I was watching a behind the scenes featurette on hanibal and it showed how they shot each scene with the focal range, shutter speed, etc. displayed at the bottom. I noticed that they were shooting alot at t-stop 5.6 and I want to do the same with my 7d. I tried shooting 5.6 with my camera but the camera does't give me the same amount of dof they were getting so I figured t-stops must be different from f-stops along with a film frame being a little bit larger than aps-c. Does anyone know what the equivalent of 2.8, 4.0, and 5.6 would be in f-stops?
T-Stop equivalent in F-Stops?
- Thread starter dtjohns1
- Start date
Rick Burnett
Section Moderator
T-stops include the actual light transmission through the lens, whereas F-stop is the ratio of the focal length over the aperature. There is some good information here:
http://en.wikipedia.org/wiki/F-number
One thing that has confused me is this; If I am setting up for DoF, wouldn't I want to know F-stop and not T-stop since F-stop is about the ability of the DoF, not the T-stop which is the light transmission. For instance, imagine putting an ND filter over a 30mm lens. You've decreases the light transmission but you've not affected the DoF. The T-stop would change but the F-stop would not. This is why I don't agree talking in T-stops makes total sense, other than matching transmission (exposure).
http://en.wikipedia.org/wiki/F-number
One thing that has confused me is this; If I am setting up for DoF, wouldn't I want to know F-stop and not T-stop since F-stop is about the ability of the DoF, not the T-stop which is the light transmission. For instance, imagine putting an ND filter over a 30mm lens. You've decreases the light transmission but you've not affected the DoF. The T-stop would change but the F-stop would not. This is why I don't agree talking in T-stops makes total sense, other than matching transmission (exposure).
Barry_Green
Moderator
T-stop is for exposure only. F-stop is for DOF.
appreciate the info guys! sorry for such a novice question. can anyone tell me what f-stop films usually use on average?(i know this changes from shot to shot and situation to situation but if you could just give me a ballpark figure for a closeup, medium closeup, full and wide shot I would greatly appreciate it.
randomname
Well-known member
I think I remember reading that most of them shoot between f8-f11
Barry_Green
Moderator
You can read about how films were shot in American Cinematographer magazine. The most commonly-repeated f-stop range is f/2.8 to f/4.
Rick Burnett
Section Moderator
Thanks
The reason for the confusion was someone in another thread had made some kind of argument that lens should be rated in T-stops INSTEAD of F-stops, and for me, that just didn't make sense (rightly so) so I didn't know if I was confused about something. Although that said, I think having both designations would be good.Barry_Green
Moderator
f/3.5 is also known as a 2.8/4 split, and yes, it's very common. And yes, on a "full frame" camera like the 5D, it means you'd need 3x as much light, to be able to stop the iris down that much farther, to get the equivalent DOF at f/5.6.
Barry_Green
Moderator
Thanks
Cinema lenses are usually labeled with either just t-stops, or both t- and f-stops.
PerroneFord
Deals in Lead
And people wonder why I say I'd rather shoot with the 7D all day every day. The 5D is a pain in the ass to light for. Of course, people who don't actually SHOOT narrative don't understand this argument.
Rick Burnett
Section Moderator
I understand. I used a 5D and was just not thrilled with full-frame. It seemed to me the 7D (and by that I mean APS-C sensor size) is really to me the best of both worlds.
Barry_Green
Moderator
... and that's why 35mm cinema film is the standard, and "full frame" vistavision isn't. :thumbsup: