| Author |
Message |
    
Richard
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, May 20, 2006 - 08:26 pm: | 
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I recently aquired a Mint Hi-Matic E. Your help is needed to clarify shutter/aperture operation.
I have installed two new 640 batteries. All lights are operating properly. As I understand this camera, the shutter also serves as the aperture. Correct?
The aperture increases and decreases when the ASA dial is changed thru it's range and shutter is fired. However the aperture does not change with various light conditions. The shutter speed changes with various light conditions up to max 2 seconds with very low light.
My question is this: At no times or conditions is the maximum aperture area fully open in relation to the size of the f1.7 lens area. Max aperture area is considerably less than the lens area with ASA ring set at ASA 25.
Is this normal? Hopefully someone who has a known good Hi-Matic E can check and advise whether this is normal.
Thanks for any help. Richard. |
tim_a
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, May 20, 2006 - 10:53 pm: |
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As you suspect, it is not operating correctly. The aperture and shutter speed should adjust according to the program line, and you should be able to see (as I do on mine) the full f1.7 aperture in low light conditions. |
Richard
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, May 21, 2006 - 04:54 pm: |
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Thanks Tim for your response. I wonder if low battery voltage may be a cause for the problem. These are alkaline batteries purchased several years ago but never used. Battery check light and Hi-Lo lights in view finder all are working.
Any help regarding repair of this condition would be appreciated. |
Reiner
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, May 23, 2006 - 02:01 pm: |
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As far as I remember the sutter should work ok if the lights of the camera are working. The first sign of decending battery voltage is that the lights do not work any more. But I did not test that at the long end that means for long exposure time and for a fully open aperture. In this case the battery is used up much more than at the short end. It might be possible that the battery just works initially but cant supply enough current for a longer exposure. This might explain your problem and as you wrote that you are using old alkalines this is very propable. You should check your camera with known ok batteries.
I often use a battery holder with AA cells and two cables with clips for such tests. Good AA cells have surely enough power. The connection of the clips is critical in this case. |
Richard Creviston
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, May 23, 2006 - 03:36 pm: |
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Thanks Reiner. That was what confused me. The owners manual states that if the check light works that the battries are O.K. But I believe that the check light may not require as much current as the shutter/aperture. Hence the aperture is changing with ASA settings but not fully opening to maximum with low light condition. I have checked the batteries with my cheap analogue multimeter and they show 1.4V each.I had planned to do exactly as you suggest using two AA cells in series and rig an insert to the battery compartment and observe the aperture when firing the shutter. I was reluctant to buy new 640 batteries due to limited budget and feared that the camera was defective even though it appears never to have been used.
Can you comment on the previous responder's statement regarding change of speed with change of existing light? It was my understanding that the aperture is controlled ONLY by the ASA setting and that shutter speed was controlled by changing light conditions. Am I correct in that assumption?
My sincere thanks for your help with this problem. Richard. |
Reiner
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, May 24, 2006 - 11:39 pm: |
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Richard,
as Tim states the camera follows an internal program line. Current ASA speed and light conditions imply a fix combination of aperture and speed. Double ASA speed but half the light will cause the same combination of aperture and speed. The same light but a different ASA speed will cause a different combination of aperture and speed. There is no isolated effect of the ASA setting on the aperture. That would not make any sense since if you use a fix ASA setting for a given film the speed allone is not variable enough to control a broad range of lighting conditions.
The ASA setting is actually realized so that it causes a different light reading. If you look onto the CDS cell with a loupe or with sharp eyes you will see a perforated mask before the CDS cell. The ASA setting rotates the mask. Doubling the ASA setting will double the area of holes in the mask and double the amount of light which reaches the CDS resistor. This is more accurate and more robust than a realisation via the electrical way (sliding contacts on carbon resistor stripes) and all cameras I of that class I know about do it like that or similiar. |
