I thought P-TTL worked with A lenses..
------------- Thibouille
John Francis a écrit :
[EMAIL PROTECTED] mused:
Quoting Francis Tang <[EMAIL PROTECTED]>:
*gasp*!
Could this be true? Noone in Singapore can confirm whether M-series lenses work okay with the *ist-DS (okay, I presume the DS is not so different from the D wrt lens compatibility). The brochure for the DS only lists K-A and newer lenses as being "compatible".
So, how well does it work opn the *ist-D? Can anyone confirm whether this is also the case for the DS?
In addition to reading whatever replies this post attracts, you might want to go through the archives for both facts and opinions on *istD and pre-A lens compatibility. This subject has been discussed a lot with regard to the *istD and I seem to recall there was a very recent post about the Ds as well.
ERNR
The definitive summary:
The *ist-D and *ist-DS behave basically identically with any given lens. Exactly how you perform certain operations differs slightly, but there is no difference in the capabilities, just in the way to get at them.
With F, FA and FA-J lenses you get full functionality, and all modes.
With A lenses (and the lens set to the "A" position) you obviously lose autofocus (unless you're also using the AF 1.7X adapter). You're also restricted to only the central AF sensor[1], and TTL (not P-TTL) flash.
With older K-mount lenses, or with any lens with the aperture ring not at the "A" position, you only get hyper-manual exposure mode.[2] This is effectively manually set exposure (shutter speed set on the body, aperture set on the lens), but with a quick one-button way to have the camera set the 'correct' shutter speed. (On the *ist-D this uses the green button; on the *ist-DS it's the AE-L button).
Because these cameras lack the aperture simulator coupling they have no way to directly read the aperture set on the lens. As a result, metering (either for the one-touch shutter setting above, or for the exposure check that is activated when you engage the DOF preview) is performed by briefly stopping the lens down to the taking aperture. (I believe the only metering available uses center-weighted mode).
M42 screw-mount lenses (using the screw-mount to K-mount adapter) behave in the same way they do on all K-mount bodies; the aperture ring on the lens will stop the lens down immediately. The camera has no way of detecting this, and so will actually work slightly better with these lenses than with pre-A K-mount lenses!
[1] I have no idea why this restriction is necessary.
[2] If the appropriate Pentax Function is set, the camera will trip the shutter if the body is set to Aperture Priority mode. But the body will not stop the lens down during exposure; the camera will meter, and shoot, with the lens wide open.
