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Krafty5260
Tinkerer
Username: Krafty5260
Post Number: 7
Registered: 02-2008
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, March 04, 2008 - 03:22 pm: | 
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Okay,now that I have disassembled my first camera, I'm looking around inside and beginning to clue in on what happens and how, but I'm baffled by ASA adjustment. The aperature opens the lens wider to let more light in. The shutter speed affects the timing of the shutter. I know ASA is the chemical reaction of the film emulsion, but what is happening mechanically when the ASA value changes inside the camera. I'm sorry to be a numb-skull, but it just isn't sinking in. Is it a meter value setting, or what? I don't think my Petri 2.8 has an ASA knob, but it has a disk in the top of the rewind knob that makes reference to some types of film, but doesn't connect to anything inside the camera. I don't get it.
As usual, all help is gratefully appreciated.
Michael |
Canuck_curt
Tinkerer
Username: Canuck_curt
Post Number: 19
Registered: 03-2007
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, March 04, 2008 - 07:09 pm: |
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Your Petri wouldn't benefit from having an ASA adjustment. This is how you set the meter on metered cameras. Older cameras often had an ASA reminder dial like yours, only meant to remind you of your film ASA so you can adjust the shutter and aperture yourself accordingly. |
Rick_oleson
Tinkerer
Username: Rick_oleson
Post Number: 528
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, March 04, 2008 - 07:34 pm: |
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As you suggest, the ASA setting is purely a meter setting. If your camera has a meter in it, setting the ASA tells the meter how sensitive your film is, so that it can indicate combinations of aperture and shutter speed that are appropriate for the film you are using. Beyond providing this information to the meter, the ASA dial has no mechanical function.
If the camera does NOT have a meter in it, the ASA dial is nothing more than a reminder to tell you what film you have loaded. |
M_currie
Tinkerer
Username: M_currie
Post Number: 114
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, March 04, 2008 - 07:38 pm: |
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As noted, it's just a reminder, and not a very useful one either, since it's so easy to forget to update it or accidentally move it. And if you're consciencious enough to have set it every time, you're probably conscientious enough to have remembered to set your meter, or to have made a note somewhere else.
I have often wondered why so few camera manufacturers have provided us with that neat little slot in the back to hold the end of the film box (or any other little slip of paper). Now that's a brilliant idea, it seems to me, that should have become universal. |
Steve_roberts
Tinkerer
Username: Steve_roberts
Post Number: 12
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, March 05, 2008 - 05:06 am: |
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Shame that the reminder slots on the cameras I have with them are either too small for the box end or the box end is too thick! I shove a piece of blank card in and just write on it (turning it over when Side 1 is full, of course!)
Steve |
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