Re: [APML] Mamiya 645 knife-edge focuser

["Phillip Jones" <starfest@comcast.net>]

Bill,

Yes...it was our discussion at Okie-Tex that led to my researching this when
I got home. My response from Ted at Hutech led me to believe they didn't
have the supplies necessary. Making a KEF is an option, but I would prefer
to have an out-of-the-box solution already designed for the Mamiya 645. The
fastest I would be shooting is at f/5.9 (Tak FS-128 + focal reducer).

Next time we meet at Ft Griffin (I'm going Fri Oct 24 because of kid's
birthday party on Sat), I would love to try it.

I'll converse more with Ted to see what could be made, but may need your
assistance on this.

-Phil

----- Original Message ----- 
From: "William R. Mattil" <wrmattil@ix.netcom.com>
To: "Discussion of Film Astrophotography" <astro-photo@seds.org>
Sent: Saturday, October 11, 2003 3:47 PM
Subject: Re: [APML] Mamiya 645 knife-edge focuser


> Phil,
>
> Somehow I get the feeling that *we* have had this discussion before ...
> but I could be experiencing a senior moment. But here is my take on
> this.... Hutech's knife edge can be adapted to the Mamiya with little
> difficulty assuming that a T-Ring/C-Mount is available. Then its a minor
> problem of the correct adapters and making a precise measurement from
> the outside of the camera lens mount to the film plane and then
> duplicating that measurement. I would be very surprised if Hutech
> wouldn't have most of the bits needed to do this.
>
> Now about the Stellar Technologies Product..... This is a bit of an
> issue for me because I have one. And at f/6 it basically works pretty
> well (note: this does not mean that the Hutech knife edge isn't an
> improvement though). So if you are leaning this way it *probably* can be
> made to work. But at anything faster than f/6 its a crap shoot. I have
> literally ten's of negatives that are very blobby (some even show the
> central obstruction) where the STI focuser said it was ... er....
> focused. :^( This is at f/4 which I admit is an extreme case and
> furthermore Richard's instructions leave out some rather important
> points, especially at f/4. The ronchi screen basically become a "knife"
> at a point thats very close to focus and then the usual proceedure with
> a knife must be used. IIRC this is left out, or glossed over in the
> manual for the STI product.
>
> My advice, such as it is, would be to take the safer route and build a
> knife edge based upon the Hutech part. It would be cheaper too ..... But
> if you are local to the Dallas area and have a Nikon camera I can let
> you use the STI and see if it works for you.
>
> Regards
>
> Bill
>
> -- 
> William R. Mattil |
> wrmattil@ix.netcom.com | http://celestial-images.com
> (972) 399-4106 |
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