Dear Benjamin,
Scotty Cameron believes that the optimal putter loft is 4 degrees. His process of arriving at this conclusion is to study the depression that the ball initially rests in at address on the surface and to use high-speed cameras to observe how the ball comes out of the depression, depending upon different lofts at impact. His conclusion from this process is that 4 degrees is the best. His Studio putters all come standard at 4 degrees loft, 71 degrees lie, and 35 inches. See
Studio design specs. Here is
his explanation of the process. Here is a picture of the mat in the Scotty Cameron studio, where these studies are performed:
I don't think Scotty's process is exactly correct. As I understand his studio work, he uses an artificial carpet that has a speed equivalent to about a Stimp 15 green. This is not the same sort of "depression" that golf balls really rest in on real greens. The density of the artificial fabric / material is more than the density of grass blades on a fast green, the structure and resilience of the artificial material is stiffer than grass blades, and the subsurface is not earth or turf but more artificial material. These differences mean that the studio "depression" is more uniform, probably deeper, and with stiffer sides than found on a real green. In Scotty's studies, he finds that too little loft is not sufficient to get the ball out of the "depression" without some loss of distance and perhaps line. He says:
"With not enough loft the ball doesn’t clear the edge of the depression, causing a loss of speed and direction. With too much loft the ball launches and has a greater chance of being misdirected." So at the too-little-loft end of the issue, the character of the "depression" is critical. Unless you actually run tests on real greens and correlate the loft with real "depressions", the findings don't mean much.
No one diagrees that too much loft is bad. The issue is how little loft can you get away with.
According to Dr Norman Lindsay, who is in my view the top scientist studying these issues, MINIMAL loft is the goal. He writes:
"Some loft is necessary to lift the ball at impact, particularly on slow greens. But loft generates backspin and raises the sweet spot, so choose a putter with the minimum loft that suits you. As well as imparting topspin, vertical gear effect lifts the ball slightly so less loft is required." Notice his recognition of the need for different loft on different speed greens ("particularly on slow greens"). In addition, one impact feature that he stresses is "oblique impact" for less backspin and more forward roll at the start:
"Gradual loft reduction (face roll) can be used on the bottom of the putter-face to introduce a small amount of negative loft. This generates topspin by oblique impact, even though the ball is hit on the upswing on this part of the putter-face. This arrangement is especially beneficial for length control on long putts."
According to this, then, an "oblique impact" with a little negative loft is OK on real greens today, so long as the greens are not shaggy. Actually, Dr Lindsay prefers impact HIGH on the putter face, where there is some minimal positive loft, as this promotes "gear effect" to reduce back spin and promote forward roll. So his recommendation is for MINIMAL POSITIVE loft at impact for putters with low and recessed centers of gravity on normal greens today.
All this assumes that design loft and dynamic loft are the same -- that is, that the sort of handling of the putter thru impact doesn't significantly alter the loft presentation of the putter face to the ball thru impact by adding or subtracting loft. Golfers who forward press at the beginning or who have a "hands ahead" style of stroke or who use goose-neck putters with the hosel leading the putter face thru impact or who use certain setups that shift the bottom of their stroke targetward off the center of the body all have some delofting thru impact that takes away from the design loft. In contrast, a golfer who simply "putts the bottom" in the middle of his stance with a neutral, symmetrical action of the stroke, playing the ball slightly ahead of the bottom of the stroke, with a neutral setup and a putter with the hosel close to the putter face edge, presents the design loft "as is" at the exact bottom of the stroke, and as the putter face moves forward into the back of the ball, the natural rising / arcing of the putter head past the bottom will add a little dynamic loft. The farther forward beynd the bottom of the stroke that the ball is positioned, the more loft at impact is increased.
If the issue is adjusting the design loft with the player's dynamic loft to the green speeds usually played to optimize performance, the analytical process would start with the typical greens and then proceed to an understanding of the golfer's stroke dynamics, and only then move to the issue of design loft. In my experience, on most greens today (i.e., good clubs with greens usually Stimping around 9-10), 4 degrees loft is not the minimum, and something closer to 2 degrees is fine. If the golfer presents 2 degrees to the ball on a Stimp 9-10 green, the ball gets out of a real depression just fine.
Incidentally, if a golfer with minimal design loft has a concern about the sufficiency of loft when he might play a slow green, with a deeper initial depression, he can still use the minimal looft simply by playing the ball a little farther forward in the stance. This only works correctly, though, if you have a straight stroke thru impact, and not a gating stroke path.
What I suspect may really be involved with cotty Cameron's 4-degree design is a marketing choice to make putters that can be used by a wide variety of golfers, especially those who have been taught to use a forward press or a hands-ahead stroke style. Unfortunately, the "market" of average golfers drives the design process. For professionals, the whole process is one of fitting the optimal loft in their game, on their greens, their putter choice, and their stroke styles. Wanna bet that pros don't really end up with a custom-fitted Scotty Cameron putter with 4 degrees of loft, or if they do, that they are as good at putting as they could be with less loft?
Cheers!
Geoff Mangum
Putting Theorist and Instructor
Geoff Mangum's PuttingZone
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