View Full Version : Tessar falloff

Craig Wactor
20-Jan-2006, 17:44
I have seen that most tessars (and tessar type lenses) are listed as covering around 60 degrees. I know they are infamous for having a dramatic loss of sharpness (coma?) toward the edges. Does the 60 deg. include this not-sharp area? I guess I am asking if anyone knows the angle of illumination for tessars, or the circle of illumination for any focal lengths (say 210mm?).

Also, what are your opinions of tessars as a taking lens? There are so many bunk hits for "tessar" when searching LF.info that it is hard to find if the lenses are decent performers. I am interested in lenses that are sharp in the center and very not*sharp around the edges, to get that look of the earliest of photos.

Jim Galli
20-Jan-2006, 18:22
If fall-off is what you're after, why bother with Tessars when Rapid Rectilinear's are ubiquitous and cheap? For serious fall-off with just a single sharp plane though, the famous old Petzval design is still king.

Robert A. Zeichner
20-Jan-2006, 18:26
The series IIb Tessar is reputed to be a very fine lens. The Yellow dot version (coated) has been compared to the Commercial Ektar. The IIb is an f6.3 where the Ic series are f4.5. The IIb is a little less common, but considered by some a better lens. They were made by both Zeiss and Bausch & Lomb from about 1910 to 1960. They were available in lengths from 3-1/2" to 23-1/2". These lenses were available as barrel lenses as well as mounted in Volute and Compound Shutters of various types. A friend of mine, now deceased, used to swear by Yellow dot IIb's and I've seen some of his 8x10 Ektachromes enlarged to 30x40 and I have to agree he made some impressive pictures with them. They are not known for great coverage though, as you have already discovered.

Ernest Purdum
20-Jan-2006, 20:14
Manufacturer's ratings are based on a circle of sharp definition. Many of them are considered quite conservative by many contributors to this forum.

The "earliest photos", particularly those of people (not necessarily just portraits) were mostly made, as Jim Galli has pointed out, with Petzval lanses. These were made for very many years, particularly by Dallmeyer and Darlot, though by many others as well, and show up on eBay very frequently. Many of these, though, are physically too large for most modern cameras as they were intended for huge studio cmeras.

One point not well recognized is that most magic lantern "projection" lenses were Petzvals. These usually sell very cheaply and are apt to be found in smaller sizes than the "brass cannon" taking lenses. They lack provision for stopping down, so must either be shot wide open or sloitted for makeshift Waterhouse stops. In a 1950's (I think) survey of professional studio photographers, two were using Petzval projection lenses wide open.

David A. Goldfarb
20-Jan-2006, 21:03
Tessars can make great portraits, but I agree that a Petzval is probably more what you're after.

Craig Wactor
21-Jan-2006, 15:55
Are Petzval lenses usually labeled as Petzval? Or can I guess that most old brass cannon sized lenses are going to be of a Petzval design?

David A. Goldfarb
21-Jan-2006, 16:07
Often not, but 19th-century brass lenses that are around f:4 or 4.5 are often Petzval-types.

Ernest Purdum
21-Jan-2006, 17:22
Brass cannons are either Petzvals or Rapid Rectilinears. The sure way to determine which is which is to look at front and back groups. R.R. lenses are symmetrical, while Petzvals differ substantially front and rear. Very commonly, R.R.lenses have names like like Rapid Symmetrical or Aplanat. As David A. Goldfarb pointed out, Petzvals are usually faster than the R.R. types. ("Rapid" often meant about f8 at that time.) Unfortunately, if they had Waterhouse stops (usually long ago lost) there is more often than not no aperture indication on the barrel.

Ernest Purdum
21-Jan-2006, 18:00
I should, perhaps, have mentioned that if the name of the lens includes the word "Portrait" it is almost surely a Petzval or a Petzval derivative (Dallmeyer and others made some changes to the original design. These changes are usually considered desirable).

Be conscious of physical size. An 11" Type B Dallmeyer Portrait has a 4.2' flange diameter. It's also heavy - too heavy for the front of a lightly built field camera.

Craig Wactor
21-Jan-2006, 22:05
Thank you guys for all of the help! I'm off to ebay....

John Kasaian
21-Jan-2006, 22:19

Some tessars are very generous when it comes to sharp coverage. The Nikor 450M and the 14" Commercial Ektar come to mind.

I'll second Ernest Purdum's comments on magic lantern lenses being a good way to get a Petzval cheap. They are a bit of a 'hit and miss' affait when it comes to coverage. I've got a little Darlot that barely covers 4x5 and a much larger McIntosh that will handle 5x7. I'll speculate that the bigger size the Petzval, the greater the coverage---but thats only speculation based on two lenses, so....?

Good Luck!