EF 100-400mm f/4.5-5.6L IS USM or Extender EF 2x III

I recently purchased my first L lens, the 70-200 f4 IS. I love the image quality so far. My only negative is I wish I had more reach for field sports. I'm trying to decide between the 2x extender or a 100-400 f/4.5 - 5.6 L. Pros for the extender are cost and size / weight. What are the cons of going that route?

I'm a novice about this so apologize in advance if it's a dumb question.

A 2X on your 70-200 f/4 will put you at f/8 and most cameras will not AF at that setting.

Autofocus will be slower with the extender.

bob_r wrote in post #16734021
A 2X on your 70-200 f/4 will put you at f/8 and most cameras will not AF at that setting.

And even if they do, I think the will be limited to the center AF point.

If you need more reach on a regular basis get the longer lens. An extender costs you IQ, focus (or focus speed if you stick with the 1.4), and aperture.

bob_r wrote in post #16734021
A 2X on your 70-200 f/4 will put you at f/8 and most cameras will not AF at that setting.

So, would the 1.4X put me at f/5.6? If so, would a 60D autofocus at that setting?

IlliniFan99 wrote in post #16734042
So, would the 1.4X put me at f/5.6? If so, would a 60D autofocus at that setting?

Yes, but not as quickly as it would without the extender.

Yes it can focus at f5.6 but the AF will be slowed down by 50%.

Illinifan, where are you located?

IlliniFan99 wrote in post #16734042
So, would the 1.4X put me at f/5.6? If so, would a 60D autofocus at that setting?

The 70-200/4L IS with a 1.4x TC on a 60D (for 98-280/5.6)... AF works great. Barely any reduction in speed..or accuracy. It's a nice combo.

That said, 280 is still kind of short for wildlife and birds(and big field sports).

gonzogolf wrote in post #16734068
Illinifan, where are you located?

The Dallas area.

Why?

IlliniFan99 wrote in post #16734257
The Dallas area.

Why?

I thought if you were in Illini-land I could let you try the 700-200 with the 1.4 and the 100-400 to see which you might prefer, but Dallas is a bit far away.

gonzogolf wrote in post #16734276
I thought if you were in Illini-land I could let you try the 700-200 with the 1.4 and the 100-400 to see which you might prefer, but Dallas is a bit far away.

It is.

Appreciate you thinking of me however.

Your dilemma is the same one I went through last year: loved the f4 IS but found it a bit short for the sport I photograph.

I tried it with a 1.4 extender (as others have said, you lose AF with the 2x), and while it worked fairly well, the extender did slow down the AF somewhat. I came to the conclusion that I was going to need a different lens. One of the things I really liked about the f4 IS was its size and weight, so the 100-400 was a bit of a stretch for me; I'd already sold a 70-200 f2.8 because I hated carrying it around. So I rented the much smaller 70-300L ... and was blown away by the quality. The extra 100 mm was enough for my needs, and the lens was only slightly heavier than the f4 IS.

I dithered for several months, but in the end I got a once-in-a-lifetime deal on a used 70-300L, so I bit the bullet and sold my f4 IS. It was a wrench to see it go, but I haven't regretted getting the 70-300L; it's an outstanding lens, lightning-fast AF, terrific image quality.

Bottom line: if your f4 IS is often too short, you're probably going to be better off with a different lens. An extender is fine for occasional use, but not, IMHO, as a regular solution.

I've had pretty good luck with 1.4tc, but the 2x often look quite soft. As others notes, focus is slower and you'll be at f8. 100-400 is a wonderful lens. If you buy a good used unit, you will get close to 100% value back if you re-sell.