Just for the record I really appreciate Todd's comments since he's used the product. I also really like the IS. I see a lot of guys use regular optics and tripods and they know more than me I'm sure but if they haven't used both side by side and money wasn't the issue then it's not really a good comparison...
Thanks you sir, As I stated there is better glass out there. The Canon glass is still quite respectable as Canon is responsible for much of the movies we watch and photography we look at. The IS feature just makes them more user friendly than anything else out there.
My hunting style made them the go to glass for me. If I was static hunting a couple thousand acres I might run some German non IS glass. However I glassed probably 30+ SECTIONS a day and often put over 250 miles a day on my truck. Drive to a high spot and glass from a county road. Repeat. All day for months on end. The speed with which you can glass using IS in that scenario is unbeatable. By the time my customer had his Leica, Zeiss or Kowas on the window mount or tripod, I was already sticking the truck in gear and heading to the next high point.
The original question was if you could see a deers head in shade at 1.5 miles and would the IS 18x50 be capable. Since I have done this hundreds of times I answered yes.
I have probably not seen tens of thousands of deer that were bedded in the shade in areas I glassed. Whether you see something or not doesn't mean it wasn't there.
Seeing anything n the shade at 1.5 miles is going to be very dependent on THOUSANDS of factors.
How clear is the air? After a good rain and with no mirage it can more than DOUBLE glassing efficiency no matter the glass used.
How big is the rack and what color is it?
What color is the background?
Is the head moving at all?
Is the mirage like the Sahara desert?
Lots of factors effect how well you can glass and whether you will see something.
To me 1.5 miles is CLOSE RANGE glassing. I regularly glass up to 10 miles away or more on wheat fields. It is very important for me to be able to cover MASSIVE amounts of ground. IS is superior to any tripod mounted system on the planet for that job.
Most of what you can see at over 1 mile is more affected by atmospheric conditions than whether your glass is German, Japanese or even from the Phillipines.
A set of German high power binos or slaved spotters will be CLEARER than the Canons. 50% of the time you won't be able to use the increased German clarity due to atmospherics. The other 50% of the time you will still see more game with the Canons because of the speed of the system.
Just my real world experience using hundreds of different high end glassing systems for a living. They are not the standard choice for most guides as they aren't 100% waterproof and aren't as bulletproof as a set of Leicas. Put two guys on a high point with a set of IS and tripod mounted stuff and the IS guy will do just fine.
All glass is a COMPROMISE. Canons IS were just the best compromise for me. I ran them most of the time but had a set of German 8-15 binos at all times, as well as various spotters and several sets of bigeye binos and slaved spotters.
Most of the time if you couldn't see it with the Canons, the conditions weren't good enough to see it with anything.