Beyond feel &amp; experience, is there a rule conductors use for ritardando in terms of  (a) its rate, (b) its change in rate, and/or (c) the relationship between the final tempo and the tempo of the piece?

(In getting my software to execute a ritardando, I employed over four measures a measure-by-measure decrease in tempo, and what sounded "right" to me ultimately was decreasing the tempo by 4 bpm, then a further 9, then a further 16 (pleasing pattern) to arrive at 127/156 (close to 3/4) the original tempo.)




Question: How to make a photo background fully white?
Answer: You don't do it in Photoshop. You start in the "studio". 

This website explains a lot of jewelry photography. 


  When photographing pearls, by using only one light source positioned above, the pearls will appear rounder with more dimension.


Assuming you don't want to photograph pearls, take with you that they are using a single light on top, with a lightbox all around it. If you don't have a flash with a diffuser slightly larger than your subject, you could use some other lamp. If you don't have a lightbox, you could buy one (cheap), or you can use some white paper to reflect the light onto the subject.

Use a white acrylic sheet as your surface. (Or paper). Adjust your exposure so that the background is already almost overexposed.