T2.8

[Daniel Browning]

Please don't confuse F-stops and T-stops... huge difference.

I understand your annoyance. It also bothers me a little bit when people discuss DOF and focal lengths using T-stop notation, or, similarly, discussing exposure with F-stops.

But it certainly doesn't matter when the lens doesn't have an actual exposure difference, and even for lenses that do have it, the difference is often quite minor, so I don't think it's appropriate to say it's a huge difference, even to a pedant.

 

[Armstrongfilms]

But it certainly doesn't matter when the lens doesn't have an actual exposure difference, and even for lenses that do have it, the difference is often quite minor, so I don't think it's appropriate to say it's a huge difference, even to a pedant.[/QUOTE]

the difference IS huge fella

just to clarify lens stops:

f-stop=geometric aperture - "fractional stop"
t-stop=photometric aperture - "transmission stop"

the difference is the MTF from one lens to another even of the same manufacturer/focal length/mount, etc. f-stop is simply a fractional number based on the size of the lens, i.e. a f 2.8 is really focal length/2.8. meaning you are using a fixed % of the photon gathering elements within the glass. thats why it is "geometric aperture"
t-stop refers to the actual amount of light that passes through the lens (T ransmission stop)and onto the film, ccd, cmos, or whatever. they are far more accurate and consistent between different lenses and manufacturers. so you cannot just call your f-stop markings t-stops unless you have tested the individual lens and its MTF. anyone who has rented high end glass knows the difference means consistent exposure with variable focal lengths. so a f 4.0 on a 72mm lens means an aperture of 18mm. an f 4.0 on a 80mm lens is 20mm, which means, yes, exposure compensation is needed. resolution and contrast are directly affected.

i seriously doubt that RED will test every lens coming out on every scarlet so look for f-stops to be the standard on ANY fixed lens system. and please do not ever, ever call your f-stops t-stops cause it sounds cool.

 

[combatentropy]

Please don't confuse F-stops and T-stops... huge difference.

How much?

 

[Virum]

i seriously doubt that RED will test every lens coming out on every scarlet so look for f-stops to be the standard on ANY fixed lens system. and please do not ever, ever call your f-stops t-stops cause it sounds cool.

Then why is RED claiming T2.8 on their website/brochure instead of f2.8? There has to be a reason.

combatentropy, I seem to remember the difference between a t-stop and a lens' f-stop is usually around 1/3 of a stop difference (f-stop being a smaller number of course), but it all depends on the lens, whether it is a zoom or a prime, etc. Lots of factors, there is not fixed general answer.