I have recently been shooting architectural interiors, and more often been worki ng in very cramped, quarters with either a 47mm (XL) or 75mm lens. With both le nses (the 47mm in particular), the light drop-off is dramatic towards the edges. The interiors are typically not that bright to begin with which further compou nds the dimming effect. More often than not, the near and far critical focus poi nts (I use the 2 point method) are at these dim edges of the image. My camera i s setup with a Boss screen which I find better for focus, and fairly difficult f or visualization due to the inability to view the whole image without moving you r eye at an angle to the screen around the outer edges of the image.
In order to focus at points near the edges of the screen, you must orient your l oupe at an angle to the screen to be in-line with the direction of the light ray s. I'm finding tilted loupe focusing to be somewhat error prone.
I am considering another focusing process with these lenses and would like other people's feedback. I know what I'm proposing may be somewhat non-pure from a m athematical standpoint, but would be interested if others think it is of practic al use.
With these lenses the center of the image is quite bright and very sharp on the screen. I am still proposing using a 2 point method, but reorient the camera on the tripod so it's directed at the near focus point and then do the same for th e far focus point. After arriving at focus, then frame the picture for the shot .
This certainly makes focus *much* easier with these lenses, however is there som e fundemental flaw with this approach?