Dating 24" Darlot Pill Box and your thoughts about it

**Mark Sawyer** · 10-May-2018, 22:50

Originally Posted by Jon Wilson

If the FL is measured from the Waterhouse slot to the image on the wall it would be 28 inches and 23 inches from rear of lens.

If you're shooting wide open (with spherical aberration), measure from the lens. If measuring from a stop (blocking the spherical aberration), measure from the stop. That's how focus shift works, changing the focal length as you stop down. That's also how soft focus works, soft being one focal length, sharp being another focal length. And that's also how males and females work. Males and pixies, I'm not so sure...

**Steven Tribe** · 11-May-2018, 01:10

This would have been a 95mm. Makers had the opportunity to view their lenses naked and always used their unmounted diameters in their catalogues!

95mm is a less than common size. I don't have Darlot's catalogues but the Lerebours et Secretan had a 95mm landscape which had a focal length of 90cm. They even had ones of 110mm (Two versions - 90 and 120cm efl) and 160mm.
The same lens was used as the front achromat in their 95mm lensed Petzval. But there were 3 versions of the 95mm Petzval - so the shorter/faster one may have an achromat which matches your focal length.

95mm diameter achromats were not that popular a size. Most makers went from 81mm to either 90mm or 100mm plus.
Hermagis is the only other maker I can find (only a quick check) who had a 95mm.

**Jon Wilson** · 11-May-2018, 05:23

Originally Posted by Mark Sawyer

If you're shooting wide open (with spherical aberration), measure from the lens. If measuring from a stop (blocking the spherical aberration), measure from the stop. That's how focus shift works, changing the focal length as you stop down. That's also how soft focus works, soft being one focal length, sharp being another focal length. And that's also how males and females work. Males and pixies, I'm not so sure...

Thank you Mark. That is a very helpful description. It made my “light bulb” come on.

**Jon Wilson** · 11-May-2018, 05:27

Originally Posted by Steven Tribe

This would have been a 95mm. Makers had the opportunity to view their lenses naked and always used their unmounted diameters in their catalogues!

95mm is a less than common size. I don't have Darlot's catalogues but the Lerebours et Secretan had a 95mm landscape which had a focal length of 90cm. They even had ones of 110mm (Two versions - 90 and 120cm efl) and 160mm.
The same lens was used as the front achromat in their 95mm lensed Petzval. But there were 3 versions of the 95mm Petzval - so the shorter/faster one may have an achromat which matches your focal length.

95mm diameter achromats were not that popular a size. Most makers went from 81mm to either 90mm or 100mm plus.
Hermagis is the only other maker I can find (only a quick check) who had a 95mm.

So, any lens pencil writing or lens serial number scratching?

I truly appreciate the benefits of your knowledge. I know the edge of the lens has “Darlot” penciled. I will take a closer look this weekend and post better pictures of the lens edge.

**Steven Tribe** · 11-May-2018, 09:16

Can the lid holding the pill box be screwed off the main barrel? If it is soldered, without any trace of an internal thread, then it (the main barrel and the lens) is from a very large Petzval.

**Jon Wilson** · 11-May-2018, 17:44

Originally Posted by Steven Tribe

Can the lid holding the pill box be screwed off the main barrel? If it is soldered, without any trace of an internal thread, then it (the main barrel and the lens) are from a very large Petzval.

Yes Steve, you hit the nail on the head....the lid is soldered on and there isn't any trace of a thread. It must have started as part of a large petzval or cobbled by someone who had various parts. The glass does have "Darlot" penciled on edge (I do promise to post more pics of the lens edge this weekend).

What are your thoughts on the waterhouse slot which has a "sleeve"? Thought a sheet of film could be shape smaller apertures.
Jon

**Jon Wilson** · 12-May-2018, 13:47

here are more and hopefully clearer pictures of the lens edge. The "Darlot" is light in pencil on the edge. Next to Darlot is "Paris". Then a symbol or initials, not sure what, maybe some Steve, Mark or someone else can identify it. There appears to be a "1" and then "48" maybe the 1 refers to it being the first lens on the original petzval? 48?

Steve, if this meniscus is 95 mm lens, how large of a petzval would it have come from?
Thanks. Jon