Re: On USM and KAF2/KAF3 (was Re: End of K-mount?
Antti-Pekka Virjonen wrote: On the other hand I think there is no need to implement USM at all. The shaft/pin drive methods works about as fast and good as the USM competition and it allows the lenses to be cheaper without the motor. For wide-angle to short telephoto lens, your point is right. But for long telephoto lens, especially those without internal focusing, USM is much faster. Another major advantage for USM is that it is very silent, which is important for wildlife or concert photography. Regards, Henry Chu 14/2/2003 _ MSN 8 helps eliminate e-mail viruses. Get 2 months FREE*. http://join.msn.com/?page=features/virus
Re: On USM and KAF2/KAF3 (was Re: End of K-mount?
That would be "overkill". Canon EOS bodies can use either type of AF lens without having a switch to choose between them. If you were going to use AF at all, why would you NOT want the advantage of the USM? The only real choices we need are: AF or MF. We already have that. Len --- From: "Alan Chan" <[EMAIL PROTECTED]> Reply-To: [EMAIL PROTECTED] To: [EMAIL PROTECTED] Subject: Re: On USM and KAF2/KAF3 (was Re: End of K-mount? Date: Thu, 13 Feb 2003 17:00:49 -0800 Perhaps it could be done with a switch on the lens to determine which AF method was used? Something like "AF/USM" switch. When the switch was in "AF" position, the power for the "USM" would be disconnected and the lens acted like a regular Pentax AF lens. When the switch was set to "USM", the conventional AF mechanism would be disengaged and USM would click in. But that creates a dilemma, since future AF bodies should or might support current AF lenses, you might actually have the choice to use either AF methods when USM lenses were mounted on USM bodies. The situation is a bit like digital/analog flash system. Nikon chose to integrate analog support in digital flashes while Pentax chose to integrate analog support in AF digital bodies. However, if Pentax would ever release USM lenses, it would be highly likely to follow what Nikon did - USM lenses must be used on newer bodies which support both AF method. regards, Alan Chan _ Help STOP SPAM with the new MSN 8 and get 2 months FREE* http://join.msn.com/?page=features/junkmail
Re: On USM and KAF2/KAF3 (was Re: End of K-mount?
Perhaps it could be done with a switch on the lens to determine which AF method was used? Something like "AF/USM" switch. When the switch was in "AF" position, the power for the "USM" would be disconnected and the lens acted like a regular Pentax AF lens. When the switch was set to "USM", the conventional AF mechanism would be disengaged and USM would click in. But that creates a dilemma, since future AF bodies should or might support current AF lenses, you might actually have the choice to use either AF methods when USM lenses were mounted on USM bodies. The situation is a bit like digital/analog flash system. Nikon chose to integrate analog support in digital flashes while Pentax chose to integrate analog support in AF digital bodies. However, if Pentax would ever release USM lenses, it would be highly likely to follow what Nikon did - USM lenses must be used on newer bodies which support both AF method. regards, Alan Chan _ STOP MORE SPAM with the new MSN 8 and get 2 months FREE* http://join.msn.com/?page=features/junkmail
Re: On USM and KAF2/KAF3 (was Re: End of K-mount?
gfen <[EMAIL PROTECTED]> wrote: >Is it then possible that USM lenses will be AF backwards compatable with >any body that doesn't not support KAF3? It's certainly technically possible, but the real question is whether it's economically practical. You'd have to have both conventional and USM focusing systems in the lens and have a mechanism that disconnects the conventional drive mechanism when it detects power at the power zoom/USM contacts. This would increase the price beyond what USM in itself would add. I suppose a manual select switch would also work but it seems inelegant and would be annoying for those who have an AF body with the KAF3 mount and one with KAF2 and used the same lens with both. Automatic detection and switching seems the way to go and it might just be too costly except on big dollar lenses. -- Mark Roberts Photography and writing www.robertstech.com
Re: On USM and KAF2/KAF3 (was Re: End of K-mount?
> Is it then possible that USM lenses will be AF backwards compatable with > any body that doesn't not support KAF3? I guess everything is possible but it is highly unlikely. Pål
