## View Poll Results: In your opinion how many shutterless lenses are there around the world?

Voters
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• over 1 million

18 85.71%
• under 1 million

3 14.29%

# Thread: Slip on focal plane shutter

1. ## Re: Slip on focal plane shutter

The speed the shutter curtain travels is going to vary with the angle of tilt somewhere on the order of R * cos theta for a tilt of theta from the vertical for your typical rate of travel R. If you replace gravity with a constant force k (say from a rubber band) then the tilt would be less of a factor, perhaps make the travel horizontal. Interesting product.

2. ## Re: Slip on focal plane shutter

Since Ron has made the claims of accuracy, I would like a question answered...

A couple years ago I looked into making a behind-the-lens guillotine type shutter. The basic design is overly simple. Then using a modified Speed Graphic shutter with actual calibrated speeds. It all sounded simple until one single thought screwed the whole idea up...

The accuracy of the shutter speed can only be calculated for one single lens focal length, one single focal distance and one single film size. Change any of those and the real shutter speed at the film plane changes. That's why guillotine shutters died out while the Speed focal plane shutters lived on...

If you want to think simply, try holding a 3 foot stick from the tip and wave it back and forth. The tip you're holding is considered the back of the lens. Place your imaginary film at any point along the stick. The stick waves back & forth at a constant speed (as does the shutter). The stick itself represents the thin line of light that passes through the slit in the shutter as it travels. As you move from the 'film' towards the rear end of the stick, the effective speed of the stick passing by the 'film' increases. This would be the same as changing the focal length of the lens or the focus distance. A guillotine shutter can not possibly give the same exposure at the film plane for a varying distance of lens to film. As far as gravity goes, that's a 'gimmee' and why I looked into a controlled shutter curtain with a constant speed.

If you've found a way around this, I'd sure like to hear about it...

3. ## Re: Slip on focal plane shutter

Originally Posted by Ron Lee
I realize that everyone can't be pleased all the time especially if they have been rode hard and put up wet and been left with a raw disposition. Those I ignore, the ones who knows all about everything. You'll find one in every crowd. In my 68 years in life I have run into many of those types. Its better to ignore and prove them wrong with their own theory. With over 500+ shots with the shutter and an accurate Luna Pro, not one shot was incorrect. The proof is in the pudding, and it taste so good. The Newton law I understand but how many of the general public understands. When in Rome speak Italian!
Ron,
still speaking nonsense? It is clear that your technical expertise in this field is of the same order as your knowledge about the focal plane. Your honesty is in question, so serious it is. Hopefully the people you mislead with your claims will understand it from the Ebay description of your "precise" shutter. If not they will be defrauded of their money, to put it plainly... You'd better to tell them honestly that with your "precise" shutter they cannot make tilts with the front standard, use lenses of a different diameter without loosing the shutter speed - to add to the list of other sources of imprecision...

4. ## Re: Slip on focal plane shutter

If I sent you a shutter to test, would you return it afterward?

5. ## Re: Slip on focal plane shutter

I would but I'm in Europe for the moment and to send it back would cost me more than I would like to pay for the proof. But no amount of testing can remove the basic physical limitation of the construction (inclination sensitive beside all the other imprecision sources also those mentioned by RichSBV).

6. ## Re: Slip on focal plane shutter

Originally Posted by GPS
I would but I'm in Europe for the moment and to send it back would cost me more than I would like to pay for the proof. But no amount of testing can remove the basic physical limitation of the construction (inclination sensitive beside all the other imprecision sources also those mentioned by RichSBV).
wow! you bash on the guy in public, (a simple kind PM would have sufficed i would have imagined) and then you will not even try it because of a few pennies of shipping cost! damn!

7. ## Re: Slip on focal plane shutter

The Thornton Pickard shutter( http://licm.org.uk/livingImage/Shutters-Blind.html ) wasn't even close to the film plane (as much as 12" in some case) but slightly behind the lens and used a curtain with a constant slit cut in it, similar to mine, and governed the speed of the scan by the tension of the return spring when cocked. The Packard wasn't close either. Regulating the speed of travel with a given opening in the curtain can render same exposure as by regulating the opening with a constant speed. Take any lens and modern shutter, you have a choice of combination to get the same exposure. Whether the light regulator is in front of or in rear of the lens makes little difference, it still regulates the amount of light striking the film. I will admit that there is a small deviation in travel speed curtailed by drag resistance and an unmeasurable amount of resistance caused by a light breeze, unless you are shooting in winds that would topple your camera. What matters is the end result, that you get the exposure that you want without having to use calculus to figure the variables that will not have any effect on a film that has a greater deviation within itself. Take a box of film, load a couple of holders, return the box to the cooler and in a couple of weeks you find that the speed of the film has changed in the film holders. I think that you will agree with me that in photography there is no need to split hairs. If you find that you over exposed use the zone system to compensate. My last word is my shutter works by the method of practical application.

8. ## Re: Slip on focal plane shutter

I have been using quite successfully for about 4 years now a speed graphic focal plane shutter on the front of my Deardorff, behind my lenses. The concept of the stick is valid with the exception being that what is moving at the end of the stick is a point and what is moving at the film plane with a slot shutter is a slot and the size of the slot varies with the focal length, being larger the longer the focal length. I believe the change in the slot size at the film plane compensates for the change in the speed of travel.
My experience with many sheets of film has shown that concept of a slot shutter at the front of the camera is a valid concept.
I think is a interesting product and am happy to see that there are some others who realize that there is a gap in the current market for a reasonablly priced univeral shutter.
I agree that some of controlling mechanism like a spring or rubber band might be an improvement and add some consistency, but I have not used the shutter so I can speak from experience.
The proof would be in the pudding so to speak. Test the gravity shutter against a calibrated shutter and check it out. It would be simple to perform. I would volunteer to do this but I cannot add another task to my current list, but maybe another fellow forum member would be willing to do this test and post the results.

9. ## Re: Slip on focal plane shutter

It is good to see that there are some who have a bit of common sense. I would like for someone to prove to me what the difference of light control in front and in rear of the lens would be. I have a 12" lens with a leaf shutter that I have shot two plates, one with the leaf shutter and one with my shutter attached and for the love of Gd I could not find one ounce of difference. The shutter is between the lens group in the leaf shutter and I don't have a packard to compare shots in front and in back of.

10. ## Re: Slip on focal plane shutter

The front mount shutter was introduced in the late 1800's as evident of the Thornton Pickard front mount model as seen here; http://cgi.ebay.com/g60-ANTIQUE-wood...Q_trksidZp3907.
m263QQ_trkparmsZalgo%3DSIC%26its%3DI%252BC%26itu%3DUCI%252BIA%252BUA%
252BFICS%252BUFI%26otn%3D14%26po%3DLVI%26ps%3D54
and someone said it wouldn't work. This one looks to weigh quite heavy. Could be the reason for the decline. If I had the money I would pick it up just for the antique value.

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