My primary purpose in buying the f/4 was to use it for macro shots without killing my back. Here are the two lenses under exactly the same conditions. NO editing at all has been done on these two images.

Using my shop chair, I rolled up as close as I could to get the shot using autofocus. There is a considerable difference in minimum focus distances between the two lenses! NOTHING was changed on the camera settings.

Now the shots at about 25' with the 2x TC

And finally the same shots with no TC

Oh what the heck...Mr. Owl after editing in LR and Topax PhotoAI (70-200 2x TC) and cropped

Looks like the f4 holds it's own.

Looks to me like the 2.8 has more detail and contrast but not by a mile for sure. There must have been something wrong with the copy I bought because it was very noticeable between the two as well as autofocus speed seemed much slower. Might be worth trying another copy.

I would agree that the 2.8 has the better detail and better in low light. But, if I am going out for both birds and macro with the 2x TC I would bring the f4. I am very happy with the IQ of the lens. Plus the f4 is lighter. I will probably keep both for awhile. I’m still teaching (1/2 time) at Winona State and will probably teach one more year. I want the $$ for more toys!

You must have receive a bad copy.

I notice that the f4 is slow to focus unless you use the focus limiter which is fine with me, I keep it set on macro and it focuses plenty fast.

I am trying to learn (remember) to keep switching the focus limiter to the appropriate setting! It really makes a BIG difference!!