6x9 & 6x12 roll film backs?

[davetravis]

Hi All!
We've got about 3 feet of snow in CR, and I'm getting hungry for some new gear and new print sizes!
I just bought the Beseler 45MXT with Dichro color head, and I want to try some wide format stuff on Ilfochrome.
My questions are about those roll film backs that you put on on 4x5 cameras.
I've never owned/used 4x5, but I think I can figure out everything but this:
When I use the roll film that is smaller than the 4x5 film, how do the lens angle of view translate into the 6x9 or 6x12 size?
How do I know exactly how much image that is on the ground glass will be captured on the roll film?
Does this make sense?
DT

 

[David A. Goldfarb]

You can mark the groundglass to show where the edges of the frame are, either by measuring and penciling them in, or using something like the free gg overlays you can download from satinsnow.com.

 

[davetravis]

Thanks David, that sounds easy enough!
This will be the shortest thread in Apug History!
DT

 

[naturephoto1]

No it won't Dave,

Here is a link to a table that will give you an idea of the comparison of focal lengths in different formats:

http://lensn2shutter.com/35mmchart.html

Hope this helps.

Also, as David has said you mark the GG. You can place the opening of the holder over the GG and just make an L for each of the 4 corners on the GG (or overlay) and identify which is which format. You can mark them in different colors if that is an aid.

Rich

 

[davetravis]

Thanks Rich,
Does this make sense?
I want the "standard" a.o.v. that I'm used to in my 6x7 90mm lens:
35mm format would = 45mm lens, 4x5 format would = 180 mm lens.
On the 4x5 GG I would capture the entire a.o.v. only if I were actually shooting 4x5 film.
By using the 6x12 roll film attachment, I will in essense be "cropping" in the middle of the GG for the verticle dimension???
Guess you're never too old to learn something new!
DT

 

[Lee L]

Well, I was going to upload a spreadsheet in the ISO standard open document spreadsheet format for you to use to calculate angles of view, but it looks like APUG doesn't allow that format. I'll see what I can do about posting elsewhere and using a link.

Lee

OK, here's a link to try: http://leesimages.googlepages.com/angleofview.ods

This is an openoffice spreadsheet in an ISO standard format. Openoffice is available for free from openoffice.org for OS-X, Windows, unix, and linux. M$ will be catching up with this format starting with Office 2007 and encouragement from M$ for third party vendors to write translators.

You can enter your own film image dimensions and focal lengths in mm with this spreadsheet and it will calculate the diagonal dimension and coverage angles in degrees for the horizontal, vertical, and diagonal dimensions.

 

[naturephoto1]

Hi Dave,

Looking at the table and trying to determine the equivalent:

90mm for 6 X 7 = 45mm for 35mm = 140mm for 4 X 5

The 140mm or more likely a 150mm as a standard lens would project and cover the 4 X5. The "cut out" of the reducing back whether 6 X 7, 6 X 9, 6 X 12 will record what is seen on the ground glass for that size. The 6 X 12 would record on film the center area and not include the area above and below that central area on the ground glass.

Rich

 

[Lee L]

Dave,

Because the proportions between 6x9 and 6x12 are so different, you need to know which coverage angle you want to duplicate: horizontal, vertical, or diagonal. The "standard" translations I've seen usually go with the equivalent diagonal coverage, but that's slightly misleading with the change in aspect ratio you're dealing with.

150mm is the 4x5 horizontal (long dimension) angle equivalent to 45mm on 35mm film.

Lee

 

[mark]

I hate the pencil marks on the gg. I made a mask out of black paper that goes over the gg when I am shooting 6x12. removes real easy when I want to go full frame.

 

[mgb74]

I've used a piece of clear plastic - the material used for making overhead projections (remember those) in printers. It outlines the film coverage well and still allows me to see what I'm leaving out.

 

[Robert Hall]

There are several back types out there, make sure the one you intend to buy is compatible with the back.

My Canham uses a graflex back and this will work with the graflex type backs.

I don't know of many current wooden view camera backs that would support this type of back.

Horseman makes different types of roll film backs as well. Make sure you get the right kind.

 

[Dan Fromm]

There are several back types out there, make sure the one you intend to buy is compatible with the back.

My Canham uses a graflex back and this will work with the graflex type backs.

Veeeeery interesting.

Do you mean Graflex brand back or Graflex back as originally used on Graflex SLRs? I ask because the second is a subset of the first. Most Graflex brand roll holders are in fact made for the Graflok back and won't attach to a Graflex back.

Graflex Inc and predecessors' terminology was unnecessarily confusing. Graphic back = garden variety spring back as used on many view cameras, has fixed focusing panel. Graflex back has one slider above and a sort of recess below. Graflok back has a slider above, a slider below, and a removable focusing panel; the focusing panel must be taken off to attach a roll holder made for the Graflok back to the camera.

I have trouble, now that I think of it, believing that Mr. Canham would sell a camera with a Graflex back. Accessories, including sheet film holders, for them are just too scarce.

Cheers,

Dan

 

[mark]

He meant Graflok.