Canon 300mm and 2x telconverter. Help

I just rented a Canon 300mm 2.8 IS and a Canon 2x teleconverter to experiment a little. I was very disapointed. The pictures are going to the trash because they are all fuzzy.
I had to take the rentals back so this morning I set up a port bottle (full so I would not skew the outcome)and took pictures of it from approx. 25 feet. The 300mm shots were good and I tried the 300 with a 1.4X and it was reasonable but the 2x combined were really fuzzy. I used the 2x with my 100-400 and it was good.
FYI the set-up was
No IS
Mirror lock-up with a 10 second delay before remote shutter release.
My questions are. Is this normal with this lense?
and
Should I be thinking about a 500mm with a 2X or will this be the same story?
Rick T

Something's not right, Richard. That combo typically produces images with some degradation in IQ compared with the straight 300 and 300/1.4 TC, but not as bad as you indicate. I've seen excellent images with the 2 TC on both the 300 and 500.

Ithought so Steve but I can't figure out what. I was careful to set up all the tests the same ???
Rick T

Richard,,,,I have the 500 f4 IS and prefer the 1.4x. The 2x isn't as sharp but still gets an acceptable image.

Ithought so Steve but I can't figure out what. I was careful to set up all the tests the same ???
Rick T

Hey, Richard. I routinely use the 300mm f/2.8 with the 2x on a 40D or 30D body for bird photography (til I can afford the 500mm IS!) with often excellent results. Of course focusing is slower with the 2x, but with practice you should be getting sharp images. I even occasionally use this setup hand held (and you know how heavy that is) with good results.

You didn't say what body you're using. That may make a difference...Gail

Gail
I was using a 40D and had good results with my 100-400mm ???
RT

No way should a 1-4 with the 2X outperform a 300 IS with a 2X. I believe the latter combination has been said to rival the 600 IS by itself. That I can't swear to, but I have gotten many excellent shots with the 300/2X. I would not use a remote release, would use IS. I assume your 2X is a 2X II, and suspect the problem is the rental lens.

Gail
I was using a 40D and had good results with my 100-400mm ???
RT

Richard
I also have used the 100-400 extensively for bird photos (without the 2X) and the results were never as crisp as the 300 WITH the 2X. The 300 f/2.8 IS really is an excellent lens. As Cliff suggested, the problem may be the rental lens. Perhaps you can try a different 300 f/2.8 rental on your 40D and compare. That way you'll know for sure...
Gail

Cliff. What is a 2X II ?
Also the 300mm worked fine on its own but no better than the 100-400. I turned off IS because it was dead still on a tripod.
RT

Richard, the II is simply the updated/upgraded version of the 2X. The 300mm on its own should be sharper than your 100-400.

Thanks Steve. My results were that they were about the same at 300mm.
RT

Hi Richard,

I have the 300 f2.8 and both Canon tele-converters. The sharpness of the lens is excellent with no loss of image quality at all with the 1.4xTC. I often have to check the EXIF data to confirm that I was using the 2xTC because I can't tell by looking at the image. Your rental equipment must have been faulty.

BTW, I always have the IS turned on, in mode 2, on the tripod.

Thanks Buck
That is encouraging. I think I need to try a different rental place.
I would use IS for ll for panning but if there is no movement I think it is better to go with no IS.
RT

Rick, did you try Photo Service or Lozeau? Photo Service has many more lens selections to rent from.