TC or Crop? Is there a consensus? Please help!

[heptagon]

If needed i use the 2x iii which gives amazing results in good light and for slow moving subjects. With the 2x 8x more shutter time is needed, 4x because of 2 stops less opening and 2x stop because of doubled focal lenght. from my experiance its better to cop a picture than pushing up iso by 3 stops, as iso 1600 looses lots of detail compared with iso 200 on the crop body.

For the 70-200 L IS II you could add another stop to the light requirement for stopping down from f/5.6 to f/8 with extender instead of useable f/2.8 without extender. So that would be 16x more light required. However there might just be enough light for all directly sun-lit subjects. If you can shoot at f/16 without extender, you can shoot at f/8 with extender.

 

[hendrik-sg]

For the 70-200 L IS II you could add another stop to the light requirement for stopping down from f/5.6 to f/8 with extender instead of useable f/2.8 without extender. So that would be 16x more light required. However there might just be enough light for all directly sun-lit subjects. If you can shoot at f/16 without extender, you can shoot at f/8 with extender.
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You are right, stopping down stop may improve the image quality. The 70-200 ii i dont know, but with the 300 2.8 i nearly never had lighting conditions where i get an improvement by stopping down, as motion blur is worse than "lens softness" or "converter softness".

 

[Mt Spokane Photography]

The lens is fairly new, I love it. These are difficult shots due to the distance.
Reported Settings. These are what is recorded in EXIF and, in the case of stacked TC's the f stop is wrong. I used AV setting of f/11, but the aperture of the lens would have varied according to the TC with it being stopped down more without a TC
Also, it was a winter day and the light varied from shot to shot so the shutter speeds varied according to available light.
No TC - 1/2500 sec f/11, ISO 800
1.4X - 1/3200 sec f/11 ISO 800
2X - 1/3200 sec f/11 ISO 800
1.4 + 2X - 1/2000 sec f/11 ISO 800 (not the actual equivalent aperture)
It might be interesting to redo them with my 1D MK IV, but in our near 100 degree weather, the air is too turbulent, and the 1D MK IV is going to be sold soon.

Another thing is: Did you scale the images made with the TC or change the focal length? Comparing the length of the tower by hand doesn't give a magnification of 2x or 2.8x compared to the 1.4x (maybe this is also done on the webpage). I ask this because scaling images is also often problematic and there is quite some discussion on how you should scale the images in order to provide a "fair" comparison.

What we can conclude however is that taking images with a TC is much more complicated than using the bare lens.

They are crops, so the scaling cannot be measured when you crop a image. As noted, I cropped them to show the tower at about the same height, except that the no TC crop resulted in a 100% crop so it is a little smaller. If the objective is to see which combination produces the most detail of a distant object, a crop works best.
Full images are linked below to avoid taking up bandwidth for users.
No TC
http://www.mount-spokane-photography.com/Photography/100-400mm-L/400mm-no-tc-2603/1179530174_evXBt-X3.jpg
1.4X
http://www.mount-spokane-photography.com/Photography/100-400mm-L/400mm-14X-2600/1179529520_E4yYv-X3.jpg
2X
http://www.mount-spokane-photography.com/Photography/100-400mm-L/400mm-2X/1179528230_FVjWy-X3.jpg
1.4X + 2X
http://www.mount-spokane-photography.com/Photography/100-400mm-L/400mm-2X-14X/1179528853_BdbVA-X3.jpg

A 50mm shot for comparison. Try scaling it

 

[heptagon]

You are right, stopping down stop may improve the image quality. The 70-200 ii i dont know, but with the 300 2.8 i nearly never had lighting conditions where i get an improvement by stopping down, as motion blur is worse than "lens softness" or "converter softness".

The 70-200 II with 2x extender just doesn't look right at F/5.6 at F/8 there is a big improvement. It's about on the sharpness level of the 400 L F/5.6 when shooting between F/5.6 and F/8.

As far as i know the 300 F/2.8 is already a very sharp lens wide open. But it's hard to actually find the reason for softness at long focal ranges as focusing problems and various vibration sources also play a role.

For me a subject in direct sunlight and the lens on a monopod with IS on and the camera (550D) on iso 400 max worked pretty well but only half of the shots are satisfying. Selecting a higher iso destroys detail and you cannot sharpen the image anymore without adding a lot of grain. So the situations where using a TC actually makes sense are pretty limited.

 

[heptagon]

You linked to scaled versions of the images but i found the originals in your gallery

It's pretty hard come to a definite conclusion regarding the quality. Also at the shot with the 2x converter a cloud is on the main tower reducing contrast and it seems like some kind of noise reduction is employed. Additionally there may be air turbulences and slight focusing errors etc.

I think most people will be happy with the 1.4x extender on any tele lens F/4 or faster but the 2x extender is only a compromise.

A 50mm shot for comparison. Try scaling it

That's quite impressive!

 

[Mt Spokane Photography]

You linked to scaled versions of the images but i found the originals in your gallery

It's pretty hard come to a definite conclusion regarding the quality. Also at the shot with the 2x converter a cloud is on the main tower reducing contrast and it seems like some kind of noise reduction is employed. Additionally there may be air turbulences and slight focusing errors etc.

I think most people will be happy with the 1.4x extender on any tele lens F/4 or faster but the 2x extender is only a compromise.

A 50mm shot for comparison. Try scaling it

That's quite impressive!

Yes, there are flaws in the test, a distant object miles away is not really the best type of test, that pesky air, clouds, water vapor, etc change all the time. Also, from a wooden deck, someone walking in the house might affect it.

Its pretty clear that a 1.4X does a good job with a 10mp 1D MK III. The result with a 18mp 7D might be different, I might setup on concrete one day and try that. I now have a laptop holder on my tripod, or can use a long USB cable and focus / capture remotely to get the best possible image. However, something closer might be better.

I really do not use my 100-400mm L with TC's, its too much of a bother for any possible gain. I can crop most of the time, and other issues usually out prioritize using a TC.

Here is a cropped image of a female redwing blackbird as she dropped from our crabapple tree to the ground to pickup sunflower seeds. I loved the way I could AF on the bird right thru the clutter of the tree with my 5D MK II. I always was wondering at those who could not AF with it. 100-400mm with no TC.

 

[Skulker]

If its occasional wildlife I would crop, basically for the reasons given above. But mainly because I find that putting the 100-400 on a 2XTC is pushing it a bit on the 7D as far as IQ is concerned. And of course there is the AF issue, ie it wont.

This makes me think I must try the TC's and the 100-400 on the full frame.


EDIT
Having tried it, its a pain not having AF, my type of shooting tends to want a quick shot.