PDA

View Full Version : Lenses without indication of focal distance



lungovw
9-Mar-2009, 16:59
Hello,

Many lenses produced back in the XIX century have no indication of focal distance. However it is very common to find samples with "series" and N 2, 4 ...

Was that a standard shared among lens makers? Can we say that more than often a lens marked as N2 will work as a normal lens for a quarter plate, or any other statement alike? Any insight about that?


Cheers


Wagner Lungov

Ernest Purdum
9-Mar-2009, 18:49
"Series" designations indicate the design of the lens. Foir example, a Zeiss Series V is an extreme wide angle lens, while the Series VII and VIIa lenses general-purpose convertible types.

Within a particular lens line, "Number" designations indicate the focal length but there is no standardization, so you have to refer to a catalog to go from number to size. Fortunately, if you have in mind a particular lens you'd like to know more about, it's more than likely that somebody here on the Forum will have the necessary catalog.

CP Goerz
9-Mar-2009, 23:32
If you measure the focal length at infinity and then the aperture opening at wide open and divide one by the other you'll quite often have a good indicator of lens design. The next part is to gauge the thickness of the cells and check if there are any air spaces, after that its child's play.

Ole Tjugen
10-Mar-2009, 04:13
"Series" designations indicate the design of the lens. Foir example, a Zeiss Series V is an extreme wide angle lens, while the Series VII and VIIa lenses general-purpose convertible types...

As a case in point, a Zeiss "Serie VIIa" will be a pair of "Serie VII" cells.

Before the lensmakers started making fanciful names, they would often use a "serie" designation.

In many cases, smaller No. means a shorter lens - and a No.2 from a German maker is often either a 150mm lens or one fit for use on 9x12cm. But some makers numbered the lenses in the series in the opposite way, so that a No.6 would be for 9x12cm and a No.1 for 50x60cm!

Ask, and someone will find it in a catalogue.

Jim Galli
10-Mar-2009, 09:32
The answer to your question is generally no.

Series is more about purpose and formulae. For instance in Wollensak land, a series II is always a general purpose of the tessar type. III is a wide angle. IV is an entry level lens, a dialyt. etc. Then the consecutive numbers are the graduations upwards in size. But no make matched any other make. There's no reason to assume a Goerz series iii no. 4 is close to a Voigtlaender Series IV #4. In fact, one is a 9 1/2" lens and the other is about 13" if I recall correctly. Voigtlaender was particularly frustrating. A series II #4 can be miles away from a series IV #4 even with both sharing the same name, Euryscop. Very little rhyme or reason to try to get a handle on. The lens Vade Mecum is about all we've got and it's only helpful maybe 60% of the time.