Fax film as it was called is far from a poor mans profilometer. It is a way to get a three dimensional representation of the cylinder surface. Profilometer reading are two dimensional, being pulled from a straight line contact and making inferences from there. If you are really serious about cylinder bore surface work you would do both because each shows a different range of characteristics.David Redszus wrote: There is a little trick that might be useful to the amateur engine builder to help visualize and inspect the honed surface.
First hone the cylinder using what ever techniques or process you like. Wash the honed surface throughly to remove all oil and loose metal particles from the surface and grooves. Obtain a 2 to 3 in square of acetate film and a small can of acetone from the hardware store. Paint the honed surface with a liberal amount of the acetone and while still wet, apply the acetate film and hold firmly in place against the cylinder wall for about 2 minutes.
The acetone will dissolve the acetate and will form a casting of the honed surface which can be viewed under a microscope using a side light. The shapes of the plateaued islands, the grooves and the micro grooves on top of the islands will be clearly visible. I call it the poor man's (that includes virtually all racers) profilometer and its a great way to visually compare various honed surfaces.
Fortunately, as in many things, the laws of "good enough" apply to this stuff. If you stay within the range of accepted industry practice you do not often get into too much trouble. When you decide to stray far afield in search of opportunity you may sometimes discover that going out of the proverbial box only demonstrates the reason that the "box" came to exist in the first place. Risk and reward stuff...