Non-SMC triplets

overmywaders · Joined: 27 May 2009 Posts: 49

I have been using some old triplets for UV work. In comparing them to SMC modern lenses, I find that they pass more visible light as well as more UV. Since coatings often increase the passage of light, I suppose the fewer glass interfaces account for the triplets' efficacy.

I use the following:

Schneider-Kreuznach Jsogon 40mm 4.5
Ludwig Meritar 50mm 2.9
CZJ Triotar 13.5cm 4.0
Isco-Gottingen Isconar 100mm 4.5

The Meritar and Isconar take in so much light that at night most of the town suffers a temporary brown out as incandescent bulbs yield to the Meritar's momentary black hole. At midday the street lights come on for a moment in a three-block radius of my camera, whenever I click the shutter. I've tried stopping the lenses down until they scream, but with no measurable effect. As I type, the town council is drafting an anti-triplet ordinance - restricting the use of triplet lenses to the hours of 1:00 am to 5:00 am.

Have others also encountered these problems.

Spotmatic · Joined: 18 Aug 2008 Posts: 4045 Location: Netherlands

Yes, I think that walking in the sun without applying sunscreen could cook your brains.

kds315* · Expire: 2021-03-09

Well, Reed,

no many here will understand what you talk about .... Wink

An uncoated lens surface takes about 4% of light, so for a triplet (uncoated) that would be 6 x 4% = 24% so I honestly doubt the lights went off...

SMS shoudl reduce that to ca 0.3% per surface, so that would theroretically be 1.8% - BUT you won't hardly see any UV anymore...

Welcome here btw.!

overmywaders · Joined: 27 May 2009 Posts: 49

Klaus,

I am new here. Six months ago, if someone said "Manual Focus", I'd have assumed they were discussing a Mexican revolutionary. Now, after having to manually focus daily, I am a deep well of ignorance.

I do like the triplets, though. BTW, if I have a faux triplet (4 elements/3 groups) does the resin cement interface for the rear group require light transmission calculations for eight surfaces, six surfaces, or ten surfaces?

kds315* · Expire: 2021-03-09

Laurence · Expire: 2016-06-19

overmywaders - I think you went in over your waders to cause the street lights to change. Laughing

In any case, funny story! Good to see you here!

overmywaders · Joined: 27 May 2009 Posts: 49

Laurence,

Great inventions and discoveries are often met with skepticism. I recall that my invention of the Pisscalator raised similar problems. See http://www.overmywaders.com/cblog/archives/89-The-Pisscalator-Illustrated.html

Klaus,

I did some checking. The 4 element/ 3 group lens I am referring to is old, and probably cemented with Canada Balsam, so transmission for my purposes - 340-400nm - should be excellent. Canada Balsam has approx. 90% transmission at 340nm+; but plummets almost straight down in the shorter wavelengths, reaching 0% transmission by 290nm.

I'm thinking that, since optical crown glass has an index of refraction of 1.5339 at 435.8nm and Canada Balsam has an index of refraction of 1.54; and they share almost the same transmission rate in high UVA, I can just consider the faux triplet as a true triplet, ignoring the additional interfaces. Does that make sense?

Thanks.

Regards,
Reed