How to align ground-glass with holder?

keithostertag · Nov 12, 2017

I have been unable to locate a 5x7 to 4x5 adapter for my 5x7 Cambo, so I'm considering making one. I mostly want to use it for a roll-film holder (Horseman/Graflok).

How does one make the adapter so that the ground-glass is exactly the same distance from the lens as the film in the holder?

For instance, is there a standard distance from the surface of a film holder to the actual film surface? Or in my desired case, from the surface of the roll film holder to the film surface? I'm guessing those are the same...Could it be that distance is the thickness of the ground-glass itself?

I've never attempted anything like this, and my workshop skills are minimal. Can you recommend a source or tutorial that would give me some ideas on how to proceed?

Thanks,
Keith

keithostertag · Nov 12, 2017

I'm envisioning something like this one on eBay: item 252568290566

RalphLambrecht · Nov 12, 2017

keithostertag said:
I have been unable to locate a 5x7 to 4x5 adapter for my 5x7 Cambo, so I'm considering making one. I mostly want to use it for a roll-film holder (Horseman/Graflok).

How does one make the adapter so that the ground-glass is exactly the same distance from the lens as the film in the holder?

For instance, is there a standard distance from the surface of a film holder to the actual film surface? Or in my desired case, from the surface of the roll film holder to the film surface? I'm guessing those are the same...Could it be that distance is the thickness of the ground-glass itself?

I've never attempted anything like this, and my workshop skills are minimal. Can you recommend a source or tutorial that would give me some ideas on how to proceed?

Thanks,
Keith

You could contact Steve Grimes and have it done (Google is your friend)

shutterfinger · Nov 12, 2017

http://home.earthlink.net/~eahoo/page8/filmhold.html
Graflex roll film holders are the same film depth as 2x3 film holders.
120 roll film is .0035 to .0045 inch thick, 4x5 sheet film is .007 inch thick.
The ground surface of a ground glass should be the same distance from the edge of the back frame as the emulsion side of a piece of film loaded in a holder.
A straight edge is laid across the back frame and measurement is made at several points across the film holder then the ground glass is shimmed/mount ground down to match.
If you are going to use the 5x7 ground glass then insert a 5x7 holder with a sheet of film in it into the back. With the back frame removed, lay a straight edge across the back frame making sure the straight edge is not on a high area on one side then measure from the straight edge to the film surface. I usually split the film into thirds vertically and horizontally and measure at the center of the resulting 9 segments. Remove the holder and measure the ground glass, it should match the film measurements precisely.
A smaller ground glass can be used on the adapter wit it set to the distance of film in the roll film holder as measured by the same procedure.

chris77 · Nov 12, 2017

pm me if you need assistance.
my diy 5x7 back for toyo camera.

keithostertag · Nov 12, 2017

@shutterfinger- thank you, that's very helpful as a start.

I'll probably be using a 4x5 Sinar ground glass, since that's what I have on hand.My thought is to make a board to fit the 5x7 back, then cut a rectangle in it slightly smaller than the 4x5 ground glass, then build onto the back a framework to hold a holder (using spring clips of some type to press the holder flat down against the back), then make a holder for the ground glass for which, as you say, "The ground surface of a ground glass should be the same distance from the edge of the back frame as the emulsion side of a piece of film loaded in a holder" using shims of some sort. So in practice, I put the back on, I slide the frame that holds the ground glass in, I focus, then I exchange the ground-glass holder with the roll film holder.

According to the chart you referenced, the Depth-to-film-surface of a 2x3 is approx .2 inches, so if I build a holder for the ground glass with front face of 1/4 plywood then I would need to shim the ground glass holder approx .05 inches? Am I close in my thinking?

How do I measure such small distances/thicknesses accurately? What do I use for (where do I buy) shim material that would be appropriate?

@chris77 - thank you, I will PM you later in the week. Looks like your back is made with metal? I have zero tools or skills working with metal (and not all that much with wood)...

btaylor · Nov 12, 2017

Making a back looks very difficult to me. You've got to make a holder for the groundglass and then come up with the springs and rails to mount a holder, then make everything work to a very high degree of precision, reliably. It seems to me the easiest and most precise thing to do would be to modify an existing 4x5 back assembly to your camera, then all you have to come up with is a flat surface with a hole in it. I bought a complete graflex graflok back assembly years ago for a project and never used it, you can find them on eBay. I also have an 8x10 to 4x5 Linhof reducing back I bought in error, that could possibly be cut down and adapted if you're interested.

keithostertag · Nov 12, 2017

You may be right... depending on the availability/price of an appropriate back. I have been looking, thus my link earlier. I might consider yours, but as I've said I don't really have the tools to cut metal accurately or easily. PM me with more details of what you have?

Ian Grant · Nov 12, 2017

Having made my own back for a 6x7 field camera I built last year I wouldn't hesitate to build a 5x4 back. Getting the register correct was very easy and the Graflex RH10 roll film backs are held with sliders like on a Graflok back.

However I have a few spare Speed/Crown 5x4 backs and would use one to make a reducing back for my 7x5 Senecas, mine are all spring not Graflok but I don't use RF backs on my LF cameras. I would suggest looking for a Graflex Grafpk back and making your own adapter back.

Ian

shutterfinger · Nov 12, 2017

keithostertag said:
How do I measure such small distances/thicknesses accurately? What do I use for (where do I buy) shim material that would be appropriate?

https://www.ebay.com/itm/6-inch-150...529401&hash=item2a6add9f76:g:gZkAAOSw3ydVjuch is the sample, amazon, hardware stores, auto parts stores, tool supply stores are other sources.
https://www.ebay.com/sch/i.html?_fr....H0.Xshim+stock.TRS0&_nkw=shim+stock&_sacat=0 for shim stock.
Use Baltic Birch Plywood as it does not warp like other plywoods. Veneer can be used as shim stock also.

RalphLambrecht · Nov 12, 2017

keithostertag said:
@shutterfinger- thank you, that's very helpful as a start.

I'll probably be using a 4x5 Sinar ground glass, since that's what I have on hand.My thought is to make a board to fit the 5x7 back, then cut a rectangle in it slightly smaller than the 4x5 ground glass, then build onto the back a framework to hold a holder (using spring clips of some type to press the holder flat down against the back), then make a holder for the ground glass for which, as you say, "The ground surface of a ground glass should be the same distance from the edge of the back frame as the emulsion side of a piece of film loaded in a holder" using shims of some sort. So in practice, I put the back on, I slide the frame that holds the ground glass in, I focus, then I exchange the ground-glass holder with the roll film holder.

According to the chart you referenced, the Depth-to-film-surface of a 2x3 is approx .2 inches, so if I build a holder for the ground glass with front face of 1/4 plywood then I would need to shim the ground glass holder approx .05 inches? Am I close in my thinking?

How do I measure such small distances/thicknesses accurately? What do I use for (where do I buy) shim material that would be appropriate?

@chris77 - thank you, I will PM you later in the week. Looks like your back is made with metal? I have zero tools or skills working with metal (and not all that much with wood)...

RalphLambrecht · Nov 12, 2017

I have a device for that and it is for sale; it's very precise down to 1/1000m;email me for pics if interested rwlambrec@gmail.com. Not cheap($300) but perfect for your project

Ian Grant · Nov 12, 2017

shutterfinger said:
https://www.ebay.com/itm/6-inch-150...529401&hash=item2a6add9f76:g:gZkAAOSw3ydVjuch is the sample, amazon, hardware stores, auto parts stores, tool supply stores are other sources.
https://www.ebay.com/sch/i.html?_fr....H0.Xshim+stock.TRS0&_nkw=shim+stock&_sacat=0 for shim stock.
Use Baltic Birch Plywood as it does not warp like other plywoods. Veneer can be used as shim stock also.

I use a similar calliper, I buy a lot of Mahogany sheet of various thickness and by chance two pieces glued together was exactly the correct T distance, I also have mahogany veneer but it wasn't needed.

Ian

E. von Hoegh · Nov 12, 2017

When I first got a wooden view camera, I needed to make some lens boards, using a holecutter on a drillpress and a table saw. Having worked as a machinist I knew about cutting away material to reveal the part you wanted but had zip for experience with wood. The first ones were let's say functional, but with familiarity the became much nicer, especially when I learned to use a router.
You'll need to be able to make clean accurate cuts, measure accurately, use the tools SAFELY! I cannot stress safety enough, both power and hand tools are sharp.
Look at old wood cameras, how the backs were attached, for good and simple ideas. Make a drawing to work from, it can be rough but get the dimensions correct. Maybe talk to a cabinet maker, it's certainly doable.
Good luck

John Koehrer · Nov 12, 2017

T-distance. There are ANSI standards for the lol' devils.

http://home.earthlink.net/~eahoo/page8/filmhold.html

John Earley · Dec 11, 2017

Thank you John, I've been looking for those T specifications.

mikemgb · Dec 11, 2017

When I built a 4x5 back for my 5x7 Gundlach I used a Graflex spring back. I made a board to fit the camera, cut a hole in it then screwed the Graflex back to it. Using a complete back made it very easy.

Jim Jones · Dec 11, 2017

Some of the dimensions in the often cited information in link #15 are obviously wrong. The distance from the face of the film holder (the "T" distance) to the back of the film is indeed 0,197 inches. It's too close to my bedtime to publish corrected data tonight. I've made several 4x5 adaptors the easy way by robbing old press or view cameras.

Christopher Nisperos · Mar 7, 2020

chris77 said:
pm me if you need assistance.
my diy 5x7 back for toyo camera.

Chris! Hello.

My name is Chris, too .. Plus, like you, I'm also located in Paris. I came across your post because I'm looking for hints in building a [4x5] ground-glass incorporated film holder to determined focus calibration for my PolaConv (Polaroid 110A converted to take 4x5 film — no longer in production*) that is supposed to be 4x5 ready, but my images are all out of focus!

I could be doing something wrong, but I'm check the thing with both a rool film back and a sheet film holder. The former manufacturer, an Italian architect who seemingly was just having fun with CAD design and digital printers, doesn't respond to emails and I can't locate his telephone.

I would like to use this camera with film holders and/or Grafmatic magazines soon, so if you could give me some tips as to how to go about it, I'd be happy to meet up you for coffee (or wine!), on me! I'm in the 11th.

Best,

Christopher aka Chris!

* My camera is currently packed away, so I hope it's OK to include this link to a flickr page with lots of photos of the camera in question:

https://www.flickr.com/photos/marcolucifora/albums/72157644100585838/with/14107226434/

Dan Fromm · Mar 7, 2020

Chris, your confection seems to have a Graflok back. Get a 4x5 Graflex (brand, not camera fitting) film pack adapter. Measure carefully, put in shims (try paper) to position a GG 0.197 inches (5.004 mm) from the front of the FPA's front surface. This will put the GG in register with a standard 4x5 film holder. And then adjust the camera's RF so that it agrees with the GG.

How to align ground-glass with holder?

Attachments

Privacy & Transparency

Privacy & Transparency