1. ## Trousse Parisienne Casket Lens Set

Hello,

I recently acquired a lens set and would like to know more about it. It consists of a brass main body with front and rear threads and an aperture iris that goes from 1 to 6. It has a total of 8 threaded cells, one which appears to be an extension the others are lens elements marked 25, 35, 45, 55, 65, 75 and 85. It is labelled Trousse "Parisienne" No 829.

Any ideas? The focal lengths are puzzling, but I assume there is some matrix of combinations yielding a (large) variety of final focal lengths, as well as f stops.

Any insights are appreciated.

John

2. ## Trousse Parisienne Casket Lens Set

Just a guess - maybe the marked dimensions are focal lengths of the individual cells in cms. It might be worth popping one on and seeing if it roughly in the ball park - keep in mind that using single elements typically displaces the nodal points, so measuring bellows extension might not be a good way to go but comparing the relative image sizes (and if possible to some other marked lens) should give you a pretty good idea.

When you combine cells, the combined focal length is typically got by using the formula 1/F = 1/f1 + 1/f2 - d/f1*f2

where F is the combined focal length, f1 and f2 are the focal lengths of the two individual cells and d is the inter-cell distance.

Cheers, DJ

3. ## Trousse Parisienne Casket Lens Set

The apertures are going to be a problem. These sets came with a table translating the 1 to 6 markings of the diaphragm into actual f stops of the various combinations. Like Waterhouse stops, these tables nearly always get separated from the lens. A procedure that is laborious, but works, is to assemble a combination, focus it to infinity, then point it at a blank wall. Take readings off your groundglass, using your darkcloth if necessaary to prevent extraneous light from influencing the reading. Now switch to a known lens, again set to infinity. If the lighting hasn't changed, stop down the known lens until the same readings are obtained and record them. Now you can make your own chart.

4. ## Trousse Parisienne Casket Lens Set

Sounds remarkably similar to an Emil Busch Vademecum set (mine goes from 15 to 75cm and has aperture marks from 1 to 5). My guess is that it's a meniscus set (Petzval, right DJ?). Does the barrel have a drop in slot by any chance?

5. ## Trousse Parisienne Casket Lens Set

No drop in slot - do you have a table with your set for focl lengths and apertures?

6. ## Trousse Parisienne Casket Lens Set

hi i have a busch set with no chart afriend helped me establish f-stops 1 st find your focal lenght then measure the iris size that will give you a f-stop that will correspond to the numbers on your lens , maybe some one with the formular can help ?

7. ## Trousse Parisienne Casket Lens Set

Don't know about the Vade Mecums - could be single menescus types or maybe rapid rectilinear types depending on vintage, I guess. For figuring out f-stops, the simplest solution would be to measure the iris size and you will have a millimeter scale. Divie that by the focal length being used for the f-stop. Cheers, DJ

8. ## Trousse Parisienne Casket Lens Set

Unfortunately, the formula is based not on the actual iris size, but the effective or apparent iris size. The actual iris size is only the same as the effective size for single, not compound, lenses. To measure the effective aperture, a rather uncommon and expensive gadget called a traveling micrometer is used. It looks at the lens from the front through a little telescope, is lined up with one size of the iris, then shifted over to the other side and the amount of travel measured. People have made gadgets that do this with sufficient accuracy, but its quite a bit of work. The formula is simple enough. Focal length divided by effective aperture equals f stop.

9. ## Trousse Parisienne Casket Lens Set

Here is an F stop and focal length guide from a Busch Vademecum set, it will probably work for you as most sets were somewhat universal in nature........

[IMG][/IMG]

10. ## Trousse Parisienne Casket Lens Set

Thank you so much, CP.

Does anyone have the formula to go to the combined focal lengths?

J

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