35mm "ground glass" for adjusting focus

[portocar]

Hello

where can I get a small 35mm sized "ground glass" I can use on my Rangefinder camera in order to adjust the rangefinder and get accurate focus.

It would be great if i could find a small 35mm sized "ground glass" that has a loupe already attached to it.

Thanks

 

[Jamie Pillers]

A piece of scotch tape will often serve the purpose.

 

[Phil_F_NM]

Old focusing screens work very well. They are durable and not too expensive. Sometimes you can rob one out of a cheap broken SLR.

If you have an M mount rangefinder, the obvious, and best, solution is to purchase an M8 or M9. Those are perfect lens adjusting tools.

Phil Forrest

 

[Steve M.]

Yep, stretch a piece of frosted scotch tape across the film plane, and use a magnifying glass from the 99 cent store.

 

[Derwent]

Grinding one yourself is a piece of cake, and is more accurate than frosted tape....
I've made several for both 35mm and for medium format stuff.
I used 400 grit aluminium oxide powder and 1000 grit to finish, which was the hardest theing to get hold of.
Cut the glass using a regular glass cutter, grind the sharp edges off on a regular emery sharpening stone, put some water and grit on one piece of glass and lap it to another then evnetually go for the finer grit which makes it brighter and relap then clean up with water and youre done.
If you don't want to get involved with getting glass, cutter, grit etc let me know as I've got spares and enough supplies to make dozens.
I'll send you one if you cover postage plus a couple of dollars for the materials etc, say $2 plus postage cost and one's yours!
No loupe attached but stick one on with hot melt glue or contact adhesive or something and youre done
PM me if you want one.

 

[Mr_Flibble]

Some film sleeves have frosted backs. I cut one of those to the right size and use that over the film plane.
Scotch-tape over a strip of plastic cut from an old CD jewel-case works well too.

 

[bigeye]

I've done it both the 1st and 2nd way here: collimator

 

[Gabriel M.A.]

Just beware: the thickness of the ground glass may add a bit of an "offset" to your adjustments. I would advise using a clear strip of developed film. Meaning, of course, unexposed, yet developed; "clear" as in "transparent" and without an orange mask if possible. The film being 35mm.

I once made the mistake of calibrating my Rolleiflex with the old (original) ground glass when using ground glass with different thickness on the viewer. Best to use same thickness. But that's mostly off-topic.

The point is: for a rangefinder camera, use actual film to calibrate for actual film.

 

[mdarnton]

If you want to grind your own, an easy source of grinding grit is valve-grinding compound. You may even be able to get your car repair guy, or a machine shop, to give you a dollop out of their big can. Clover lapping compound is a common brand.

Tape sounds a bit dodgy to me, but if you make glass, make sure it sits on the right rails, and between the right rails.

 

[batterytypehah!]

I got mine from American Science & Surplus (sciplus.com). Doesn't come in 35mm width, so you need a glass cutter.

They still carry it, and it's cheap, but you may want to hang around and shop more since there's a minimum shipping charge. It's a fun place.

Just beware: the thickness of the ground glass may add a bit of an "offset" to your adjustments.

Has never been a problem for me. You need to place the matte side towards the lens, though.

 

[sevo]

Just beware: the thickness of the ground glass may add a bit of an "offset" to your adjustments. I would advise using a clear strip of developed film. Meaning, of course, unexposed, yet developed; "clear" as in "transparent" and without an orange mask if possible. The film being 35mm.
(...)

The point is: for a rangefinder camera, use actual film to calibrate for actual film.

The thickness of the glass will only matter in film systems that are rear aligned or where there is no removable pressure plate. The former makes it tricky to adjust 120 cameras by substituting a ground glass for the film, the latter is the reason why you need the appropriate matte frame for your holder system to adjust sheet film cameras/backs (and have a hard time adjusting thread mount Leicas).

35mm (135) film however is front (rail) aligned - all you need is place the ground glass rough side forward on the film window rails. The only issue you'll have is that a ground glass will not replicate any residual bulging of the film - if you have to nail it that accurately, you may want to experiment with matte film and a transparent glass pressure plate.

 

[Derwent]

Yes.
The frosted side of the glass aligns perfectly to the film rails at the film plane.
No issues.
Collimator method is good too.
Have done the trick of using a known good SLR as a makeshift Collimator with a focus target at the film plane.
Set up a Contaflex Super B that way and it's focus is fine.
Slightly non standard way of doing it but it worked!