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Sony NXCAM NEX-FS700 CineAlta
4K EXMOR sensor with SDI, slow-motion recording.


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Old January 15th, 2013, 04:35 PM   #1
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FS700 and FPS question

I'm recording in 1080/24P FX, just for the record is it recording at 24 or at 23.976 fps?
I'm going to calibrate my new L-478D Sekonic light meter and I have the option of selecting
one or the other and I want to be as accurate as possible. thanks!
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Old January 15th, 2013, 07:38 PM   #2
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Re: FS700 and FPS question

Unfortunately I don't own an FS700 (yet) so I can't answer that question, but the most useful program on my PC can -> MediaInfo

It's super useful when you are given media from an unknown source
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Old January 15th, 2013, 07:39 PM   #3
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Re: FS700 and FPS question

Quote:
Originally Posted by Kajito Nagib View Post
I'm recording in 1080/24P FX, just for the record is it recording at 24 or at 23.976 fps?
I'm going to calibrate my new L-478D Sekonic light meter and I have the option of selecting
one or the other and I want to be as accurate as possible. thanks!
It is 23.97.
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Old January 15th, 2013, 11:57 PM   #4
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Re: FS700 and FPS question

Chris thanks.
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Old January 16th, 2013, 01:46 PM   #5
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Re: FS700 and FPS question

0.03 fps is not going to make any appreciable difference to exposure measurements. Even if your using t-stops rather than f-stops the difference really isn't worth worrying about.
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Old January 16th, 2013, 02:36 PM   #6
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Re: FS700 and FPS question

thanks Alister. BTW I enjoyed your gamma workshop in NYC.
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Old January 17th, 2013, 09:54 AM   #7
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Re: FS700 and FPS question

t-stops are simply f-stops that take into account the internal light loss in a lens. No lens transmits 100% of light through to the sensor/gate, and every lens is different... some are less efficient than others. Still lens manufacturers just ignore this fact, but the professional film lens manufacturers like Panavision, Zeiss, Arri etc... real motion picture lenses in other words... decided it was worth it to mark lenses a little more carefully (or anally).

T-stops are never read from a light meter only f-stops. There is no computation involved in setting the stop on a lens marked in t-stops. This light loss transmission factor is determined by the manufacturer and the lens is marked accordingly.

I only comment to say this to Kajito: Don't worry about t-stops since it is something you don't have to give any thought to... I'm sure Alister wasn't purposely trying to muddy the waters by bringing up t-stops in his response, but it seemed like it might cause confusion...

But Alister is correct that the discrepancy between 24 and 24.976 is in fact imperceptible so don't worry about that either.

:)
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Old January 17th, 2013, 12:17 PM   #8
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Re: FS700 and FPS question

You will often find an exposure difference the equivalent of a stop between different lenses set to the same f-stop. If lenses are calibrated and use T-stops then your exposure will be more accurate and it should be identical no matter which lens you place on the camera, there is nothing anal about this. You can even get low cost lenses calibrated in T stops like the Samyang cine range. Most light meters give you an exposure setting based on f-stop only and make no allowance for different lens light losses and normally assume only a very small or zero light loss. Therefore when using a light meter and lenses with f-stops your exposure will almost always be just a little bit less than "perfect"and vary from lens to lens.

If you use T stops you will have consistent exposure from lens to lens. Once you have worked out whether you light meter makes an allowance for transmission losses you can simply add or subtract that offset from it's readings to get "perfect" and repeatable exposure every time. The main benefit comes when swapping between prime lenses to re-frame. With T-Stops your exposure will remain constant, with f-stops it may vary.

But, all of this is overkill as differences in gamma, where you point the light meter, the accuracy of your grey card etc etc will men that there is always a degree of inaccuracy or uncertainty when using a light meter. Really when using a video camera, the best light meter is either a waveform monitor or make use of the histogram, both of which will be giving you the actual exposure levels as seen by the camera and take into account things like gamma, transmission losses, ND filter variation and so on. Light meters can be useful when you don't have a camera available, but really they are a relic from the past and we have much better and much more accurate tools available today.
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Old January 17th, 2013, 12:39 PM   #9
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Re: FS700 and FPS question

Agreed!
If you are using a light meter on a video shoot, you should check it against a waveform monitor or histogram anyway. Light meters can be very useful for working out lighting ratios without having to constantly look at a monitor, but to set the exposure, I hope folks are relying on better, more reliable tools!

Light meters are a necessity for film shoots, and a good way to eat some extra time on a video shoot.
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Old January 17th, 2013, 01:17 PM   #10
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Re: FS700 and FPS question

thanks guys for explanation. I just recently started to use a light meter and find it helpful in certain situations although I do agree it takes up extra time and effort.
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