Need help, please.

[Coraki]

I came across a JC Penny 28mm f/2.8 with on a Canon AE-1P. I know the red dot is usually for focusing when using IR, but what is the red "R"? I tried finding the information online with no luck. The lens looks like this one below. Thank you.

 

[Zen1300]

Ok, pretty cool. I used to work for JCPenney. I was amazed to look at old catalog pages and the things they sold. I looked on ebay and there are a few of these available.

This site shows Nikkor lenses with a Red R for IR focusing. Other lenses of that era also had the red R indicating IR. The red dot in this case is the index mark.
Nikon F TICK Mark Lenses

 

[Coraki]

Ok, pretty cool. I used to work for JCPenney. I was amazed to look at old catalog pages and the things they sold. I looked on ebay and there are a few of these available.

This site shows Nikkor lenses with a Red R for IR focusing. Other lenses of that era also had the red R indicating IR. The red dot in this case is the index mark.
Nikon F TICK Mark Lenses

Thank you. I'm going to be using some EIR these next few weeks. It's been sitting in the freezer for 10 years and now I have the opportunity to use it.

Ya, I remember those old catalogs that were thicker than phone books.

 

[Zen1300]

Ok, I was so intrigued by this lens, I just picked one up just for the fun of it.

 

[Coraki]

Ok, I was so intrigued by this lens, I just picked one up just for the fun of it.

Have fun! Let me know how you like it. I've seen a few mixed reviews. I think it just comes down the individual lens.

 

[TCampbell]

That's the focus point for infra-red film. You'd focus as if for normal film, then whatever the focus distance is on your focusing ring... just tweak the ring over so that distance is positioned at the red dot and now it's focused for infra-red wavelengths of light.

Different wavelengths of light bend different amounts as they pass through the lenses. The shorter the wavelength, the more it bends. The longer the wavelength, the less it bends. That means that when visible light is focusing on the film plane, the IR light is focusing at a point that's just a tiny bit beyond the film plane. If you didn't adjust focus to compensate, you'd end up with out of focus images. But your eye cannot see the IR light to focus it. Hence the lens has that extra dot for IR which shows you how much you'll need to adjust focus to compensate the focus to be accurate for IR.