Fresnel lens in Linhof Technika IV
Juan F. Sanz Cervera
A few months ago I bought a 4x5 Linhof Technika IV. The back had a
Fresnel lens between the ground glass and the lens, and I suspect that
the back in this camera is not designed to have a Fresnel lens there.
For instance, I measured the position of the film plane in my holders,
and it turned out to be the same as where the Frenel is sitting, not
that of the goundglass. Besides, the reference mark that signals the
plane of focus coincides with that position, not where the groundglass
really is. My question is: does anybody out there know whether the
backs in Linhof Technikas (model IV) are designed to have a Fresnel
lens between the groundglass and the lens. I suspect that in this
particular case the groundglass should be between the lens and the
Fresnel.
Any information would be highly appreciated.
Regards,
- Juan F. Sanz Cervera
e...@clark.net
Juan F. Sanz Cervera (js...@post.uv.es) wrote:
: A few months ago I bought a 4x5 Linhof Technika IV. The back had a
My Technika III has the fresnel on the lens side of the groundglass. I
bought the camera from its original owner, who never worked on it or had
it serviced. (He bought it in Munich in 1958.) I know someone else,
though, who has his fresnel (same groundglass and same fresnel!) on the
viewing hood side. We both get sharp negs! It would be a good idea to
contact Bob Salomon about this one! I recently cracked my groundglass in
a fit of hamfistedness, so I'll have to do it, I guess. Hope they still
have some!
But this leads me to an observation; since the groundglass and the fresnel
are the same thickness on my dial caliper, who cares? The groundglass and
fresnel lenslets are within a few thousandths of an inch, so any error
should be well within the various infinity stop/back position/filmholder
thickness/cam error tolerances.
Regards,
Ed Lukacs
Charles Petzold
I had a similar question with a Crown Graphic I bought. I strongly
suspected that the fresnel was added by the previous user, and I wondered
if s/he did it correctly.
I too started measuring the internals, but then I decided that none of that
mattered if I was able to accurately focus on the ground glass. I used a
tripod and focused on the ground glass on something very close, as close as
the frame and bellows allowed. That's where the focusing is most critical.
One Polaroid demonstrated that the ground glass/fresnel combination was OK.
(A photo of a bookshelf from a close sideways angle is great for this. Just
remember the title of the book you focused on!)
-- Charles
Juan F. Sanz Cervera <js...@post.uv.es> wrote in article
<33532f14...@news.uv.es>...
chris hauth
I recently added a Linhof Fresnel to my Master Technika. According to
the instruction pamphlet the Fresnel is placed "over the ground glass
with the grooved side towards the lens".
Chris
Boris Mohorko
Master Technica has originally Fresnel over the ground glass. Two spring
clips.
Juan F. Sanz Cervera <js...@post.uv.es> wrote in article
<33532f14...@news.uv.es>...
Michael J. Buchmeier
Linhof has manufactured a combination fresnel-ground glass called a
"Linhof Super Screen" in the past. Bob Solomon could advise as to
current availability. The Super screen was frosted on the lens side
and had fresnel grooves molded into the viewing side (the material was
optical grade polycarbonate). A second clear glass called a Linhof
ground glass protector with grid markings for 6x6,6x7,6x9 and 6x12 was
placed over the super screen on the viewing side. I bought one of
these sets around 10 yrs ago and put it on a Wista Field which I was
using at the time and found it to be quite bright compared to the
factory screen. I only wish I had kept it when I sold the camera.
Michael Buchmeier.
Juan F. Sanz Cervera
I e-mailed my original question to Bob Salomon, and this is what he
kindly replied:
>Old cameras were adjusted for the fresnel placement before the ground glass.
>Current and the proper placement is behind the ground glass.
>
>Marflex can readjust the ground glass position to enable ou to use a modern
>fresnel properly.
>
>You can reach them at 201 808-9626.
>
>Bob
This agrees with what some people have said, but I still believe that
if I put a Fresnel between the lens and the ground glass the focusing
plane is not the same as that in the film holder. Obviously, some
testing is in order, something similar to what was published in a
recent issue of View Camera magazine: set an array of flat things with
enough detail (dollar bills were used in the article) at increasing
depth at close range, focus on one of them, and see if you get that
one in focus when you process the film. I'll post my results.
Thanks to everybody who answered my question!
Regards,
- Juan
Bob Salomon
In article <335a05f2...@news.uv.es>, js...@post.uv.es (Juan F. Sanz
Cervera) wrote:
> I e-mailed my original question to Bob Salomon, and this is what he
> kindly replied:
>
> >Old cameras were adjusted for the fresnel placement before the ground glass.
> >Current and the proper placement is behind the ground glass.
> >
> >Marflex can readjust the ground glass position to enable ou to use a modern
> >fresnel properly.
> >
> >You can reach them at 201 808-9626.
> >
> >Bob
>
> This agrees with what some people have said, but I still believe that
> if I put a Fresnel between the lens and the ground glass the focusing
> plane is not the same as that in the film holder.
The film plane in the Technika is adjustable by service to correspond to
the film placement in the holders.
<Obviously, some
> testing is in order,>
Since a IV is 30 or more years old testing is almost mandatory as you have
no idea if the camera is in or near factory spec. If it is then the film
plane adjustment is correct.
> something similar to what was published in a
> recent issue of View Camera magazine: set an array of flat things with
> enough detail (dollar bills were used in the article) at increasing
> depth at close range, focus on one of them, and see if you get that
> one in focus when you process the film. I'll post my results.
This supposes that the lens is corrected for this range and for flat field
objects.
This does not assure you that it is working properly for 3d objects at
1:10 or 1:20 where most scenes are photographed.
The best, quickest and most accurate method to make sure everything is OK
is to let a serviceman look at it and measure it to factory specs.
--
HP Marketing Corp. Gepe, G-O Lighting, Giottos, Heliopan, HP Combi-Plan-T, Kaiser, Linhof, Rimowa, Rodenstock, Rollei, Sirostar 2000
Juan F. Sanz Cervera
On Thu, 17 Apr 1997 18:39:13 +0100, ir00...@mindspring.com (Bob
Salomon) wrote:
>In article <335a05f2...@news.uv.es>, js...@post.uv.es (Juan F. Sanz
>Cervera) wrote:
>
[...]
>
><Obviously, some
>> testing is in order,>
>
>Since a IV is 30 or more years old testing is almost mandatory as you have
>no idea if the camera is in or near factory spec. If it is then the film
>plane adjustment is correct.
>
>> something similar to what was published in a
>> recent issue of View Camera magazine: set an array of flat things with
>> enough detail (dollar bills were used in the article) at increasing
>> depth at close range, focus on one of them, and see if you get that
>> one in focus when you process the film. I'll post my results.
>
>This supposes that the lens is corrected for this range and for flat field
>objects.
>
>This does not assure you that it is working properly for 3d objects at
>1:10 or 1:20 where most scenes are photographed.
>
>The best, quickest and most accurate method to make sure everything is OK
>is to let a serviceman look at it and measure it to factory specs.
While I agree that the best way to determine whether the plane of
focus is correct would be to have it checked by a technician,
sometimes this may not be possible (or even necessary) for a variety
of resons (economic, time, etc.) However, I cannot agree with Mr.
Salomon's assessment of the simple and effective method that was
described in the View Camera magazine for checking ground glass
placement. To me, it is quite clear that if the plane of focus that I
see in the groundglass turns out to be the same in a test photograph,
that means that the ground glass and the film holder are placed at the
same position. For this kind of test, it doesn't really matter whether
you use a flat field lens or not or whether you are focusing too close
for great resolution: if what you see focused in the ground glass
comes in correct focus in the test photograph, then it's fine. If,
besides this, measuring the depth of the film holders and the depth of
the back with a micrometer you get the same value, shipping the camera
to a technical service is not only unnecessary, but also seems a waste
of money for amateur photographers. I agree that more exacting
applications might require extremely accurate focal plane placement,
but that hardly is the normal requirement: most people photograph
three-dimensional objects, not just flat planes. Besides, if one
considers that most LF photographers own different film holders that
differ somewhat in film plane placement the question of exact
groundglass placement suddenly takes a new perspective... :-)
Michael J. Buchmeier
For those of you in Europe who may be interested
in London there is a shop called Linhof and Studio Ltd.at:
Pump House
10 Chapel Place, Rivington Street
London, EC2A 3DQ
tel: 0171 729 5734 or 5751
fax: 0171 729 5787
They feature Linhof and Gandolphi-both new and used and also usually
have a good selection of used lenses.
Michael Buchmeier
Juan F. Sanz Cervera
On Thu, 17 Apr 1997 11:22:00 GMT, js...@post.uv.es (Juan F. Sanz
Cervera) wrote:
[...]
>
>This agrees with what some people have said, but I still believe that
>if I put a Fresnel between the lens and the ground glass the focusing
>plane is not the same as that in the film holder. Obviously, some
>testing is in order, something similar to what was published in a
>recent issue of View Camera magazine: set an array of flat things with
>enough detail (dollar bills were used in the article) at increasing
>depth at close range, focus on one of them, and see if you get that
>one in focus when you process the film. I'll post my results.
>
[...]
Well, I finally checked whether the focus plane is the same as the
standard film holder plane in my Super Technika IV after removing the
Fresnel. I used the simple kind of test that was recently described in
View Camera magazine: in my case I set up five poker playing cards
(the King, Queen an Jack have enough fine detail for focusing)
parallel, perpendicular to the film plane, and at increasing distance
(1 centimeter). I focused on the center card to get (more or less) a
1:2 reproduction on film, using a 210 mm f5.6 lens, wide open.
Processing the film revealed that the center card was perfectly in
focus. The conclusion is that my Technika should not have a Fresnel
between the groundglass and the lens if standard film holders (Lisco,
Riteway) are used. By the way, this result coincides with what
another LF user, Dan Kreithen, kindly told me in an e-mail message.
At the same time, I also checked the accuracy of groundglass placement
with a Tachihara and a Speed Graphic that I also happen to own (too
many view cameras! says mi wife ;-) and they also turned out to have
the groundglass in correct position. The Tachihara uses a one-piece
groundglass (plastic in fact) - Fresnel combination that must be
placed so that the frosted side is closer to the lens (it was in the
wrong position when I bought it!). My Pacemaker Speed Graphic seems to
be designed to have a Fresnel between the groundglass and the lens. If
no Fresnel is used, the groundglass must be shimmed back by about 1mm.
I hope this will help clarify the situation to others who may have
doubts about the right placement of the groundglass/Fresnel in these
cameras. At any rate, the test that I used is simple, fast, and
accurate enough for its purpose, and can be used with any view camera.
Bob Salomon
In article <3359b46f...@news.uv.es>, js...@post.uv.es (Juan F. Sanz
Cervera) wrote:
The proper positioning of the focus plane in a Linhof is cotrolled by the
adjustments of the 4 shims that are under the groundglass.
If a fresnel is to be positioned in front of a ground glass in a Linhof
the shims must be adjusted to accommodate the added thickness of the
fresnel.
If the fresnel is to be placed behind the ground glass (as on all Linhofs
made over the last 2 decades) the shims are then adjusted accordingly.
If the camera was originally designed for the fresnel in front it could
have been re-adjusted by service at a later date.
While your test may have placed your mind at ease the adjustment of these
shims are very critical and can easily lead to less than critically sharp
results if misadjusted.
It is best to let a properly equipped service man check the placement so
you can be assured that the camera is in factory tolerance. Your test does
not determine this.
Bob
Bob Salomon
Modern fresnel screens have a smooth shiny side and a grooved side. They
have no frosted side.The smooth side faces the eye
On the other hand some enhanced screens like the Super Screen combine a
ground glass and a fresnel in one. On these there is a grooved side and a
frosted side. With these the frosted side faces the lens.