IR film and Bessa R

[FrankS]

There is no problem with this, right? Anyone have experience and results to share? (I've heard that some cameras are not IR light-tight or have other problems with IR film.)

When I do a wedding (2 or 3 a year) I use a Nikon F4 for colour negs, and a Mamiya 6 for B+W. (+backups) I like to take along another camera with Kodak high speed B+W. I'm thinking now that my new Bessa R would be the perfect camera for this.

 

[Nick R.]

Don't you own a Hexar? Wouldn't that be a better bet for IR?

 

[FrankS]

Hi, Nick. I've used the Hexar AF with great success as a colour candid snapshot camera and especially later in the day at the reception. It focusses in the dark and balances flash/ambiant light very well.

 

[Nick R.]

I was thinking along the lines that I had read that the Hexar AF could be programmed to autofocus with infared film.
I'm not sure what kind of filters you plan on using but in general, being as IR doesn't focus in the same plane as visible light, the rangefinder and distance marks shouldn't line up correctly with IR film in the Bessa. I remember some old cameras came with a red line on the distance scale for shooting IR. The 50mm Nokton on my R doesn't have such a mark. I would think that without a rangefinder and having no distance marks would make on-the-go shots at a wedding pretty tough.
I'm planning to buy an AF very soon.

 

[Stu :)]

I've had no troubles shooting Kodak HIE and Konica 750 IR.
Also if found Bessa Rs on pretty much on the mark when it comes to metering 3200 ISO film.

Also didn't have any trouble when I changed lenses either.

Just remember to black tape up the film window.

Stu 🙂

 

[FrankS]

The Hexar AF is a great little camera. Point and shot simplicity if you want it (with aperture control input) and full manual if you want it, though the manual focussing is a bit finicky and it's much easier to auto focus on the subject (or an alternative subject the same distance away, and hold focus with partial pressure on the shutter button, and recompose.

The Kodak high speed infra red film is fast enough with a red or orange filter on a sunny day that a middling f-stop can be used which compensates enough for the focus shift of IR light. The Canon and Leica 50mm lenses I have have the IR focussing mark. Interestingly, the Russian Jupiter 8 and Industar lenses do not have that IR focussing mark.

 

[Max 2.8]

The Hexar AF is a great little camera. Point and shot simplicity if you want it (with aperture control input) and full manual if you want it, though the manual focussing is a bit finicky and it's much easier to auto focus on the subject (or an alternative subject the same distance away, and hold focus with partial pressure on the shutter button, and recompose.

The Kodak high speed infra red film is fast enough with a red or orange filter on a sunny day that a middling f-stop can be used which compensates enough for the focus shift of IR light. The Canon and Leica 50mm lenses I have have the IR focussing mark. Interestingly, the Russian Jupiter 8 and Industar lenses do not have that IR focussing mark.

Reviving this post. I am trying infra red film soon after learning how to developement my own BW film. I am using a Bessa R with 35mm skopar and 50mm nokton, also realised that there's no "R" marking on both lens, so are all my russian lens.

Has anyone solved this problem? Or found a estimation for these lens?

Cheers
Max 2.8

 

[pvdhaar]

I looked at the markings on my 50/2 Hexanon. The IR mark coincides with the f4 DOF marking *further* than where you focus. So if you stop down 2 stops, DOF will take care of the difference for a 50mm.

Alternately, if you don't want to change DOF, you could do the following. First focus normally, note the distance, and then focus *closer* so that the noted distance will line up with the aperture marking two stops *further* from the central one.

For a 35, DOF is a bit deeper, so you probably can get away with doing this but using/guessing 1.5 stop markings instead..

 

[Max 2.8]

I looked at the markings on my 50/2 Hexanon. The IR mark coincides with the f4 DOF marking *further* than where you focus. So if you stop down 2 stops, DOF will take care of the difference for a 50mm.

Alternately, if you don't want to change DOF, you could do the following. First focus normally, note the distance, and then focus *closer* so that the noted distance will line up with the aperture marking two stops *further* from the central one.

For a 35, DOF is a bit deeper, so you probably can get away with doing this but using/guessing 1.5 stop markings instead..

Thanks pvdhaar,

Does this technique applies to all distance on the distance scale?

Cheers
Max 2.8

 

[pvdhaar]

Yes.

For instance on the 50/2, when I focus at infinity, and then line up infinity at the f4 mark, the actual focus is approx. 10m (30ft)

When I focus at 1.5m (5ft), and the line up 1.5 m at the f4 mark, the actual focus is somewhere around 1.4m (4.5ft)

Hope this helps..

 

[daveozzz]

I use a light red filter and find that the focus adjustment isn't necessary with it. There still a lot of visible light coming in in that situation. Maybe with an IR filter it would be different.

 

[pvdhaar]

daveozzz,

the problem is not the light level, it's the wavelength of IR. Lenses are designed for the colours you can see, and can focus these correctly (although APO design is sometimes required to bring all colours to the same focal point).

IR wavelengths are different, they are focussed in a different plane than visible light, and hence require re-focussing.

 

[Max 2.8]

Regarding APO, someone in forum.clubsnap.com says that bessa's lens are corrected already. hence no need correction for distance, that why no "R" mark...

This is confusing! 😕

 

[Max 2.8]

Yes.

For instance on the 50/2, when I focus at infinity, and then line up infinity at the f4 mark, the actual focus is approx. 10m (30ft)

When I focus at 1.5m (5ft), and the line up 1.5 m at the f4 mark, the actual focus is somewhere around 1.4m (4.5ft)

Hope this helps..

i see, this i understand.... 🙂

 

[pvdhaar]

Regarding APO, someone in forum.clubsnap.com says that bessa's lens are corrected already. hence no need correction for distance, that why no "R" mark...

This is confusing! 😕

I can imagine, because that statement doesn't hold water. APO has nothing to do with IR-marks. Think about it this way:

If you let light fall through a prism, you see a spectrum, every wavelength (colour) bends differently through glass. Lenses consist of multiple elements that try to bring these different wavelengths together again in a single spot. Which of course is impossible because you want the lens to do something useful as well; it's either perfect but doesn't do a thing or it is able to form an image but isn't perfect.

Ordinary lens design allows two different wavelengths coming from the same point to exactly fall in the same spot. The rest becomes a somewhat diffused blob. We live with that because these lenses are affordable. APO design allows three different wavelengths to exactly fall in the same spot. And again the rest becomes a somewhat diffused blob. We live with that because these lenses are expensive enough as they are. These three wavelengths are typically chosen to cover the key colours the human eye can see (like as in the cones in the retina).

Bringing the IR wavelengths into the same spot too would either go at the expense of one of the wavelengths for ordinary vision, or cost a bucketload of money to realise. So, we live with lenses that work for visual light and we refocus for IR...

 

[pvdhaar]

Mirror lenses, Apochromats,Super-achromats, and ultra-achromats have low enough chromatic dispersion not to require refocussing for IR.

That's not something that holds in general, it's entirely up to the lens designer's decision on which wavelengths are chosen to optimise for.

By the way, if anyone is intimidated by the terminology, monochromats bring one wavelength at exact focus, achromats work for two, apo for three, and super-apo for four wavelengths..

Of course it's possible to design a super-apo to work for R,G,B and IR, but they're expensive because of the design as well as because of the different sorts of glass used, and the production tolerances required..

..The other ones may well hide the focussing error behind DOF (e.g. a 55mm somewhere between f2.8-f4).

 

[Max 2.8]

Wait, wait, wait....You guys are talking too "fast" . And out of topic, I not using SLRs, just my Bessa R with 35mm Skopar and 50mm Nokton.... 😕

Just simple answers will do, correct or not to correct the focussing distance....he he... 😀

 

[Doug]

I recall reading on CVUG e-list that Mr K was specifically asked if the 90mm APO were indeed apochromatic, and he replied it was not, but close to being so.

 

[Max 2.8]

I see... Thanks 😀

 

[Poptart]

B The other extreme was a window made to pass long wave IR, did not pass visible at all. Also found some Wratten 88a filters, cut off visible and pass the Near IR that I was interested in.

I thought the 87c was the opaque ir filter . . . regardless, you can cover a flash tube with it instead of the lens and make your own ir light! I was trying to make one with Rosco color filters last night and my elf now has 7 layers of filter pack and it still produces visible light. But I'm going to try it anyway.