I want to try Macro


1947lcs

Link Posted 31/07/2013 - 11:20
I have A smc 1:2 50mm and that asks for the focal length when I fit it. This is why I thought the zoom would also ask.

Les
K5, DAL18-55,SMC 50mm f2,DA 55-300, SCM F 35-70 and all the help I can get.

Mongoose

Link Posted 31/07/2013 - 11:25
the A series lenses don't know their focal length so they will ask for focal length. It's only the F series and later which have the necessary chip inside to report their focal length to the camera.
you don't have to be mad to post here



but it does help

johnriley

Link Posted 31/07/2013 - 11:30
I may be mistaken, but I thought I had had A lenses where the focal length was recognised.

I could be wrong, but if I'm remembering correctly then maybe there was an overlap period where updated chips were used. Something similar happened when some late Super Takumar lenses actually had SMC coating.
Best regards, John

Mongoose

Link Posted 31/07/2013 - 12:06
you could be right there John, it would hardly be unprecedented.

My understanding is that there's a digital pin which was added to the mount for the F-series, which allows communication between the camera processor and a chip in the lens. The earlier lenses actually don't have chips at all, they just have pins which are connected to ground or not and the combination of connections encodes the characteristics of the lens.

It's entirely possible that some late A series lenses actually have the digital version of the mount if they were introduced after the F series was created, I'm thinking mainly of lenses intended for use with the MZ-M?

I know that some late M-Series lenses actually have the aperture stop down mechanism which was introduced for the A series.

We're all old enough to know that rules often don't hold 100%, but generally I'd expect an A series lens to need a focal length set, and an F series lens to set it automatically.
you don't have to be mad to post here



but it does help
Last Edited by Mongoose on 31/07/2013 - 12:08
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