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Red line on Zenzanon lens
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PostPosted: Tue Nov 13, 2018 6:47 am    Post subject: Red line on Zenzanon lens Reply with quote
Hi

I'm trying to find out what is the red line on this Zenzanon lens https://thumbs.worthpoint.com/zoom/images4/1/1215/16/bronica-zenzanon-ps-50mm-3-lens-sq-sq_1_bfe4f9fd22f2815edea87e20be0a6507.jpg

I mean the vertical line just slightly to the right of left f/8 line in the focus distance scale (not sure abotu the exact terms in English). I tried to find in some manual but couldn't find a lens that has that line and also a manual available online (that I could find at least).

Thanks


PostPosted: Tue Nov 13, 2018 7:04 am    Post subject: Reply with quote
Infrared infinity mark.
IR infinity varies from visible light infinity.


PostPosted: Tue Nov 13, 2018 8:03 am    Post subject: Reply with quote
luisalegria wrote:
Infrared infinity mark.
IR infinity varies from visible light infinity.


Not quite ... it's the i/r focus reference point. Basically, you focus the lens "as normal", make a note of the focussed distance on the lens, then move the focus ring until this noted distance aligns with the red mark. Then fit your filter and make your exposure ... it's not an intuitively fast process Wink


PostPosted: Tue Nov 13, 2018 11:32 pm    Post subject: Reply with quote
kypfer wrote:
luisalegria wrote:
Infrared infinity mark.
IR infinity varies from visible light infinity.


Not quite ... it's the i/r focus reference point. Basically, you focus the lens "as normal", make a note of the focussed distance on the lens, then move the focus ring until this noted distance aligns with the red mark. Then fit your filter and make your exposure ... it's not an intuitively fast process Wink


That's something I've never read or heard about, and fascinating to me.

Not intuitive, to be sure. Wink


PostPosted: Mon Nov 19, 2018 5:00 am    Post subject: Reply with quote
Thank you.

So here's a follow up question...
This was a "riddle" someone asked. I'm guessing out of everyone he asked, I'm most likely to ask on an online forum. Some of the others would probably only google "lens red line" and other similar things. This is what I did at first (a bit more than just that) and couldn't find anything.

Then I tried to come up with other ideas, like trying to find manuals for those lenses (he had 50mm and 80mm Zenanon lenses if I remember) and couldn't. I then tried to find a lens that has that red line and a manual available online, but couldn't. I did find some lenses with lines in different colours (e.g. some Nikon MF lenses), but being colourblind I couldn't really tell, since it was very different (not a single red line among the other lines).

So... if there wasn't an online forum like this, how would I be able to find out what it was?

Thanks again


PostPosted: Mon Nov 19, 2018 7:56 am    Post subject: Reply with quote
clarnibass2 wrote:
Thank you.

So... if there wasn't an online forum like this, how would I be able to find out what it was?

Thanks again


RTFM Wink ... details like this were usually documented in the user manuals of the day, else any publication on the use and application of infra-red film would have probably detailed it. It's something I've "always known", so it must have been written down somewhere relevant !

I do still have some "proper" books, possibly even the data sheet from one or more packs of infra-red film squirrelled away somewhere ... if I get enthusiastic I'll have a dig about one evening Smile
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