Image Circle of Contax 645 Lens

[Alan Johnston]

Thank you Christoph - that is everything I need to know. I have been using the Contax 645 120mm Macro with the Sony a7RII (via NAM-1) and I love this lens, even though I have the Sony FE 2.8 Macro in some circumstances I prefer the Contax. I now can get started using the 645 35mm with the Mirex, my first foray into Tilt/Shift - inspired by Satoru Murata's images.

 

[wallpaperviking]

Anybody know how much "rise" you can get when using the Contax PC 35mm on a 33mm x 44mm back?

Thanks in advance!

 

[Audii-Dudii]

Anybody know how much "rise" you can get when using the Contax PC 35mm on a 33mm x 44mm back?

While I can't answer that question, in a related vein, I can show that a Contax N 17-35/f2.8 zoom at 35mm/f8 and focused at infinity, will not only cover a 33x44 sensor, but do so and still have a bit of room for movements:

FYI, the illumination circle is actually a bit larger still, but the lens has a baffle installed over the rear element to limit the coverage to only the area where the image quality still holds up.

Even at 21mm/f8, there's still enough coverage for a 33x44 sensor with maybe a millimeter or two left over for movements:

Mind you, I wouldn't necessarily recommend this lens for use with a sensor that large, but if you can find a camera to mount it on (its flange-to-sensor distance is 48mm) with a digital back on the other side, don't need a shutter (for example, I photograph mostly at night with long exposures) and really need a wider-than-35mm focal length, it's potentially an option to consider. It certainly has the characteristic Zeiss "look" and can get the job done with a single shot when it's not possible to stitch one's way to happiness when a wider FoV is necessary. <shrugs>

(FWIW, I've been successfully using it on a [modified] Toyo VX23D view camera, with a Sony A7R serving as a poor-man's digital back, and there's plenty of room for movements when it's used with a modest 24x36 sensor.)

 

[wallpaperviking]

Very interesting indeed!

And at 17mm?

 

[wallpaperviking]

any room for movements on a 24mm x 36mm sensor?

 

[Audii-Dudii]

any room for movements on a 24mm x 36mm sensor?

At 17mm, there is some room, but not a lot ... 3-4mm, max:

The coverage is about the same at 18mm, but starts increasing at 19mm, where there's ~4-5mm of movement available.

FYI, here's a test photo I took at 17mm, with ~3mm of rise, of a house down the street, using the A7R as a back:

As you can see, there's some darkening of the upper corners starting, but for most photos, I can live with it. (Of course, for most of my nighttime photos, it's not an issue at all, what with the mostly black sky overhead and all, but YMMV.)

But there's no way it will cover a 33x44 sensor.

And for the moment, there's no way to control the electronic aperture with the lens mounted on the camera (although I'm working on that and expect to successfully transfer the guts of a Kipon adapter into my modified Toyo, where I am using a modified Contax N 26mm auto extension tube to mount the lens on a custom recessed board and a modified, generic, Sony E-mount auto extension tube to mount the body. Both of these mounts have electrical contacts built-in and use wires to connect them to the other side, so it's not a big deal to splice-in the Kipon circuitry. I actually have it all working on the bench, but because I've changed direction and am now building a smaller, lighter, custom camera around a modified Toyo Robos rear standard, I haven't bothered to install it into my existing camera. (And FYI, it's not possible to easily use the guts of a Fringer adapter, either, because the electrical contacts on both sides are connected directly to a single circuit board, unlike the Kipon, which mounts the contacts on each side on separate circuit boards and connect them to an intermediate circuit board via ribbon cables. As such, there is no easy way to separate one side of the Fringer adapter from the other side, whereas the Kipon adapter effectively does this at the factory. Which is a shame, because I was really hoping I could use it to control the apertures of both my Contax N and Contax 645 lenses when used with the same modified Toyo, but given my limited skill level with electronics, separate setups will be required instead. But I digress...)