Yes.
Note: The lenses of almost all motion picture cameras use T-stops (measure
of light transmission). At one time in the industry, before the excellent
coatings of today and when the lenses of these cameras were mounted on
turrets, there could be a significant difference between an f/stop and a
T-stop and between one lens and another. Even with the advent of zoom
lenses, the problem continued when shooting scenes with several cameras
using different lenses. You might detect the difference on the silver screen
because you would be seeing the results side by side and in time and
overlapped. I've read that the human eye can detect a difference of about
1/3 stop and some films exaggerate this (high contrast films). Photographs
are not usually viewed as same scene side-by-side, and even when they are,
the change doesn't take place overlapped in 1/30th of a second. In a print,
or adjustment of a slide for the printed page, it may be nearly impossible
to detect small differences that might be obvious on the silver screen. Some
camera lens makers publish the maximum T-stop of their lenses. The f/stop
and T-stop of a pinhole camera are the same.
T-stop determines light transmission accurately and DOF and diffraction
closely.
F/stop determines DOF and diffraction accurately and light transmission
closely.
Mirror tele's throw everybody off. When they say they're f/8, what do they
really mean?
Regards,
Bob...
-------------------------------
"In the carboniferous epoch
we were promised perpetual peace.
They swore if we gave up our weapons
that the wars of the tribes would cease.
But when we disarmed they sold us,
and delivered us, bound, to our foe.
And the gods of the copybook headings said,
'Stick to the devil you know.' "
--Rudyard Kipling
From: "Yoshihiko Takinami" <[EMAIL PROTECTED]>
> Hi,
>
> On 2001.09.24, at 20:39, [EMAIL PROTECTED] wrote:
>
> >> I have heard remarks that a 200/2.8 prime will transmit more
> >> light than an 80-200/2.8 zoom. Is this true? I thought a
> >> 200/2.8 was a 200/2.8 whether it be a prime or part of a zoom.
> >
> > I'm with you 2.8 is 2.8. Two different lenses, if calibrated properly,
> > should deliver the same amount of light at the film plane when set to
> > 2.8.
> > No ifs, ands, or buts!
>
> The aperture value simply depends on geometry as William and
> Nenad wrote before. I should add that not only surface light-
> loss but also vignetting reflects the amounts of light coming
> through the lens.
>
> There is T-value which depends on the amount of light through
> the lens. When you set the two different lenses at the same
> T-value, they deliver the same amount of light at the film
> plane.
>
> I do not consider it too much to say that two different lenses
> with different constructions deliver the different amounts of
> light at the film plane when set to the same aperture value.
>
> BTW, the differences between the amounts of light through the
> lenses do not seem very big.
>
> Hope this helps.
-
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