Originally posted by Not a Number The OEM adapter when installed properly sets the aperture linkage lever to a position that enables stop-down metering. While the K&F adapters appear to have cutouts for the aperture linkage. I could not say by the photos if the cutout is in proper position for stop-down metering.
Good observation and comment
Too expand a little...A proper adapter (flanged or otherwise) has a cutout to engage the aperture position coupler on a "non-crippled" K-mount. When the adapter is fully engaged, the coupler will be at the position for maximum aperture (required for stop-down metering). The position of the cutout slot has historically been a potential issue with brand-X adapters when used with bodies having non-crippled mounts (K, KM, KA, KAF, KAF2).*
Originally posted by timw4mail I've used a few different knock-off M42 adapters, and have yet to have an issue with stop-down metering.
It is not issue with "crippled" K-mount bodies (all Pentax dSLRs) or with adapters for other than K-mount. Even then, most reputable dealers are aware of the problem and bad slot placement is something I have not read of in a long time.
Steve
* Bad slot position has symptoms similar to poorly machined adapters with improperly shaped bayonet tabs that allow the adapter to over-rotate in the mount; that being inappropriate bias applied to the meter output.