Large shutter design - help for project

[TheToadMen]

Wow,
Nice challenge. Let us know how it goes.

The front element on the lens is over 4", which is why I will have to go with a DIY option, plus the camera is a 'cheap and cheerful' trial to see how cheaply you can make a 5x4 camera and lens.

The larger lens I am making would be something like a 150mm f1.3, a slightly smaller lens I am also making would be a 71mm f0.87.

I might simply use the faster wider lens on the speed graphic and use the focal plane shutter but I would like to shoot wide on my DIY camera and I would also need quite a fast shutter speed (ish) for portraits on either.

Here is my issue, with ISO 6 paper in brightest sunlight shot fully open I would need a shutter speed of 1/2000s, in shade it would probably be something like 1/125s which is where the issue is.

I am perhaps thinking about a fast blade shutter, pivot at one end, blade covers, uncovers and then recovers the lens powered by a spring or band, could make that like a half moon or something.

I am thinking making a rotary shutter powered by a rubber band might be good,

[lem22]

Sounds like a really interesting project. I can't help but wonder where one might find a lens with a diameter of 110mm. Hope that's not a dumb question.

[m1tch]

Ok, I have taken delivery of a few older cameras from something I won on ebay - I was just bidding as there was a Purma special and I wanted a spare one lol there were 2 127 box brownies with 2 different simple shutters, plus my cheap point and shoot plastic camera.

On closer inspection they all basically have a spring loaded blade that is flicked and the spring then returns the blade to its rest position, the older Kodak had a much slower shutter with a few more moving parts which covered the opening whilst the blade retracted back.

Here are my comments on the way some of these simple shutters worked:

Plastic camera - shutter blade is pivoted and attached to a spring, on firing the shutter a spring loaded finger is released and flicks the shutter blade open and is then closed via the spring, fairly fast shutter speed
Newer 127 camera - shutter is pivoted and attached to a spring, lots of other spring loaded parts are also attached to stop double exposures etc but it basically releases a spring loaded finger much like the plastic camera
Older 127 camera - 2 distinct movements, on firing the shutter opens and closes, on release of the button it all returns back - on pressing the shutter one blade moves forward which is connected to a second blade, both are pivoted, once the first blade moves and spring has enough force it pulls the second the second blade trips and shoots forwards. On release of the button the first blade covers the opening until both blades are back at rest.

Here are some photos of the shutters I have:

Plastic - not much to see but the front blade is sprung:

[m1tch]

Newer 127 camera:

At rest:



Cocked - copper coloured trianular piece flicks the end of the shutter blade



Shutter is spring loaded, quite a fast shutter

[m1tch]

Older 127 camera:

Shutter blade on top moves down on the press of the button putting tension on the spring connecting the 2



Spring pulls the second shutter down once the spring tension increases between the 2



On release of the shutter the first blade is curved and covers the opening until everything is back to the rest position.

What I have learnt about the simpler shutters is that it seems that all that is needed is a pivoted shutter blade which is spring loaded, the other end of the shutter arm is then flicked and then released which then lets the shutter spring back to rest - the power of the spring gives the shutter speed.

I am going to mock up a possible design on how I could create a larger version of this, due to these cameras having all sorts of fail safes and other features (like putting a flag in the view finder informing of a shot being taken) it might be quite simple to make something.

I will have a think and work something out that is simple, cheap and effective

[m1tch]

The Q1 has been built:

150mm f1.3



Looks pretty good on the speed graphic (not attached so not 100% perfect)



Crazy crop on the NEX3 though! Image of bicycle across the other side out the window free lensed, 150mm f1.3, ISO 200, 1/160.