Mark Fine and I asked questions about blindness in Bunkers, Pits & Other Hazards...
"...Is it acceptable to not see a hazard? When a visitor to The Old Course complains about the surprise of finding a hazard hiding amongst the holes, caddies often reply that the hazards have been there for 500 years, “How can anyone consider them hidden?” “A hazard will only be blind once,” is another common response.
The notion that all hazards must be seen is an interesting debate. The position opting for complete visibility has more chance when the scenario is that of a shot played from a tee, but even so, where does one draw the line at how far or how off to one side? If there is peril along an edge, why can’t there be more peril on down? Do we have to see it? An argument for seeing hazards is that this makes them part of the show. Of course, the interesting thing about golf is that each player—except from the tee—defines where the next shots will be played to a hole. The architect, the greenkeeper and the playing partners are not a part of this decision. The golfer is alone in this trek...
In the blindness department we are faced with degrees of the condition. A hazard or feature may be fully blind, partially blind or temporarily blind. The Dell hole at Lahinch is an excellent specimen to dissect. Here we have a green set behind a dune and it is also surrounded by other dunes. It might be said that on most days the cup is “fully blind.” But this is temporary, because the cup can also be set way right where it is possible to see, sometimes, the upper part of the flagstick. Now it is said that the hole is “partially blind.” This leads to a conclusion that the former pin position behind the dune completely, is then “temporarily blind.” We made mention earlier that the position of the cup each day is marked by a white stone which gets placed to denote where the pin is set."