Help needed for a frankencamera

[Phildjii]

Hi,

I have always loved images from the Xpan with the 45mm. It feels to me like the perfect image ratio and field of view for the look I’m after. But as a hobbyist I just can’t justify the expense for a used Xpan.

I have seen many home-made "frankencameras" –like this one on Flickr– and thought building a light alternative to an Xpan would be a fun project. By light I mean both not too expensive, and not too heavy/bulky. So I did my research, found a body that would suit well (Nimslo 3D)… and then got lost in lens specifications.
I’m used to 35mm and APS-C and know equivalence, but there are two aspects that had me confused:

- First, the Xpan itself. With the 45mm, it is often said to be equivalent to a 25mm. A Hasselblad documentation actually states "Corresponding lens focal length (24x36 mm format) : 25 mm". It seems misleading. If you shoot the Xpan in 24x36 mode, it is very much a 45mm.
 What I think they mean is: to get an "equivalent" image that fits in a 24x36 mm frame you need a 25 mm lens and need to crop the image to 13x36 mm.

As an Xpan image is 24x65, pretty much the width of a 6x7 image, what I need is a 45mm lens made for 6x7. Am I correct?

- Another confusing thing to me is lens coverage. Equivalence between 35 mm and APS-C is easy as coverage is the same. Here it seems to be the opposite: my film always has the same size, but lenses have widely differing coverages.

If I understand correctly, with a 24x65 film size, a 45 mm with 6x7 coverage is roughly twice narrower than a 45 mm that covers 4x5. So if I ever used a lens that covers 4x5 I would need a 90 mm or so? Is that correct?

I guess the corollary question to the knowledgeable members of this forum is: do you know a lens that would give me roughly the same view as an Xpan, doesn't cost an arm, and is on the small side?
Keep in mind I’m an amateur, I don’t have quite the same requirements for sharpness and distortion and general quality as you do. A so-so lens for you would probably be enough for me.
Thank you!

 

[MattKing]

Welcome to Photrio.
I would suggest avoiding 35mm "equivalency" considerations, because any attempt to evaluate such equivalencies is of little use when one changes the vertical/horizontal aspect ratios.
The reference to a 25mm equivalency is actually a reference only to the short dimension of the frame - assuming the camera is held horizontally, the field of view in the short (vertical) dimension is the same as when using a 25mm lens on a standard 24mm x 36mm frame on 135 film.
You are correct that you need a lens that will cover a 65mm piece of film. As such, a lens designed for a 6x7 (or 6x8 or 6x9) camera would be best.
If you want something with a wide field of view, that ens needs to have a relatively short focal length.
Excluding issues about dealing with built in shutters, something like a 50mm lens for the RB67 might serve you well.

 

[Phildjii]

Thank you Matt!

assuming the camera is held horizontally, the field of view in the short (vertical) dimension is the same as when using a 25mm lens on a standard 24mm x 36mm frame on 135 film.

Ah, interesting. I thought the long dimension would be more important for such a panoramic format, and always saw it as a "cropped 6x7". Now I understand it can be seen as an "elongated 24x36", which makes the "25mm equivalence" much more straightforward.
RB67 lenses are indeed interesting beasts with their leaf shutter, if a bit on the heavy side.

 

[Dan Fromm]

OP, is your goal to build a camera or to make high aspect ratio prints?

The Xpan produces a useful 24x65 mm strip on 35mm film. 30, 45 and 90 mm lenses are offered for it. They all have to cover at least 70 mm. Horizontal angles of view are, respectively, 95, 72 and 40 degrees.

If you want to make high aspect ratio prints and can live with nominal 6x9 (actually 2.25" x 3.25", 56 x 82 mm, and the long side of the format's length varies between makes/models of cameras and roll holders), get a 2x3 camera that accepts interchangeable lenses.

Matching the Xpan's lenses' horizontal angles of view on 2x3 will need, respectively approximately 45, 55 and 115 mm lenses.

The least expensive way to get the prints you want is probably to buy a 2x3 press camera that can focus a 45 mm lens and a 2x3 roll holder to fit it. I use a 2x3 Century Graphic, which will focus a 35/4.5 Apo-Grandagon. I know this because I have the lens. It will also mount and focus a 45/4.5 Apo-Grandagon, which I don't have, and a 47 mm Super Angulon (f/8, f/5.6, both less expensive than a 45 Apo-Grandy, I have an f/5.6er). And of course it will handle longer lenses.

The 2x3 negative/transparency gives better cropping opportunities than a 24x65 mm strip.

Dan "Who needs an Xpan anyway?" Fromm

 

[Phildjii]

Thank you Dan!

OP, is your goal to build a camera or to make high aspect ratio prints?

The goal is to build a camera that uses 35mm film. I'd like to stick with 35mm for a few reasons: easier to process and scan, more film choices, lower cost… Also I already shoot in 35 mm so it is know territory.

 

[Dan Fromm]

Thank you Dan!

The goal is to build a camera that uses 35mm film. I'd like to stick with 35mm for a few reasons: easier to process and scan, more film choices, lower cost… Also I already shoot in 35 mm so it is know territory.

Well, then, match the Xpan focal lengths, using lenses for 6x7 cameras.

I've never chased these things because few will cover the formats I use. There are very few 30 mm rectilinear lenses in shutter with much coverage.

Good luck, have fun.