I agree with Steve 100%. A 4/3 lens of the same focal length needs to
be opened a stop wider than a 35mm lens for the same depth of field.
But, of course, the 4/3 lens at the same focal length will only have
half the field of view. For equivalent field of view (half the focal
length) the 4/3 camera has greater depth of field at any equivalent
aperture.
And f/2 is f/2 is f/2 for exposure determination.
I've never hear the image noise claim but it sounds like some silly
internet lore to me.
Chuck Norcutt
On 11/17/2010 4:08 PM, Stephen Troy wrote:
> At 03:46 PM 11/17/2010, Andrew Fildes wrote:
>> I'm of the understanding that a f0.95 lens is a true f0.95
>> regardless of sensor size - after all, if I put a medium format f2.8
>> lens on a 35mm body, it's still f2.8 AFAIK. But there is a
>> persistent theory that a 0.95 on an FT sensor is really equivalent
>> to a true f1.7 or some such. I really don't understand the thinking
>> behind this claim. Anyone care to opine on this and help me make
>> sense of it before I make some claims in print.?
>
>
> That claim primarily relates to apparent depth of field - a f/2.0 DZ
> lens on 4/3 will give the same apparent depth of field as an f/4.0
> lens on full-frame cameras, as you have to enlarge the 4/3 image more
> to make a same-size print. This can be an advantage if you need
> greater depth of field, a disadvantage if you want shallow depth of field.
>
> This difference is mitigated somewhat in that the f/2.0 DZ lenses are
> wonderful wide-open, while many full-frame fast lenses have to be
> stopped down to f/4.0 to remove softness and light falloff in the corners.
>
> For exposure, f/2.0 is f/2.0. I have yet to see a light meter that
> asks your film/sensor size.
>
> Some claim f/2.0 on 4/3 also acts like f/4.0 full-frame for image
> noise, but there are far more variables that cause image noise than
> sensor size, so I don't buy that argument compeltely.
>
> Steve Troy
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