Advantages of Back Shift

[Greg Liscio]

I am ready to purchase an Ebony SV45U or SV45U2, the difference being the SV45U2 has back shift.

I know that back shift permits moving the film while keeping the lens in the same perspective. I'd like to know what other advantages you have realized, and what your opinion of this feature overall is.

Thankee

[erie patsellis]

Back movements are used to alter or correct the geometry of the image, even in a field camera I'd consider them essential for my work.

[Andrew O'Neill]

Back movements are used to alter or correct the geometry of the image,

Not back shift, as Greg is inquiring about. Greg, I think you already stated the "main" advantage of rear shift over front shift...the image perspective isn't altered.

[Don7x17]

Not back shift, as Greg is inquiring about. Greg, I think you already stated the "main" advantage of rear shift over front shift...the image perspective isn't altered.

Back tilt and back swing modify the image perspective.
Back shift (and back rise/fall if you have it)just moves the image around in the cone of light of the lens
(and any swing or tilt applied before using shift is what changes the perspective....when you shift, you've moving within this modified cone)

[David Karp]

In addition to the benefit you mentioned, back shift is nice when you have a long lens. You don't have to reach all the way to the front standard to accomplish a shift.

[Andrew O'Neill]

Don7x17, How does back tilt and swing modify image perspective? Doesn't it just alter image geometry? What am I missing here?

[Don7x17]

You can make objects on one side of a tilt or swing change image size on the film (with respect to the other.). Weston used it a lot.

With Architectural photography its really obvious:
Its most obvious if you take an image of a building -- looking at a corner of a building so both sides are visible (135 degrees between line of sight and either plane of building side), with enough lens image circle coverage, you can make one or the other sides of the building appear square at the extreme expense of the other side.

And these movements are required in architectural photography (with view camera) to remove keystoning of buildings as you point the camera upwards to get the whole face of the building.

You're changing film to lens distance...that's why back swing and tilt change the perspective

Give it a try on your camera (presuming you have tilt/swing on rear).

Note that tilt and swing on front just changes the plane of focus.

[Lachlan 717]

I use back shift for portraits with my Petzval.

I focus with the subject centered in the frame (i.e. the sharp part of the lens).

If I want the subject (either whole person or perhaps their eyes) off center, I shift the back, leaving the subject still in the sharp part of the lens.

Only issue here is light fall-off towards one side if I am not careful.

Lachlan.

[Nicholas F. Jones]

Back shift comes in handy for me when shooting with a large and heavy camera and when the subject is upright, rectilinear, with straight lines, e.g. a building. The problem is usually to get the subject both centered and squared up. Even with a large structure, being off by just a few inches will often be painfully noticeable--and unsettling and irritating--in a big enlargement.

My usual procedure is to do my best to find the center by measurement and guestimating, place the tripod on that centerline, then use the grid on the ground glass to square the subject. But most times I find I'm a little off, that when squared the subject is no longer centered on the ground glass. So, it's either move the camera or use back shift. Back shift in other words is a much easier and more precise alternative to lateral movement of tripod and camera.

The bigger and heavier your set-up, the greater the advantage. Since my 8x10 has no back shift, I've given up using it for these centered-and-squared shots and take the 5x7 Canham instead, which does.

[Donald Miller]

If a camera has front shift then rear shift has no measurable benefit other than allowing greater lateral displacement. Since the original post asked the question of rear shift I will not engage in discussions of tilt and swing since they are not applicable to the discussion at hand.

Best regards,
Donald Miller