RE:70mm

[Jim Henderson <74023.723@xxxxxxxxxxxxxx>]

On 10 Jan 97 at 0:27, WJM wrote:


>>This is still at the official 4.5m (15ft) length the 70mm cartridges
>>were designed for? My Mamiya literature indicates 54 exposures (Bob
>>Shell's book for instance), without stating physical length. I know
>>that aerial film can be much thinner and hence longer, but that
>>still could cause problems with the film counter (how far does that
>>one go btw?) or development.
The Mamiya back has a counter up to 55 exposures--sorry about the slip of the
digit...  There are TWO reels available, however, one holds 55 exposures the
other must be the shorter one to which you refer.

>>Does it comply to 35mm HIE within one stop, or is it different?
>>Wratten #25 for me (35mm) boils down to 50 ASA, #87C eats two stops 
>>more.  

Well, "comply" is a subjective word.  Many people who list their film speeds on
the list vary considerably, and I think much has to do with meter, water, and
developer.  TMAX-RS is designed to produce maximum film speed.   My personal
experience is that HIE in ANY format size processed in TMAX-RS diluted 1:9,
processed at 70F results in an effective speed of 200 using either the Pentax
spotmeter, Minolta autoflash spotmeter, or my internal Canon F-1 meter--used
without the filter over the meter.  If you meter through the filter, you will
have to calibrate it as you describe in your FAQ.  BTW, DK-50 will also give the
same effective film speed.

>>Is this with a automatic development machine, or manual?

This processing is for either a 1-L 4x5 dip-and-dunk tank or 35mm 4-reel tank.
Development is manual, that is, by hand.

>>Found two (Kinderman reels) of them for a fraction of the (insulting) new
price, 
>>including a SS contraption to load the exposed film from cartridge to 
>>reel. I once measured that it accepts the same 4.5m film 
>>length....does that comply with your 65 shots?
>>Can it easily be loaded without this contraption?

I load the Kinderman 70mm reel by holding the reel tipped on end down on a
counter top.  I turn the reel counter clockwise on end while I feed the film in
with the other hand.  Much like loading a 35mm reel except the size of the 70mm
makes holding it in your hand something only a juggler should attempt.

>>Btw, even though in new condition: I can't get the (film back) counter 
>>running....

William, you must first load film onto a takeup reel.  The counter is activated
once film is being taken up into the second cartridge


>>Btw, did you ever try the vacuum system to see whether it makes any 
>>difference in performance? 

The vacuum system, which includes an air bulb and thin hose to connect to the
back allows the user to create a vacuum between the film plate and film.  This
is necessary when no film is advanced for a while.  The next time it is wound,
the film has a "kink" in it where it made the 180 turn around the side of the
back.  I usually just advance the film two frames and forget it  Believe me,
the film is kept quite snug against the back!

>>PS: are you aware that Beattie makes a 70mm long roll/bulk back, either with
or 
>>without data imprint? (choice of motordrive as well I believe)
>>When I asked B+H about Mamiya 70mm backs some year ago, Henry Posern
>>sent me Beatty literature; he even mentioned to be sure that all 
>>parts would be included in case of me buying used stuff. 
>>Even though a mistake, I would never have known about Beatty backs
>>otherwise....:-))

Do you have any information or references for the Beattie back??  send it to me
if not too much trouble.  Thankx

Jim Henderson
Applied Scientific Photography


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Topic No. 3