This might be old news to many here.
I've been reading lots of camera reviews the last week trying to find a suitable super-zoom camera for photographing birds when we go on vacation. Then while looking at video reviews, I came across the chap in the video below, who states the bleeding obvious.
In a nutshell, he says camera manufacturers apply the crop factor to lenses to get the 35mm/full frame equivalent, but then mislead the customers by not applying the crop factor to the F-number.
To illustrate, one example he gives is a Panasonic 12-35mm f/2.8 lens for a Micro 4/3s camera which has a 2X crop factor. Advertisers then say it's a 24-70mm f/2.8 full frame equivalent lens, when in physical fact it is a 24-70 f/5.6 full frame equivalent lens.
Then I thought back to how many supposedly "Tech Head" type reviewers I'd been reading, who went along with that type deception in their reviews of super zooms.
It also occurred to me that my actual camera has been misleading me. When I put a full frame lens on an APS DSLR, and set the lens to say F/4 and take a picture, the data in the photo says F/4 - what the lens was set to - when in fact the actual value was f/6 due to the crop factor.
Regards,
Renato
https://www.youtube.com/watch?v=DtDotqLx6nA