View Full Version : Exposing RAW Slog2?

Dave Allen
October 2nd, 2014, 02:30 PM
I was reading somewhere here by Alister Chapman that footage shot on the 7Q with the FS700 should be exposed in the 55% range.

How do you handle exposure monitoring an adjustment?

Chris Medico
October 2nd, 2014, 02:41 PM
The best way to do it in my opinion is to use a grey card and the waveform function of the 7Q.

Unless you are using a LUT the grey card should be exposed to 32% on the waveform.

The white side of the card should be around 59%.

Dave Allen
October 2nd, 2014, 08:30 PM
And if I have the 7Q LUT applied, what percentage would you advise?

Chris Medico
October 3rd, 2014, 06:37 AM
I would recommend keeping it between 45% and 55% depending on which end of the luminance curve you want to protect most.

I expose for about 48% when using shooting straight 709 gamma.

Dave Allen
October 4th, 2014, 07:19 PM
Thanks Chris!

Colin Elves
October 5th, 2014, 03:03 PM
I think you might find that a little noisy. I'd put a grey card around 50% I guess (I use my grey card for colour balancing only!) - you want to expose at least a stop above 'correct' exposure to avoid having a noisy image. I wouldn't use the LUT at all - everything will just look wrong.

BTW CD have plans in place for exposure corrected LUTs - i.e. ISO 500, ISO 1000 equivalents, to help with this.

Dave Allen
October 6th, 2014, 12:33 AM
Convergent tells me that the REC709 LUT control when enabled only appears on the screen and does not affect exposure nor apply to the recorded image.

Colin Elves
October 6th, 2014, 02:53 AM
You're right, it's a viewing Look Up Table, so doesn't affect the recorded image.

The point is that it's set 'correctly' and correctly means it is a standard conversion from the Slog2 feed as specified by Sony. The problem with that is that Sony have set the 'correct' exposure for the camera as ISO 2000, as that is the exposure point that 'maximises' the Dynamic Range of the camera. The problem with *that* is to get the 'maximum' DR from the camera Sony are pushing the shadows *a lot* and that introduces a lot of noise to the image.

Personally, I've found the best approach is to expose the image one or two stops above 'correct' and then bring the exposure down in post (often just pulling down the shadows). This drags the important bits of your image up and out of the noise and gives you nice clean blacks. And this is why I find the LUT a bit useless because if you 'overexpose' by two stops with the LUT on it looks awful - everything looks blown out.

The downside of this approach is that you lose 1-2 stops of DR (i.e. you get 11 stops rather than 13) - but in most situations you don't need the full DR of the camera.

Dan Keaton
October 19th, 2014, 09:57 AM
Dear Colin,

Thank you for posting your recommendation for exposing the Sony FS700.

I agree completely.

Just to confirm, the Odyssey7Q LUT's are for viewing only, at least at this time.

Thus, the recording is not affected in any way by pressing the LUT button.

I also recommend over-exposing by 1 to 2 stops (and no more.)

This is the best way to achieve low-noise images from the FS700, in my opinion.

On the Odyssey7Q, when you press the LUT button, you are applying the LUT to the image on the monitor, and this LUT is also applied to the Waveform Monitor, Histogram, Zebras, etc.

We recommend using Picture Profile 7, reset to factory defaults, then one can select Rec. 709, Rec. 709 800% or S-Log 2 in the gamma menu setting within the Picture Profile 7.

If you select S-Log 2, then the LUT button will be active and usable.

(I recommend selecting S-Log 2 to get the best possible image out of the FS700, but some may want to record in Rec. 709, or Rec. 709 800%.

The Odyssey7Q will put out a message if, for the recording mode that you have select, you need S-Log 2. If you see this message, please enable Picture Profile 7, with Gamma = S-Log 2, and ensure that this is a factory default Picture Profile 7.)

For proper exposure, please leave the LUT button off (on the Odyssey7Q), and use the Waveform Monitor, Luma, in Full Screen ,to set your exposure.

Then when you turn the Waveform Monitor off, you will see a S-Log 2 image, but it will be properly exposed.

If you turn on the LUT, then the monitor image will be Rec. 709, but it will be overexposed.

If you have to show a client, you can then reduce the exposure, but I recommend that you turn off the LUT, then re-expose, for the lowest noise image.

I hope this helps.


Dave Allen
November 25th, 2014, 09:12 PM
If ones over exposes by 1-2 stops, is this done by setting exposure to 40-50%, then literally watching the lens F stop numbers as one opens up one to 2 stops more, or can this just be done by increasing the exposure percentage a designated amount expressed as a percentage number?

And since SLog2 in Picture Profile 7 is recommended for RAW shooting, anything different recommended when shooting in 4KRAW to 4K ProRes setting?

Chris Medico
November 25th, 2014, 09:48 PM
In my opinion you should use the stops on the lens because depending on where you are in the curve the values will change at different rates. It will be easier to keep track of what you are doing with the lens.