Split darkslide on 4x5?

Donald Qualls said:

The other reason you might want to do this even if your lens has more than adequate coverage is for the same reasons you'd usually use rise/fall or shift: to control the field of view independent of the perspective. If you're shooting architecture this matters more than it would with landscapes, but even out in the wild, converging trees tend to annoy the eye, even if the viewer doesn't know why.

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Thats what I meant when I said "in order to frame my shot." In a large percentage of my LF photos I point the camera in the right direction, center all the bubble levels, then fine framing adjustment is done using rise/fall/shift rather than using the tripod.

abruzzi said:

... If you're using a lens that doesn't cover 4x5 or barely covers 4x5 (like the 90mm Angulon) then there may be a benefit to adjusting the lens to center over the half frame. But for a 90mm Super Angulon, I probably wouldn't bother unless I needed to in order frame my shot. (mostly I use rise/fall/shift for final framing of the image without needing to adjust the tripod.)

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A question because I rarely use extreme wide angle (for the format) lenses. On 4x5 and using 65mm to 90mm lenses -- would there be any distortions caused by the lenses that might have to be taken into consideration if using the top (or bottom) half of the projected image from the lens vs. using the center half?

Vaughn said:

A question because I rarely use extreme wide angle (for the format) lenses. On 4x5 and using 65mm to 90mm lenses -- would there be any distortions caused by the lenses that might have to be taken into consideration if using the top (or bottom) half of the projected image from the lens vs. using the center half?

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That is a good question, that I probably don't have a great answer to. My hunch is that for less well corrected lenses wides you could have some pin cusion distortion, or whatever the reverse of that is called (where the bending deflects toward the center not away from the center.) Using only the top or bottom half would probably mean that the distortions would all be in the same direction rather than the top bending up and the bottom bending down--everything would bend up or everything would bend down. But if you are using a lens that covers 4x5 not centering the lens over the upper half or lower half is just showing you that half of what a straight 4x5 shot would show, so you're not moving into the far reaches of the image circle.

Probably the biggest issues (to my mind) is that any distortion in the lens may no longer be centered--but againyou'll see the same effect if you use movements. the most noticable, especially with small image circle wide is probably that any vignetting won't be consistent. I'd worry about that more with a 65mm or 75mm lens than I would with a 90 or 100, but if you are shooting chromes it could call for a center filter (and they are getting hard to find and expensive.)

abruzzi said:

pin cusion distortion, or whatever the reverse of that is called

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The opposite of pincushion is barrel distortion. That said, I agree with everything you wrote above. Using movements to center the exposed section of negative behind the lens is probably the best way to be sure any distortion or vignetting is at least centered.