Again, I don't do a lot of macro work so if I'm missing the big picture, please forgive me. I do understand that these lenses are not really macro, but rather are just closer focusing lenses due to the level of close focus they can do.
I get that you get the best magnification/focus ratio at the longest focal length. Do you always in every case want the maximum magnification? Wouldn't it be limiting for closer work if you only had the option of 1:1 focusing?
In other words, with the lens in question (vivitar 35-105mm 3.2-4). As it came from the factory, it only has the extra focus range at 105mm (when you zoom to 105mm, you can then turn the focusing collar further than you can at all other focal lengths). It is limited by an L shaped bar in the lens (at 105mm, a tab on the focusing collar gets past that bar so that the focusing ring can turn into the additional close focus range). If you remove that L bar which I did, You still have identical close focus operation at 105mm (nothing in the way the lens actually functions has changed). With the bar removed though, you have improved close focus at all focal ranges as the lens can now focus into that extra range at all focal distances. Sure it may not be macro or even a lot of extra magnification/close focus at the shorter focal lengths, but its still improved close focus. Why put that limiting bar there in the first place. You are unnecessarily limiting the close focus abilities of the lens.
Did I explain that well enough or did I just confuse the issue more?
Edit:, I was thinking that perhaps the lens wasn't designed to focus close at shorter focal lengths, but based on the photos I took, that wouldn't seem to be the case. The middle photo is at 35mm with it at the closest focus (in the extra macro range). Perhaps its a flat field issue, which I at first didn't think of, but flat field or not, wouldn't the extra close focus be of benefit at all ranges in some circumstances?
http://public.fotki.com/ripit2/marco-limiter-removed/