Which Petzvals have the Dallmeyer modification?

[Steven Tribe]

The swap of the order of the rear pair of "Petzvals" doesn't create a lookalike "Dallmeyer" patent Petzval! Both Dallmeyer rear cells are redesigned and so are the later clones.

Now the whole question of light (and near visual) wavelengths is a fantastic topic in Photography, viewing and registering on different media. I certainly don't have all the answers! Is is logical that if the early Petzvals needed a % change after viewing focus in order to focus the blue/uv wavelengths for ortho type, then most colour wavelengths would have been dramatically out of focus - even if not seen by the emulsions. Would panchromatic emulsions be unusable on these early Petzvals, would some wavelengths be always of out of focus?

[Mark Sawyer]

...Would panchromatic emulsions be unusable on these early Petzvals, would some wavelengths be always of out of focus?

Panchromatic would be the easiest to use on the old Petzvals. Because panchromatic film matches the human visual spectrum so closely, what you see is what you get for focus. No corrections at all.

I work a lot in wet plate, one of those very-orthochromatic processes, and I find only a slight correction is needed. When focusing, I just err on the short side of the acceptable range, and that does it pretty well.

[goamules]

The only re-design by Voigtlander that I know of is the 1878 modification wherein Voigtlander cemented the two rear elements, resulting in a less-sharp lens. (Obviously, that modification is pretty recognizable when you disassemble the rear, so it's not on any Petzvals I've seen.) Can you point me to any information on the 1850's redesign?

Actually Lerebours was the one that first corrected the actinic vs visual problem in Petzvals. Voigtlander, being the original Petzval, were guilty of the problem. Lerebours fixed it. Some sources here http://www.largeformatphotography.in...or-Voigtlander

Quickly, others adapted the Lerebours correction. Here is an ad for Ross' new "Orthographic Petzvals", which correct for the difference between actinic and visual light. Hard to read, but it's in the The Athenaeum, 1859

[Mark Sawyer]

Actually Lerebours was the one that first corrected the actinic vs visual problem in Petzvals. Voigtlander, being the original Petzval, were guilty of the problem. Lerebours fixed it.

Hmm, maybe that's why I need so little correction compared with what was recommended in very early photography. Talk of actinic vs. visual focus seemed to die down after the mid- to late-1860's. Do you have a date on the Lerebours correction, and what it involved? (And I wonder if that's why Tony's very early Voigtlander was so soft?)

[Jody_S]

Well, I have some news about this. In my newly acquired Le reve data booklet, I can see that from about 1875, Gasc & Charconnet, made a version of their Quick Acting Petzval, called B in their catalogues, which is described as " imite ceux de Dallmeyer". Now I happen to have a quick acting G&C Petzval sold by Bryant in the USA and I noted that the rear cell had the 2 lenses mounted separately - without giving a thought to what this might mean. It does, indeed, have the Dallmeyer rear layout. Adjustment can only be made by taking off the rear cell and screwing the inner cell.

These were made in 3 sizes:

13cm efl, lens diameter 54mm
16cm efl, lens diameter 70mm
25cm efl, lens diameter 81mm

It is last one I have.
It might be a good idea to check your Bryant/G & C lens!

Does your lens resemble this, by any chance? I swore I wouldn't buy any more but they're like potato chips.

[plaubel]

Talk of actinic vs. visual focus seemed to die down after the mid- to late-1860's.

In general - no.
Late cameras up to the 20century, with meniscus lenses, further have had the focus shift
Refocusing per formula (or following onboard tables), or using a yellow filter while focusing has been the trick.

[Steven Tribe]

Does your lens resemble this, by any chance? I swore I wouldn't buy any more but they're like potato chips.

I have checked P et P and there are no visible differences between the "Ross" and "Dallmeyer" versions. Both were made in the size 13cm efl with total lens diameter of 54cm - which is the one you have bought, I think! The Ross ones were made in much larger sizes as well. This what the rear cell looks like on the Dallmeyer clone. Can only be unscrewed by taking out the lens.

I checked my similar clone - a Derogy- and it is built up in an identical way. P et P describe 4 series of plain Petzvals, but mine must belong to one of the first two series (serial number). But no information there about a Dallmeyer copy!

[Jody_S]

I have checked P et P and there are no visible differences between the "Ross" and "Dallmeyer" versions. Both were made in the size 13cm efl with total lens diameter of 54cm - which is the one you have bought, I think! The Ross ones were made in much larger sizes as well. This what the rear cell looks like on the Dallmeyer clone. Can only be unscrewed by taking out the lens.

I checked my similar clone - a Derogy- and it is built up in an identical way. P et P describe 4 series of plain Petzvals, but mine must belong to one of the first two series (serial number). But no information there about a Dallmeyer copy!

Thanks. I'll check when it arrives.

[Mark Sawyer]

In general - no.
Late cameras up to the 20century, with meniscus lenses, further have had the focus shift
Refocusing per formula (or following onboard tables), or using a yellow filter while focusing has been the trick.

Focus shift occurs on lenses (such as meniscus lenses) with significant spherical aberration. It's remedied by re-focusing after shutting down the aperture.

Using yellow filters while focusing on orthochromatic film would have an adverse effect; you'd be focusing on yellow light, while blue light would be making the actual exposure on a different focal plane. Yellow filters have quite a few uses historically. Kuhn furnished them with early Imagons because he was largely a landscape photographer, and liked the yellow filter's effect of darkening the sky and brightening foliage. It was also though to be a contrast enhancer on b&w films, and could negate some of the effects of chromatic aberration without causing much loss of light. Yellow filters were also used with isochromatic films to give them a more panchromatic effect. In portrait photography, yellow filters reduce freckles and blemishes, and supposedly improve skin tone.

[Steven Tribe]

I have been able to find the series from Derogy which included the "Dallmeyer" alternative.

The answer was in the diameter of the lenses. Derogy gave these as the physical size, not the visible size when mounted. Mine is 88mm which appeared in the second list of Petzvals - both these first two lists date from 1870. My serial puts it in the 1870's. Why should there be two, apparently identical Petzval series from the same date? Well, there is some difference in speed. But within the series there is also quite a lot of variation, especialy for no. 27 and no.28, which have identical focal lengths for lenses that are 88 and 108mm across.

Checking my lens, which I assumed must be no.27, with a focal length in the catalogue of 25cm, I find a figure of 30cm focal length from the WHS. Is this a back focal length in the catalogue? I think it must be, as the same three lenses appear in the later series with the "extra" focal lengths measured up to the WHS stops.

1870. 1890.

no.27 88mm lens fl 25cm. no.6. 88mm lens fl 30cm
no.28. 108mm lens fl 25cm. no.7. 108mm lens fl 31cm
no.29 135mm lens fl 35 cm. no. 8. 135mm lens fl 42cm

The increasing differences between 1870 and 1890 for the larger sizes is what you would expect from the longer barrels.
Anyway, here is the list which may contain ( or always, perhaps?) "Dallmeyer" Petzvals. Focal lengths are back measures.