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Aria viewfinder information MM vs AE lenses

Neil,

> Nikon FA for sure, and I think F3. I thought it was pretty common, but > perhaps I'm mistaken? Probably some Oympus OMs, because they measure > light OTF during exposure, so if they have Tv or P mode then they > would do it too, most likely. Many cameras meter off the film for > regular exposure, not just for flash. No?

Again, I believe that cameras don't meter off the film for ambient light reading, only for TTL flash exposure. I've got a Nikon FA brochure somewhere I can check out...and if I find I'm mistaken, I'll let you know...or if you have a (credible) reference you can point me to that shows this, I'd like to know about it.

Regards,

Austin
 
Erik,

I expect the Av stop-down to be as accurate as the aperture ring, given the mechanics. For action specific to the MM feature (implements Tv and P), the accuracy will certainly depend on correct calibration of the camera body AND the lens.

Robustness of the levers is obviously a potential problem compared with a mount like Canon EOS (which has no such projections), but I have nothing bad to report. Mounting a C/Y lens is a bit fiddly, to be sure.

Neil,

My understanding from photo.net is that OTF gives the dynamic exposure adaptability you mention, but is a rare feature (Pentax LX, Olympus OM-2 and OM-4 may be it). The experiment is to fire Tv in a dark room, then turn on the lights: if the shutter stays open then there's no OTF. Meter beforehand to establish appropriate light levels. So far, I observe no OTF for RTS.
 
Erik,
To get back to your original question, all of the information above is essentially correct although some of the remarks confuse me. I have an Aria and use both AE & MM lenses. Here is the scoop with AE lens mounted:

In manual and aperture priority (Av) mode the set aperture is displayed in the viewfinder and is also correctly communicated to the exposure computer. The latter is important because metering is done with the lens wide open and the computer must know what the aperture will be at the time of exposure.

If you have an AE lens mounted and accidentally select shutter priority (Tv) or (P)rogram mode the camera will ignore the mode selection and operate in aperture priority mode, behaving as described above.

If you have an MM lens mounted and select Tv or P mode, again the Aria meters the light with the lens wide open and only adjusts the aperture (and/or shutter speed) an instant before firing the shutter. Thus you can rely on the aperture & shutter information displayed in the viewfinder (just prior to exposure) to be the parameters used to make the exposure.

Hope this helps.

Mike.
 
Austin:

<<Can you name a camera that adjusts the shutter speed after stopping the lense down, when in shutter priority mode?>>

In a sense, the Aria does this. In Tv mode, (using an MM lens) if a correct exposure cannot be acheived by adjusting the aperture, the selected shutter speed will be overridden (shifted). However, as you have pointed out, this all happens simuntaneously and before the shutter is released. There is no OTF metering in the Aria.

As for the Nikon FA; I have checked the manual and it uses OTF metering only for TTL flash exposure. Even in this case I believe the OTF metering information is used to adjust the flash duration rather than the aperture or shutter settings. I too am unaware of any SLR that alters the shutter / aperture parameters AFTER the shutter is released. But there are lots of cameras out there about which I know nothing.

Regards,

Mike.
 
All -

Very interesting discussion.

In summary then, for both types of lenses, the set aperture is correctly displayed in the viewfinder and correctly communicated to the exposure computer (and presumably the D-9 databack as well). All metering for both types is done with the lens wide open.

Rico -

You're definitely right about the Pentax LX being able to adjust once the shutter's been tripped. (See http://www.mir.com.my/rb/photography/hardwares/classics/pentaxlx/metering/metering.htm)

The Olympus manual for the OM-4T doesn't fully detail this, but the specs indicate for cw-average 'TTL Direct "off-the-film" Light Measuring' which I presume is the same.

By the by - does anyone know what percentage of the image area the Aria spotmeter covers? I haven't seen numbers on this - as a point of reference, the OM-4T brochure says it covers 2%.

Cheers,

Erik
 
Eric:
<<By the by - does anyone know what percentage of the image area the Aria spotmeter covers?>>

Someone wrote a review of the Aria (unfortunately I can't find the url) in which it was stated that the spotmeter covers an area slightly larger than the microprism circle in the center of the viewfinder. Hope this is of some help.
Regards,
Mike.
 
I simply cheated, and referred to p.226 of the manual. The spotmeter covers the microprism collar, a 5mm dia circle. This circle is marked on all four Aria screens.

A 300mm lens is needed to achieve 1° spotmetering with an Aria.
 
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