VTA Cartridge

Yes, looking from the side, if the front surface is perpendicular to the record surface (easy to tell from the reflection of the cartridge on the record surface), you are in the ballpark.  Depending on manufacturing tolerances and the tracking force you are working with, perfectly perpendicular may not necessarily get you the ideal VTA/SRA.  But, from that reference point, it is a matter of slightly raising and lowering the arm pivot point to find what sounds best.  Particularly with line contact type styli, small changes in VTA  can be quite audible.  Generally speaking, with the nose of the cartridge pointing down (raised pivot point), the sound will be brighter and more sibilant.  I set my VTA for normal thickness records.

Just because the sound is getting better going in one particular direction, does not mean that going in the other direction is not worth trying.  Sometimes, changes do not have consistent results, so it does take experimenting with movement in both directions around your perpendicular reference point.  Extreme movement up and down will also affect other aspects of alignment, including tracking force, so that must be taken into account.  

Dear @audiosens : What are you trying to achieve? where or why do you have some doubts on your today cartridge/tonearm overall set-up?  I read that you have 40 years in audio that means you have more than enough experiences about but for your OP that's not exactly rigth.

"""   that it is a way to have a good VTA ? """, certainly not because depends of the stylus shape and thickness of each LP and other factors and that's why I'm asking you those questions.

R.

rauliruegas Beacause I read that on some turntable it is better to add a spacer between the arm pivot, but other say no... and then after all, my turntable by ear sound OK

melm  Good observation, I try with the light and I see the shinning line, thank's

lewm , yes tuning by ear is a correct way, I will trust my ears.  Thank's