Generally speaking, I think that for the 2x controversy it's possible for everyone to be right:
- The quality of the original lens matters the most: the 2x TC magnifies what is being captured. (Yeah, obviously.)
- Imperfect copies of either the base lens or the TC will skew the final image.
- Air quality between the lens and the subject matters — temperature differences in the hood (think cold days from a warm car with the window down), temperature differences between the ambient air and the ground (or water), etc. all create thermal currents that skew the result because the image entering the glass might be subject to shimmer, which will be magnified. The closer the subject, generally the less impact from shimmer (hood aside).
- Similarly, light spill and other factors will also be magnified and skew a casual inspection. Uncontrolled light really kills TC outcomes.
- Use of digital aids, like DLO, can make a monstrous difference.
I think within one's own stable of lenses it's possible to form a solid opinion on whether a copy of the 2x TC is working or not. I think that it's a very subjective thing to take a sentance-or-two answer from someone else and apply it to one's own situation. Obviously credibility of the source counts for a lot, but situation and the
transparency into the scenarios counts for more.
I have used EF II and III 2x extenders with close outcomes. When I test, versus just chimp on images, I try to equally to fill the frame with a subject — easy enough to do with a tripod and stand-in subject. My 300 f4 IS works very well with DLO, my 70-200 f4 non-IS is for emergency use only when any serious distance is considered — like what I'd put between me and a mamma bear with cub — but if I just want a close at hand duck or chipmunk then it's actually pretty fine with some minor editing.
For my copy of the II, light control is imperative for quality outcomes.
Can you draw anything from that? Well, if you have a 300mm f4 IS and a 70-200 f4 non-IS and you trust me to do this decently then yes. If you have any other lens or don't trust me... I'd consider the bullet points, a good friend or camera store, and some education by the Digital Picture.
I have found that my friend's 70-200 f/4 IS ii with 2x III makes perfectly fine images with DLO turned on. For anything but the most critical work when travelling light I wouldn't blink to slap that on, get some great shots when travelling light, and print the outcomes.
Sucks if you get a bad copy. These are expensive experiments! It helps a lot of you have a sympathetic camera store with long aisles.
