After viewing some of the threads here I feel I have to comment on what I think is over-use of correction of converging verticals; whether that be by PC lenses, LF technique or simply software correction.
I do appreciate that each image has to be considered individually; there are often technical reasons why a picture may not be as desired (we can not always be at the appropriate taking position, for example), but it seems to me that some people look upon perfect verticals as correct, even though there might be very strong distortion as a result.
Many years ago I came across a "rule of thumb" (but unfortunately I can't remember where I found it or what the exact numbers were, so if anybody can fill in the gap I'd appreciate it). Basically what it boils down to is the angle of the back (film plane) compared to the viewing angle:
If you measure the angle from the horizontal your camera needs to be to take the shot (assuming the building has vertical sides ), anything up to n degrees (unfortunately this is the figure I can't remember ) can be shot with the film plane vertical (and corrections, movements, etc. made elsewhere). Between that and 16 degrees you should halve the difference between n and 16 degrees. Over 16 degrees = ( 16 - n / 2 ) + n
This would be easier if I could remember n
If for now, as an example, we assume n = 4 degrees, then if the camera is 10 degrees pointing upwards, the back should be around 7 degrees from vertical to allow for some correction, yet distortion should not be obvious; this should give a more natural looking image.
Has anyone else here used a similar approach, or better still can someone fill in 'n' for me?
Re: Architecture technique
I think it is totally an aesthetic consideration,as you say,evaluating the particular image. When I think that a grate wa lens should have some barrel distortion I can live with it and I even like it.
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