Will this work as a shutter?

[Richard K.]

OK a few of my lenses are too wide or protrude too far to use with the Sinar Auto Shutter. Is there a shutter that can clamp on (and with variable diameter) to the front of a lens?

If not, will this work: make a rectangle with a square hole cut in it big enough to view the entire front lens element. Have another rectangle cut with a slit of same width but of varying heights. Incorporate a system that will keep them together while the one with the slit starts with slit above the opening and slides (free-falls) past the opening and stops once the slit has completely cleared. It would be solid above and below the slit to prevent light passing other than through the falling slit. Workable? I calculate that a 1" slit would be roughly a 1/15 s exposure, a 4" is 1/8 s and 1/4" is 1/30 s - can someone confirm? (I just simply used that d=16 t ^^2 (d= 1/2 g t-squared) )

[Richard K.]

I guess what I'm asking about in the second example is kind of like a front mounted focal plane shutter...

[eddie]

you can front mount a packard. or get a recessed lens board that has a packard on the rear. (like this) (http://www.largeformatphotography.info/forum/showthread.php?t=63009) or just send me the lenses that stick through and i will use them.

[Paul Fitzgerald]

Richard,

search here or google 'guillotine shutter', it's what you describe, usually powered by gravity and rubber bands. Can be made from foam-core and an old dark slide.

Have fun with it, post pics when it's up and running.

[Peter K]

Richard, drop-shutters where used in the early days of photography up to now in sensitometers. But ceased because of low efficiency and too slow for modern materials.

Have fun

Peter

[Don7x17]

front mounted drop shutters work fine with modern materials....here's an example of a long Knuckler with TMY 400 8x10: (at f5.6 with a soft focus lens)
http://www.apug.org/forums/groups/tonopah-nevada-picture2908-harlan-tmy-400-1-8-sec-5-6-thh-cooke-420mm-soft-set-2-5-ron-tinchner-shutter-front-mounted-scan.html

and

http://www.apug.org/forums/groups/tonopah-nevada-picture2883-jim-galli-cooke-lens-soft-set-2-5-ron-tinchner-shutter-1-8-sec-f5-6.html

and

http://www.apug.org/forums/groups/tonopah-nevada-picture2760-per-volquartz-420mm-cooke-soft-set-2-5.html

and here's an image of the arca swiss 8x10 with the lens and shutter (the lens weighs over 13 pounds and is huge...that's not 4x5! the lens board is 171mm x 171mm). It sits on an Arca Swiss B-2 ballhead. Yes, that clothespin on the shutter is the shutter release (although there is also a socket for a cable release, this one is a whole lot more fun!)

http://www.apug.org/forums/groups/tonopah-nevada-picture3333-camera-justice-tonopah-style-judge-jury-executioner.html

So the front mount shutter works just fine with modern materials.... and this particular shutter was made of carbon fiber materials and does not use any rubber bands - just gravity... and its adjustable to give 1/8 to 1/250 times (via slit width). It works fine with TMY and TriX.

[Peter K]

...here's an example of a long Knuckler with TMY 400 8x10: (at f5.6 with a soft focus lens)
The images are only aviable for registered members.:mad:

[Richard K.]

Outstanding Don. The shots and the aparatus! So, how does one adjust for:

a.) barrel diameter (my lenses vary from about 2.5" to 5.5" (19" Sigmar)
b.) slit width (shutter speed)?

Then:
Where, how, does one get one (is this a Ron Tinchner (?) Shutter) or is this home-made?

Many thanks for the reply, Don. This may be exactly what I need and I love the fact that it's gravity powered! :D

Holy crap - 3:30 A.M. ! I better get to sleep!! :eek:

[Richard K.]

The images are only aviable for registered members.:mad:

It seems that they'll let just about anybody join. They let me :D I just clicked join but I can leave if there are Tonopah dependent requirements...

[Richard K.]

But ceased because ...... too slow for modern materials.

Have fun

Peter

It should be fun...I get 1/125 s for a 1/64" slit (but that may be thin enough for significant diffraction effects!). Better to use 1/4" slit for 1/30 s...

[eddie]

Holy crap - 3:30 A.M. ! I better get to sleep!! :eek:

har har har! it is 9:30 am here...sucker!

[Richard K.]

har har har! it is 9:30 am here...sucker!

Er, Eddie, I don't know how to quite tell you this...but...we live in the same time zone :eek:

[Richard K.]

Getting back to the original thread...

Would a falling slit not produce uneven exposure top to bottom due to the different slit velocity due to gravitational acceleration? This could be minimized I suppose the more one starts the slit above the lens but there will still be a difference. Is this not a visible (on the neg) problem?

[Len Middleton]

Richard,

There is the Jim Galli patented shutter, see: http://www.apug.org/forums/forum44/22200-jim-galli-shutter-barrel-lenses-drum-roll-please.html

I have no affilication with the gentlemen, nor know what his current royalty rates are for useage / reproduction of his device. :D

Regards from just down the road,

Len

[Paul Fitzgerald]

"Would a falling slit not produce uneven exposure top to bottom due to the different slit velocity due to gravitational acceleration?"

That's where the rubber bands come in, evens out the acceleration and allows for faster speeds with the larger sized slit.

[SAShruby]

Er, Eddie, I don't know how to quite tell you this...but...we live in the same time zone :eek:

He must be in Europe ;)

[Don7x17]

Outstanding Don. The shots and the aparatus! So, how does one adjust for:

a.) barrel diameter (my lenses vary from about 2.5" to 5.5" (19" Sigmar)
b.) slit width (shutter speed)?

Then:
Where, how, does one get one (is this a Ron Tinchner (?) Shutter) or is this home-made?

Many thanks for the reply, Don. This may be exactly what I need and I love the fact that it's gravity powered! :D

Holy crap - 3:30 A.M. ! I better get to sleep!! :eek:



This was a prototype. Ron (Lee) is working on an improved version.
Barrel diameter could be easily solved by a softwood ring on the backside with three nylon screws (a technique for many filter holders).
Changing slit is done by changing the ratio of the two cards that form the shutter -- and this is done manually.

This topic was pontificated upon by many of the armchair "experts" in this forum, many of who said it could never work.... (like so many net forums, the "experts" far outnumber the experts....)

http://www.largeformatphotography.info/forum/showthread.php?t=51309

[jnantz]

is ron responding to emails ?
hugo z tried to reach him
with no response ...

[Richard K.]

This was a prototype. Ron (Lee) is working on an improved version.
Barrel diameter could be easily solved by a softwood ring on the backside with three nylon screws (a technique for many filter holders).
Changing slit is done by changing the ratio of the two cards that form the shutter -- and this is done manually.

This topic was pontificated upon by many of the armchair "experts" in this forum, many of who said it could never work.... (like so many net forums, the "experts" far outnumber the experts....)

http://www.largeformatphotography.info/forum/showthread.php?t=51309

I read through this carefully and I wonder if Ron has compensated for the fact that the sheet of film will be under-exposed at the bottom compared to the top due to the slit accelerarting as it falls? Also, if a slit could move at constant speed, then the size of the lens doesn't matter, the effective shutter speed would be the same (exactly true only for a true focal plane shutter but fairly close otherwise) regardless of lens diameter - certainly you don't need twice the travel speed for a lens with twice the diameter! The uneveness I would worry about but it seems to noy be a problem - is the neg compensated for in development?

[Richard K.]

The uneveness I would worry about but it seems to not be a problem .....

Possibly because the falling slit rapidly reaches terminal velocity due to friction?

[Paul Fitzgerald]

The you-tube link shows a nice drop shutter, part2 shows the cable release set-up well.

Drop shutter (http://www.youtube.com/watch?v=8odb2oeBrJA)

[Richard K.]

The you-tube link shows a nice drop shutter, part2 shows the cable release set-up well.

Drop shutter (http://www.youtube.com/watch?v=8odb2oeBrJA)

Excellent, thank you. Is this one that can be purchased?

[SAShruby]

The only problems with those shutters would be if you use lots of tilts, or angled shots. Spring would be required to move slit.