I learnt something new today!

Dave Wilkinson

Dave Wilkinson

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After all these years, I thought I'd seen most old photographic gadgets, but was fascinated today - when an aquaintance showed me a really useful item. It was for testing Leica screw-mount lens focus accuracy. Just like a tube really - with a 'female' thread in one end, and a ground glass screen in the other - 24x36, it had a tripod mount - for examination with a loupe, to ascertain critical distance. No doubt some of you will have one?, but I've never seen one mentioned here.
Dave.
P.S. ever one for experimentation, I shall soon be firing -up the lathe in an attempt to produce one of these things!:)
 
Dave Wilkinson said:
After all these years, I thought I'd seen most old photographic gadgets, but was fascinated today - when an aquaintance showed me a really useful item. It was for testing Leica screw-mount lens focus accuracy. Just like a tube really - with a 'female' thread in one end, and a ground glass screen in the other - 24x36, it had a tripod mount - for examination with a loupe, to ascertain critical distance. No doubt some of you will have one?, but I've never seen one mentioned here.
Dave.
P.S. ever one for experimentation, I shall soon be firing -up the lathe in an attempt to produce one of these things!:)
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I think the one that I saw was British made, but the owner said there were at least one other, c'mon guys - someone must have one!
 
Hi Dave
Periflex made one.
I have one in my store cupboard somewhere.
If you are interested drop me an email.
jesse
 
Think I saw something like this on That Auction Site a while ago, but it was a Periflex accessory!?!?

Periflexes have 39mm LTM as well, but lens and camera construction are radically different, the Periflex has a periscope like finder on top! Lens register was different too, I didn't think it was usable for Leica!?!?!

Anyone a picture of a thing like this? Brian possibly? Hugely interested now that the M8 is gone and I still like lens hacking!
 
Sounds like a simplified 'focuslide.' I have a Zeiss accessory that I got in a box of crap on an eBay auction, which is somewhat simpler. It is spring-loaded and inserted into the film gate of a 35mm camera, which puts the ground-glass at the level of the film if film were loaded. Then focus and check the distance scale against known distances. Works a treat. However, it needs a camera body to be of any use.
 
jesse1dog said:
Hi Dave
Periflex made one.
I have one in my store cupboard somewhere.
If you are interested drop me an email.
jesse
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thanks for the offer!, as a retired toolmaker - I make most of my own adaptors and other gizmos, it gives me something to do - when the weather's bad, or I don't feel like going out shooting!.
Just been looking through my collection of brass and bronze off-cuts, and I feel a day on the lathe and miller coming-on!:)
Dave.
 
Periflex made one (I had one), and so did at least one British accessory manufacturer, maybe two. Stewartry, maybe? And A.N. Other? No, nothing like a Focuslide, nor like the spring-loaded thing Bill had.

Cheers,

R.
 
hans voralberg said:
Dave you think you could make an M mount version as well? Would it be difficult/costly to mill the camera-mouth?
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It won't work. The problem is that M mount cameras have a spring-loaded film pressure plate so you will never get an accurate enough measure of back focus because as soon as the device touches the pressure plate, the flange to plate distance changes. Been there, done that. We ended up building a phase detection device like is used in AF systems inserted into an old back plate via a hole drilled in it and individually adjusted to the M6 body it was used with. Out the back of the camera it was wired up to a computer.

Eventually the project it was part of ended and the guy who owned it wanted his M6 back, so we pulled the whole thing apart.

Marty
 
Freakscene said:
It won't work. The problem is that M mount cameras have a spring-loaded film pressure plate so you will never get an accurate enough measure of back focus because as soon as the device touches the pressure plate, the flange to plate distance changes. Been there, done that.
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I think you have been there - doing some thing totally different! - this device does not touch the pressure plate, or the camera - for that matter!, so nothing can change!. Basically it's a tube with a lens mount at one end, and a ground glass at the other, and of course - an ACCURATE distance between the two!
BTW your own scientific experiment sounds fascinating! - perhaps in your eagerness to share - you did not read my OP?. as this device definately does work - having been marketed for several years!
Dave.
 
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I did read your post, but I misinterpreted the explanation of the device. I've never seen such a thing - but I can see how it would have been very useful, particularly before WWII when servicing a lens would have involved pulling apart a hand-adjusted and shimmed mechanism.

Marty



Dave Wilkinson said:
I think you have been there - doing some thing totally different! - this device does not touch the pressure plate, or the camera - for that matter!, so nothing can change!. Basically it's a tube with a lens mount at one end, and a ground glass at the other, and of course - an ACCURATE distance between the two!
BTW your own scientific experiment sounds fascinating! - perhaps in your eagerness to share - you did not read my OP?. as this device definately does work - having been marketed for several years!
Dave.
Click to expand...
 
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