Diy 8x10-4x5 reducing back

MTGseattle

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I may build one for myself. Are there any pitfalls I need to keep in mind? My lens board to ground glass distance doesn't really matter unless I am out of bellows for a given focal length.

What about somehow getting the film plane a lot different from the ground glass? I feel like that could cause major havoc. All I'm thinking right now is a salvaged graflok assembly from a speed graphic mounted in a custom back frame.

I searched, but I didn't find any other intrepid journeyers down this path.
 

abruzzi

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I think your easiest approach is to start with a 4x5 insert for another camera, then attach it to a 8x10 insert for your camera.

Start with this and just make a piece to attach it to:

Toyo View D45A 4x5 Rear Standard and Film Back- Large Format | eBay

Find many great new & used options and get the best deals for Toyo View D45A 4x5 Rear Standard and Film Back- Large Format at the best online prices at eBay! Free shipping for many products!
www.ebay.com
 
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MTGseattle

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This will be used on a Osaka(Tachihara) 8x10 field camera. That's why I was thinking graflok from a speed graphic. I'll look closer at that listing though. thanks.
 

btaylor

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Or perhaps modify a 4x5 reducing back from another 8x10 camera to fit the Osaka.
 

Don_ih

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If you decided to make your own holder-retainer in a custom-made back, you could ensure that the gg matched the film by wrecking a film holder and turning it into a ground-glass holder. You'd put the frosted side of the glass against the flanges that hold the film in the holder. Not ideal, but it would work.
 
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MTGseattle

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I've looked in the usual places for used reduction backs from the other makers. Obviously Deardorff commands a premium, and other more distressed options are missing quite a few parts that would make the endeavor pointless.

I do somewhat enjoy wood working, which is part of the idea here, and aside from whole camera kits, I haven't seen the back I need come up for sale in about 1 year.

I also don't wish to destroy a working camera to make a part for mine hence the "Parts" Speed Grpahic or something like the listing @abruzzi linked to above.
 

awty

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Or you can simply measure the distance from the front of the lens board on both the ground glass and then the film holder without the dark slide.
 

awty

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Go for it, Ive made several backs to fit various cameras using salvaged backs. Just measure the film plain and make sure it matches the ground glass. Hardest part is making it light tight and secured. Adhesive felt if help full.
 

Don_ih

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awty said:
Or you can simply measure the distance from the front of the lens board on both the ground glass and then the film holder without the dark slide.
Click to expand...

Of course. I was suggesting a no-measurement method.
 

Andrew O'Neill

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Making a 4x5 back shouldn't be all that difficult. When I was making the back of my 14x17, the most critical measurement was the distance from the inside of the back to ground glass... it must be of same thickness as your film holder. I measure with a gauge the woodworking teacher had at my school, then used a router set to same depth. My ground glass is just some plexi that I sanded by hand.
 
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MTGseattle

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OK. @awty and @Andrew O'Neill that was my main concern. I am correct in that if the focusing point (ground glass) ends up way off from the film plane of the inserted holder, I would never have an in-focus negative.

I'm a bit confused regarding measuring lens board to film plane on a camera with a bellows since it's widely variable within the overall bellows movement. Is that a number I need to be concerned with? Obviously, I could pick an arbitrary extension point, lock it down and measure but still?

If I was dealing with a non-functional camera I could simply hold a straight edge across the rear standard "box" and perform all of my measuring that way. I can use the same technique to measure the in-camera plane of the 8x10 back to the ground glass at least.

Here's the funny thing: I swear I have a homemade back for Burke and James 8x10 to 4x5 somewhere. I remember getting one with that camera, and I do not remember selling it. It's simply not in my 2 usual spots for storing infrequently used gear. I'm my own worst enemy when it comes to organization. Time to ransack the basement I guess..
 

Andrew O'Neill

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The most critical measurement is the inside edge of the film holder to film. That should be the same thickness as the ground glass from inside edge to glass. Ignore the bellows to film plane. If those two thicknesses do not match, even though you can focus a sharp image on the ground glass, stick a holder in and take the photo, you will find the negative is unsharp...
 

btaylor

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Of course the critical film/groundglass distance (they must be congruent) lies in the back itself, unrelated (other than it be parallel to the back) to the position of the standards. I had a complete 4x5 Graflok assembly at one time, grafting it to a homemade back panel would have been pretty simple as long as the hole was in the right place and it was square. An off the shelf item like that would save a lot of time and effort as well as accepti any Graflok compatible accessory. Just a thought.
I also made a simple way to test the congruence of the gg and film plane: I drilled 5 good sized holes (4 corners and the center) through a film holder septum, removed both dark slides and groundglass. I put an exposed piece of film where unexposed film would normally be in the holder. Using a lupe I could then focus the camera on a focus target on the film. After removing the modified holder and reinstalling the groundglass if focus was the same I knew was good to go.
 

Don_ih

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The film is 5mm away from the front of a 4x5 film holder, by ANSI specifications.
 
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MTGseattle

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Thank you all for the help. I found the one I was pretty sure I had. I now have a complete 4x5 Graflok assembly. It's mounted in a frame that doesn't work on my intended camera, so the wood working shall begin.
 

MSStudio

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No need to get overly complicated. Basically, you need a light tight connection to the camera, a method to hold the film flat and an indexing to know when the film is perpendicular to the light path from the lens.
 
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MTGseattle

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It's in the works. I simply wanted an excuse to try some fun joinery. I then backed myself into a corner (of basic joinery) with my first cuts so it's now way simpler than I intended but the glue of phase 1 is drying.
 
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