Shashin,
I don't need to show anything, there are enough people here who experience this, also many who claimed like you that such "craziness" for precision is non-sense and who came back from that.
Just have a look at the videos at Alpa's site, it shows and explains it perfectly.
You look at your images and they are sharp: yes of course they are. But are you sure your sharpness plane is exactly at the exact place/distance you have set it on your scale?
Shashin, you seem to purposely want to misunderstand and to distort what I am writing, 3 times now: I did say that it is not the camera which needs precision/adjustment, but the sensor/lens which do not necessarily have the same tolerances from one unit to the other (see some posts here and elsewhere from others).
"you cannot get sharper than where the plane of focus is": obviously, yes of course. But it is the precision of this sharpness plane, thus the sharpness at the exact point (plane) where you want it which is important for some. This is what I considered as "maximum sharpness".
"I assume not all backs have to be shimmed": obviously not, but much more than you would imagine, without speaking about lenses.
"how much will an Alpa body and lens mount expand from say -40F to 90F?": that's another issue, and yes, you are perfectly right here, but not only an Alpa, ALL cameras/bodies/parts of the setup. This is something manufacturers will have to deal with sooner as you might think.
I think it doesn't need to continue arguing. If you are happy with your results that's the most important. I have simply pointed out something which we daily have to deal with at Alpa, "Sensor position and planity/curvature".
Best regards
Thierry
Thierry, please show this. Say two landscape images shot at f/11 at half the hyper focal distance (the plane that will still have infinity in the DoF) with a difference of 0.01mm shim (you can use the Zeiss standard CoC of 1/1500 of the format diagonal for DoF). Describe how object distance was determined and where that plane is. If you say this makes a difference then it should be easy to show.
BTW, how much will an Alpa body and lens mount expand from say -40F to 90F?
Now, I have used reflex systems like Hasselblad, Mamiya, and Pentax. A reflex system will need tighter tolerances than an Alpa because the ground glass and mirror need to be in the right place or each will compound focusing errors. I look at my images and they are sharp. They are sharp where they are supposed to be sharp. A shim will just move that plane. Yet, in my images, I can see where the plane of focus is. You cannot get sharper than where the plane of focus is. Even with my sliding GG on my Linhof, no focusing error, so I am confused by your claims.
BTW, my advice was just to order the adapter and determine if there was a problem--I assume not all backs have to be shimmed. I was not referring to the construction of the Alpa. You may be right that Phase, Leaf, and Hasselblad have really bad QC but on average they should get the sensor in the right place. Why assume there will be a problem? (I have seen the Optech video on shimming and they are really shimming the camera to a point closer than infinity--infinity is just not something that is far away.)
But anyway, I would be happy to see some evidence. I really don't think hearsay is very helpful when your customers could be using targets that are not at infinity and then of course they will think the back would need to be shimmed.
