Suddenly a hole in my m7 curtain, how is this possible?

[mmradman]

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Yeah, "just a bit".  For cotton* cloth ignition temparature is round 200 degrees C, for titanium it is somewhere round 1,600 degrees C.

*assume fire retardant/resistant cloth still round 400 degrees.

edit - link added

https://www.tayloredge.com/reference/Science/ignition.html

 

 

Edited May 11, 2021 by mmradman

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[adan]

7 minutes ago, jaapv said:

Titanium can burn as well - it is just a bit more resistant than cloth.

And conducts away the heat much faster. The entire metal curtain gets a little hot, but the focus pinpoint does not get as hot, locally.

_____________________

On the original question, the afternoon sun burned a hole in my M4-2 shutter in 2003 - in less than 30 seconds.

Literally, Picture A showed no leak, and Picture B made 30 seconds later showed the fog from the leaky hole.

And that was carrying the camera over my shoulder between A and B, which means it was bouncing around a little.

Lens was a 35mm f/2.0 - I have to assume I left it set to f/2.0, to let in enough radiance to burn the cloth that quickly.

And it was up here at 5280 feet elevation, with crystal-clear Colorado sky (no haze, no clouds to diffuse the sun).

[jaapv]

18 minutes ago, adan said:

And conducts away the heat much faster. The entire metal curtain gets a little hot, but the focus pinpoint does not get as hot, locally.

 

That is right - it means the whole camera will burst into flames...

[adan]

36 minutes ago, jaapv said:

That is right - it means the whole camera will burst into flames...

Metal shutter, but not Nikon....

https://petapixel.com/2010/08/25/man-blows-a-fireball-and-burns-up-his-canon-5d-mark-ii/

[Michael Geschlecht]

Hello Everybody,

Back around the time that people first walked on the Moon I had a pinhole appear in only one shutter curtain. Not both. I took the camera to Leitz who repaired in an esthetically challenged manner with some sort of applied, apparently liquid, "something". Up to & including today there has NEVER been any problem with this repair.

Best Regards,

Michael

[jaapv]

5 hours ago, adan said:

Metal shutter, but not Nikon....

https://petapixel.com/2010/08/25/man-blows-a-fireball-and-burns-up-his-canon-5d-mark-ii/

Oh - but it is a Canon... Of no import then

[Danner]

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[nitroplait]

On 4/23/2020 at 9:26 PM, Sailronin said:

As noted above, lens pointed to sun with lens cap off.  I had this happen to my first SLR,  an old Miranda back in the '70s.  

How would that happen to an SLR? Did Mirada's have MLU?

[TomB_tx]

6 hours ago, nitroplait said:

How would that happen to an SLR? Did Mirada's have MLU?

The first Miranda did not have an instant return mirror, so the mirror would stay up until the film was advanced.

[nitroplait]

1 hour ago, TomB_tx said:

The first Miranda did not have an instant return mirror, so the mirror would stay up until the film was advanced.

OK, but that would be a Miranda T from the mid 50's then.

[adan]

3 hours ago, nitroplait said:

OK, but that would be a Miranda T from the mid 50's then.

He said the accident occurred in the 1970s - he didn't say the camera was new.

[nitroplait]

22 minutes ago, adan said:

He said the accident occurred in the 1970s - he didn't say the camera was new.

Yes he said it was old. I’m not accusing anyone. The only non-returning mirror cameras I was aware of, are those with central shutters which wouldn’t have that problem since the shutter is of metal and inside the lens - like Hasselblad and Contaflex.

[TomB_tx]

Before the 2nd model Asahiflex, common 35mm SLRs used cloth focal plane shutters and mirrors that didn't return until film was wound. Most were German, like the Exakta and some Zeiss models.