Superzoom and extenders

I am ready to get a longer/wider lens for my birdwatching than 400mm f/5.6.

Now, since I do general photography, too, it would be really nice if I could use a e.g. 300mm f/2.8 with extenders to get to 420 and 600mm. I own the Mk III versions of both the 1.4 and the 2.0x. I know that I like the picture quality well enough on my 200 f/2.8 prime and the 70-200 iS2.

However... I don't like what the extenders do to the autofocus speed. The 2.0x extender in particular is terrible in that it often lets the lens search in the wrong direction first. I originally attributed this to being at f/5.6 max but I have been told it would be a lot better with a native 400mm f/5.6.

What would the situation be like with the 300 f/2.8? Anybody using that for birds?

Due to the way my gear is packed and transported I don't have a problem with the new toy being as heavy as it wants to but it would be nice if the thing wasn't too long, after removing whatever you can remove. I suppose that is precisely why Canon made the 400mm DO, is it? Would a 400mm DO + 1.4x be substantially better with AF than the 300 f/2.8 + 2.0x?

I am a great fan of the 400 DO but (from my trials of 3 of them) I don't rate it with extenders. As a bare lens the examples I have tried showed very good sharpness and excellent resolution - so if you want 400mm then it's great but if you want 560mm it is so so and if you want 800mm it's record shots only. On the other hand I get very good IQ with my 300 F2.8 L IS Mk1 + 2 x Mk3 extender (though you need reasonable light) but I agree the AF is not exactly sprightly, though it is almost invariably accurate (1D4/1DX). Using the focus limiter and pre focusing can reduce this but it won't be fast.
I have used the Canon 400 F5.6 and own the Canon 800 F5.6 lenses and the both focus much faster than a Canon 300 F2.8 lens with a 2 x extender. However they don't really function that well when you add extenders to these F5.6 lenses.
The bottom line is that if you need xxx mm then go for that lens (if you can!) resorting to extenders is always a compromise, but it can be much cheaper!
I have been very pleased with the Canon 300 F2.8 L IS Mk1 + 2 x Mk3 (not Mk2) extender but it is a compromise and you have to work within it's limitations, but the results can be very good.

uOpt wrote in post #16865661
I am ready to get a longer/wider lens for my birdwatching than 400mm f/5.6.

Now, since I do general photography, too, it would be really nice if I could use a e.g. 300mm f/2.8 with extenders to get to 420 and 600mm. I own the Mk III versions of both the 1.4 and the 2.0x. I know that I like the picture quality well enough on my 200 f/2.8 prime and the 70-200 iS2.

However... I don't like what the extenders do to the autofocus speed. The 2.0x extender in particular is terrible in that it often lets the lens search in the wrong direction first. I originally attributed this to being at f/5.6 max but I have been told it would be a lot better with a native 400mm f/5.6.

What would the situation be like with the 300 f/2.8? Anybody using that for birds?

Due to the way my gear is packed and transported I don't have a problem with the new toy being as heavy as it wants to but it would be nice if the thing wasn't too long, after removing whatever you can remove. I suppose that is precisely why Canon made the 400mm DO, is it? Would a 400mm DO + 1.4x be substantially better with AF than the 300 f/2.8 + 2.0x?

You don't say what camera you have, that can make all of the difference in the world.
The Canon 5DIII and the 1D series (all) are the only ones that can really make the extenders work like they were designed to. Not that the extenders don't slow the focus, it does, but on my 1DmkIV and my Canon 400mm 2.8 IS lens, I leave on my Canon 1.4mkIII extender. It's not bad at all, and, I can more times than not, pixel peep if I want, it's that good. (I almost always use all of my shots viewing at 100%, cropped maybe some, but not reduced in size) I have had really good results using my Canon 2.0mkIII extender too, but there's no way that I would leave that on all of the time. I usually reserve that to a documentary shot, but I'm usually surprised at the detail I get when I do use it. There is no way that I would use my 2.0 for BiF though, but, I always use my 1.4 for that.
Also, I have never used a Canon 1.4 or 2.0 mkII version of the extenders, I had the Kenko 1.4 and 2.0 before. I was happy enough, but there is a slight edge over the two brands, in my belief. I did try to use a Kenko 1.4 and 2.0 on my older Canon Xsi and my T2i, I never tried again, it sucked so bad that I put them up until I finally saved and got my 1DmkIV and 400mm 2.8...

If you have ANY other camera other than the above, I would sure borrow or rent an extender before you buy. I can't really remember anyone on this forum that was happy using them on other cameras. If you use them on a lot of cameras for a static shot, then, and only then will you probably be satisfied. That's the way I see it anyway, this has been a thing here for a lot time, and it will always be a "thing", because nobody wants to spend a LOT on a big giant lens that is capable.

Randy

I have the 300mm f/2.8 IS II and use it, together with the 1.4x and 2x TC IIIs regularly for birds. The prime lens is outstanding. The lens plus 1.4x TC is just like having a 420mm f/4 prime (AF speed and IQ aren't affected) and the lens + 2x TC loses a little AF speed plus a very slight drop in IQ. I do mean very slight, you'd need to compare 100% crops against a 600mm prime to see it. As pointed out above, choice of camera is important, I use the above combinations either with my 1Dx, 1DIV or 5DIII, all of which work very well together. That's not to say that if you have, say, a 7D, you couldn't get great results as well. An example of 5d III + 300mm + 2x TC III below. Note that this is also an 85% crop and was taken handheld using the IS stage III (which activates IS at the point of pressing the shutter button):

I plan to use the 7d and have a 5d2. I used a 1d2 with my existing lenses and extenders and it did not do better than the 7d.

I'm somewhat confused by your thread title. You called this thread "Superzooms & Extenders", yet all of your questions seem to be about prime lenses, not superzooms (although you do mention that you have a 70-200).

Did you have any questions about superzooms that you simply forgot to ask when you wrote the thread?

Oops.

Ok, I know my lens is not a superzoom, but I can speak to the extender part of the subject. I use a 2x III with a 70-200 II. I like the IQ, but the AF is not good. I use it for birds that are setting. If your focus is fairly close to the previous AF setting, then the focus is fairly fast. However, if you move from a close to a distant subject, it might be 2 to 5 seconds before it finds focus.
The focus is a big compromise with the 2x.
Once it locks on, I am liking the result, so I live with it. Tamron 150-600 is on order. Then the 2x will probably be for sale.
I use it on a 7D.

I got this Sapsucker fairly high in the tree with the 2x.

IMAGE LINK: https://flic.kr/p/mAGZ​4D

I have 70-200 with the extenders. AF speed sucks at least with 2.0x.

Just trying to find out whether the the superteles (sorry can't correct thread title) would be better.

Tom Reichner wrote in post #16880083
I'm somewhat confused by your thread title. You called this thread "Superzooms & Extenders", yet all of your questions seem to be about prime lenses, not superzooms (although you do mention that you have a 70-200).

Did you have any questions about superzooms that you simply forgot to ask when you wrote the thread?

I think he meant supertelephotos.

I was using a 2x mk3 with my 70-200 f2.8 mk2. I found the autofocus ok but I did tend to prefocus so there wasn't too much work to do if possible. I have very recently bought a 300 f2.8 mk2 which is an awesome lens. The af with the 2x seems better than with the 70-200 but i am still in the early days of using the new kit. I will probably invest in the 1.4x mk3 soon and expect that will be better for e.g. bif where af speed is critical. IQ is excellent even with the 2x.