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dave
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, November 24, 2004 - 10:43 am: | 
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I remember being told that light entering thru the viewfinder would not affect exposure,ie when in use on a tripod or similar.
But looking thru my olympus I noticed that the time changed as I moved my eye away ie it got faster.
Also my dynax 5 comes with a cover for the finder what is correct? |
Jon Goodman
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, November 24, 2004 - 12:11 pm: |
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Light entering the viewfinder can alter your results if you are using an SLR with an auto mode. The light sensors in many cameras take their reading from light passing through the pentaprism (Miranda being an exception, some Mamiya-Sekors as well), and if you brighten the pentaprism by feeding more light in through the eyepiece, you'll be likely to get a different aperture/speed value. Chinon, Fujica, some others recognized this and added a tiny metal blind in some of their cameras to eliminate the problem. Don't know what else to add...I'd suggest covering the viewfinder window if I was using the auto mode.
Jon |
Jim Brokaw
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, November 25, 2004 - 12:46 am: |
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It matters where the exposure sensors are located. Some SLR's use sensors located on the pentaprism, which measure the brightness off the focusing screen. These camera designs are affected by light coming through the eyepiece opening when your head and eye are not there (mostly) blocking light from that direction. Some cameras have shutters to block out this light when used on a tripod, etc.
Other camera designs locate the light measuring sensor in the mirror box area, either on the mirror e.g. Miranda, Mamiya-Sekor) or in the bottom of the mirror box. Because the light coming in the eyepiece opening has a much longer path to travel the light sensor is much less likely to be affected. On Olympus camera models, the OM-2 (on auto setting), OM-2s, OM-3 and OM-4 use a light sensor in the mirror box area. |
Ezio
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, November 25, 2004 - 12:48 am: |
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In addition to what Jon said, there may also be a problem when taking very long exposures (say, several minutes) even with the camera in full manual mode. Under such circumstances, some light will unavoidably filter down through the viewfinder and around the mirror (unless the mirror box seals and foams are in perfect conditions), and although this will of course not effect the exposure time it is liable to show on film. The problem would become even worse if the light behind the camera happens to be stronger than entering the lens (for instance, the photog is using a head lamp). |
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