Hmmm... the first black horse is not in a superframe - he is behind the vertical, if only slightly. So is the chestnut in the low frame. I know that things are different everywhere, but my trainer would shoot me for either of these frames. The horse must always be seen to stretch his neck out from the shoulders towards the hand. If he is behind the vertical, he is showing that he lacks confidence in the hand.
What you want is a telescoping gesture - like this very green horse just learning to lift his back by stretching his neck: http://www.blueberryhill.dk/index.ph...ask=view&id=64
As the horse becomes more collected, he will lower his hind end by "sitting" in the transitions - and as the hind end lowers, the front end will come up. But always the neck must stretch towards the hand and always there is the telescoping gesture.
In the end, there is no correct frame. The famous German riding master Müseler knew this, and in his book he put a "picture of the perfect frame" - which was an empty square
The correct frame is the one which allows the horse to carry his rider without injury or stress at whatever schooling level that horse is at. The frame can be anything from long and low to Grand Prix collected. But the nose will never come behind the vertical if the horse is ridden correctly.
"On the bridle" and "on the bit" are unfortunate expressions which have been invented in later years in an attempt to create a multi purpose translation of various expressions in German and French meaning that the horse accepts the rein aid, is obedient and calm.
When the horse accepts the rein aid and is obedient and calm, he will flex his poll of his own volition. But flexing the poll does not make the horse accept the rein aid, or become obedient or calm. This is the unfortunate misunderstanding which leads to rough and uneducated solutions like simultaneous pulling on the reins and pushing with the leg.
Holding on to the outside rein and pulling on the inside will flex the poll as the horse will have nowhere else to go But then that has nothing to do with dressage - that's just plain force.
Sorry to butt in. Couldn't help myself.