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RF 400, or EF 400 with adapter?

Started Jul 11, 2021 | Discussions thread
John Sheehy Forum Pro • Posts: 26,688
Re: RF 400, or EF 400 with adapter?

Vladyslav Kosulin wrote:

EF 400 2.8 and RF 400 2.8 are same price new.
If you switched to MILC, then RF 400 is obvious choice unless you already have EF 400 or can get it used for, say, 8K or less.
They are optically identical, and most specs are the same.
RF has 0.5 stop better IS, not sure EF with adapter can claim this 0.5 improvement as well.
RF 400 is compatible with RF 1.4 and 2.0 extenders. EF 400 with EF-RF adapter can use EF 1.4 and 2.0 extenders (not sure if this combo affects the AF speed).
RF has focus distance window removed.

You need to take manufacturers' "stops of stabilization" with a pound of salt. Those figures are not about critical micro-stability, but the CIPA standard used by the industry, which is about post card viewing at 450mm. A system could add blur through error or quantization and still increase CIPA stops, so long as that added blur is not very large, but it may be large enough to affect critical shooting negatively with lots of necessary cropping.

I'm not saying that I expect the RF version of this lens to have such a problem; just that the CIPA stops are not some magic global dampening factor that follows down into fine details.

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Beware of correct answers to wrong questions.
John
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