FS7: Cine EI with SmallHD 502 and LUTs

J

joobny

Member
Hi,

I recently purchased a SmallHD 502 to use as a replacement monitor for my FS7. It appealed particularly as it enables me to apply a LUT while still being able to view the waveform but a couple of things have left me a bit confused.

In order for the FS7 EI switch to affect the appearance of the footage being viewed on my SmallHD 502, I have to turn on the Rec709 (800%) LUT for SDI2/HDMI in my FS7 menus rather than on the 502. But this means that the Waveform on the 502 begins to read the LUT values rather than the underlying Slog values.

And if I turn on the Rec709 (800%) LUT on the 502, then the 502 waveform will read the underlying Slog footage but when I'm deliberately under or overexposing the image being viewed through the LUT will be over or under exposed too.

So, I found Alister Chapman's '709 exposure compensated LUTs' and added them to my 502. This means I can view the waveform on the 502 as it reads the over/underexposed Slog footage but I can use one of the exposure compensated LUTs so that the footage looks correctly exposed on my 502.

This is the way that I'd like to work as it means I'm still monitoring what the Slog footage is doing while viewing the footage through a LUT that makes it look correctly exposed. However, can anyone tell me what the six Slog2 and Slog3 values are for 90% white when overexposing and underexposing to one, two and three stops?

Or is there another better method of using the SmallHD 502 with Cine EI that I'm completely missing? Perhaps it should be the six Rec 709 (800%) values for 90% white when oxerexposing and underexposing to one, two and three stops that I should be looking for? That way I would still be able to use the EI switch on the camera itself...

Thanks!
 
Forget EI as a concept. Slog 3 is best at about 1000, use a regular LUT and make the lutted image look a little bright, or build a LUT with 1000ISO (aka a -1 compensation)

If you need to expose at 2000, you are best just seeing a 'thin' image.

Also check the RGB WFM on the 502, I have it fully screen as my first 'page' on the monitor.

S
 
Hi joobny,

personally, I would suggest considering feeding the SmallHD a signal with S-Log3 applied as a LUT (rather than Rec709800%) if you want all the 'pretty' LUTting to be done in the monitor. That way, the waveform (which as I recall is always before the LUT in SmallHD) will always have the same values - as for native ISO - and you will only need one LUT whatever CineEI you choose (and I think that CineEI is a very useful tool even if you stick to rating the camera at one ISO). All you need to keep an eye on is clipping, and for myself I don't tend to have difficulty with that (I use internal MLUTs on my Sony F in CineEI).

However, since your preferred approach is to know 90% values for different CineEI ISOs, here they are:
ISO S-Log2 S-Log3
500 84% 79% 2-Stops
640 80% 76%
800 76% 73%
1000 72% 70% 1-Stop
1250 67% 67%
1600 63% 64%
2000 59% 61% Native
2500 55% 58%
3200 51% 55%
4000 47% 52% 1-Stop
5000 43% 49%
6400 39% 46%
8000 36% 43% 2-Stops

Ben
 
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:happy:

You could also just line your waveform monitor up to 90% IRE with a white card (or white piece of paper) and lower your lens aperture one stop at a time and observe the new IRE value.
 
Hi joobny,

I promise, those should be the values according to the specs - I've just had to go through calculating all of those as it's not a table I have a use for myself but quick for me to knock up if it helps someone,

Mind you, I'd be interested to hear how you get on - always trying to recheck myself,

Ben
 
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