Zitat von Gonz <[EMAIL PROTECTED]>: ... > > The AF does NOT 'see' the same thing as the screen. When the position of > the AF > > module (that sits under the mirror) relative to the lens is different to > the > > position of the screen, both result in a different focussing position of > the > > lens. So if images taken using the Autofocus appear sharp, then maybe the > > focussing screen is out of alignment. > Is there a diagram that shows what the AF path is? How does the AF see > the image if not through the focusing screen, i.e. if its under the > mirror, then how does it see the image?
I will try to find a diagram and provide a link. Basically the mirror is half transparent so that some light goes through it. This is then reflected by another smaller mirror that folds out behind and directs the light to the AF module that sits in the bottom of the mirror house. If you inspect your camera with the lens talken off you can see some of it. > However, using a 1.4 lens with manual focus on a ist D screen without > focussing aids is a worst case scenario. If you really want to rule out > focussing errors on your side you need to use a magnifier or refconverter in > the 2X position. > > > I need some help understanding how this helps. The ist D finder image is small if compared to film SLRs, especially those meant for manual focus. Also, the finder screen does not have focussing aids such as microprisms or a split image field. This means that the error margin that you have when focussing manually is relatively high. This is not a problem when the lens is stopped down a little and/or if the resulting prints are viewed under normal viewing distance. However, if you use a fast lens (like a 1.4) wide open AND want to inspect 100% crops of the resulting image on a computer screen it is well possible that your focussing was not accurate enough for this extreme setup, i.e. it did not fall within the shallow DOF range of the lens. About the only thing you can do to improve accuracy here is to focus with the help of a magnifier or a refconverter attachment using its 2x magnifying position. This certainly is nothing that you would want to use for normal photography work. All it would tell you is wether the camera screen is out of alignment (in which case it would have to be adjusted by Pentax) or if the error is more on your side. Regards, Sven
