1 ACCEPTED SOLUTION
Doing a test with the version iii extender would be the best way for you to decide if the upgrade is worth it for you.
With current sensors, you really have to decide whether you are better off cropping versus using an extender. I am going to be shooting some outside stuff later today and for fun shot the same subject from the same distance using an EF 400 f2.8 IS II with and without the version II 1.4X extender. Here are a couple of comparison shots below with the bare lens cropped to basically the same subject size for both conditions.
The EF 400 f2.8 is one of optically sharpest lenses Canon makes so even with the degradation via the extender it is still sharp but the results are noticeable. This was using my 1DX III, the same setup with my 5DS R would likely bias the results even more towards cropping.
Just a little more data to help you decide whether it is worthwhile to upgrade from an early to later version of an extender. The better high ISO performance of newer bodies helps offset the old problem of losing a stop with the 1.4X but with the denser/higher MP sensor it makes cropping a much more viable option also.
First image is bare EF 400 f2.8 IS II, the second with the 1.4X and both were shot from exactly the same location. The last image shows why the loss of depth of field is a drawback to the use of the extender, only about a 3" loss for this combination at the distance I was shooting but if I had used the extender with the last image it would have been an issue.
Rodger
I use the 1.4x mk III extender with the new 100-400 zoom lens on occasion and found the focus not quite satisfactory until I removed a clear lens filter. If I left the lens filter in place and removed the extender, the focus was sharp. I'm interested in hearing others experience/knowledge with this topic.
Just for fun, I'm posting two images shot at 560mm (Canon 100-400 F4.5-5.6L IS USM Mark II + 1.4X Mark III Ext) with no clear uv protector. I should have had a better shutter speed for the skydivers, as it was difficult tracking them as I had no warning when they would jump. Cheers.. G
@ebiggs1 wrote:"Sounds like a good reason to simply remove the filter, and go without one"
The filter did not remain on it for long. Two of my closer friends had the same lens and filter issues. We all sold it and bought, in my case bought another, the 400mm f5.6L. Even without a filter the 100-400mm is not as sharp as the prime. Besides the first 100-400mm has additional problems not just not liking filters. It really soured me and probably why I never bought the current version of the 100-400mm which I am told is much better. No first hand experience with it.
I have not used the 400mm f/5.6 nor the original 100-400mm. The 100-400mm II is razor sharp, even wide open.
