RF Native Lens Cropped vs 1.4x vs 2x

[Fast Glass]

Well something you have to consider is the affect of overall IQ or how far you subject is.

If you are very far away, you have to have some kind of resolution on target you'd have to have the 2x on and crop from there. Crop too heavy and it will look that way.

You also can't escape the increase in noise which is proportional to bumping up ISO with crop. You are not gaining light by not usingan extender. You increase perceived noise at the same output size with cropping just as much as using the extender and bumping it up. Used to be in the old'en days when using the 1Ds III as your body of choice. You had a native ISO 1600, expanded 3200. So it wasn't always a simple matter of just bumping up the ISO or pushing it past in post. So sometimes cropping was the solution. Sensor tech was not there yet.

Today with say the 1Dx III, it handles noise like a boss and a native ISO of 100,000!!!!!!

I'm just tossing in more variables in the mix and more scenarios why you might want to use the 2X. I would suspect you only have so much room to crop that regardless of the softness just having enough sensor and resolution on target will be more important.

Also, If you make another test like this. Maybe do it outside so you are able to use ISO 100 on all your shots and not inducing detail killing noise. Also with the exposures being so dim and white balance off. It kinda plays tricks with my eyes and makes it more difficult to judge them. I can still tell what is sharper. But them being the same exposure and WB would be nice.

Also, did you manually focus these results? I would not trust the AF for critical results. Because some look like they may have been miss focused by a significant amount. It looks much more than softness on at least one of them. The 2X results.

Just my 2 cents anyway.