Infrared focus point for Hasselblads

[scinysnaps]

How do you focus for infrared film on Hasselblads?
I have 2 old C* lenses. Can't seem to find and IR dot as on a Nikon lens.

[Q.G.]

The hard way, i'm afraid.

Where the IR index would be depends on the lens type and wave length.
What lenses do you have, and what wave length would be the one you're going to use?

[scinysnaps]

I have a 80mm C* and a Distagon 40mmC*
I am thinking of using the Rollei Infrared film

[Ed Sukach]

The more I think about it ...

Unless the film is LOCKED into a *very* short-wave UV area and a severe UV filter ("opaque" to normal vision) is used I don't think the "UV" compensation mark is useful, or even appropriate.

With a relatively mild filter, #25 Red or so, the light affecting the film is alredy modified, so the image on the ground glass, visible to "usual" vison, would be focused properly, anyway.

I have done a fair amout of IR, with Konica and a #25, and was troubled with many exposures out of focus. Analyzing: I had first focused with the #25, then shift using the IR dot. NOT good. Even focus wthout the #25, place it on the lens and shift. Still, the correction from the shift to the IR dot is too large.
I will use the available IR films, I think Kodak's is no longer available, I'll focus WITH the #25 in place and forget andy tweaking, as if it was plain old B&W film.

One thing I have not done yet is to compare IR and plain B&W film with the #25 filter. It would NOT surprise me to find that there wasn't much difference.

[msage]

How do you focus for infrared film on Hasselblads?
I have 2 old C* lenses. Can't seem to find and IR dot as on a Nikon lens.

Hi
I have never adjusted for focus (4x5, 120 and 35mm).
Michael

[martinhughesireland]

I never adjust focus either
In theory you should change focus but in the real world it makes no real visible difference
The only exception might be for macro photography or if your shooting with a very narrow DOF, then you might notice it...

Just get out and shoot a role and focus as normal....

M

[Q.G.]

I have a 80mm C* and a Distagon 40mmC*
I am thinking of using the Rollei Infrared film

The IR mark is 10.5 mm to the right of the focus index for the Planar, and 5.5 mm to the right of the index mark for the Distagon.
Both for 800 nm.

The spread is quite large going through the bandwidth from 660 nm to 900 nm: from about 5 mm to almost 15 mm to the right of the visual focus mark on the Planar, and 2.5 to 7.5 mm on the Distagon.
So stop down a bit more than you would otherwise, to get DoF to help a bit.

If you want trouble free focussing, get the Sonnar-Superachromat or UV-Sonnar. No correction needed, everything in focus from deep blue (UV in the latter case) to IR, all at once.
What you would need is a lot of cash to get you one of these lenses.

[Q.G.]

The more I think about it ...

Unless the film is LOCKED into a *very* short-wave UV area and a severe UV filter ("opaque" to normal vision) is used I don't think the "UV" compensation mark is useful, or even appropriate.

The more i think about it, noone mentioned UV and UV index marks.

[Ed Sukach]

Oh boy..... another "Senior Moment"!!!

You are correct ... I was thinking "Infra Red" - "IR" - and writing "UV" - just the opposite.

Howevertheless ... I think IR indices are no longer needed/ appropriate ... evidenced by their omission by Hasselblad/ Zeiss.

[scinysnaps]

[QUOTE=Q.G.;908956]The IR mark is 10.5 mm to the right of the focus index for the Planar, and 5.5 mm to the right of the index mark for the Distagon.
Both for 800 nm.



Would this be with the 25 red only or does it apply to the IR 87/87C as well?