For me, there's an "optimum" angle of around 135-160 deg (between forearm and upper arm) which is the best to maintain control and power, and straightening the arm beyond that just results in lost power and control. 

What angle between the forearm and upper arm do you guys use at the point of contact?

Why?

Firstly some of those pics actually reinforce my point, it's not 180 deg but about 160 to max 170 deg, you just selected camera angles that make it look straight. I'm not talking about the 90 deg bent arm looping that most European loopers prefer. The arm must have at least a small "V" shape. 

Another point is that these pictures are probably chosen at points where they're performing loop-kills and not loops during rallies (i.e. continuous looping)

I still maintain my point that extending your arm too straight (i.e. when u lose the "V" shape), will result in loss of power and control. 

Fingers not that hard heh, just relax and give your bat a little bump with your middle finger (if you're penhold) or index finger (if you're shakehand) for FH. For BH use your thumb to bump instead...

penhold grips are so complicated....

I have a pretty straight arm technique, and I can still use grippy rubbers equally well (I would say the performance in mid-range looping with grippy rubbers even exceed Chinese sticky rubbers), but unfortunately grippy rubbers suck in serving and short game which affects my game much more than looping... :( On BH it's another story though, coz we can use the new BH over-the-table loop to pretty much receive everything, there's no need for the "short game" there. 

I think penhold looks cool, stylish and unorthodox, which is a major + factor for me, if I could have started my TT training all over again, I would have gone for penhold instead of shakehand. 

In fact I can play penhold casually...it's just 3 levels below my shakehand play...

If you grew up on shakehand you would find the topspin on shakehand much easier than penhold heh...

Sadly it would take quite a few years to restart using penhold to get to the level I am at now, and there are many things that are so different between penhold and shakehand (esp the degree of pronation on the forearm on FHs), that just causes havoc when switching over. Also the BH "factor" is irreplaceable with penhold, I just get so much more speed, power and stability compared to RPB (which has a weakness in blocking IMO) and TPB. 

I use one of the slowest setups (you can see in my sig) for over 2-3 years of my development, so no chance for me developing a lazy game haha... 

+1 that was what i was talking about, 135-160 deg is about the optimum, so that you still maintain the V-shape

Actually the SH big boys use fingers just as much as the Penholders. It's just that it's not as obvious when looking at the stroke. Some of them will even let go of the thumb and index and use the pinky+ring finger. Look closely at some of those bat up, wild, side-spin strokes, that's what they are doing.

Another SH/PH shot heavily dependent on fingers, is the disguised float/underspin loop. Again, this explains why in some loop to loop rallies, one player puts the ball deep into the net then stares at his bat.

Then there is the down the line no-loop loop. Used a lot against defenders. The looper spins one deep. The next ball he fakes to loop but instead, the ball fades and even double bounces on the table. Loads of control from the thumb+fingers are necessary here to get it right.

I agree that SH users use a lot of fingers too, but it seems that it's way simpler than penhold, basically apply pressure using index finger for FH, thumb for BH. But pinky+ring is just to stabilise the blade, nothing more IMO, they serve as the "fulcrum" for the index/thumb. 

I'm not too sure how you do the disguise float/underspin loop, or the double bouncing fake loop. Could you show us a video where that happens?

The pinky + ring to stabilize the blade is the first level.  What is also possible is that you can actually get some extra torque and control from them if you do not let the handle sit in your palm, but let it sit in your fingers.   Again, I have big hands so this might not be something everyone can do, but I think that as you understand the theory of control and power and individualize your stroke, many things are possible and one should be wary of generalizations.  One could get a lighter set up so that the weight allows for fingers to add this element.  Timo Boll, as a common simple example, pushes on the forehand with his finger directly underneath his blade but does not do this for other forehand strokes.  A player at my club plays his forehand with his finger in this position (directly behind the blade) but changes it when he goes over to backhand strokes but does this finger on the racket face position more when he goes to all out forehand looping.  So just begin with the understanding of the basics, and try out things as you get better.

Notice how close they are to the table, thats when they will have more tense arms. The straight arm loop isn't used all the time. They will use it when they are off the table when they need more spin, like when they are on the run or when they have enough time like vs a chopper. But still there are some that use it more often and some that don't open up the arm all the way. 

the most important is your back, which generate power, and your leg which enhance power.

http://www.youtube.com/watch?feature=endscreen&v=qgqcQZ-NmpI&NR=1

Could also explain why a lot of people have problems with super hard, tacky rubbers. They use a very short arm when striking the ball.

I would say that the straight arm technique is very advanced, your footwork has to be marvelous to always be at the correct distance for a perfect arm extension. Your timing has to be perfect as well.

I tried using a straight arm loop for a while, paired with tacky hard rubbers. I gave up after about a year of trying. My friend, who uses a softer rubber, started seriously out playing me.

Yes my attacks were blazing fast but I had like a 60-70% shot percentage whereas he was more like 75%-85%.

The straight arm technique paired with a hard rubber was just too demanding. I no longer have access to cheap coaching and can only play about 6-8 hours a week.

I'd estimate it'll take me a good 3-4 years before my straight arm is consistent enough..

And let's be honest, straight arm + tacky vs bent arm + soft grippy really isn't going to make much of a difference when you're < 2000.

I believe straight arm + tacky merits consideration if you're young (under 15) and have access to good coaching..and are willing to spend the first few years doing 80% drills, 20% play. 

+1

 

This matches my experience for the most part.  The only thing I would say is that soft grippy doesn't mean you can't use a straight arm loop - in fact, my loop drive for third ball is Xu Xin straight arm.  It just throws me out of position if I don't end the point, and I don't think the energy expended is worth it.

http://www.youtube.com/watch?v=0TlD2qG5DMc&NR=1&feature=endscreen - http://www.youtube.com/watch?v=0TlD2qG5DMc&NR=1&feature=endscreen

especially at 0:22