Graflok backs and focusing screens - interchangeability ?

[Luddite Frank]

I managed to break the focusing screen from my 4x5 Pacemaker while cleaning it. :bang:

Camera has a Graflok back with pop-up focusing hood.

I have a second complete Graflok back ( bearing the Singer stamp) and mounting frame that I had aquired to make a reducing back for a 5x7 camera.

Are all Graflok focusing backs/screens interchangeable ?

It would be attractively convenient to just swap the focusing screen assemblies... would the focusing scale / infinity stops have to be re-adjusted ?

 

[degruyl]

If the ground glass rests all the way in the frame, you can just pop it in and screw down the retaining clips.

Does that answer your question?

I can't say whether the particular back has the same focal plane as the other, although in theory they should. Remember, these backs are meant to be interchangeable.

 

[Roger Hicks]

As the film register is nominally constant, the GG must be too. By 'GG assembly' I assume you mean frame and springs -- in which case, if they'll swap, yes, it must be OK, as both the GG frame and film holder are located by the same plane. The entire back may or may not be the same thickness (the bit that mounts on the camera, with the GG frame behind it).

Cheers,

R.

 

[Luddite Frank]

Roger and David,

Thanks for your replies...

The part I was hoping to swap would be the complete screen and metal focusing hood, which would be removed to insert a roll-back or pack holder.

Was not planning to touch the metal frame that is held to the camera body by screws.

I am thinking that these Graflok pop-in parts are standardized, in the same fashion as interchangable lenses ?

When I removed the screen and fresnel assembly from the original hood, I found four thin black washers under the springs that hold the glass in the frame - am not sure if they are for shimming the glass or what...

Eventually I will get a new screen/fresnel and repair the original hood assembly...

Cheers !

LF

 

[degruyl]

Was not planning to touch the metal frame that is held to the camera body by screws.

You mean the part that holds in the springs? Right you should be able to replace one graflok assembly with another. I am pretty sure that is what Roger meant. It works similarly to the lens board, if I am remembering correctly.

This is how the roll film backs work.

 

[Roger Hicks]

If the screen/hood goes it without hanging up, it will work. Sorry: I was thinking of another design when I said 'springs'.

Yes, it is quite likely that shims were used to adjust the exact position of the glass.

Cheers,

R.

 

[sevo]

I am thinking that these Graflok pop-in parts are standardized, in the same fashion as interchangable lenses ?

It is a bit more complex. Strictly speaking "Graflok" is the sliding rail clamping mechanism - and film holders with the corresponding notch are compatible with any back with Graflok clamps. However, the removable spring loaded ground glass frame slid into Graflok backs is brand or even camera specific - they are not interchangeable among my Linhof, Graflex, sinar and Plaubel cameras.

Sevo

 

[Solinar]

Roger and David,

When I removed the screen and fresnel assembly from the original hood, I found four thin black washers under the springs that hold the glass in the frame - am not sure if they are for shimming the glass or what...

WHY THE FOUR WASHERS - If someone had simply replaced the original Graflex ground glass with a slightly thicker plate of glass that would explain the 4 washers.

Whoever replace the original GG used the washers to reduce the pressure on the "new" replacement glass - so it would not crack.

That's all cool and hunky dory - only if the Graflok frame for the focus panel was intended to have both a plastic Fresnel in conjunction with a ground glass plate. I call the plastic Fresnel panel an - Ektalite screen - because it sounds cooler than Beattie or Maxwell.


***********************************************

One thing to worry about is whether or not the removable Graflock frame for the focusing screen was meant to have a combined ground glass and plastic "Ektalite" fresnel focus screen.

The textured side of the ground glass and the Fresnel pattern of the Ektalite screen face each other - which moves the focus point away from the lens by a mm or two - i.e. the partial thickness of plastic Fresnel. I can't remember if it is 1/2 or 2/3rd's the thickness of the plastic Fresnel.

On a Graflok focus panel without an Ektalite screen the metal frame around that the GG has "four raised bosses" - upon which the glass rests.

The ground glass does not sit flush against the bottom surface metal frame.

On the Graflok focus panel with an Ektalite screen the "four raised bosses" have been machined by a millimeter or two - to move the focus registration forward by a mm or two.

The Ektalite panel still doesn't sit flush in the entirety of the metal frame.

My worry with the washer trick is did someone try to install an Ektalite/Fresnel screen on a focus panel designed for only ground glass.

http://graflex.org/helpboard/viewtopic.php?t=5096&sid=15b3308b95782233a08df25ad2b9d52f

http://www.graflex.org/helpboard/viewtopic.php?t=2628&highlight=ektalite

 

[Luddite Frank]

WHY THE FOUR WASHERS - If someone had simply replaced the original Graflex ground glass with a slightly thicker plate of glass that would explain the 4 washers.

Whoever replace the original GG used the washers to reduce the pressure on the "new" replacement glass - so it would not crack.

That's all cool and hunky dory - only if the Graflok frame for the focus panel was intended to have both a plastic Fresnel in conjunction with a ground glass plate. I call the plastic Fresnel panel an - Ektalite screen - because it sounds cooler than Beattie or Maxwell.


***********************************************

One thing to worry about is whether or not the removable Graflock frame for the focusing screen was meant to have a combined ground glass and plastic "Ektalite" fresnel focus screen.

The textured side of the ground glass and the Fresnel pattern of the Ektalite screen face each other - which moves the focus point away from the lens by a mm or two - i.e. the partial thickness of plastic Fresnel. I can't remember if it is 1/2 or 2/3rd's the thickness of the plastic Fresnel.

On a Graflok focus panel without an Ektalite screen the metal frame around that the GG has "four raised bosses" - upon which the glass rests.

The ground glass does not sit flush against the bottom surface metal frame.

On the Graflok focus panel with an Ektalite screen the "four raised bosses" have been machined by a millimeter or two - to move the focus registration forward by a mm or two.

The Ektalite panel still doesn't sit flush in the entirety of the metal frame.

My worry with the washer trick is did someone try to install an Ektalite/Fresnel screen on a focus panel designed for only ground glass.

http://graflex.org/helpboard/viewtopic.php?t=5096&sid=15b3308b95782233a08df25ad2b9d52f

http://www.graflex.org/helpboard/viewtopic.php?t=2628&highlight=ektalite

Hmm... okay...

So far, I'm only popping-out and changing complete focusing screen / hood assemblies, not swapping glass-only.

The screen I did remove for cleaning and subsequently broke was the composite ground-glass & fresnel, held together with black binding tape around the edge... the glass broke, the fresnel is fine...

After that experience, I was not about to tempt fate by pulling the screen from the the other assembly. 😉

All that said, my Pacemaker dates to about 1949-50; don't know when the fresenel screen became available.

The Singer screen / hood must be from at least the 1960's... the die cast frame that holds the screen bears the same casting number on both sets of hoods...

The later screen has three sets of frameline (?) "corners" in black lines, plus a
cross-hairs at center. The other screen was plain (?).

To re-iterate, the only things I'm swapping at this time are " pop-out" bits - no tools required.

Thanks for the help !

 

[sevo]

Hmm... okay...

So far, I'm only popping-out and changing complete focusing screen / hood assemblies, not swapping glass-only.

If they fit and pass a focus comparison, you're ok.

After that experience, I was not about to tempt fate by pulling the screen from the the other assembly. 😉

There is no risk to it. The matte side of any regular screen faces the lens and sits on the proper shims and spacers if the back is already adjusted. Any traditional screen on the same shims would be in plane, its matte side being in the same position. The notable exception are screens sandwiched with a lens side fresnel (once popular, but IMHO brain-dead as you cannot get the fresnel out of place for precision work without recalibrating the back) and some fancy modern ultra-bright screens that sandwich a gel between two glass panes (I hate them as they tend to fail in hot or cold weather). But even if it is off focus, all you have to do is to adjust by adding or removing shims.

Sevo

 

[Ezzie]

I should have read this thread before collimating my DIY 4x5/6x12 project. I marked the wrong side og the fresnel apparently (which I naively thought to be the ground glass). Even if the few frames I've shot up until now were ruined by a light leak due to a warped Graflok back, I could see consistent front focusing. Good thing the lens box is detachable and can be sanded down easily.