What if cameras were rated by true ISO and lenses by t-stop?
 

http://www.dpreview.com/news/2012/04...tele-cine-lens

Re: What if cameras were rated by true ISO and lenses by t-stop?
 

On 18/04/2012 9:48 a.m., Alan Browne wrote:
> On 2012-04-16 22:35 , RichA wrote:
>> http://www.dpreview.com/news/2012/04...tele-cine-lens
>>
>
> The t-stop of almost all SLR lenses is not worst than the geometric
> aperture - at least not enough to matter. A very few SLR lenses have a
> t-stop that is worse, and in the case of apodization filtered lenses,
> variable t-stops.

It matters enough for video production - particularly when different
lenses will be used in multi-camera scenes. If there's a visible
exposure difference between cameras/lenses, an extra layer of complexity
is added to the editing process. For still photos, it would make no
difference to the intended output, or is trivial to adjust in PP.

>
> It would be nice if the "natural" (unity gain) ISO of the camera were
> declared. eg: on my camera which begins at ISO 100, the unity gain ISO
> appears to be somewhere around 150 (looking at noise graphs; various
> sources).
>