Down amongst the oldies

[Neil Purling]

Would a anastigmat of the Dagor, Dialyte or Protar type differ in sharpness and contrast and in the balance of same across the plate.
There has been some debate as to whether they as as good as modern lenses, but I am thinking of what they were like compared to the Zeiss and Goerz version of the rectilinear type.

[Dan Fromm]

Neil, it depends on the lens.

There are many dagor types, many dialyte types. Some were made into the '70s and '80s and as far as I'm concerned qualify as quite modern. Protars are another matter.

I have a 210/7.7 dagor type made in the '70s that shoots beautifully on 2x3 and that ought to cover 5x7 and then some equally beautifully.

f/9 dialyte type Apo Nikkors don't have large coverage but within their coverage are very good indeed.

The 130/6.8 Goerz Doppel Anastigmat, probably made in the mid-1920s, that you sold me as a Dagor is a no name dialyte type that I don't regard as good enough to use. My 130/6.3 CZJ Tessar, made in early 1912, is also an anastigmat and is much better than good enough to use; on 2x3 it is up to my newer lenses with similar focal lengths.

As I said, it depends on the lens. What are you trying to get at?

[Neil Purling]

I wish I had never seen that 130mm Goerz, an unfortunate experience for both of us.
I have since got a genuine 130mm Dagor.
However I was wondering if to acheive the wide field coverage of lenses like the Dagor they traded some central sharpness compared to a aplanat for example but were able to keep the same sharpness across the whole field.

[Dan Fromm]

Neil, if Ole Tjugen replies he'll tell you that early anastigmats aren't as sharp as good aplanats. He's reported that many times. Modern anastigmats, including, I think, f/6.3 Tessars from the very beginning, are another matter.

Cheers,

Dan

[Ole Tjugen]

Dan, what I'll tell Neil is that the best Aplanats are sharper in the center than even the best Anastigmats - possibly until the recalculation of the Tessar in the late 1940's.

The best Aplanats are stunningly sharp in the center, but field flatness, coma, astigmatism and so on makes the sharpness drop off quickly toward the corners.

Lens design is always about compromise. For example the wide-angle Aplanats traded aperture (and a little central sharpness) for wide coverage, and faster "portrait" lenses have less sharp coverage.

Anastigmats achieved a wider field with good sharpness, but sacrificed a little of the "peak" sharpness to achieve this.

The Dialyte type was considered to be the sharpest of the early anastigmats; however the 8 glass/air surfaces gave them inherently poor contrast in the days before coating. I have two 1930's Rodenstock 135mm f:4.5 Eurynars. One is "original", the other one has been coated by some previous owner. Having tried them in a head-to-head comparison I can confirm that the sharpness is equally good, but the contrast is very different making the uncoated one look far softer.

The more popular cemented anastigmats (like the Dagor) had far better contrast, at the cost of a little evenness in sharpness.

It's not only the difficulties in cementing three elements together that has led to many Dialytes still being made, while Dagors are now limited to the 550 XL.

[Neil Purling]

It seems that sharpness is quite influenced my personal judgement, and here one many be judging a old lens against modern peers.
that would be a little unfair.
Does the early 20th century Goerz (Germany) Dagor leave spherical aberration under-corrected which might soften the image?

I have two aplanats in transit and one of them is a extra-rapid (f5.8) example. It's maker suggests it would be a fine lens for portraits when wide open, with its extra rapidity being a advantage. Then if you stopped down it comes in handy for group shots.
I think I am going to have an interesting time testing these lenses.

I am sure I have a old Kodak lens which may be a meniscus type, which I haven't seen for ages. It seems like they are very popular in Japan because they are unsharp.

[Ole Tjugen]

My favorite Dagor-type lens is a 150mm Zeiss Doppel-Amatar, which seems to have a special kind of "vibrancy" for lack of a better word. I have no idea what it is, but my (contemporary, ca. 1920) 180mm Goerz Berlin Dagor just isn't the same. The (again, same age) 210mm O. Simon Anastigmat, another Dagor-type, is somewhere between the two.

The only thing this "proves" is that not all 3+3 Dagor-type (to exclude the "reverse dagors" like the Angulon) are the same.

Meniscus lenses and Periskops are different, too... :)

[Scott --]

Ok, where on Earth can I go to learn what da hell you guys are saying?! :eek:

[Ole Tjugen]

Just hang around here, Scott -- we'll have you shooting Doppel-Anastigmats and Aplanats soon!

[Uli Mayer]

"the best Aplanats are sharper in the center than even the best Anastigmats - possibly until the recalculation of the Tessar in the late 1940's."

Ole,
could you please substantiate your statement by citing sources? And could you please tell how big this "center" zone is ( in degrees off axis) ? Which were the "best Aplanats" and the "best Anastigmats" that were to be compared, and who actually did these tests?

There were so many recalculations of the Tessar - more than thirty, mainly by Wandersleb and Merté - that I don't understand why you just highlight the one of 1947 by Harry Zöllner. What makes it especially relevevant in this context?

[Ole Tjugen]

My main source is Hans Schmidt's "Photographisches hilfsbuch für ernste Arbeit", 2nd edition, Berlin 1910. He was extremely sceptical of Aplanats and considered them almost useless, and then says about the dialyte and double-Gauss (uncemented doble-anastigmats) lenses that they "are sharper than all other anastigmats, almost as sharp in the center as the best Aplanats". He admits (somewhat grudgingly, is the impression I get) that in the central 30 degrees (to 15 deg. off axis) the aplanats are as least as good as anastigmats, and the best may well be superior.

The Tessar is relevant in that it's a well-known construction with a very long life in professional photography, and is known to give very good sharpness. In my own samples there is a small but definite improvement in maximum on-axis sharpness after 1947; the difference between a 1912 and a 1946 version is far smaller. As far as I can see.
Aplanats from Emil Busch or Suter that I own are definitely sharper on axis than pre-WWII Tessars, 1970's Symmars and possibly the 1930's Eurynar. My 1950 Tessar is, along with a 2002 Xenar, the only lenses which I'm certain have better on-axis sharpness than the old Aplanats.

No, I haven't done "scientific" or even reproducible tests. I've just examined negatives shot with different lenses under otherwise comparable conditions, on the same film stock and the same processing. Examination was done with a microscope at 40x enlargement.

[Glenn Thoreson]

I don't think I want to get too involved in this, but Ole, I have a 135 Eurynar, too. They're good, yes? I like old Aplanats and Rectilinears, too. I agree, they are biting sharp in the center, and with careful use the corners won't be noticeably bad. I'm not sure what everyone sees in the Dagors.
They're not a bad lens, but I don't think they live up to the hype they get. There are better options.

[Neil Purling]

Glenn: What are the edges like with that 135mm Eurynar? Never mind about the corners, I found the centre of the only dialyte I had to be incredibly sharp. You couldn't use the edges, even for a 10x8 full frame print. I found that out when I tried to photograph a local pre-historic stone monolith.
Mine was of 130mm focus.

Ole: You judge the qualities of your lenses by examination of the negative.
What are actual prints like from the negatives you have made?
I wondered what sort of enlargement it would take to notice the decline of sharpness away from the centre?

[Uli Mayer]

Ole,
we have a lot of common ground here. But I think there is no need to defend aplanats by side-by-side comparisons with anastigmats (inevitably involving strict test procedures) which almost certainly would expose the aplanat as losers . Let's just say: aplanats can be surprisingly sharp, and in the right hands they were fully sufficient to produce some of the greatest photogragraphs ever made (Weston's "Peppers", for example). It may be too far-fetching to say that, but sometimes I have the feeling there there may be a second law of reciprocity saying: 'the more short-coming the photographer's eye, the better the lens he requires'.

Since your German is better than my English, I' ll refrain from translating this beautiful statement by Hans Harting:

"Dass der Steinheilsche Aplanat auch später unter den buntesten Bezeichnungen sehr beliebt war, verdankt er seiner verhältnismässig grossen Leistungsfähigkeit. Es wäre überhaupt sehr nützlich, wenn wir uns heutzutage von Zeit zu Zeit daran erinnerten, dass auch vor der Einführung der Anastigmate gute Aufnahmen gemacht wurden. und dass auch die Reproduktionsanstalten in den achtziger Jahres des vorigen Jahrhunderts mit den alten Weitwinkeln Vorzügliches leisteten."
(H.H., "Photographische Optik", 1948 p.85)

They still do today. (Remember the "Auge auf Reisen"? :) )

Cheers
Uli

[Jim Galli]

I would agree with Ole. The Aplanat formula fails out of center, but in the center it is inherently simpler and contrastier than the anastigmats. You could say the same thing about the Petzval formula as long as you stay in the center sweet spot. I have an 18" f12.5 petzval type projector lens that I'm dyeing to cobble onto a Nikon. I believe it would stand up in some situations as good or better than gazillion $$ Nikon glass. Of course I'm out on a limb and will back down real quick because my measurement method is seat of the pants. In the 1940's or '50's Wollensak ressurrected the old Aplanat type for use on a brand of copy cameras called Tasope. They realized that as long as the user only needed the center area these lenses are incredibly sharp. That said, you need to be smart about trade off's. To me there's nothing worse than a picture that is supposed to be clinically sharp that goes to pieces in the far corners. If I were going for sharpness and trying to make aplanats work, I'd stick with lenses much longer than normal for the format. ie on 4X5 an 11 - 13" aplanat should be sharp everywhere.

[Dan Fromm]

Neil Purling asked "I wondered what sort of enlargement it would take to notice the decline of sharpness away from the centre?"

Neil, it can be calculated, at least roughly. Take a look, if you will, at Chris Perez' and Kerry Thalmann's formal lens tests. Visit http://www.hevanet.com/cperez/testing.html . You'll see that they measured on-film resolution in line pairs/mm at the center of the fields, partway between center and edge, and at the edge.

If you accept that a nice sharp print needs resolution of at least 8 lp/mm on paper, you can calculate the greatest enlargment possible for good negatives taken with a lens they tested as (resolution on film)/8. It really is as simple as that.

Modern, well, at least post-WWII, dialyte types can be very good. Look at the results Perez & Thalmann got with Apo Ronars. Better than they got with Artars. FWIW, I've got good results on 2x3 from a 150/9 Apo Ronar and from 305, 420, and 480 f/9 Apo Nikkors; all of these are dialyte types.

Good luck, have fun,

Dan

NB, I'm using the trick Jim Galli advocated, i.e., the lenses I mentioned above are much much longer than normal for my format.

[Neil Purling]

I have had the Beck lens & Unicum shutter CLA'd and both the Unicum and the B&L aplanat lens out of the old Autographic needed custom drilled Graflex lens panels.
I won't ever recoup the money I spent. However if I learn something from burning a good few sheets of film it was worth it.
The two WA aplanats I have are approx 135mm and a 6" Wray. Obviously they are both in barrel. They are something to try later.

[Uli Mayer]

Jim,
an Aplanat design is not "inheritently" simpler than anastigmat designs. The Aplanat formula is just more limited, and not because of the 6 radii of curvature, 4 thicknesses and 1 air-space, the designer had to get by with, but because of the few glass types available then. If the designer wished to keep astigmatism at bay, his glass choice became even more limited, since then all lenses had to be made of flint (according to Flügge).

A basic dialyte design isn't in itself more complicated than an Aplanat. Eight radii, 3 air-spaces and today's huge assortment of glasses with all kinds of refractive indices and partial dispersion actually make it much simpler to influence aberrations without compromizing other corrections. An Artar has also only 4 glasses. And I bet it's 'sharper' than your best aplanat, even if only the smallest angular field is considered.

[Neil Purling]

I received my Beck lens and the re-mounted ex-Kodak Autographic bausch & Lomb Aplanat.
Grimes seem to assume the packages might have to survive a war zone.

The Beck is in a ancient Unicum shutter, for which I need a bulb and short tube to trip the shutter without shaking the front standard.
I have only shot with the ex-Kodak Bausch & Lomb aplanat so far. I have a small Polaroid in my hand and have shot one sheet of VPS.

When shooting with these lenses I suppose that one would have to re-check focus after stopping down. There is focus shift I ought to be aware of?

[Uli Mayer]

Aplanats are prone to focus-shift because of inherent zone-errors, i.e. rays entering the lens' center, and rays that come in from outer lens areas do not focus on the same plane. When focusing with the lens fully open one tries to find best focus for rays from all zones. By stopping down, rays passing outer zones are cut off. This shifts best focus. The smaller the lens' zone errors, the smaller its 'aperture difference' or focus-shift.

[Neil Purling]

I have only been able to shoot a few sheets with the Bausch & Lomb aplanat
It is of around 130 - 135mm focus and does seem to cover the 4x5 frame.
I think I need to shoot some more tests. I am looking for a wire fence with one really flat panel, a brick wall with oblique lighting and some block paving. They should tell me something about sharpness.
Was field curvature more of an issue with longer focus aplanats? Normally the area I focus on is located around a central 'box' because that is easiest with the only loupe I have. I cannot examine the outer edges on the g.g. screen.
I have not shot anything with the Beck aplanat. Member Ernest Purdum is helping with a bulb air release to suit the ancient Unicum shutter. I hope it will be able to hold the shutter open and allow me to focus.

[Dan Fromm]

Neil, they're not anastigmats. They have astigmatism. This means that if an Aplanat/RR is focused on a vertical line it will be out of focus on a horizontal line in the same plane. I saw this effect on the GG very clearly when I focused my late unlamented Celestron C-90 on a window screen. You should see the same when you're able to focus on a wire fence.

[Neil Purling]

I have taken some shots of a outdoor table, it is composed of narrow planks of wood.
What I did was to focus on a particular join, marking the spot with chalk for reference.
The view of the table is therefore also a series of lines across the frame.
How does field curvature appear? If focus is at one join in the centre, would the edges appear sharper in front of or behind that point of focus? If I am not making sense do tell me!
I have not explored the question of astigmatism as yet. I ought to shoot a cycle wheel, but the only truly flat plane test subject I have is the brick walls of the house.
I have also need to look again at my technique when focusing stopped down.

[Gene McCluney]

If you line your camera up square with a brick wall, no tilt or shift. Focus on the center of your image. If the lens is well corrected the image should be equally sharp out to the edge, and the vertical mortar joints between the bricks should be sharp also. If the lens is undercorrected, or has field curvature you won't be able to get the center and edges of the brick wall to focus at the same point. You should do these tests with the lens wide open. Stopped down, most lenses perform better, and this hides some of the issues.

[Neil Purling]

For whatever reason the B&L lens, if focused at one point for the centre of the image the edges seem sharper at a nearer point. More tests are needed to confirm this.
I am testing on some ancient Ansco (expiry date 1957). It really neads a pretty strong anti-fog additive.
Damn stuff is on a very thick base compared to anything I can buy today.
To sharpen my technique with this lens it is good enough if I am burning through a good few sheets.

[Ole Tjugen]

For whatever reason the B&L lens, if focused at one point for the centre of the image the edges seem sharper at a nearer point. More tests are needed to confirm this.

That's field curvature. The field can also be curved the other way, but that's more rare and likely to be a result of overcorrection.

Sometimes field curvature can be used to good effect: Quite a few 19th century street scenes show an impossible depth of field, with the far distance, near street and buildings on either side equally sharp. Then you discover the fuzzy lamp-post in the middle of the scene, and realise that it's not depth of field, but field curvature...

[Jim Galli]

That's field curvature. The field can also be curved the other way, but that's more rare and likely to be a result of overcorrection.

Sometimes field curvature can be used to good effect: Quite a few 19th century street scenes show an impossible depth of field, with the far distance, near street and buildings on either side equally sharp. Then you discover the fuzzy lamp-post in the middle of the scene, and realise that it's not depth of field, but field curvature...

Group photographers would arrange a group so everyone landed in the sharp plane. Similar to what old timers did with a Cirkut camera....but different.

[Neil Purling]

Regarding the apparent field curvature I am experiencing with the B&L lens:
How do you compensate for this field curvature Ole?
I have not done any landscapes as yet so I am not sure how strong the effect would be when focused at or near infinity, but I assume it is about the same.
Do you focus on something around the centre that is in a more distant spot than the particular part around which the image is composed?
I hope this is making some sense to you.

[Ole Tjugen]

Neil, there's nothing "apparent" about field curvarure: With many old lenses, it's very real!

There are two basic ways to deal with it: Either stop down enough to "hide" it in the DoF, or use it / ignore at larger stops.

With flat subjects, you can focus so that the sharpest area is a ring about 1/3 out from the center of the image. Stopping down can then bring the center into the DoF sharpness, and the corners will be less soft than if the center were focussed optimally.

But it's a lot more interesting to use the curvature in the picture :D

[Neil Purling]

As it has been proved to me with my negatives the problem is very apparent at close quarters. Is it easier to hide field curvature in the DOF at long distances?
If you are shooting landscapes how do you manage?

[Uli Mayer]

Neill,
I fully back what Ole said in his last post. Even better than compromizing center sharpness for more sharpness at the periphery is it to turn this aberration into an advantage.

Curvature of field might be helpful for all kinds of motives, provided you put something distant in the center and there are nearer objects on the sides - from tree-lined roads to narrow streets to church interiors etc. The old lens simultaniously focuses "far" and "near" on the bowl-shaped image plane , whereas a lens fully corrected for flat field must be stopped down to bring everything in focus. (Maybe one of the reasons why Ole loves his Angulons so dearly :) )

Astigmatism is quite a different kind of field curvature. It would be severely present in your lens, if on photos of that brick wall either the vertical or the horizontal mortar lines were in focus, but never in both directions at the same time - however you focus. Weaker astigmatism will only show in reduced resolution and contrast - which might be welcome especially when doing portraits.

[Neil Purling]

I haven't got to try the Beck Biplanat for this effect. I was going to do so yesterday. However, when I tried the shutter it fired, but the two blades stuck half-closed. the only way to fully close them is to re-cock the shutter. I looked and there was no evidence of a foreign body to jam them. It had run perfectly when I unpacked it. It is the same on all speeds.

[Neil Purling]

The B&L aplanat is mounted for my Graphic which doesnt have any swing option.
If I were photographing one side of a street with receding perspective the curved field might be a help, similarly when photographing a locomotive in a station when it is a front 3/45 view. Be worth experimenting by shooting parked cars from a similar angle & comparing to my Dagor, which is of the same focal length.

Ole advised focusing on a area 1/3 of the way out from the centre of the image to try and achieve a better balance of sharpness with a flat subject. Since I usually compose on the area of the thirds that is where a point of interest usually is. I will try it and see what the result is.
One wonders what one would have used for landscapes when a aplanat had field curvature. Did most lenses had the same affliction so people just stopped way down?

[Uli Mayer]

All aplanats suffered from curvature of field and astigmatism. But the designer had options to balance these aberrations against other ones according to the purpose for which the lens was to be used. This is the main reason why there were made:

"portrait aplanats" ( usually 1 :4.5, in long barrels to narrow the field by mechanical vignetting);
"group aplanats) " ( generally shorter barrels, and speed reduced to 1: 6.3)
"landscape aplanats" ( 1:8 - 1:11 even shorter mounts, but with wider fields)
"wide angle aplanats" (1 : 18, tiny lenses that covered up to 100° when stopped down to F32 or smaller)

The new glass types made by Schott and Abbé, which allowed removal of astigmatism, made an end to resorting to such means and limitations. Only then a wealth of lens designs could be figured out and refined that hitherto wouldn't even have been as good as an aplanat.

[Ole Tjugen]

Aplanats aren't really that bad when it comes to field curvature - try a single meniscus or half an aplanat to see how bad it really can be.

If you look at old prints, you will often find that the same photographer used the same lens on different plate sizes. The larger plates often show severely fuzzy corners, which is what you get when you use a lens outside its intended image circle!

Interestingly one of my casket sets has one rear cell which seems to have been adjusted for maximum field curvature - the others are RR (aplanats), but this one has an extra glass and a horrendous field curvature. So much that it must have been done on purpose!

[Neil Purling]

I bought a job lot of lenses on ebay primarily for an unknown 6 1/2 x 81/2 f16 Extra Wide Angle. The EWA is a aplanat.

It turns out that one of the three is a projector Petzval in its focusing tube. It needs a bloody good clean & there is one tiny spot that might be sign of fungus, which a clean should eradicate.

I wonder if I could get it front mounted to a shutter or maybe it would be cheaper to buy a Speed Graphic for its focal plane shutter?

[Dan Fromm]

Neil, everyone should have a Speed Graphic. And I say this even though I shoot most of my lenses in barrel front-mounted on a #1.

[Ole Tjugen]

Even better is one of these: A Speed Graphic with universal iris lens mount! :D

[Ernest Purdum]

Front mounting is a simple job for any competent machinist, though he may need a lathe capable of cutting both inch and metric threads. How practical it is depends on the lens. If the mounting threads aren't too large and the angle of view not too wide, obtaining the shutter is the major factor in the cost. Most projection Petzvals would require a really big shutter, an old #4 or #5.

[Gene McCluney]

An issue with front mounting of wide angle lenses, is mechanical vignetting from the shutter, if you are wanting coverage on larger film formats.

[Neil Purling]

With a wide angle aplanat like the anonymous 6 1/2 x 8 1/2 or my Wray 6" that each cover 90 degrees. Is field curvature over the area of their intended coverage weaker, the same or stronger than a regular f8 aplanat?
Anyone had the likes of my Wray front-mounted into a modern shutter?

[Neil Purling]

A long time has passed & I am not so prosperous now....
I actually had that Beck Biplanat re-mounted into a Copal ~1 by S.K. Grimes. That lens is amazingly sharp in the centre at f5.8.
If you look at the bush on the left side of the frame and the bench on the right you can see how sharp they are compared to the lap fence where the point of focus was. The second image shows the Biplanat when used at f 22.
The third image is the Bausch & Lomb R.R. lens in a Kodak Ball-Bearing shutter robbed from a #1 Autographic.
I also cemented a no-name f8 brass lens into the front of a Polaroid MP4 Copal shutter that has no diaphragm. I can't recall that I ever got around to testing this lens against the ex kodak lens in image #3.