There are a couple of things worth noting in this photo. First, obviously, it is Passiontide since the crucifix and statues of the reredos are veiled. Next, this is not one of the "Private Masses" said by the priests of the house each day. If it were, the server would have been wearing his cappa. As the server (whose identity is lost) is wearing a surplice (the proper vesting on a lower rank feast or ferial) not a cappa, this is a community Mass. It was the custom, in the Order in those days that, in addition to the private Masses, that there be two conventual Masses a day. A Low Mass after Prime where the brothers would receive Holy Communion, and the sung Solemn Mass, in the later morning, where only the celebrant (and lay people present) received. The rest of the friars, priests and brothers, sang that Mass.
You will also note that no antependium and carpet are used, a common practice in Lent and Passiontide. The lighted candles are the middle ones of the large six. Only two are lighted as it is a ferial; on a 2d-class feast, two would have been lighted; on a 1st-class solemnity, all three. The candles picked for lighting would naturally be those which were longest, and you can notice that the ones lighted are, indeed, the tallest.
On the Epistle side you can see the lighted Sanctus Candle, which shows that the Sanctus is over. And you can see that Fr. Hilary's arms are extended beyond his shoulder (moderately, as the rubrics require) and so this is immediately after the Consecration. He will return to the posture with the hands just visible above his shoulders after bowing for the prayer Supplices te rogamus. You can also see the triple candlestick just visible to the left of the Sanctus Candle. The six candles on the two of these (one on each side of the altar) would all be lighted as Sanctus Candles on solemnities. Four total (two each side) is the rule for 2d class feasts. Finally, you can see one of the twelve dedication candles of the chapel on the wall. These are lighted only on the anniversary of the dedication.
My thanks to Fr. Hilary for passing on this photo.
