everything is mastered to digital eventually, unless you want to cut some vinyl.
"look ahead" limiting, all it is, level measuring before a microsecond (number of samples) delay, which allows a limiter to kick in to avoid "overs".
Popular, because it forgives people who fucking up when getting levels in the digital domain.
In analogue, not so neccissary, as you can run very hot before tape screws up.
Facilities which advertise digital mastering rather than just mastering are often those who............just don't have any analogue gear
In the recent past it was essential to have analogue alongside digital mastering gear, in particular for projects recorded in 16/44.1, which sounded hard, raw, the equivalent of audio sandpaper. Dumping stuff like that onto a 1/2" machine (sometimes pretty hot!) would warm it up substantially.
Now things are changing a lot. Material recorded in, or mastered to 24/48 or 24/96 is in general smooth and full, and it would be benificial to the sound and quality of sound to keep the project in the digital domain.
However, the above all depends on quality of equipment. For instance, most material recorded in Pro Tools using Digidesign I/O can benefit from analogue processing. If the project had been recorded in Pro Tools using higher quality I/O, it would normally not be neccissary.
Example:
Standard - digidesign 888/24 - flat
Apogee 888 - Average +2dB below 80Hz +3dB above 6000Hz
Lucid ADA - +3dB +3dB
Stagetec - +5dB +3dB
In other words, big difference.
I find today you'd use the tape option less and less, personally, if I feel analogue treatment is required, I'd first run the material through an atomic squeezebox stereo compressor.
One of the best advancements today are machines like the Alesis Masterlink, which allows me to receive material at prestine quality instead of the usual 16 bit crap.
