Joseph, sure I read your posts. It's just that we were speaking apples and oranges. You said that "object to image distance" was changing.
I'm used to know that with the front cell focusing the image conjugate is not changed, what changes is the subject conjugate.
And yes, the front cell focusing focuses by changing a little bit the focus length of the lens, making it a short zoom.
Anyway, if it clears things for you, it's all right...
Thanks- yes, I think those tests helped clear up my original question-
Ernest, that may be the case, I'll have a look and see if I can find any evidence...
Bettersense, I've calibrated a helical to a camera before, and I think I'd be more concerned about accurate focus in the near scale, rather than infinity-
50 feet can be quite close to infinity anyway, depending on your focal length and maximum aperture-
Yes, the front cell focusing affects the SA. Normally it is considered that the front element focusing can be acceptable up to 1m of close distance focusing. It seems to me, that what is worthwhile for you is exactly on the opposite side of the scale, so perhaps you could have that 1m as a starting point...Originally Posted by Ernest Purdum
All of us (including British armed forces in WWII) who used Super Ikontas and Ikontas and their front element focusing cousins must have been very forgiving and Zeiss wasted engineering effort in designing Zeiss wedge incorporating coupled range finders for these front focusing Tessars. Again, much depends on having front standards parallel to film plane: my experience in camera retailing and "dealing with" pros and advanced amateurs was to seldom find parallel to each other front standards and film planes. Correcting that in large and medium format produces improved images. Bernie
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