need teleconverter recommendation

Wilt wrote in post #15456669
Consider this...

• photozone.de measures MTF resolution in 'line pairs per frame height' (i.e., how many pairs of black lines separated by white space, across the full height of the frame, whatever the frame size)
  
• photozone.de has shown only about 10% decline in MTF values when using Canon 70-200mm zooms with Canon 1.4x teleconvertor
  
• photozone.de measures MTF of 2530 at f/4 on 15MPixel APS-C with 70-200 f/2.8 IS II
  
• photozone.de measures MTF of 3719 at f/4 on 15Mpixel FF with 70-200 f/2.8 IS II
  
• we can interpolate MTF of 3347 (90% of 3719) at f/4 (actual f/5.6 due to TC) on 15Mpixel FF with with 70-200 f/2.8 IS II and 1.4x TC

IOW, the FF image will still have more total resolution with the TC than the APS-C camera without TC!

Wow. That's pretty interesting.

You will lose some image quality with a converter. I have used Canon's converters for years with good results. Some lenses perform very well (superteles) and some are only decent with good light (zooms)

Overall they are nice to have as they add some versitality and are not too expensive.

coeng wrote in post #15456105
I don't know why but I feel myself leaning more towards the Canon 2X III over the 1.4X III. I know I'll lose another stop going with the 2X over the 1.4X but this way I'll be covered from 70mm-400mm rather than 70mm-280mm if I went with the 1.4. That's a big difference.

I just picked up the 2Xiii for use w/ the 70-200 2.8 IS II. Couldn't be happier. (My first L lens.)

coeng wrote in post #15456105
I don't know why but I feel myself leaning more towards the Canon 2X III over the 1.4X III. I know I'll lose another stop going with the 2X over the 1.4X but this way I'll be covered from 70mm-400mm rather than 70mm-280mm if I went with the 1.4. That's a big difference.

Most seem to have good results with the 1.4x but not so much with the 2.0x. However, you have the lens that might work very well with the 2.0x as it is very sharp to begin with.

I bought a used kenko 1.4x Pro 300 DG to try on the 100-400 and found the IQ to be unacceptable as well as no AF. I took the same TC and put it on the 200F2.8 and wow works great (focus is good but slow). Unless your PP you would never know it was on the lens.

A couple of days ago there was a canon 1.4x II for sale on the forum for $200....