Extender Question

I just got a 70-300 f/4-5.6 L IS USM without doing my research and discovered my EF 2x II extender isn't compatible. (It sort of works at 300mm).

So I guess the question is if there's any extenders on the market compatible with this lens or do I return it and get a 300mm f4 L? I was planning on selling my 70-200 f2.8 L to help pay for it. Would like the extra reach to get more into wildlife.

Kenko TC are much more forgiving than the Canon ones and allow many more to be mounted as well. Their 1.4x is quite good actually. I use their 1.4 and Canon's 2x III.

Thanks. Looks like they have 2x that should work.

Speaking of doing research, you should check https://www.dpreview.c​om/forums/thread/42063​39.

DannyC71 wrote in post #18705645
I just got a 70-300 f/4-5.6 L IS USM without doing my research and discovered my EF 2x II extender isn't compatible. (It sort of works at 300mm).

What do you mean by "it sort of works"? It shouldn't AF at all on any camera, unless you tape the pins, or use live view. No Canon supports f/11 AF in OVF mode. I've had no luck tricking my 7D2 into AFing at f/11 in OVF mode; it just hunts and hunts and hunts, like it doesn't see anything at all. Maybe the more advanced 1DxII OVF AF will focus at f/11 under good conditions or with some lenses when tricked, but I haven't heard anything one way or another when I've brought it up.

So I guess the question is if there's any extenders on the market compatible with this lens or do I return it and get a 300mm f4 L? I was planning on selling my 70-200 f2.8 L to help pay for it. Would like the extra reach to get more into wildlife.

If you have a 6D or any of the older f/5.6 AF cameras, then a Kenko DGX 1.4 may allow decent f/8 AF. AF is not fast, but reliable for stills on the 6D with the DGX at f/8. Some versions of the DGX (like the one I have) don't work with the 7D2 and some newer cameras which officially support f/8 AF. IMO, the 6D OVF AF sees well with f/8 optics, even in fairly low light, but does not have fast drive and Canon disables f/8 OVF AF with its converters.

Do you have a local store where you can try a DGX 1.4 between your body and lens? When you upgrade your body, though, an older DGX may become useless.

Good read. Thanks.

What I meant by "sort of" was that I could actually mount it with the lens zoomed out to 300, but it wouldn't auto focus, it tried, but wouldn't.

I have a 6D. In all honesty I'm not anything close to a pro and my gear is probably beyond my skills. I fell into the trap of having to have all the zoom ranges.

I've also noticed that everyone seems to be discussing 1.4x as opposed to 2x. Is that just a matter of personal preference or is there a more technical reason?

TeamSpeed wrote in post #18705650
Kenko TC are much more forgiving than the Canon ones and allow many more to be mounted as well. Their 1.4x is quite good actually. I use their 1.4 and Canon's 2x III.

Me too, but there are many Kenkos, with very different behaviors. I have both the Pro 300 DG 1.4, and the Pro 300 DGX 1.4 version, an early one with no color dot coding. The DG works like a TC is supposed to; it reports itself to the lens, which can disable AF if the f-number goes too high. The DGX both talks to the lens, and intercepts the communication between the body and lens and change it (out of TC protocol). That worked great with my 6D and 7D, but crashes my 7D2, so I can't use it to get all-points f/8 AF.

Allowing f/8 AF and getting useful f/8 AF are two different things, though; not all cameras are equal at f/8 AF.

DannyC71 wrote in post #18705657
Thanks. Looks like they have 2x that should work.

Slow down. With a lens like that, you should probably start at 1.4x, unless you are an outlier photographer who is willing to manually focus, or use live view. I don't know the sharpness of your lens, but if it is not *very* sharp, what you're going to get with a 2x is better sampling of details (less aliasing), but not a lot more of them, with acuity. I think that's worth doing, if it doesn't cost you too much in spontaneity, but most people are after sharp pixels and if you are like most, you may not like the results.

So you get more but not enough to be worth it?

DannyC71 wrote in post #18705688
What I meant by "sort of" was that I could actually mount it with the lens zoomed out to 300, but it wouldn't auto focus, it tried, but wouldn't.

I have a 6D. In all honesty I'm not anything close to a pro and my gear is probably beyond my skills. I fell into the trap of having to have all the zoom ranges.

I've also noticed that everyone seems to be discussing 1.4x as opposed to 2x. Is that just a matter of personal preference or is there a more technical reason?

Do you want to AF, or manually focus? AF ability drops precipitously as you up the f-number of the optics. 1.4 can give good AF, and 2x can disable it completely, or make it hopeless.

Are you expecting sharp 100% views? The more you magnify your pixels, the more you lose that, not that there's anything wrong with that, per se, but it may not be what you want. Up to a certain point, TC magnification may get more quantity of somewhat-acute-looking details, but after a point, it gives better sampling of the lens with softer 100% pixel views.

DannyC71 wrote in post #18705699
So you get more but not enough to be worth it?

It all depends on what you are after. I would use a TC on a relatively soft lens, as long as I could get focus. I value proper sampling. Most people don't, and only like TCs when they give somewhat sharp 100% pixel views.

I will sacrifice the quality of sampling to get AF by removing the TC or using 1.4x instead of 2x, though, when focus is not otherwise practical or possible.

"I just got a 70-300 f/4-5.6 L IS USM without doing my research and discovered my EF 2x II extender isn't compatible. (It sort of works at 300mm)."

how can it sort of work if it does not fit?

I would not advise using any 2X with that lens.

The Kenko 1.4x should be a good option.

300mm x2 = 600mm

Just a few years back there was no affordable way to get 600mm worth looking at. Now there are a number of excellent 150ish - 600mm zooms.

If you want a 600mm zoom I would strongly urge you to get that.

If you want a 300mm zoom with the occasional 400ish, then the lens you have a with a 1.4x will do nicely.

If you want a 400mm zoom, then get one of those, Canon Sigma and Tamron make excellent ones.

i'm seldom happy with the results from even a 1.4 TC with the lenses I own. I think the best "teleconverter" you can get is a camera with 1.6 crop sensor.