ok so i bought the 70-300L IS USM and i love it! but now im wishing i had more distance! so stick with the 70-300 or go the 100-400? ive heard the quality and sharpness is less in the 100-400 and obviously you cant go any lower than 100mm but you get the extra 100mm and can be used with the 1.4 extender! grrrr im so torn between the 2  

Well, the 100-400 can get quite soft at the long end so in many situations I never felt comfortable going over 300. The IS system on the 70-300 is far superior allowing you to use it comfortably in less light. I never had much success with TCs on the 100-400. You need a lot of light and not sure about the 1.4 but with the 2x you lose AF.

I'd stick with the 70-300L.

I'm not advocating jumping ship from the 70-300L per se, but I have shot with my 100-400 on bodies ranging from entry-level Rebels up to a 7D now, and while it is no EF 400mm F2.8, I have never hesitated to zoom out all the way out to 400mm for a shot. Assuming you have it stopped down a bit (F7.1-F9) it has always done just fine for me. I know some people have had issues like crazy with their copies, and I was one of them for a while, but after micro-adjusting the AF, I was golden.

I have heard the 70-300L is quite nice however. Don't bother with converters on the 100-400, it's a lost cause. You're better off getting a EF 400mm F5.6 and cropping at that point, which I did when the 100-400 was misbehaving, although I rarely use it nowadays

N Peterman

Quoting NPeterman (Reply 2): Assuming you have it stopped down a bit (F7.1-F9) it has always done just fine for me.

Same here - worked wonders for me. I feel as though my copy is good but it also comes down to atmospheric conditions.

Ask yourself how much you shoot in the 70-100mm range and if you'd benefit more from having either the 30mm at the wide end or 100mm at the tele end.

Quoting NZ107 (Reply 3): Ask yourself how much you shoot in the 70-100mm range and if you'd benefit more from having either the 30mm at the wide end or 100mm at the tele end.

Agreed. But also keep in mind that a 30mm difference between 70 and 100 is a magnification factor of 1.43, while a 100mm difference between 300 and 400 is a magnification factor of 1.33. So 30mm at the short end makes more of a difference, zoom-wise, than 100mm at the long end, though it's pretty close. Ultimately it's up to you and what you need.

Wait, just to check, you have the 70-300 IS USM, or the 70-300 L IS USM? I ask because I read your post wrongly the first time.

Quoting vikkyvik (Reply 4): Wait, just to check, you have the 70-300 IS USM, or the 70-300 L IS USM? I ask because I read your post wrongly the first time.

The white one  

Yes the white one :P the L series

Been to manchester today and im sticking to the 70-300. even at 70 i couldnt fit some of the big uns in.

Chris,

Hope MAN was up to expectations. Next time you need to do a weekday as it will be busier!

The images certainly looked sharp on your preview screen, but feel free to send a few over.

Karl

Thanks Karl i loved every minute of it. busy compared to what im used to and such a variety. will defo be up there very soon again.