBack.

I like your lens shade! A poor man's compendium. Very clever.

[Michael Kadillak]

Kens questions is a pertinent one and something that I have been dealing with for some time. I personally find that this should not be an issue with 4x5, 5x7 or 8x10 when the springs of the ground glass back are of sufficient strength and the seat of the holder to the camera is mated properly. Weak springs or binding dark slides create problems with the use of the dark slides as Ken described. With the spring back of sufficient strength and the dark slides moving smoothly (Pledge and a slight smoothing with an emery board) I find that I do not even need a dark cloth over the camera. Where I find this is an issue is with panoramic cameras like my 8x20 with the long dark slide and other ULF formats like 11x14 and 12x20.

For my ULF cameras I make a habit of always putting a dark cloth over the back prior to inserting a film holder. I then use two small bunge cords with the small hooks on them to go over the darkcloth that is over the camera back hooking these to the wooden frames. Not to strong a bunge, just sufficient to keep things from bowing out. This keeps the dark cloth in place but also prevents me from unintentionally not replacing the dark slide as square as it needs to be replaced. When I used to have any angle less than square during insertion I would bow the front of the rear of the holder ever so slightly and minor amounts of light would creep in.

I also find that with the bunge cord in place I can have two hands free to grab small 4-6" sections of the dark slide from the top and bottom and manage the perfectly square reinsertion procedure much more effectively. There is nothing more frustrating than to see that light seep in your developing trays on your negatives.

[cdholden]

Is there some kind of simple clamp that we could use ?
Any suggestions ?

I've never seen a need for much more than a tight grip with the left hand while maneuvering the slide with the right (even being a lefty!).

Ken,
Have you tried a squeeze clamp (aka pistol grip clamp)? You would have to find one with a deep distance from tip of clamp to tension bar. Most of them are pretty shallow.
For example, see this: http://www.amazon.com/Bora-540612-Pistol-Clamp-12-Inch/dp/B0035YGLVA
Chris

[Michael Kadillak]

The problem that you inherently have with any clamp is that there will always be an offset between the two places that need to have pressure applied - the edge of the camera and the area on the outside edge of the ground glass frame where slight pressure needs to be applied. Even with a deep clamp face they are hard to work with. Clamps work best where there is no offset involved.

[GPS]

...
Is there some kind of simple clamp that we could use ? Once the film is in the camera, lock the clamp. Then remove the dark slide, shoot, and replace the dark slide. Then unlock the clamp and remove the film holder.

Such a clamp has to be lightweight but strong. On wooden cameras, it can't damage the wood. And it has to be affordable and readily available.

Any suggestions ?

Ken,
such a "clamp" is easy to make, provided you allow a slight modification on the gg back assembly. It can be a flat spring catching a groove (or many other similar ways) permanently attach to the gg back assembly so that you don't need to think of it to put it there and away all the time.