Stacked TC IIIs on 300/2.8 II Brief summary

[AlanF]

We have been having discussions about stacking 1.4xTC III and 2xTC III on telephotos. I have done some testing using a 70D, and here are some brief conclusions, incorporating what others have already written and discovered.
1. Stacking requires a 12mm extension tube placed between the two TC III extenders.
2. The 2xTC III must be attached to the lens and the 1.4xTC to the camera.
3. The camera exif records only the effect of the 2xTC - the pair attached to a wide open f/2.8 records as f/5.6.
4. The 300/2.8 focusses manually at all the usual distances, and the same is reported for other telephotos.
What I found from the 70D today is:
5. AF works only at intermediate distances (approx 30-80m, give or take) and not closer or at infinity in both live view and phase detect. (The 5DIII also didn't AF).
6. IQ is quite good.

Here are two shots of Egyptian geese at about 20-30m. The stacked TCs required manual focus which I did through the viewfinder, rather quickly, resting the lens on the ledge of a hide. The full shots are reduced to 1200x800, the crops of the heads are 100%. The goose standing is done with just the 2xTC attached. The sitting goose with the 1.4x + 2x.

Both are wide open (f/5.6 with 2x, f/8 with 1.4x+2x), iso 640 and 1/3200 or 1/1000s.

 

[Mt Spokane Photography]

Alan, were you or did you try using live AF on the 70D? I'm just curious, since it supposedly focuses to f/11

 

[AlanF]

Same focus limitations as for normal viewfinder (phase detect) AF. It would only AF for the intermediate distances. It was very accurate then.

 

[AlanF]

The 5DIII has the same problems with a very limited mid-range AF, not focussing close or far away.

 

[tron]

My EF1.4X II could be stacked with my EF2X II. But I decided I am not interested in that and part-exchanged my EF2X II with EF2X III. Now I put my EF1.4X II on sale so as to replace it too with the EF1.4X III version. I believe that the EF2X III must be more than enough. But then again I do not have a 300mm 2.8L IS II to test. I have a 500mm f/4L IS II. So I believe 1000mm f/8 tops should be enough.

However, since I have some 3rd party extension tubes I will test the shorter one with my teleconverters...

 

[candc]

i have the canon 1.4xiii, 2xiii, and kenko pro 300 1.4x. i don't have the 300ii but i use the sigma 120-300 and at 300 plus canon 2xiii and kenko pro 1.4x (the fit no need for tubes) af works but is iffy on the 70d, it works surprisingly well on the 6d? i don't see myself using this combo because iq drops pretty far, probable better on the 300ii

 

[Jack Douglas]

AlanF, thanks for making the effort to provide this feedback. Do you think AFMA is a factor here? I guess the camera wouldn't be able to recognize/remember the combination??

Do you feel the result is better than a crop of less than full stacked? Did you play with sharpening the stacked result?

Maybe you've answered this previously, but you're gaining more experience daily. So, assuming you need reach to frame a stationary subject, does the 70D outperform the 5D3 in good light in any regard, considering the various aspects of IQ?

Jack

 

[AlanF]

AlanF, thanks for making the effort to provide this feedback. Do you think AFMA is a factor here? I guess the camera wouldn't be able to recognize/remember the combination??

Do you feel the result is better than a crop of less than full stacked? Did you play with sharpening the stacked result?

Maybe you've answered this previously, but you're gaining more experience daily. So, assuming you need reach to frame a stationary subject, does the 70D outperform the 5D3 in good light in any regard, considering the various aspects of IQ?

Jack

The AF is so limited for the stack that I used manual focussing through the viewfinder so AFMA doesn't come into it.

When I got good focus, the results were very acceptable. Using a tripod for a static subject, for moon shots etc, I think the stacked TCs could give an advantage. I got a reasonable shot of a bittern in reeds at the very limits of resolution which was at least as good as just using the 2xTC. But, the whole rig is too cumbersome for my hand held shots, which is what I want to do. And the loss of AF is a killer.

The 70D does give better resolution than the 5DIII, with DxO noise reduction and a bit of PP. But, this comes into play when you are cropping so much the results are never going to be spectacular whichever camera you are using. I am very happy with both the 70D and 5DIII, but the 5DIII will be my workhorse. I expect to test the Tamron 150-600 the week after next. My guess is that it will perform significantly better on the 5DIII. Its sharpness is very similar to that of the 100-400, and that lens is much better on the FF than crop. You need a very sharp lens to get the best from crop sensor.

 

[Jack Douglas]

Thanks AlanF.

Jack