Do i owe you $15.00 or are you arguing in your spare time.
LOL
Dave(sorry, just had to)Brooks
> A list member recently contacted me off-list
asking whether it was
> possible to use a certain Pentax DA lens on Canon cameras. I don't want
> to reveal the list member, but I'm sure they won't mind me posting my
> answer as a general piece of info, I thought it might be of interest,
> and perhaps de-mistify things...
>
>
> >Would it be possible to put a Pentax DA 16-45 on a Canon camera with an
> >adaptor?
>
> It is not feasible. Notice I didn't say that it's not possible, just not
> feasible. The reason why is that the Pentax DA 16-45mm lens has no
> aperture ring, so if it is mounted, via an adapter, onto a Canon EOS,
> there is simply no way to change the aperture. Simple as that.
>
> So the answer is that it is very possible to mount the DA 16-45 onto a
> Canon with an adapter, but unless someone take the lens apart and
> designs a way of manually changing aperture, then you will be stuck with
> the maximum aperture of f/4, and no way of stopping down. Electronic
> control via the camera is not possible, or maybe it is, but at many
> hundreds of times the cost of the lens. An expert could probably spend
> weeks designing and rebuilding the lens to allow EOS control - but
> that's daft, right ? ;-)
>
> >What about metering is that affected at all?
>
> When I put my K15mm or my A*85mm onto my 1D, it basically behaves like
> an old fashioned stop-down manual lens from the days of old. I switch
> the camera to manual (M), I put the lens on, and I focus on a scene,
> then I decide what aperture I want to shoot at, say f/8, so I stop the
> lens down to f8, and a half press of the shutter button and the camera
> literally looks at the amount of light coming through and tells me to
> set the shutter speed (say) to 1/250th sec. I do this buy using the main
> dial (small revolving dial on top near shutter release), moving it until
> 1/250th sec is shown in the viewfinder, and then I fire the shutter.
>
> The only other way to use one of these lenses with the Canon is this:
> instead of selecting manual (M), I select aperture priority automatic
> (AV). Now, when I use the K mount lens, I first of all focus on the
> scene, then I select the aperture I want to use (say f/8 again), and as
> I turn the aperture ring, and at the same time have a half-press on the
> shutter, the camera is changing the shutter speed to match,
> automatically. So as I come to rest the aperture ring at f/8, the camera
> has already set the shutter speed at the correct 1/250th sec, and away I go.
>
> It's as simple as that.
>
> Obviously, the camera has no electrical connection with the lens, so
> (for instance) it does not know what the focal length of the lens is,
> nor the aperture being used. All it knows is what the amount of light is
> coming through the lens. And if it knows that the ISO is set to (say)
> 200, and it knows the amount of light, then it can figure out the
> shutter speed required to expose the scene correctly. An external light
> meter can do this. A lot of photographers can do this by sight.
>
> So now you can see why it is vital when mounting a Pentax or Nikon or
> Contax lens on a Canon camera that the lens has an aperture ring to
> manually adjust the amount of light coming through.
>
>
>
>
>
> Cheers,
> Cotty
>
>
> ___/\__
> || (O) | People, Places, Pastiche
> ||=====| http://www.cottysnaps.com
> _____________________________
>
>
