You just need to experiment and see what works for you. As with most things there's no stock answer - necessity to adjust will depend on a number of things including your bp adjusting habits in PS, your paper, your output profile, rendering intent, the nature of the image itself, etc. The important thing is that it gives a final control of a critical and sometimes problematic area in prints - the black areas.
In my case I leave it at the default 50 unless I observe a problem in the first paper proof. In particular, it solved my problem with overinking of blacks on Arches Infinity which resulted in shiny blacks. I slide it to 100 for this, but if I print the same image on PremiereArt it works fine at 50. Note that the control is actually quite fine (ie minimal effect) so I wouldn't fret about the difference between 20 and 30 for instance. In fact I tend to use it at either 50 (mostly), 100 (if Arches problem shows), or 0 (rarely, with b/w prints).
> The "default "50 is wrong.
For you perhaps. It appears to match the "pre-slider" versions of IP and works well for me for most situations. I've read some reviews that claim a setting of 100 matches the pre-slider version but this is definitely wrong or else setting it to 100 wouldn't have fixed my AI problem which I previously had to fix with ink reduction.
- DL
