Burning holes in your shutter - 2 questions

[nickthetasmaniac]

G'day everyone, I was taking a walk and pondering the meaning of cloth focal-plane shutters (as you do), and two rather oddball questions popped into my head...

- Would leaving your lens at it's MFD (rather than infinity) significantly lower the chances of burning a hole in your shutter curtains?

My thinking - The sun is essentially at infinity, so by leaving my lens focused at infinity (which I usually do), I'm bringing the sun into focus on the shutter. This is basically how I started fires with a magnifying glass as a kid... Would leaving the lens at MFD project the sun as a big diffused 'bokeh ball'?

- Is it possible for the shutter curtain to actually ignite inside the camera? Ie. flames and the like...

Thanks 🙂

 

[peterm1]

I do believe I have heard it recommended to focus at MFD. I have not tried it though.

I have never heard of ignition inside the camera however. Though logically there has to be some degree of burning if a hole is being burned, I would expect this to be suppressed by the relative lack of O2 inside a small enclosed box. And in support of this I have certainly never seen or heard of more than a pinhole or a bit larger being the result.

PS I have effected a repair to such a hole by using a small amount of black "liquid electrical tape" (available widely in hardware stores and auto parts stores). I have also seen such a curtain repaired by gluing a small patch of spare curtain material over the hole. This was done by a technician however.

 

[Huss]

Once when I was bored... I conducted an experiment with my M3. I held the shutter open at B, and put a piece of paper where the shutter would be. At infinity and with the lens wide open (a 50mm lens), it would burn through the paper in a few seconds. Stopped down it took forever..
I did not try mft because I wanted to burn a hole.

 

[K14]

I've always kept mine covered whenever possible. The guys on Dual Survival would have had fire much quicker carrying a Leica. 😀

 

[Doug]

Useful experiment, Huss!

Long ago I worked at a camera shop in Rapid City. The show windows faced west. We would put spacers under the lenses of display cameras to tilt them up so window shoppers could see them better. I recall two occasions when I took out a used camera for familiarization and found the shutters had multiple holes. One was a barnack Leica and the other a Nikon S2. We made sure after that to display them with the lenses set at MFD...

 

[Freakscene]

1. It sure slows it down. I just repeated Huss’ experiment (thanks for the materials and methods!) in my back yard with an MP, a 50/1 Noctilux and regular office paper. At infinity and f1 we had smoke and a hole very quickly. At mfd and f1 it was very slow. Stopped down to f16 I got bored waiting for something to happen.

2. My guess from this experiment is you could definitely get some smoke. A fire? Maybe, but as an Aussie kid who also spent their youth igniting things with a magnifying glass you’d remember that it is hard to do unless you have a few layers of fuel. With only one layer all you get is a rapidly appearing hole and the energy is no longer being transferred. My guess is the nce you have a hole things cool down rather rapidly.

Marty

 

[retinax]

The shutter is a bit in front of the focal plane, i.e. depending on the focal lens, the sun should be focused on the shutter curtain when the focus for the film plane is at intermediate or near distance.

 

[wolves3012]

I did a similar experiment some years ago - there's a thread on here somewhere. I used some leftover pieces of shutter cloth to see if I could burn holes with a camera lens. I can't remember the figures but it was amost instant at f/2, pretty fast at f/4-f/5.6 and by the time I got to f/16 it might be scorched if you had the time to wait and could hold it on the same spot.

By the way, the shutter itself is just in front of the film plane, so at infinity the image on the shutter is slightly OOF anyway (not sure it's enough for safety though) so worst-case is probably to set the lens at a bit closer than infinity? [EDIT: Retinax beat me to it]

 

[David Hughes]

I have often wondered if it would work with the camera placed on a flat surface, so the blind would be vertical and the lens axis horizontal. Would the sun be too high in the sky to be within the FoV?


Regards, David

 

[Huss]

The shutter is a bit in front of the focal plane, i.e. depending on the focal lens, the sun should be focused on the shutter curtain when the focus for the film plane is at intermediate or near distance.

You're forgetting about DOF at infinity. It doesn't matter which is why shutters get burnt.

 

[Huss]

Another thing.. this will damage any shutter in an RF kamera. Not just Leicas. A metal shutter blade would get scorched/warped etc. It is just that with a cloth shutter it happens much quicker.

 

[Goodtimes]

Leica M262 Combat ready by Joan, on Flickr

To prevent any such problem on any of my cameras this is how I carry them around.
The small leather bag is actually a jewlery pouch. It is attached to the body strap and can be pulled from the lens and shade in a half second, still hanging on the camera. It also protects from shocks, dust and sprayed water and cannot be lost like an original lens cap could be.

 

[Ko.Fe.]

Your layers of protection have serious flaw. The pillow from jewel box is missing on the top plate. You need one with your current strap.
It is most garbage strap I ever have. I have to remove German engineered attachment pieces and replace them with normal quality, made in China rings.
The reason, sooner or later somehow one of those Leica crafted attachments will disconnect and camera will fall of.
It did twice. I decided not to wait for third time.

 

[Ambro51]

“KamraKondom”. 🙂. If you wanna talk “heat”, try my 6” F8 Refractor pointed at the Sun. It would melt the camera!

 

[mthomas]

You guys are scaring me. I thought I was sufficiently forewarned after looking at DAG's site.

Marc

https://www.dagcamera.com/store/p145/How_Long_Does_It_Take_To_Burn_a_Hole_in_A_Shutter_Curtain?.html

 

[Phil_F_NM]

I carried two film Leicas all over Kuwait and Iraq in 2004 where the sun is known to be a bit intense, and I never burned my shutters. I never paid attention to the possibility either, I had other things keeping me occupied.
Phil Forrest