[LargeFormat] Some simple lens coverage tests with paper negatives

[Jim Hemenway]

Hi Richard:

Thanks for noticing my poor attempt to catalog my lenses for use.

The front cell is marked as follows:

PROTAR VII Focus 23 1/4 In.   BAUSCH & LOMB Optical CO. ROCHESTER NY.
U.S.A.  No 3217344

The rear element is marked the same and is No 3217343

When using both elements the approximate focal length is 340mm.

I measured the focal length at approximately 590mm with the rear cell
behind the lens, and it's approximately 560 with the front element on
the front.


I also have a very beat up 16 1/2 inch Velostigmat Triple Convertible
whose focal length is indeed 16 1/2 with both cells.  But, when using
either of the individual cells, either in front of or behind the
shutter, the results are very fuzzy on the groundglass when focused as
best as I can... looks somewhat like the corners of the paper negatives
from the APO Ronar CL 300mm.  The rear cell of this Velostigmat is
unmarked.

I didn't take any shots with the 16 1/2 inch as it has been stripped of
a shutter and an iris.  All that remains is the carcass of a Packard
shutter.  I plan on eventually asking SK Grimes the cost of putting the
cells into a modern shutter.

BTW, the Protorlinse (from the 8x10, the one that vignettes on 11x14)
)does not have matched cells, the printing style and the general look of
the rear 41cm cell makes me think that it is perhaps 20 years newer than
the front 59cm cell.

I'm very appreciative of any information which you can provide about
these lenses.

After going through this bunch of lenses, and until I get rich, I'm
going to shoot 11x14 with the 360 Symmar-S... a wonderful lens,  and the
420 APO-Ronar-CL at around f45 - f64... which should prove okay until I
get the Velostigmat mounted.  I also want to shoot a chrome or two with
the Protar VII at 340 and 590mm to see if I get any nice results.


Oh! One other thing if you have any info... the 210 Ultragon and the 210
Gerogon look almost identical in my hands except the the Gerogon has a 6
blade iris and the Ultragon has 5 blades.  Do you happen to know if they
are both made by Rodenstock?
-- 

Jim - http://www.hemenway.com



Richard Knoppow wrote:
> 
> ----- Original Message -----
> From: "Jim Hemenway" <Jim@hemenway.com>
> To: "Large Format Group" <largeformat@f32.net>
> Sent: Saturday, March 22, 2003 6:39 PM
> Subject: [LargeFormat] Some simple lens coverage tests with
> paper negatives
> 
> >>
> > The 23 1/4 Protar used with both cells focuses at about
> 340mm.
> >
> > The Protarlinse which came with my 8x10 and which focuses
> at about 310mm
> > with both cells, vignettes. I didn't test it with the 41cm
> or 59cm
> > cells.
> >
> > http://www.hemenway.com/lens_coverage
> >
> > --
> >
> > Jim - http://www.hemenway.com
> >
>   I am curios about the 23-1/4 Protar, is this the marked
> focal length of each cell? I can not find this focal length
> listed as either a Zeiss or Bausch & Lomb lens.
>   The closest FLs are:
>  Zeiss; 23" two identical 23" cells having a combined FL of
> 13" at f/6.3 Coverage at small stops (probably f/45) 21-1/2"
>   Bausch & Lomb; 23-1/8" Combined FL for two identical
> cells; 13-1/4, f/6.3
>   B&L states coverage at full aperture is sufficient for an
> 8x10 plate.
>   Typically, a Convertible Protar with equal Fl cells has
> coverage of perhaps 55 degrees wide open increasing to about
> 70 or 75 degrees at f/45.
>   The individual cells cover about 45 to 50 degrees when
> stopped down to about f/36 to f/45.
>   My Zeiss Protar individual cells have surprizingly good
> quality and the combined lens is excellent.
> ---
> Richard Knoppow
> Los Angeles, CA, USA
> dickburk@ix.netcom.com
> 
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