Docter f4.5 210mm Tessar

[r.e.]

My understanding is that this lens will cover 5x7.

The late Ted Harris said in the following thread (four posts from the top) that it was a regular part of his 5x7 kit: http://www.largeformatphotography.in...ghlight=docter

Also, Chistopher Perez has a web page that discusses this lens (http://www.hevanet.com/cperez/test/Germinar.html) in which he quotes Kerry Thalman as follows:

At f4.5, the 210mm Tessar makes a good portrait lens for the 4x5 format. Stopped down, it makes a great general purpose lens for the 4x5 or 5x7 formats.

Does anyone know at what what aperture the lens covers 5x7?

Also, am I correct in my understanding that the lens was optimized for f22?

If anyone has photographs made with this lens, and cares to post one or two or to send my a copy via personal message, I'd be grateful. If possible, I'm especially interested in knowing the aperture at which the photograph was made.

Thanks.

[Arne Croell]

Docter (and, before 1991, Zeiss Jena) listed an image circle of 250mm at f/22 for this lens. f/22 is indeed the optimum aperture ("Arbeitsblende" in German) according to the manufacturer. The Docter MTF curve I have is at f/8 and ends at an image circle of 222mm.

[IanG]

It'll cover 7x5 @ f4.5 easily.

As Arne says both Zeiss and Docter stated the optimum aperture for these Tessar's is f22, but the theorists state that past f16 "Diffraction" caused problems. It's the actual usage that matter and at f22 edge and more particularly corner sharpness reaches a peak.

I have a few LF Tessars 135mm-150mm-165mm but no 210mm but all give sharpness comparable to my modern Symmar's & Sironar's at f22.

Ian.

[Bjorn Nilsson]

I havn't got any pictures made with a Docter Tessar (which is a very rare brand), but there are plenty of pictures out there which shows the characteristics of the Tessar in general. (I.e. almost sharper than the Plasmats (see below) in the center and nice sharpness towards the edges when stopped down.)
You should know that the "Tessar" name was patented to Zeiss some 100 years (or more) back. Since then the patent for the lens construction is long gone and long before the 2:nd war many other companies produced their own Tessars under their own names. E.g. Schneider names them "Xenar" and there are plenty of other examples, also quite recent ones.
The Plasmat lenses (a collective name for lenses such as Symmars, Sironars etc.) does have better coverage and better edge sharpness when stopped down, but then it's a more modern construction and as it has more lenses and glass-air surfaces it's more dependent on good anti-reflex coating. All Plasmat lenses of today are multi-coated, while the Tessars/Xenars/... never had anything more than single-coating, simply because it wasn't needed.

So, in short, while Docter is a rare brand which is no longer produced, the Tessars and similar are very good lenses which have been around for 100 years or so.

//Björn

[r.e.]

Thanks to Arne, Bjorn and Ian for commenting, and to Arne for sending me the MTF document.

Much appreciated.

[Emmanuel BIGLER]

Hello all
In order to be compliant with present celebrations in Berlin, I am happy to mention that I own a 210 4.5 Jena Tessar, probably pre-1989. A shutter-less model.

210 mm has been the "normal" focal length for the 13x18 (5x7") format for decades.
250 mm @ f/22 is consistent with the rule of thumb stating that tessars will cover about 60° @f/22 i.e. their focal length plus 15%.
60° of coverage for a 210 yields a circle of 242 mm.