Which is better?
This image shows a comparison between the older short trigger on the right, and the newer taller trigger on the left. Both are in Iwata CM-SB airbrushes.
If you've searched for upgrades for your airbrush, by now you might have noticed that some companies are selling a "tall trigger upgrade." There's a lot of reasons why this might sound like a good idea.
First of all, a taller trigger gives you a greater mechanical advantage, or "leverage." In other words, you can pull the needle backwards with more force with a taller trigger.
Secondly, a taller trigger travels further to move the needle, which creates more distance or "throw" to control the paint. In theory, a greater degree of throw means a higher number of incremental movements for the needle resulting in more precision.
However, there are two problems with this. One, extra force is not necessary when operating an airbrush trigger. There is no need to have more force, because the airbrush needle is easily moved. The down side is that when the trigger is taller, more trigger travel is required to move the needle, which requires more work. The bigger problem is that further movement of the trigger requires additional muscles to move it. Almost all of these muscles are found in the forearm, using gross motor movement because they are used to extend the finger, rather than close the finger.
The image above shows movement associated with a taller trigger. Although creating detail doesn't require this much movement, the muscles used with this finger position require muscles located on the forearm which are connected to the finger by long tendons.
Instead of using a taller trigger, what if we used a shorter trigger? With a shorter throw, less work is required, and the fingertip can be utilized to control the airbrush rather than the forearm muscle. The fingertip is controlled by muscles in the palm and use a much more precise fine motor movement.
A different finger position is possible with the shorter trigger. If the first joint of the index finger is placed over the trigger, then the tip of the finger can pivot up and down to move the needle back and forth with much greater precision than the forearm muscles.
The concept of short throw is not new. Many race cars use short throw shifters for greater efficiency when shifting. The shorter trigger enjoys greater efficiency of movement, and more control of the airbrush when held in the position above.
Click here for an excerpt from Dru Blair's Skull video, where he discusses finger position.