Front shutter / business opportunity ???

[john_galuszka]

<p>Over the years there have been a lot of posts here about bad shutters in need of repair, etc. For example, if you have a Copal size 00 shutter, it is almost impossible to get a reasonably-priced fix. In most cases the glass is good, the aperature adjustment is good, but the speed adjustment is very bad.</p>

<p> A way to get around this problem would be to set the original shutter to T, then add a new shutter in front of the lens to get various speeds.... HOWEVER the most common shutter for this situation is the Packard shutters which have only one or two speed settings -- usually 1/15 or 1/25th second. What is needed is a modern (spring-controlled?) version of the Packard, but one with settings for T, B, 1 to 1/500 second (or even just to 1/100 sec ... something which gives us some adjustments) which can be put infront of a lens to salvage old lenses.</p>

<p>It would be great if this shutter had a large diameter and could be attached to various lenses via standard filter step-down rings.</p>

<p>This would also be useful for people using barrel lenses. For example, I have a wide-angle 8x10 lens, but when mounted in an Alphax shutter, the shutter itself causes vignetting, so I can't get the full circle of coverage of the lens whereas the thin Packard shutter would do this, but then I am limited to one speed. If there was a thin, front- mounted, variable speed shutter, I could use this lens to get the 6X36 extreme panorama shots that the lens is theoretically capable of producing.</p>

<p>Are there any Chineese camera makers viewing these pages? This is a business opportunity. Make something like this at a reasonable price, and you probably will have a slow but steady customer base for years to come.</p>

<p>You build it and I'll buy it!!!!</p>

[joseph_wisniewski]

<p>I see two things in the way of your idea.</p>

<p>Front mounted shutters in front of wide angle lenses show up in the picture at high shutter speeds. (Interlens shutters only cause the shutter shape to appear in the bokeh, and they're a lot smaller). Because you're talking a huge shutter (in front of wide angle lenses, you could be looking at a 70mm-100mm aperture, while you might only need 25mm interlens) and "a reasonable price" I'm seeing a practical speed more like 1/10 sec, not 1/100. And 1/500 is a pipe dream...</p>

<p>The diameter of a 3 leaf shutter is 3x the aperture. You've got a 200mm "flying saucer" sitting on your filter mount. Some lenses might have trouble dealing with that. Also the front yokes of some cameras, because it's so far off axis.</p>

 

[dave_s]

<p><em>For example, if you have a Copal size 00 shutter, it is almost impossible to get a reasonably-priced fix.</em><br>

<em> </em><br>

I don't think I've seen a Copal 00, but that's not to say they don't exist! If you're talking about a Compur 00, I have had two of them overhauled by Carol Miller at Flutot's Camera for a fair price. As per routine, she did a stellar job.</p>

<p>Your idea of a modern Packard-like shutter is interesting, but the market for it would be downright microscopic-- maybe a few dozen a year. It would not be profitable for a manufacturer to take on the design, production, and marketing costs. IMHO anyway.</p>

[marc_batters]

<p>I too, have thoughts along this line, but rather then a shutter in front of the lens, somehow adapting/cutting a through-slot, inside the existing shutter housing to allow a guillotine shutter to pass. <br /> Much like the water house stop, but my idea would use a thin strip of metal like a large, long feeler gauge, or a strip of metal like a machinist's metal pocket rule. <br /> Several different ones, all cut to the same overall length, but each having a different guillotine length spacing, or opening size.</p>

<p>With all of the guillotine strips cut to the same overall length, the photographer would learn, (with practice), to slide each guillotine strip through the shutter at the same speed. <br /> The different exposure speeds would be achieved by selecting guillotine strips with various sized openings.</p>

<p>Of course, this is just an idea, and maybe an idea that in the end, would require a lot of tinkering, with no greater benefit over just using a piece of cardboard held by your hand on the front of the lens. <br /> Shutter training, ala Karate Kid? Wax on; Wax off; Wax back on (very quickly).<br /> I guess for this latter method to work, you would have to practice catching flies with chop sticks, too.</p>

[joseph_wisniewski]

<p>Marc, the interlens shutter is near the coincident nodal points of the lens. In plain English, it's at the best place to put the aperture mechanism. It's the most afocal (no light focused) point in the optical path. That causes two effects.</p>

<p>First, at any speed where you'd have a traveling slit, instead of one curtain fully opened before a second curtain starts to close, the shutter is effectively "open" the entire travel time. All that happens is that you turn the aperture into a sequence of slits cut into a circle. So, you don't have any real "motion stopping" ability, you have a longer, but proportionally dimmer, exposure. Like stopping down, except that the aperture is a slit shape, so the result is DOF that is deep in one dimension, shallow in the other.</p>

<p>The second reason is that being in a non-focused location helps keep the shutter from showing up in the image, but it still affects the image in various ways, including depth of field (and bokeh) and resolution, due to diffraction peaks.</p>

<p>The reason common shutters have either 3 or 5 blades is so those effects are distributed in a 6 or 10 pointed star pattern, which is relatively "easy" on the image. They don't use even numbers, even though a 4 blade is more naturally balanced than a 3 or 5, because diffraction peaks reinforce each other. A 4 blade produces four pointed "cross" patterns, with a stronger pattern than the 6 points produced by a 3 blade. A traveling slit produces a 2 point pattern, essentially a "line", so strong it can cross an image. That is why they are only used at the focal plane, because in any afocal location, they add a strong "line streak" diffraction characteristic.</p>

[john_wills]

<p>You could try to make a guillotine shutter that will fix on the front of the lens info here:<br>

http://www.largeformatphotography.info/guillotine-shutter/guillotine-shutter-construction.html<br>

and a video of one working here:<br>

http://tinyurl.com/65jn2dx<br>

I think that if the price was right and it worked - maybe with elastic band assist to allow some flexibility on camera angle. It could be a worthwhile enterprise.<br>

Its just a pity that I have no design/ manufacture / construction skills whatsoever. :-(</p>

<p>nn :)<strong> </strong></p>

[camera_conjurer]

<p>It isn't almost impossible to get a reasonably priced fix on a Compur OO shutter. Why would you even write that?</p>