2017 Update: It is hard to believe I have been using this ball head for 7 years and has served me trouble free. It has been a great buy! Quality wise is in line with RRS products, this ball head is well made and engineered.
I had originally purchased a Gitzo head for my macro photography work but I was disappointed with the Gitzo due to the quick release and how the camera would slowly slide while rotated to portrait mode and so, I broke down and switched to the Acratech GP-s Ballhead. May I say that this is one of the finest heads and the Acratech website offers splendid videos and tutorials on its use along with their other accessories. I do recommend this head if you have moderate capacity weight requirements, DSLRs with normal to medium telephotos are no problem for this head.
The Good: Precision Quality Machine Work. Has three knobs to allow fine adjustments and correct tension. Holds your camera snug and firm. Easy to use and work with. Their video explains and demonstrates using the tensioner knob, which after watching the video I said – oh that is what it's for. The tensioner allows you to dial in a correct amount of drag to prevent your camera from flopping around when you loosen the main knob. Thus if you are using camera and lens combination but don't want it "LOOSE" when you reposition, then simply adjust the tensioner to get the right drag, hard to explain quickly mastered, link below.
This head allows a wide range of positions and angles with large rubbery knobs for adjustments. If you are into panoramas as well the head allows for that and can be re-arranged to perform as a pan head, simply use a tool to take the top off and mount the head upside down, instant pan head. It also employs a leveling bubble in the design.
The head offers various quick release types for Arcaswiss, as well as “lens” mounts. I encourage you to check out the Acratech Web Site for all the additional accessories and other heads.
Other Notes: In the field, this head works great and I am very satisfied with its performance. For anyone with large hands you may find the knobs a bit small but nothing serious. The ball head is secure and can easily carry my D810 and 200mm f4.
Out of 10 stars, this is a solid 9
Thanks for stopping by the site, The TrueToad