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.

__

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.
_________

[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...
__

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

--
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.

[Lachlan 717]

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.

No; that's only a small subsection of the reason. It's a combination of many factors such as these lenses being projection lenses, an antiquated system of designating focal lengths (3B, 5A etc), aperture-less design and/or antiquated aperture markings.

These are generally old lenses; don't assign modern nomencliture to them.

[goamules]

A rough guide with photography Petzvals (not magic lantern ones) is their focal length is often approximately the length of their barrel. A lens that is physically 6" long, often has a 6" focal length. The larger the size, you usually add a little more for focal length. I have a Vitax sitting here that is about 12" long. But it's focal length is 16". It's basically common sense, a small lens is not going to cover a big plate. The diameter of the front glass is not used to determine speed, but the apparent iris seen through that glass is. You can approximate. If the lens is 8" long, and the glass is 2 1/4 diameter, you can bet it will be an F3.8 or F4 lens with about an 8" focal length. That extra 1/4" is cut off/vignetted by the barrel structure. You will be right 86.3% of the time.

[Joe Smigiel]

Thanks guys, so basically it's non photo sellers not knowing how to describe the lens ...

Be very suspect of anything on eBay described as a "Petzval" lens. To many sellers, including photographers and "I'm not-an-expert" non-photographers, anything with a rack-and-pinion focus or brass barrel is often described as a Petzval. I've seen many of what I assume to be (though "I'm not an expert") triplet projection lenses or aplanats/rapid rectilinears listed as Petzvals. Other things frequently misidentified include "wetplate cameras" (aka any big wooden camera with a bellows) and "wetplate holders" that turn out to be contact printing frames.

Dan's antiquecameras.net (http://antiquecameras.net/petzvallens.html) site has loads of information on Petzvals and other lenses.

[StoneNYC]

A rough guide with photography Petzvals (not magic lantern ones) is their focal length is often approximately the length of their barrel. A lens that is physically 6" long, often has a 6" focal length. The larger the size, you usually add a little more for focal length. I have a Vitax sitting here that is about 12" long. But it's focal length is 16". It's basically common sense, a small lens is not going to cover a big plate. The diameter of the front glass is not used to determine speed, but the apparent iris seen through that glass is. You can approximate. If the lens is 8" long, and the glass is 2 1/4 diameter, you can bet it will be an F3.8 or F4 lens with about an 8" focal length. That extra 1/4" is cut off/vignetted by the barrel structure. You will be right 86.3% of the time.

Ahhh! Now THIS makes sense! Thank you for this bit of information!


Be very suspect of anything on eBay described as a "Petzval" lens. To many sellers, including photographers and "I'm not-an-expert" non-photographers, anything with a rack-and-pinion focus or brass barrel is often described as a Petzval. I've seen many of what I assume to be (though "I'm not an expert") triplet projection lenses or aplanats/rapid rectilinears listed as Petzvals. Other things frequently misidentified include "wetplate cameras" (aka any big wooden camera with a bellows) and "wetplate holders" that turn out to be contact printing frames.

Dan's antiquecameras.net (http://antiquecameras.net/petzvallens.html) site has loads of information on Petzvals and other lenses.

Thanks


A rough guide with photography Petzvals (not magic lantern ones) is their focal length is often approximately the length of their barrel. A lens that is physically 6" long, often has a 6" focal length. The larger the size, you usually add a little more for focal length. I have a Vitax sitting here that is about 12" long. But it's focal length is 16". It's basically common sense, a small lens is not going to cover a big plate. The diameter of the front glass is not used to determine speed, but the apparent iris seen through that glass is. You can approximate. If the lens is 8" long, and the glass is 2 1/4 diameter, you can bet it will be an F3.8 or F4 lens with about an 8" focal length. That extra 1/4" is cut off/vignetted by the barrel structure. You will be right 86.3% of the time.

Ahhh! Now THIS makes sense! Thank you for this bit of information!


Be very suspect of anything on eBay described as a "Petzval" lens. To many sellers, including photographers and "I'm not-an-expert" non-photographers, anything with a rack-and-pinion focus or brass barrel is often described as a Petzval. I've seen many of what I assume to be (though "I'm not an expert") triplet projection lenses or aplanats/rapid rectilinears listed as Petzvals. Other things frequently misidentified include "wetplate cameras" (aka any big wooden camera with a bellows) and "wetplate holders" that turn out to be contact printing frames.

Dan's antiquecameras.net (http://antiquecameras.net/petzvallens.html) site has loads of information on Petzvals and other lenses.

Thanks


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

Weight, diameter and FL.

Again, I've said this before but I'll reiterate as apparently it wasn't understood, I'm not worried about weight, and I'm not worried about the diameter of the lens, any lens big enough with the focal length that would be too long for my Bellows would not be something that I would be buying in the first place because it would cost too much, and I don't know how many petzval lenses that were made bigger than 800mm but I'm sure I couldn't afford one. So I'm not concerned with that info even though now I know that measurements can be useful for determining FL.

[SergeiR]

It's basically common sense, a small lens is not going to cover a big plate.

Not to start arguing, but it it is true for portrait petzvals only. Landscape and or just plan slow ones (f8 and dimmer) - could be quite small with quite large focal length and plate covering capacity. E.g Morrison's landscape petzvals

[Tin Can]

Ooops I forgot, this is Stone's private thread.

Just here to serve.

[Mark Sawyer]

A rough guide with photography Petzvals (not magic lantern ones) is their focal length is often approximately the length of their barrel. A lens that is physically 6" long, often has a 6" focal length. The larger the size, you usually add a little more for focal length. I have a Vitax sitting here that is about 12" long. But it's focal length is 16". It's basically common sense, a small lens is not going to cover a big plate. The diameter of the front glass is not used to determine speed, but the apparent iris seen through that glass is. You can approximate. If the lens is 8" long, and the glass is 2 1/4 diameter, you can bet it will be an F3.8 or F4 lens with about an 8" focal length. That extra 1/4" is cut off/vignetted by the barrel structure. You will be right 86.3% of the time.

A pretty good guide, but my math says you'll be "sort-of-in-the-ballpark" right 74.2%. If you don't know the particulars about an out-of-the-ordinary lens you're trying to buy it's best to buy from someone who knows the lens and can steer you right. An unknowing buyer coupled with an ignorant seller is a bad combination and voids the warranty on my 74.2% equation...

[StoneNYC]

A pretty good guide, but my math says you'll be "sort-of-in-the-ballpark" right 74.2%. If you don't know the particulars about an out-of-the-ordinary lens you're trying to buy it's best to buy from someone who knows the lens and can steer you right. An unknowing buyer coupled with an ignorant seller is a bad combination and voids the warranty on my 74.2% equation...

Haha! I 98.436792859279% agree with you ;)

[John Kasaian]

Petzvals go good with beer. Mighty good, in fact.

[Taija71A]

Petzvals go good with beer. Mighty good, in fact.

John, you shouldn't be telling the 'OP'... All of this.
He already has problems... With 'just' the Pretzels!

[jnantz]

John, you shouldn't be telling the 'OP'... All of this.
He already has problems... With 'just' the Pretzels!


don't you get the aperture by counting how many grains of salt
are on the outside and multiplying it into the outsize petsval's diameter divided by the top to bottom measurement ?

[John Kasaian]

don't you get the aperture by counting how many grains of salt
are on the outside and multiplying it into the outsize petsval's diameter divided by the top to bottom measurement ?
Precisely!:) Not enough swirlies? Quaff another pint! Still not enough swirlies? Chug a pitcher! By that time every girl in the room will start looking like Giselle Bundchen.

[StoneNYC]

Whoops

[jnantz]

Precisely!:) Not enough swirlies? Quaff another pint! Still not enough swirlies? Chug a pitcher! By that time every girl in the room will start looking like Giselle Bundchen.

you said it cuz :)