Quote - Ok, but what is bucket size, and why is it important?

This is to the best of my understanding;  I invite and encourage correction as needed.

As a means of budgeting memory usage, Poser renders small pieces of an image and eventually completes a mosaic of these little square pieces.

Bucket size refers to the pixel dimensions of that piece.  It is always square, and it is best if it is an integer power of 2, such as 8x8, 16x16, 32x32, or 64x64.

Because Firefly also looks at pixels bordering the bucket at hand, Poser will render at its quickest if the bucket size is large enough to make full use of available capacity, but if you use too large a bucket size and exceed the computer's capacity, the render engine will crash.

So, the the trick is to use the largest bucket size which doesn't exceed your computer's capacity.  This will be different for the same scene, if rendered on two computers with greatly different amounts of RAM.  It will differ between two scenes of different complexity.  It will change for the same scene if you crank up the render quality settings.

Poser 12, in feet.  

OSes:  Win7Prox64, Win7Ultx64

Silo Pro 2.5.6 64bit, Vue Infinite 2014.7, Genetica 4.0 Studio, UV Mapper Pro, UV Layout Pro, PhotoImpact X3, GIF Animator 5