Bob, I would not get to hung up on if you are shooting at 1.5:1 or 1:1. Just know that when compared to a full frame camera even though you are technically shooting at 1:1 your image would appear to be shot at 1.5:1. But really that makes little difference, most macro shooters are going to crop their images anyway so that they can display their subject as large as they can while preserving image quality... so in the end the question you are posing is not really very significant. The lens that you are asking about is going to preform as well as any macro lens out there so the question is purely academic as unless you change over to something like Canon and purchase a MP-E 65 that goes up to 5:1 mag, but as it is 1:1 is all the magnification that your going to get out of a conventional lens on your camera.

There are other things that you can do to increase magnification beyond the 1:1 ratio such as by adding extension tubes, or purchasing filters which will magnify your image... or in my case I use wide angle lenses mounted backwards to my camera.... But as far as aspect ratio it is really something that you should not get to hung up on... too many people think far too hard about the difference between aspect ratios on a full frame and a crop sensor camera. What is important is understanding the camera that you have.

Actually you are wrong, it is all about magnification, 1:1 does refer to magnification as it means that the image is projected onto the film or sensor plane at life size or 1X... most lenses have a magnification ratio significantly smaller than 1:1 in fact many zoom lenses that advertise themselves as having macro capabilities don't even come close to macro, they are closeup lenses that have magnifications somewhere in the range of 0.2:1 or 1/5th lifesize onto the sensor.

For most macro shooters magnification is very important, macro is about seeing in detail things that you would not be able to see with your naked eye....

Below I am attaching two photos to demonstrate what I am talking about, the first photo is shot at 1:1 as the very small jumping spider is next to a dime, not a quarter but a dime....

The second photo of the same spider was shot at about 4:1.. Not great photos but they demonstrate my point, this was one of my very early attempts at reversed lens and even worse I had accidentally killed that spider when chilling it to slow it down.... The third photo is of bee shot at 3:1, I think that high magnification macro is more interesting than just close ups. Close ups of flowers can be very rewarding, but when you get into bugs you want to see the eyes and other detail that a close up will not provide.