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  1. #91

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    Quote Originally Posted by Chan Tran View Post
    The Pentax LX when meter in manual doesn't measure the light off the film but rather via the piggy back mirror that reflects light to the sensor (similar to that of the Nikon F3)
    And both LX & F3 actively meter off the film plane when mirror is locked up. They differ in that the F3 does not use the patterened screen while the LX does. They also differ in autoexposure mode as the F3 determines exposure at the time of shutter trip while the LX will continue to meter the scene in realtime - varying shutter time accordingly, for as long as it takes to get a proper exposure or the battery dies.

  2. #92

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    Quote Originally Posted by wblynch View Post
    The patterned shutter curtain, rear-facing sensor and the two-part mirror, like the OM-2S, OM-PC, OM-4/ti and OM-3/ti?

    The design and technology was invented first by Olympus.

    Just sayin'...
    The 1975 OM2 may have been the first commercially released camera that implemented OTF but not the inventor. Canon has a 1969 patent for flash OTF and Minolta has a patent on OTF metering very much like that used by OM2 in 1975.

    Excerpt from -> May 1976 Modern Photography review of the OM2

    The Pentax LX may have patterned their Integrated Direct Metering system of previous patents/implementations, but I really appreciate that they took it a step further. To date, it's unassisted single metering range of - 6.5 EV to EV 20, longest aperture priority autoexposure, realtime scene monitoring for changes in light is unequaled by any camera past or present. I am not aware of an external meter that has this range.
    Last edited by Les Sarile; 01-08-2013 at 07:04 PM. Click to view previous post history. Reason: Corrected year for OM2

  3. #93

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    Quote Originally Posted by Ulrich Drolshagen View Post
    You have some beautiful images on your site! I particularly liked this one -> http://www.ulrich-drolshagen.de/gall...de/ilmenau.jpg

  4. #94

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    Quote Originally Posted by Les Sarile View Post
    And both LX & F3 actively meter off the film plane when mirror is locked up. They differ in that the F3 does not use the patterened screen while the LX does. They also differ in autoexposure mode as the F3 determines exposure at the time of shutter trip while the LX will continue to meter the scene in realtime - varying shutter time accordingly, for as long as it takes to get a proper exposure or the battery dies.
    The F3 doesn't meter at the film plane once the mirror is up. It holds the reading taken before the mirror is up and thus the shutter speed displayed in the viewfinder is the one it's going to use. It sends out a signal thru the hot shoe proportional to the intensity of the flash it reads off the film plane during exposure. For the F3 OTF is only for flash as almost all film slrs with TTL flash do.

  5. #95

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    Chan, When the mirror is down, the sub mirror reflects the light to the SPC (Silicone Photo Cel). When the mirror is locked up, the backward pointing SPC detects the light off the film plane - more precisely off the shutter curtain, as there is no sub mirror to reflect it back. This of course is very simple to test as you only have to take your F3, lock the mirror in the up position, activate the metering by half pressing the shutter, face it towards a light source and move the aperture ring and you will see the meter respond to the changes. This works this way in manual mode or aperture priority and OTF TTL flash. Meter a long or short exposure - manually or aperture priority, and once the shutter is fired it will stay on course regardless of any changes in light.

  6. #96

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    Quote Originally Posted by Les Sarile View Post
    Chan, When the mirror is down, the sub mirror reflects the light to the SPC (Silicone Photo Cel). When the mirror is locked up, the backward pointing SPC detects the light off the film plane - more precisely off the shutter curtain, as there is no sub mirror to reflect it back. This of course is very simple to test as you only have to take your F3, lock the mirror in the up position, activate the metering by half pressing the shutter, face it towards a light source and move the aperture ring and you will see the meter respond to the changes. This works this way in manual mode or aperture priority and OTF TTL flash. Meter a long or short exposure - manually or aperture priority, and once the shutter is fired it will stay on course regardless of any changes in light.
    Hi Les. Although I am not familiar with the LX as I don't have one and not very familiar with the OM-2 as I rarely ever used it. I know the F3 very well and I am sure for ambient light exposure the camera hold the reading from the SPC before it raises the mirror up. For flash exposure it reads off the film plane but it only sending out whatever the value it gets from the SPC to the flash.

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