Understanding Pezvals

[StoneNYC]

I've noticed many people tend to list the size of the petzval lenses by the width of the front and rear and also length of the barrel but I don't know how that correlates to anything.

Modern lenses can be seemingly any physical size but the lens designs change their FL etc, so what are these measurements telling people? Thanks!

[Mark Sawyer]

If they're telling you the focal length, that's something I'd think you'd want to know. If they also tell you the aperture diameter, or the front element diameter along with a "down the throat" photo, you can figure the speed. Beyond that, general dimensions give you something to make an educated (or uneducated) guess about what format it may cover. If I know a Petzval has a physical length of 16 inches, I'm much more interested than I would be in a Petzval with a physical length of 6 inches. And if it looks proportionally fat, doubly so.

Remember, many people selling these lenses know very little about photography, so make the most of whatever information you can get.

[RSalles]

Stone,

Getting a lens and focusing to infinity, measuring the distance from the nodal point of the lens to the image plane gives the focal length of the lens. The size of the image plane can be a M 4/3 or a 8x10, doens't matter. The size of the image circle is what matters - for us, apprentice portrait makers. All this can be very well known by you, but I go on: when in doubt if a "guess of a guesser" is well based ask for the distance between the nodal point of the lens and the focus plane of the image formed focused at infinity. Ask doesn't hurt,

Best,

Renato

[Keith Fleming]

There are also issues created by the very large size of some of these lenses. Will it fit on the camera's lensboard? Is the lenses weight such that it might not be wise to hang it on the front of the camera.

Keith

[StoneNYC]

Thanks guys, so basically it's non photo sellers not knowing how to describe the lens so the give its physical size, but those don't actually tell me anything useful in terms of FL or anything else except physical size dimensions.

Got it.

[Taija71A]

... Beyond that, general dimensions give you something to make an educated (or uneducated) guess about...

... but those don't actually tell me anything useful in terms of FL or anything else except physical size dimensions.

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As per Mark's comment (above)... This is All 'Very Useful' information.
--
Of course...

How you make use of it or choose to 'process' it (i.e. an 'Educated' or 'Uneducated' Guess)...
Is entirely up to -- The 'respective' individual!
--

-Tim.
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[StoneNYC]

For my purposes weight and physical size is essentially irrelevant, I don't know enough about these lenses to make any serious educated guess about is focal length or coverage based solely on the physical side dimensions of that, I would need the actual FL and the coverage number, it could simply be in the form of having the original catalog from the company and the lens designation number, such as the Darlot catalog I own is very specific about the FL and coverage so based on the lens number and name I can identify all of the important information, but simply telling the physical side of the lens doesn't help me at all, I'm not worried about its weight on my camera or anything like that, it will fit...

[Taija71A]

For my purposes weight and physical size is essentially irrelevant, I don't know enough about these lenses to make any serious educated guess about is focal length or coverage based solely on the physical side dimensions...

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Questions:

1). Do you understand... How numerical 'Aperture Values' are calculated for All Lenses?

2). Did you have the opportunity to read this 'Excellent' Article... About Petzval Lenses?
(*That Dan 'So Kindly' wrote):

http://antiquecameras.net/petzvallens.html

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If not...
Perhaps... Some reading is still in order?

If so...

You should now, be able to determine the F.L. (*And more)...
For a 'large number' of the bigger Petzval Lenses!

Thank-you!
_________

[Mark Sawyer]

The more you understand the very basics of lenses, and the more familiar you are with historical examples, the more you can deduce about a lens from a few seemingly meaningless numbers.

[Tin Can]

I'm sure many of us have lenses that would never fit on your camera, for 3 different criterion.

Weight, diameter and FL.