DIY Kalart FocuSpot-style Laser Ranging with Technika RF

[towolf]

I was thinking about a way to make hand-held shooting with my Linhof Technika more convenient.

Switching between the universal finder and the rangefinder eyepiece seemed imprecise and kind of slow while hand-holding. And since I was also thinking about focusing in the dark and whether a laser pointer might help there I combined the two thoughts and soon stumbled upon prior art: previously (www.graflex.org/speed-graphic/kalart-focuspot.html), previously (http://www.largeformatphotography.info/forum/showthread.php?58303-Mounting-a-laser-pointer-for-focusing&highlight=laser), previously (http://www.largeformatphotography.info/forum/showthread.php?26806-Laser-pointer-focusing&highlight=laser), previously (http://www.largeformatphotography.info/forum/showthread.php?1945-Focusing-in-the-dark-with-a-laser&highlight=laser), and in particular previously (http://www.largeformatphotography.info/forum/showthread.php?60697-Kalart-Focuspot-laser-pointer-retrofit&highlight=laser)

Since my Tech V doesn’t have the Kalart Focuspot port, the laser beam had to go into the eyepiece of the RF. So looking at laser pointers it was clear it would stick out, making it clumsy and probably hard to mount.

So I got the shortest one I could find on Amazon, the Zweibrueder LED lenser Laser V9 (13 EUR "used").

http://i.imgur.com/Nx3i0HXl.jpg (http://i.imgur.com/Nx3i0HX.jpg)

And I got two beams alright

http://i.imgur.com/gpVLWm1l.jpg (http://i.imgur.com/gpVLWm1.jpg)

But how to mount the 10mm laser pointer "pen" onto this 18mm wide "cup"?

http://i.imgur.com/Ba2syl7l.jpg (http://i.imgur.com/Ba2syl7.jpg)

It seemed awkward and would require something purpose-built to get axial alignment with the RF spot

http://i.imgur.com/hD9c3YQl.jpg (http://i.imgur.com/hD9c3YQ.jpg)

[towolf]

Lo and behold! The capsule at the end can be unscrewed, exposing the laser tip and a tiny circuit board

http://i.imgur.com/3FXSW3Fl.jpg (http://i.imgur.com/3FXSW3F.jpg)

It’s my lucky day. It fits right into the hole on the eyepiece. With some velcro to keep the button pressed

http://i.imgur.com/mSPKjGpl.jpg (http://i.imgur.com/mSPKjGp.jpg)

And we have "target acquired"

http://i.imgur.com/LboY4Tbl.jpg (http://i.imgur.com/LboY4Tb.jpg)

The brass tip needed to be clad in two windings of scotch tape to fit snugly. Fortunately it doesn’t obstruct anything and the GG door swings past it

http://i.imgur.com/OJEupWKl.jpg (http://i.imgur.com/OJEupWK.jpg)

[towolf]

Aligned the two spots 5m from the film plane

http://i.imgur.com/y0fRtgKl.jpg (http://i.imgur.com/y0fRtgK.jpg)

And they are sharply imaged on the GG. The parallax offset is a little annoying but it converges somewhat with distance.

http://i.imgur.com/CYvmVXAl.jpg (http://i.imgur.com/CYvmVXA.jpg)

5m alright

http://i.imgur.com/tZXcFAIl.jpg (http://i.imgur.com/tZXcFAI.jpg)

[towolf]

Visibility outdoors during day could be better. But OTOH I mostly wanted something for focussing at low light.

Here, the stem of the Ginkgo is lit

http://i.imgur.com/0pmjNyMl.jpg (http://i.imgur.com/0pmjNyM.jpg)

And it’s sharp

http://i.imgur.com/8fFaDzhl.jpg (http://i.imgur.com/8fFaDzh.jpg)

At extremely short ranges, down from 1.2m it becomes a little imprecise, but perhaps this is out of spec for the cam coupling.

[towolf]

I’m pleased to report that it seems to work very nicely at night. I can see the spots clearly until infinity, i.e. when the lens is racked all the way back, roughly 80 meters. And further than that it serves no use anyway.

[Corran]

Very nice. Thanks for your report with regard to the exact model of laser pointer. Might need to pick that up and give it a try.

[Drew Wiley]

Miniaturized decent laser distance meters are starting to come on the market quite reasonably now. Leica (not the camera division) has one for about $150 with a
400 ft range. These are far more accurate than any optical rangefinder, and have a pointer beam.

[towolf]

Miniaturized decent laser distance meters

Sure, I was using a Bosch hand held laser rangefinder (not mini by any means though) to verify the exactness of my "hack" and to make some distance scales I didn’t have. That thing is accurate to ±2mm.

But the big thing is, the external laser distance meter is not coupled to your lens. I can nail focus at f4.5 with my shitty little laser pointer. And for every continuous distance in between 1.5, 2, 2.5, 3, 5, 8, 15, 30, ∞.

Sure I can use an external laser distance meter to measure 15m, then move my tripod to exactly 15m, and set the lens to the 15m mark on the scale. But that’s just not the same.

[Corran]

I just ordered the same laser from Amazon. Thanks again.

[towolf]

One small addendum

I’ve sawed that aluminium cap in half (or rather 1/3 from the thread) and screwed it back on to relieve that circuit board. I was afraid it could snap off when lateral force is applied:

http://i.imgur.com/96eRRCW.jpg

http://i.imgur.com/LDecPCa.jpg

Now it plugs in and has some support.

[nonuniform]

Wow! I was thinking about this exact project, and poof! someone else has already done the hard work.

Thank you so much for sharing. Much appreciated.

[towolf]

It wasn’t that hard, I was just really lucky with my pick. This laser pointer was 3x more expensive than the usual "cat toy" 5 bucks laser pointers. But that brass tip was the crucial puzzle piece.

[Bill_1856]

If you lift up the leather cover on top of the RF, you MAY find the hole for a Kalart Focuspot. (Don't know if this applies to your model Technika).

[towolf]

No, not on mine. I’ve stripped it completely and ordered a new leatherette from cameraleather.com.

[Donald Qualls]

Nice. I'd have to go look to be certain, but I think the Kalart on my Speed Graphic has the Focuspot port. I might have to fabricate a mount for a small laser pointer for that. I've wanted to do some hand-held night photography (I've got a film/developer combination that gives an honest EI 5000 with reasonable contrast); the ability to focus accurately while composing would complete the capability.