Brass Knob on Petzvel / Darlot / etc

[StoneNYC]

I have not in the past really been interested in portrait images, but I've grown to really find them interesting and I was looking to maybe purchase an old portrait lens.

I'm trying to understand the differences, I'm not a lens designer and I don't understand the different lens design explanations like doublet etc., I understand that I can Google the different explanations but I don't understand how they translate into the "look".

I'm also trying to understand what the knob is for, since LF cameras of today have a bellows focussing system, I'm trying to understand if the knob on these old brass lenses are for focussing or something else?

Finally I'm trying to measure the value of a name brand Petzval, Darlot, or Voitlenger (spelling) over the B&L and no-name brass lenses.

I'm looking for something with character, furthermore I don't actually want TOO MUCH swirl, I find it dizzying and distracting, this is relative of course to my personal taste and degree, but I assume to lessen this I would need something that covered say 11x14 for my 8x10 to be more pleasant? Or an 8x10 lens design shot on 4x5? To lessen the swirl and edge changes while still giving an older lens look?

And we can't talk price now but I've been told there are no-name brands for $50 vs the $1,000+ versions? So when does decent lens optics overtake shiny brass on a shelf on the affordable scale?

And also understanding Petzal design vs Darlot, vs rectilinear vs hemispherical vs euryscope vs "portrait lens" vs whatever else there is. And how each differ in look, maybe with comparable examples?

It's a little confusing. I've spent days googling without a serous comparison so it's not like I haven't looked.

Thanks.

[Jim C.]

The knob on brass photographic lenses always seemed redundant to me since as you said, you can focus with the front and rear standards.
I have used it to fine focus on the ground glass rather than fiddling with the standards, that is if I can reach the knob
Some Petzval design lenses don't swirl, I have three, one has heavy swirlies ( Seroco 10" portrait ), very faint swirlies ( Darlot ) and a unknown brand
that has none, but a very nice soft bokeh.

Some of the terms you're asking are brand names ( Darlot for example ) versus a lens design ( Petzval ).

There's tons info here which is where I looked when I got " swirly fever" there are also examples, you can try Googling just this forum.

[jnantz]

http://en.wikipedia.org/wiki/List_of_lens_designs
http://en.wikipedia.org/wiki/Photographic_lens_design
http://en.wikipedia.org/wiki/Camera_lens

wendy o was in the plasmatics not to be confused with the lens type


are some wiki articles on different lens designs

some lenses have a defocus knob which is different ... and not used it to focus the lens ( rack/pinion system like jim mentions ).
they were used to move one of the lens groups / elements inside the brass barrel back and forth and are sometimes
numbered 1-6 - the wollensak vitax had a defocus knob ) some len designers stopped using the knob and had a ring
that was numbered and turned and pretty much did the same thing ( moved a group. ) you could move the group
and focus again if you wanted but that sort of defeated the purpose of the knob ...
i had a vitax ( sort of a petzval design ) and it had a knob which i didn't use very much. defocus systems
work best if you stop the lens down ( petzval lenses are sharp ) and they still allowed you to defocus the subject

jim galli's page has lenses and examples of what they can do / signature.
otherwise you might go to places like flickr or google and search with the lens type
and hope folks have that in the title or a tag.

often times you can get similar effects by front focusing a lens and shooting wide open
or unscrewing a group a quarter turn

[Jac@stafford.net]

[... snip good stuff ...] some lens designers stopped using the knob and had a ring
that was numbered and turned and pretty much did the same thing ( moved a group. )

Before I purge my old folders, I'll post two of the most particularly helpful posts regarding modifying lenses to get more soft focus, or to create it.

Mark Sawyer posted a suggestion that I applied to a F/4.5 14” Wollensak Velostigmat Series II. It allows us to screw the front element much further beyond the maximum of #5 softness. It is here. It was very easy to do.

Jim Galli writes of modifying a lens to be soft focus right here.

[jnantz]

Before I purge my old folders, I'll post two of the most particularly helpful posts regarding modifying lenses to get more soft focus, or to create it.

Mark Sawyer posted a suggestion that I applied to a F/4.5 14” Wollensak Velostigmat Series II. It allows us to screw the front element much further beyond the maximum of #5 softness. It is here. It was very easy to do.

Jim Galli writes of modifying a lens to be soft focus right here.

it has always amazed me how one can make
a 200+$ lens by modifying a 30$ lens ...

knowing these posts existed ...
i looked but came up empty
thanks for referring to them ...

- john

[Jac@stafford.net]

it has always amazed me how one can make
a 200+$ lens by modifying a 30$ lens ...

Oh, if only the lenses were $30.
.

[jnantz]

Oh, if only the lenses were $30.
.

lenses harvested off of folders are even less than that.
and sometimes they cover 4x5 without a hitch

[CCHarrison]

Speed course:

1. The very first lenses for Dags were landscape lenses. Originals are super rare and slow (f16-f22). Popular 1839-1844 ish...
2. Petzval desigened lenses were made for portraits - fast (F3-F6) , sharp centers. 1842-1940 ish.... From 1840s to late 1860s about 95% of all images taken with a Petzval lens. Prices range from $ 50 to thousands....
3. Rapid Rectilinears came along late 1860s - med speed (F8) - good sharpness - ok for portraits - general use lens. Popular 1870-1920. In general much cheaper than Petzvals.

Read for an in depth article on Petzval lenses I wrote: http://antiquecameras.net/petzvallens.html This article also covers the development of other 19th century lens designs.

Good luck
Dan

[StoneNYC]

My head is now spinning... I've read so much I'm almost confused... Haha, so I understand a lot now except the Hemispherical lenses, and how they differ from Euryscopes.

Also, I wish one of our fine lens collector friends lived close, I would kill 5-10 sheets of 4x5 and 5-10 sheets of 8x10 just to compare all 5 (or so) of the basic design differences between the various styles of lenses, reading about the optics doesn't tell me about the look they give, I really need to actually see images not read about the lens element structures to know what is what (but now at least I understand a LITTLE more about optics, so thanks).

I'm just surprised there isn't someone who's used all these lenses on the exact same scene to compare the differences.

Thanks so far, this is all helping toward an end goal of a first bought inexpensive brass lens. It's looking like I'm leaning toward "views" and "hemispheric" mostly because of price, I DON'T want a portrait lens as I'm not into soft focus lenses in the center, I do like the idea of aberrations in the corners and sharp in the middle, but again a nice balance as Jim C. mentioned earlier the Darlot which is what I've been looking at, but which Darlot did you mean Jim?

Thanks.

[Nodda Duma]

it has always amazed me how one can make
a 200+$ lens by modifying a 30$ lens ...

knowing these posts existed ...
i looked but came up empty
thanks for referring to them ...

- john

The difference is about 2-3 hours' labor for a good machinist, including wages and overhead. It's also cheaper to paint a room yourself vs hiring a painter. It's not that much of a mystery.