How to keep the elbow up

 just thinking out loud with young students where they generaly have their elbow high and I will try and sort them out with getting them to start their backhand from their belly button outwards and use thier feet to help them pick their target area, so down the line backhand will be more square on and to the backhand corner right leg back abit (just talking about general rally here) so their body faces the direction they are hitting to

 if you are blocking and punch blocking then your elbow is lower anyway (or should be)

I would just think about from where you bat starts from first

If you are doing the banana against the short serve or maybe doing a more powerful shot from back a bit then a bit of a high and point foreward elbow is needed

So It really depends on where your elbow is and what shot you are trying to acheive and what is coming to you

I agree try figure out understand what and how you want to do it. Shadow swing 300 times using a mirror and then go to the table and let you subconscious take over. 

I meant "bad backhands".  What I mean by circular around the elbow is that if you hold your hand with a 90 degree angle at the elbow, you should be able to do your backhand mostly by keeping the 90 degree angle the same and turning your upper arm around in a circle.  The angle doesn't have to be 90 degrees, but the circlular motion of the upper arm is key.  Many people who don't realize this confuse the backhand stroke with forehand stroke, where the dominant use of the elbow is mostly as a lever.

The elbow height is relative to the ball - it has little to do with over the table vs past the end.  What you need is to give your racket a chance to accelerate into the ball and giving your elbow a good distance from your body allows you to use it as a good moment arm.  Some people do have the power to generate good racket speed with mostly the wrist, but it is not common.  What you need is to stick the elbow out so that you can whip your wrist and racket into the ball as you turn your upper arm around - this allows you accelerate into the ball.  For the Henzell video, look very closely at what he is doing between 1:25 and 1:40.   It is more circular than forward.  The contrast is between 2:15 and 2:24.  (BTW, if this video has a flaw, it is that it doesn't stress the proper use of the upper arm and elbow).

If you are a TTEdge member, you can see Henzell's take on the sidespin flick and it is very similar to the backhand topspin vs. block so you will realize that the elbow position is more relative to the ball position to allow for acceleration and not so much about whether the ball is on or off the table.

Thanks that helps a lot especially the video I will try to focus more on pointers given.

Elbow position changes based on the shot I think for top spin balls you would need to have higher elbow position. The general concept is to keep the elbow up some and not next to the body to help generate power.