Quote Originally Posted by Ole
IR "bends" less in the lenses, so it isn't focused as much. That means that you have to pretend the subject is closer to your camera - so you focus closer. Fortunately you don't have to force your lens helical past infinity...
This is true, at least in theory. Lately I have been experiencing trouble with IR focusing ... I religiously focus and reset to the IR (red line) on the Hasselblad lenses (the older ones) --- and ... I'm obviously "out of focus".

I've been thinking ... with films that are primarily sensitive to "far" (comparatively) Infra - Red (i.e., Kodak HIE) and filters that cut off light in the visible spectrum - this IR index probably made sense - but with the "near" IR films - Konica 750, Maco 820, Ilford SFX, and what was Agfa's -- and the use of mild filtration ... R25 ... I don't think there is that much of a "shift". Seems to me, the focus of the image we see through the viewfinder (filtered) is probably *very close* to what will be recorded on the film.

I notice that there is *no* IR Index on the new Hasselblad lenses - which would seem to bear this out.

"Next" technical task - to "wring this out".