hi Yaron,
I try to understand and to clarify the situation. So, coming back to your 1st post:
I fully understand your points, viewed from your own specific context of today. Most probably, your assumptions above are based on your own applications you live with every day but they do not match with the general historical intend and use cases of the DCS tags, as I tried to describe below. Below, the stars **** refer to the discrepancy refered with the corresponding stars **** from your text above.
'ER' (= engraving reference point) that appeared in DCS 3.03 to my knowledge (where no engraver<>(****) was taken into consideration yet) is neither reserved for engraving <>(****), nor for the back <>(*): the tags ERNR and ERDR were and are still providing distances for NV and FV measurements, including for traditional PAL’s already engraved <>(****) on the front.<>(*)
To use FB as a reference for ENGMARK (as mentioned above) is again for a very very specific application. Most systems are not using FB as a reference for inking or engraving.<>(**)
So, most often 'engraving point' 'ER' refers to an already existing (not to be engraved (***) (****) ) permanent positioning reference marking used to position the lens or as reference for finding another point.
Many DCS tags are not taking 3D aspects into consideration for historical reasons, considering often there is no parallax effect: the lens in some way is behaving like a flat thin lens, with no difference between front and back engravings <> (*) for example.
BE, with the ‘B’ for 'back' provides more clear 3D information: I have the feeling that it can be considered as a reference point (-> DCS table 2) anyway, but the ‘B’ for 'back' differentiates the specific use of this point for a 3D approach.
So, I think you are reconsidering what is done since 20 years.
Anyway, I would like to better understand your concern. Maybe, for our understanding, you could illustrate what are the tags you are using that involve 'ER'. TY in advance.
Again, I do hope this helps.