Sensitivity

DavidBeier

DavidBeier

Veteran
I know this is going to sound like a stupid question but I'm super confused on the sensitivity of the F3.

For the longest time, I've heard that it was 800 ISO at 0 db in normal mode and 1600 ISO in S-Log.

Last night however, we were shooting and the camera seemed WAY darker than 800 ISO. Some have indicated it's only 800 ISO in 60i mode and not 24p but I when back and checked the Able Cine tests and they seem to indicate that it's 800 ISO in 24p. I've switched between 60i and 24p in the camera and do notice a bump in brightness at 60i. What am I mis-understanding here? Is the camera 800 ISO when in the 23.98 frame rate? Why would one even worry what it was at 59.97i since, in all liklihood, anyone who wants a super 35mm camera with prime lenses is going to want 24p.

I've got a shoot next weekend in which the speed of the camera is pretty important. We're shooting in a dark alley at night with mostly available lighting. I really need to be sure how the camera is rated at as we did all our tests with light meters/DSLRs starting with an 800 ISO rating.
 
I recommend that you get a waveform monitor, a DSC chart, and do your own rating with your own camera with your own setup at your chosen exposre level. That is the only way you can be safe because there are just too many variables to make blanket statements like "the f3 is ISO _____". Bulls*%t it all depends on your setup and how you expose.

Furthermore, the ISO number that the camera displays is completely meaningless. If we were in the same room togeher it would only take me about two minutes to show you how there can be a 2-stop swing in sensitivity just by changing a couple of picture profile settings -- yet the camera will still show the same ISO. That cannot be right.

BTW, My F3 with my normal setup is ISO 250. And with S-LOG my camera is ISO 1000. But someone would be a fool to use those numbers without knowing every detail of how my camera is setup and where I expect gray and white to be exposed.
 
I agree with Doug on the fact there are so many variables with the camera's adjustments to claim a definitive iso. However as you probably know already, the F3 is great in low light. If your not using S-log, Cine 4 will bring up the shadow details significantly.
 
Ditto to the above. I'm not sure about cine 4 but in general the F3 is slower in the cine settings than it is in plain Std 709, so if you are trying to shoot in very low light consider 709. Other thoughts are that I hope you don't intend to shoot an F3 in low light at ISO800. That camera is clean as a whistle at 12DB so don't be afraid to use it. Even 18DB is not very noisy.
Lastly consider shooting with shutter off as that gives you an extra stop and very marginal motion blur that you probably will never notice. As I understand it 709 might be cleaner with gain than S-Log but i'm not sure.

Again - test for yourself.
 
Thanks for the feedback guys. When i was writing his film, I was thinking that it was the kind of movie that could be made possible by a camera like the F3 because of its strength in low light (I actually thought the Alexa would be nice but it's insanely out of my price range). So much of the emotion of this short comes from being able to shoot in some of the natural night lights in LA alleys. That's why I'm so keen to make sure we know the camera can pull off what we need it to (if not, we might as well switch to a C300 but I've seen tests and they seem pretty comparable in low light).

I would love to do proper tests but unfortunatly, my production can only afford to rent the camera for one weekend. We got it free for this weekend from USC (they let grad students in the advanced directing take it out once a semester) but we were only given the cheap Sony lenses. Next weekend I'm shelling out the cash to rent it again along with a set of super speeds but we'll need to shoot every night from Fri to Sun so there's no way to test the F3 with the super speeds before we shoot. That's why I was hoping I could trust Able Cine's ISOs as I had those in mind when i scouted our dark alley with light meter/DSLR. I guess we'll just have to ride the gain and hope for the best (it's OK if this stuff is a bit noisy as the scene is supposed to feel rougher than the other ones). I'll be happy as long as it's cleaner than some driving shots we did on a 7D at 800 ISO.
 
All I can say is that yesterday I did a shoot outdoors mid-day with S-Log and with the maximum internal filter applied (2) and a matte box shooting away from the sun the largest f/stop possible was 5.6 and I am fairly sure that last year around this season without S-log I could have gone to at least 4 or less. When I reviewed the footage I probably should have reduced another half or full stop. I am going to have to buy some filters for outdoors because the built in ones are not enough with S-Log. It did look great with the huge contrast in brightness and never went over 100% but the highlights were very bright.
 
Yeah, I did some tests and put it around 5.6/8 with s-log at 0db also under bright sun. Now I keep a 2 stop ND on the lens in those conditions and if the light drops I just go to the #1 setting on the ND switch.
 
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