degruyl
Just this guy, you know?
My understanding is the Arista Premium is Tri-X rebranded, which will give you beautiful blacks, but as MCToumey mentioned it's a difficult film for low light if it's underexposed.
Underexposed Tri-X / Arista Premium 400 looks like fog and mud. Most films are like this, no? (or is there something out there with a clearer base?)
If it's exposed right it will be fine. Could be your camera's shutter running slow at slower speeds as well.
You meant fast.
Also, you should "worry" about falloff and reciprocity failure if it is actually a long exposure. For certain exposure times, and the film package used to have this information: it is now on kodak's website, the time has to be extended.
http://www.kodak.com/global/en/professional/support/techPubs/f4017/f4017.pdf
For 1/10 to 1/1000 there is no change in exposure, 1 second sees falloff of 1 stop (which means: if your exposure meter says to expose for 1/2 second, you expose for 1. 1 second -> 2) and decrease development by 10% (I suppose that is to reduce fog).
I doubt you are anywhere in that range, if you are handheld, but it is good to know. All of this and so much more is in the the linked technical publication. (it should be fine for Arista Premium and Tri-X, both).