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Author Topic: 645AFD metering at low light  (Read 1324 times)


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645AFD metering at low light
« on: October 04, 2008, 04:45:59 PM »


I have noticed a strange behavior of the 645AFD's exposure meter recently:
With a AF80mm lens @2.8 attached and a film back, set to 6400iso, in extra low light conditions (twilight), in P and Av modes camera sets correct shutter speeds up to 1/30 and faster. When a darker object is metered and logically the camera should set the shutter speed to 1/15 and longer, the numeral 1/30 just blinks, as in case, when a shutter or aperture limit is exceeded, and operates at 1/30, even if the object is darker. The 1/30 "limit" sometimes changes to 1/60 or 1/45. At the same time, in the manual mode the difference between the manual settings and the metered value are displayed correctly and "guide" to the correct shutter speeds, longer then 1/30.

When a digital back is attached (hasselblad ixpress 132c) and set to 100iso, in better light, but still dark conditions, the camera refuses to set shutter speeds longer then 2-4s. In this case, the issue appears in manual mode also, as the difference only shows up to 2s and does not give any correction (shows 0.0EV) when it is significantly (1-3EV and more) darker. So the only way is to set the shutter speed buy guess in manual mode using the histogram, when the camera signals about overexposure.

The issue also appears when older M645 manual lenses are used (35mm C, 120mm Macro A, 75-150mm C).

I have contacted several local colleagues, using the same camera and various lenses (both AF and manual). They have also reported, that this issue is present. In one case @6400iso 2s was blinking, @3200 the value changed to 4s etc. up to normal 30s @100iso. In other cases the results were similar.

UPD: it looks like that the camera really has some sort of a limit: the same change in available shutter speeds, as described above, also appears when exposure compensation is set. For example, @3200 iso 1/60 blinks, at 6400 - 1/30. If -1EV is set @6400iso — /15 appears and so on in both directions.  

Has anybody noticed something similar with their units? If yes, please, give detailed information about the camera model (I, II or III?), lenses used, iso, film/DB and conditions.
Is this a know feature? How can it be corrected? Or is this a malfunction of certain units?
« Last Edit: October 04, 2008, 04:58:29 PM by A.K. »

Andrey Kulpin
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