Why can’t I have LUT’s in S&Q on the F5, F55 and FS7?

This is an often asked question about the Sony PMW-F55, F5 and FS7 cameras.

There are several modes and options where the LUT’s are not available or restricted to either all on or all off. That is to say that you can’t have LUT’s on for just the viewfinder or just the SDI output, you can only have the LUT’s applied everywhere, including the internal recordings which isn’t normally desirable.

The problem appears to stem from a limitation on the number of video processing units within the cameras. Certain functions within the camera require a video processor. Functions such as adding LUT’s, reading the sensor at high speed for S&Q, providing a 4K output on the SDI or HDMI each appear to require dedicated processing and as there are on so many processors available this limits some of the options we have. I don’t know of the exact architecture of the cameras but the diagrams below represent what I think is going on and why we have limited LUT options in certain modes. Please note that there are a lot of other video processes going on in the camera and this is a very simplified overview of what I think is more or less going on.

Slide11-1024x576 Why can't I have LUT's in S&Q on the F5, F55 and FS7?
Normal operation, each output can choose between the S-Log signal path or the separate LUT + EI signal path.
Slide21-1024x576 Why can't I have LUT's in S&Q on the F5, F55 and FS7?
S&Q Motion: As there are only enough processors for a single path you have to choose between S-log only or LUT + EI only.
Slide3-1024x576 Why can't I have LUT's in S&Q on the F5, F55 and FS7?
When outputting 4K a video processor is needed to split the output signal across multiple HDSDI’s or drive the 4K HDMI. So again, you can only have S-Log or LUT’s, you can’t have both.

One way around the problem of not having LUT’s in S&Q is to use the viewfinders high contrast mode (F5/F55 only). To enable this mode you must assign it to one of the assignable buttons. The high contrast mode applies a rec-709 like gamma curve to the viewfinder image so you will have almost exactly the same contrast and brightness as you would using the 709(800) LUT. As it’s only a gamma correction it will be less saturated than the LUT, but it’s still very useful for judging exposure. Remember if you are not using or unable to use the LUT’s, the waveform and zebras will be measuring the S-log signal, even if you have the VF High Contrast mode enabled.

Another way around this issue is to use a 3rd party viewfinder that can add it’s own LUT’s. Then simply leave the LUT’s off in the camera and use the VF to apply a LUT. The Zacuto Gratical is great for this as you can not only add the LUT in the VF but also send the LUT out over the VF’s SDI or HDMI output. If you want EI then you will need to load some exposure compensated LUT’s directly to the VF and use the appropriate LUT for each EI.

3 thoughts on “Why can’t I have LUT’s in S&Q on the F5, F55 and FS7?”

  1. I just add a LUT in my monitor. All this talk about “clients need to see the image with a look”…..I wonder why they just don’t have a LUT in the monitor. A good monitor with LUT capability starts around $1200.00 US (Odyssey 7). I would think if you are shooting with an F5/55, you’d spend a fair amount on a quality monitor.
    I’ve yet to have a client looking at something and complain about the flat look of slog, because they see both slog and a LUT image.
    Much ado about nothing.

    1. It’s not so much for clients, but for making exposure assessment easy. Using the 709(800) LUT makes getting exposure right as simple as looking in the viewfinder and if it looks right, it is right. Plus then you can use EI to shift your latitude/noise as required very easily. This is a great way to shoot on the move, not everyone has a monitor attached all the time. But if you switch to S&Q then you loose the LUT’s so you also loose EI.

      1. Hi Alister, i´m new in. It´s a great site you have!
        I´m soon will shoot a longer nature and wildlife documentary with the f 55,
        and looking for some help with wich lut would be the best for.
        Almost everything will be outside, and a lot hfr.
        I´m starting to test some, but maybe i can cut off some useless time with some good tips.

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