Stacking two 1.4 tc's (1 Viewer)

Just been playing with two t'c stacked on my 70-200 f4. The two tc's are Canon and Kenko Pro so there is only one possible way of connecting e.g.
Camera - Kenko - Canon - Lens. The Kenko had the pins taped and the Canon did not - I expected the fastest aperture to show as f4 as the Kenko would stop any tc data getting to the Camera But it actually showed f5.6 which means the Camera was seeing the Canon tc |:S|
The second thing I noticed was that AF was just as quick with both converters on board as it is with only one.
Image quality was very good ( the 70-200 f4 is a cracking lens to start with). I am now going to test the IQ of 2 1.4tc stacked versus a 2x tc
(gives me something to do in this crap weather :t: )

If the reporting TC is closer to the lens, camera will see it.

macshark said:

If the reporting TC is closer to the lens, camera will see it.

Click to expand...

You are right Mac, I thought the non reporting one next to the camera would stop the data getting through to the camera but obviously this data is sent via a non taped pin.

You boys have got to much time on your hands...

I have used this technique quite a lot when I need that bit more reach. Strangely, the results (in terms of aperture and focal length reporting) seem to vary depending on the make of lens.

With Canon lenses, I get the same results as described above. Only one TC is recognised and it shows as 1 stop darker, 1.4x the focal length and autofocuses accordingly.

With my Sigma 500/4.5, the results are strange. I can use my 500/4.5 with the Kenco Pro TC and it isn't recognised. Autofocuses and reports as 500/4.5. With stacked TCs it now appears to recognise both TCs and reports aperture as F9 (correct) but focal length as 700 (incorrect - its now 1000). Clearly, it doesn't autofocus. Results can be OK - a little soft but still usable (3 cheers for Unsharp Mask!)
Example with 500 + 2 1.4 TCs

Roy C said:

Just been playing with two t'c stacked on my 70-200 f4. The two tc's are Canon and Kenko Pro so there is only one possible way of connecting e.g.
Camera - Kenko - Canon - Lens. The Kenko had the pins taped and the Canon did not - I expected the fastest aperture to show as f4 as the Kenko would stop any tc data getting to the Camera But it actually showed f5.6 which means the Camera was seeing the Canon tc |:S|
The second thing I noticed was that AF was just as quick with both converters on board as it is with only one.
Image quality was very good ( the 70-200 f4 is a cracking lens to start with). I am now going to test the IQ of 2 1.4tc stacked versus a 2x tc
(gives me something to do in this crap weather :t: )

Click to expand...

Roy, how did you get on comparing the stacked 1.4x against the 2x?

mw_aurora said:

Roy, how did you get on comparing the stacked 1.4x against the 2x?

Click to expand...

Must admit I have not done it yet Mark - I am going to do it outside on a tripod but it has been so windy (and wet) that I thought it may give a false result. Will post the results when I do it.