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[OM] On topic: film curvature problems

Subject: [OM] On topic: film curvature problems
From: Richard Schaetzl <Richard.Schaetzl@xxxxxxxxxxxxxxxxxxxx>
Date: Fri, 04 Jun 1999 12:08:55 +0200
In my opinion Omers question is very much on topic, because I not only
like to take photos with my OMs, I also like to look at the results best 
possible manner, be it by projecting with slide projector, conventional 
enlarging and printing on paper or scanning in and presenting it on the 
web or printing it with color printers.
Every chain is only as strong as there weekest link. To enjoy the full
picture rendering quality of our Zuikos somebody has to be carefuly
choose the right way to create the final image.

Omer Nezih GEREK wrote:
> 
> How does one overcome the problem of film surface curvature 

As you already pointed out film has some inevadeable curvature caused by
the gelatine/plastic combination.

> caused by
> inserting the film in a frame while scanning 

If it was caused by the frame, than it was the wrong frame type.

> The film has a natural curvature, and sometimes the
> rather stiff frames cause even more shape distortion. 

There are frames which hold the film rather loose in the frame or fix the
film just on one side, let the film move, expand, creep, so tension and
curving is avoided.

I have rather good experiences with inexpensive glasless flip frames, which can
easyly opened and closed. You may try Alfi, Plawa or Diaspeed, they can
be found also as OEM or generic brand frames of mayor photo retailer
chains.

Regarding frames with glass, I prefer Gepe mounts they are available in
most photoshops keep the film flat and dont overheat them. The only
disadvantage is the noticeable "Anti-Newton" etching of the glas. Wess
mount have an slightly less obstrousive etching, but here they are only
available by mailorder at an much higher price than Gepe mounts. Another
(dis-)advantage is the register mounting of the frame, which fixes the
slide and frames it in a way I not always like.
For scanning I guess the etching of the glas of glass mounts is to
obstrousive to be acceptable. 

A type of frames you might try for scanning are fixed glassless slide
mounts.
Wess produces glassless frames with registration and fixing on both
sides of the perforation, keeping the film flat by tensioning them. 
A similar system is used by Bonum, with the difference, that the framing
can be adjusted. An disadvantage is, that they use round not square pegs
like Wess, this puts more stress on the film perforation. 
Bonum glassless mounts are an Austrian product and should also be 
available in Swiss photoshops.
 
> In fact, the same
> problem appears on the projector, too. The overall shift from the plane
> is less than 1mm, but we're talking about 3K-something dpi...

One important thing for having flat filme/slides is to avoid that the
film is bent/curved in an permanet manner. 
Fresh developed film has an soft and wet gelatine coating. It should be
avoided that the film dries in an fixed curved state. 
For slide film this means not to project the slides until they have
dried fully. 
Print film negatives should hang and dry with weights only as long in
the drying cabinet until they are no longer visualy wet. Further drying
under stress/tension of weights would only led to curved negatives.

In this post I will not discuss solution for projecting slides, partly
because it was not Omers inital question partial because this post is
already very long. ;-)

Regards

Richard



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