Understanding Pezvals

[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 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 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 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!