Of course not. I was indeed referring to "focus confirmation". The red indicators are not as unrelated to focus confirmation as you describe them. When manually focusing, they pop up exactly when the AF sensor determines something to be in focus. As you say, the green hexagon is the final authority, but I cannot recall a case, when focusing manually, when the two indicators disagreed.


The point of some of my questions was to find out whether there are technical explanations for some of these limitations or whether Pentax just built in some incentive to use more modern lenses.

This is a matter of taste of course but I think they are slightly overdone. They look stunning but obviously unnatural.

I think a little less contrast and saturation would make them look less artificial looking. Less could be more in this case.

It appears you have a 50/1.4 already. For macro work a 50/1.7 is said to be better as the field of focus is more planar.

A 50/1.7 is also sharper from 1.7 to 2.8. Someone has suggested though, that using a lens hood on a 50/1.4 helps a lot to reduce the gap, arguing that the 50/1.7 lenses have a less exposed front element.

The main reason to still go for a 50/1.4 despite the many pros for the 50/1.7, is the bokeh which is said to be better on the 50/1.4.

BTW, 50mm is slightly short for a true portrait lens. 55mm would be better. 100mm is too long. 56-70mm would be ideal.

Mystery 1:
How can different lenses have different FF/BF characteristics on one body?

Mystery 2:
Why is it not possible to use non-centre AF points with a manual lens?

Mystery 3:
Why is it not possible to use multi-zone metering with a manual lens?

Regarding M1:
My understanding of AF is that the camera uses a feedback loop to achieve maximum sharpness. The lens should then not matter at all. My hypothesis is that lenses differ in chromatic aberrations and that the latter can throw off the prism based phase comparison. Another hypothesis is that there is no 100% feedback but that the camera always applies a small offset step after having found the correct point. This would be necessary if the optical path lengths between mount and AF unit and mount and sensor respectively where slightly different in each camera and instead of doing an optimal physical alignment, some software correction takes place. If lenses differ in how they actuate this final offset step then they would yield different FF/BF phenomena.


Regarding M2:
Centre focusing and then recomposing can introduce intolerable focusing errors when the DOF is very thin. It'll be nice to be able to use all AF points for focus confirmation. My hypothesis is that the camera doesn't know the aperture setting and if the aperture is stopped down too much, outer AF points may not work anymore. Is there a way, using information about the mount contacts, to make the camera believe that the manual lens can support multiple AF points? Not sure why even "A" lenses don't support them.

Regarding M3: I know that the camera needs to know the maximum and minimum apertures of the lens and manual lenses don't communicate them. But why not ask the user to enter this data? Again, perhaps, using information about the mount contacts, one could make a manual lens appear more capable.

With respect to M2 & M3 I could imagine that there are actually no technical obstacles but that Pentax wants people to buy their new lenses rather than being snug as bug in a rug with their old Takumar glass.

Although it is great that you can use manual lenses on your Pentax DSLR with just an extra button press added, I wonder why the following support hasn't been implemented:

Allow the user to enter an aperture value in Av mode. If it doesn't match the aperture set on the lens, tough. But if it does then you wouldn't need to dial in exposure compensation yourself. This shooting mode allows quicker shooting than "manual" + button press + shutter release.

Why can't there be a mode where the camera doesn't meter wide open and then exposes, but 1. stops down. 2. meters. 3. exposes? In other words, why can I not make the camera press the AE-L/green button itself every time I press the shutter release? Would the shutter lag be too large?

P.S.: If there really are no "technical obstacles" and Pentax indeed wants to entice users to buy new lenses, that'll be totally legitimate to me. Right now, Pentax is just the right brand for me and I'm grateful that I can play with the old glass at all. Just wondering why some things are not supported and if there is a technical explanation for it.