8x10 to 4x5 adapter backs

[ralph_barker]

I recently purchased a Tachihara 8x10, and I'm considering making a

4x5 adapter back for it, mostly for use with Polaroids and such. Am I

correct in assuming that the typical adapter back requires refocusing

to the new 4x5 film plane? That approach seems simpler than attempting

to precisely match the location of the 8x10 film plane, but I'm

curious about how other adapter backs are constructed.

[Troll]

The only thing that matters is that the 4x5 ground glass is in the same plane as the 4x5 film.

[john_cook1]

Every camera I have ever worked with has needed refocusing between backs. I first learned that the hard way when I shot a whole location shoot out of focus with a Linhof 120 roll film back on a 4x5 Super Technika.

[donald_miller1]

Typically adapter backs are complete backs that are exchanged such as the Burke and James, the Deardorff and others. The 4X5 back would need to be accurately constructed so that the front of the ground glass surface on the 4X5 back matches the T dimension of the 4X5 film holder.

[michael_veit]

"I first learned that the hard way when I shot a whole location shoot out of focus with a Linhof 120 roll film back "

 

John, I've only ever seen 120 backs in pictures and don't know exactly how they work, but how are you able to refocus after they are inserted beneath the ground glass?

[john_cook1]

Michael, the Linhof 120 back is attached in place of the groundglass. I shot hand-held using the optical viewfinder and rangefinder. I didn't learn until later that it is necessary to have a second set of stops for the front standard to use with the rollfilm back. If you work on a tripod and don't use the rangefinder it isn't a problem.

[james_driscoll2]

The sinar 8x10 to 4x5 reducing back does not require refocus-

the 4x5 GG is "sunk" into the reducing back.

 

I own one, and will be able to (not right now) take pictures of it, or

you can search for one on the web.

 

It is a rather complicated piece of equipment, but what sinar item

isn't.

 

My Sinar 5x7 to 4x5 reducing back is not in the focal plane of the

5x7 back. What I did was test at diff. distances what my

compensation via focus would be, and taped this measurement

to the reducing back. I have experienced no problems with this

method.

 

thanks

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[ralph_barker]

Thanks, all. My guess would be that Sinar is probably the exception here, in that they appear to have taken the "precision" route in their design (not a surprise). The basic design issue I'm wrestling with is a choice between keeping the focus plane the same, or designing the reducing back such that there's enough offset to allow the use of a 545i Polaroid holder, with its lens-side bulge. As the degree of precision needed to keep the focus constant between backs probably isn't possible with wood construction anyway, I think I'll opt for Polaroid compatibility.

[bob_salomon]

Until about 15 years ago, when ordering a Linhof Kardan 819 to 45 reducing back, you

needed to supply the serial number of the 810 Kardan and then Linhof supplied a reducing

back with part of that serial number engraved on it.

 

That was to ensure that Linhof machined the reducing back so the 45 back had the same

film plane position as the 810 back. This allowed one to shoot test shots on 45 and know

that the results were going to be the same on 810 film.

 

They stopped doing this as the demand for 810 cameras shrank and now just supply an

adapter that is not registered to a specific 810 Kardan.

[bob_salomon]

"didn't learn until later that it is necessary to have a second set of stops for the front

standard to use with the rollfilm back"

 

Are you saying that the stops were adjusted for the cam/lens/body and that the cam had

the lens serial number stamped on it if the camera is a V or later or, if earlier, the lens and

the camera serial # on it?

 

Or did you add a lens and use pre-existing stops that were already on the camera and/or

use an improperly matched cam?

 

In 30 years as the Linhof Product Manager I have never received a call or letter stating the

problem you state above.

[john_cook1]

Bob, it was many years ago and my memory is probably flawed. It was a brand new Technika with 6x7 Linhof rollfilm back and 210mm Linhof/Schneider lens purchased as a package in 1967 from the West Coast distributor Berkey (Colortran) through Schaffer Camera in Hollywood. For some reason, the rangefinder focus was different between 4x5 sheetfilm and the rollfilm back. The only two things I am sure of were I lost the client, and it was something stupid I did with the camera.