dumb question about 6x17 back on a 4x5 camera

[Andrea Gazzoni]

how can I view a 6x17 image on the groundglass of a 4x5 camera, with one of those optional backs made in China by DaYi?

I use a 6x12 DaYi back on my camera, but I can't understand how a 4x5 frame could not limit the projected image on a 6x17 back film plane.

thank you for any advice
andre

[IanG]

6x17 is longer than a 5x4 back as you say so there's an extension back which tapers out to allow it to fit, this has it's own screen.

Ian

[Aender Brepsom]

Hi Andre,

the DAYI 6x17 panorama back comes with its own ground glass unit that allows you to view the entire image. It sits further back than the 4x5 ground glass (which has to be taken off before mounting the 6x17 gg unit).
The DAYI 6x17 back allows to take 6x17 images within a limited focal range. With a 210mm lens for example, the width of the image is reduced to approx 150mm. IIRC, you get the full 6x17 format up to 180mm focal length.

I used to own a DAYI 6x17 back. It worked perfectly well, was solid and well made, but quite heavy and bulky.

[Andrea Gazzoni]

tell me if I understand correctly.
the back has it's own groundglass, so the image will be composed on it and this will result in a longer distance between the film plane and the focal plane of the lens.
if so, will a 90/8 lens be usable without recessed lensboard?

[Greg Lockrey]

tell me if I understand correctly.
the back has it's own groundglass, so the image will be composed on it and this will result in a longer distance between the film plane and the focal plane of the lens.
if so, will a 90/8 lens be usable without recessed lensboard?

Yes most of the time but not on a Graphlex. It's a couple of mm shy. It is fine on my Ebony however.