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Kalart Focuspot Rangefinder

 
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Sjixxxy



Joined: 27 Apr 2004
Posts: 108
Location: Midwest US

PostPosted: Sun May 23, 2004 4:43 am    Post subject: Reply with quote

Just rigged up a temp cable to send juice to my focuspot. Light is still good!

1) Though not critical in any way, is the actual spot suppose to be a spot? Mine looks more like a peanut. Sure it still focuses accurately, but would a non-spot shaped spot indicate something out of whack, or in need of a cleaning?

2) I could shoot a sheet and have this answered in 30 minutes, but its fun to post instead. A flash should overpower the spot right? It is pretty nice to have the rangefinder integrated into the viewfinder when it is in range and dark enough. Not that I'm too lazy to just move my thumb an inch and turn it off, but if it would be overpowered and not visible due to the flash, moving the thumb to turn it off could be when the best photo happens. Also, I noticed that when looking through the viewfinder that the dot sits right on the X-axis, and just a bit to the right of the Y-axis. Could use this to target from the lap or hip if I was trying to get some candid photos of friend/family, or any other situation where I couldn't keep my eye on the finder.

3) Anyone have any excess beam splitter lying around that would send/sell me a piece of? I hear it gets sold in much greater quantities then one camera will need. My finder is very hard to use though the peepholes.
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45PSS



Joined: 28 Sep 2001
Posts: 3160
Location: Mid Peninsula, Ca.

PostPosted: Sun May 23, 2004 7:05 am    Post subject: Reply with quote



[ This Message was edited by: 45PSS on 2005-12-26 19:57 ]
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t.r.sanford



Joined: 10 Nov 2003
Posts: 812
Location: East Coast (Long Island)

PostPosted: Sun May 23, 2004 11:50 am    Post subject: Reply with quote

The "Focuspot" is a neat accessory. Kalart also made a device called the "Rolleispot" that attached to the bottom of a "Rolleiflex Automat" and provided the same benefit. That benefit was even more appreciated by those using reflex groundglass focusing under low-light conditions.

The "Focuspot" has a little lens in it that collimates the beam. What you're seeing is a projected image of the lamp filament, viewed from the top of the lamp -- thus the shape. I've speculated about using one of the new super high intensity LEDs, which would give you a round spot, and could be powered by a smaller battery.

The beam is about as bright as a mediocre flashlight, so will be overwhelmed by just about any kind of flash. But if you're using Polaroid "Type 57" 3000-speed film and a "Winklight," all bets are off!

The only drawbacks I can see to using the projected spot in lieu of the viewfinder are, first, that you'd have to guess at the angle of coverage and, second, that the picture likely wouldn't be level. But it would be sharp.

It's possible to imagine an accessory that would project a frame onto the subject, but the "Focuspot" isn't it.
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Sjixxxy



Joined: 27 Apr 2004
Posts: 108
Location: Midwest US

PostPosted: Sun May 23, 2004 5:09 pm    Post subject: Reply with quote

Quote:
I've speculated about using one of the new super high intensity LEDs, which would give you a round spot, and could be powered by a smaller battery.


Attach one of those small keychain lasors to it and be able to focus on street signs 1/4 mile away. Course these days someone would see it and panic thinking they had a rifle aimed at them and the feds would come after us. Might make for a good photo though.



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t.r.sanford



Joined: 10 Nov 2003
Posts: 812
Location: East Coast (Long Island)

PostPosted: Sun May 23, 2004 5:33 pm    Post subject: Reply with quote

The idea of a laser diode pointer came up in one of these threads, with regard to use as a focusing aid. It is an attractive thought, but however low-powered the things may be, I have some concerns over possible accidental eye injury. I would be glad to learn that these concerns are unfounded.

Back in the day, lighting someone up with a "Focuspot" in a darkened room usually elicited a startle reflex in the subject, and that was long before the application of lasers to rifle marksmanship!
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Sjixxxy



Joined: 27 Apr 2004
Posts: 108
Location: Midwest US

PostPosted: Sun May 23, 2004 8:57 pm    Post subject: Reply with quote

I've always thought the eye injury stuff was just urban legend. I had one of the keychain laser when they first came out about seven years ago. I've hit myself in the eye a handuful of times, and even stared into it a few times(its really pretty). I've never received any eye damage from it. Its not like they sell the powerful ones that can cut metal to the public for $9.99 on a keychain. If they can damage from prolonged exposure, I'd be hard pressed to beleive that anyone could keep a bead on someone's eye for any period of time long enough to do any damage. I think I'll see what google tells me about lasers now.
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Les



Joined: 09 May 2001
Posts: 2682
Location: Detroit, MI

PostPosted: Sun May 23, 2004 10:35 pm    Post subject: Reply with quote

Just to state the obvious, when you use the focospot, you site the image with either the wire finder or the view finder and focus until the two images of the filiment are coincident.

I never even thought to look through the rangefinder with the focospot on.


RE: Lasers. I"m not sure how much of this is true, but I had a client that was working for "some part of the government" couldn't say which. They used lasers and rotating prisms like I use Xtol and fixer.

They needed some shots of what they did showing the laser, but their laser set up was in a clean room, a clean room either 10 or 100 times cleaner than an operating room so there was no way they would let me in their with my dry ice machine to fog the laser to get it to show.

I said I wanted to do some testing in the studio and mentioned picking up a laser pointer for my tests.

They snickered and giggled, then told me that the laser pointers aren't true HeNe lasers at all and don't behave like HeNe lasers.

So I went and bought a 4w HeNe. Now THAT laser probably could do some damage to your eye, and I've been able to put a dot a good 1/4 mile away and see it clearly. Theoretically, I could do holograms with it to, but never tried.

So this long winded story is....no I don't think those little pen lasers can do any damage at a decent distance for a fraction of a second.

What might be a bigger legal hazzard is video cameras and flash bulbs. If your at a wedding with your #25 bulbs and a another guy is opposite you with his video camera set wide open, you can take out his CCD if he aimed it just right as your bulb went off.

Les
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t.r.sanford



Joined: 10 Nov 2003
Posts: 812
Location: East Coast (Long Island)

PostPosted: Sun May 23, 2004 11:11 pm    Post subject: Reply with quote

It doesn't seem very likely that the tiny laser diode-based "pointers" could do any damage. Perhaps everyone errs on the side of caution, which isn't always a bad idea.

About 30 years ago, just before the advent of practical coin-operated video games, there was a widespread effort to apply modern electronics (modern, that is, in 1976 or thereabouts) to coin-op amusements. One game that was introduced used a very small laser as the basis for a sort of shooting gallery. It was withdrawn from the market because of concern about its potential danger.

It would be very useful to have a definitive answer to this. Facts bearing on the problem include (1) do the little laser pointers come with warnings about shining them into your eyes, and if so, (2) are those warnings grounded on anything more substantial than an entirely warranted fear of the trial lawyers and the Consumer Product Safety Commission?
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RichS



Joined: 18 Oct 2001
Posts: 1467
Location: South of Rochester, NY

PostPosted: Mon May 24, 2004 3:40 am    Post subject: Reply with quote

Les,

Your list of 'toys' never ceases to amaze me What happen to the NeNe laser? And where did you find one? Something I always wanted to play with...

Back when I actually worked inside the company I work for, they do a laser instrument. Something a bit more powerful than 4 watts and the whole idea is to burn holes in metal and ceramic specimens. It was fun to play with But you deffinitely didn't want to be on the receiving end of it! That one also had to be nitrogen cooled to fire...

And speaking of fun... Do you really think a #25 would take out an camcorder? Now there's something I never thought of I wonder if that would work with an infrared flash bulb? What did they used to say about "idle minds"?


On a serious note. I agree that the standard laser pointers are probably harmless with short duration exposure. But people do have different sensitivities and you do have to warn people against the problems of kids staring into the things for prolonged periods. Without the warnings, there would be law suits till the end of time... I tend not to stare into the pointers myself...


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Les



Joined: 09 May 2001
Posts: 2682
Location: Detroit, MI

PostPosted: Mon May 24, 2004 5:39 am    Post subject: Reply with quote

Re: The laser is sitting in the bottom drawer of my file cabinet unused and unloved. Oh and I bought it from Edmund Scientific.

Other than the experiments (which went nowhere) I did use it as a pointer for one of my slide shows for the local Historical Society.

I got home late, and left it in the car.

The next morning I head to the studio and we were trying to figure out how we could repeated position our giant soft box (12x40feet) for a three car shot. My friend said, "What I need is a laser"

I said nothing, just got to my feet and started walking out.

"HEY WHERE ARE YOU GOING?"

"To get a laser."

I came back 5 minutes later with this laser in my hand and his jaw dropped.

In my mock suprise/jewish voice is said,

"What???? doesn't every body carry a laser these days?

re: I don't have a clue about the new digitals, but the older VHS/8mm camera could be fried with a Metz. 60 series It's the same effect #5 flash bulbs have on everybody in a dim lit room when one goes off (SPOTS!! I see SPOTS!!) only with people it goes away. With CCDs it could ghost permanently or go black....(rmember the B&W film of the Beatles and all the little girls were 1/2 mile away with their box brownies and AG1s? If you look at the footage right around every flash there's a ring of black. The film so overexposed itself, it reversed. Different process but similar results

I don't know if the new infrared systems would be more or less effected.

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Sjixxxy



Joined: 27 Apr 2004
Posts: 108
Location: Midwest US

PostPosted: Thu May 27, 2004 5:16 am    Post subject: Reply with quote

Back to the LED idea. Did your specilation contain any ideas on how to actually mount an LED inside the Focuspot? My limited elctronics knowledge would probably have me breaking the glass bulb off the current lamp and attaching the LED to the two wires that the filament attaches to. Don't think I have the tools or ability to make a solder that small though. Any other thoughts on how this could be done?
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t.r.sanford



Joined: 10 Nov 2003
Posts: 812
Location: East Coast (Long Island)

PostPosted: Fri May 28, 2004 3:17 am    Post subject: Reply with quote

You'd have to look at the available keychain laser diode pointers to make a definite plan, but I think the outlines of the problem are:

(1) The existing lamp and switch are mounted in a tube that slips inside what I take to be a casting: the horizontal cylinder that extends to the rear, the 90 bend that carries the mirror, and the vertical connection to the rangefinder, the exterior of which is a sort of bayonet mount. There's a collimating, or projection, lens at the lower end.

(2) If you had a small enough pointer, the simplest approach would seem to be an adapter allowing you to slip it into the existing housing, and move it back and forth until you found the focal point of the lens.

(3) You'd need to pay some attention to the power supply. I haven't played with laser diodes, but the usual LED is very sensitive to current in excess of the very small amperage needed to light it up. A robust dropping resistor is part of every LED circuit I've seen.

I leave it to those more familiar with coherent light to say whether the collimating lens is needed at all. If it isn't (and it may not be; if it were, the laser device wouldn't work as a pointer in the first place), then if the pointer were small enough, the easiest approach might be to mount it entire, vertically, in a fitting that would mate with the bayonet in the recess atop the rangefinder. This would eliminate the original "Focuspot" altogether -- a particular benefit if you don't have a "Focuspot" in the first place!

You'd probably need to bend a small strip of metal to duplicate the small integral bracket on the original "Focuspot" that's bolted to the top of the RF housing.

An attractive feature of this approach would be that you could use the existing power supply and switch built into the pointer, eliminating the need for the flashgun battery case, or reserving it for use as a flashgun and a power supply for the solenoid.
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