Canon RF 100-300 f/2.8 IS USM

[Kayaker72]

Resolution is a funny thing in that if you do not have a subject with detail that requires that level of resolution then the additional resolution is simply not needed.

Looking at Bryan't test, the 100-300 @ 300 mm does look better than with a 2x TC @ 600 mm. Yet, the way Bryan does his test, the 600 mm test result was 2x further away. Looking at his specs, he actually used the same distance but a chart that was half the size. So, equivalent to 2x further away.

So, for 2x more "reach" I am actually impressed with the performance of the 2x TC.

Looking at your comparisons, I like the contrast the best with the naked lens, but I am seeing details/texture in the steps and the shaded sides of the step that I do not think I can see with the naked lens. That said, I think it would be easier to assess details in a subject like a bird, a pine tree's needles or something else with a lot of fine detail.

[Busted Knuckles]

Thanks for the double checks. The focus point was at the front if the steps/lower hand railing. Is there the depth of field issue re the mens room sign.

I sent both back. I was thinking of doing the optimal f stop (7.1) but seems like the difference was so small that fiddling with the 2x seems wonky.

[neuroanatomist]

Looking at his specs, he actually used the same distance but a chart that was half the size. So, equivalent to 2x further away.

The QA-77 chart comes in 4 sizes, the smaller ones are useful for long lenses. I have about 60 feet line-of-sight where I do my testing, and that's means using one of the two smaller sizes with lenses over 400mm.