Quote:
Originally Posted by Renato1
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.
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Well, in fact, it's not.
Which only goes to illustrate your point that crop factor is misleading and confusing.
The depth of field equivalent is f/2.8 to f/5.6 as you say, but the focal ratio is the same (f/2.8).
Take a bridge camera sensor as a wider example. It has a crop factor of 6 compared to a full frame. In terms of depth of field equivalency, you multiply the aperture by 6 but in terms of exposure, the true aperture is still the useful number. eg. If a scene requires an exposure at ISO 100 of 1/125 at f/5.6 with a full frame camera, it is 1/125 at f/5.6 with a crop camera or with a bridge camera.
So you can't make the blanket statement that the aperture value needs to be multiplied by the crop factor as it's just wrong.
Steve.