FS7: Let's Talk LUTs

ProfessorU

ProfessorU

Veteran
I have a client who is asking for me to shoot on the FS7 in a LUT that doesn't need much grading, but isn't log. Their impression is that there is some magical gamma I can apply to make the footage look great coming out of the camera and still give them dynamic range to change it if they don't like it.

Now I don't understand why anyone wouldn't just shoot S-log3 and then apply a 709 over the top of it to get exactly this, but he seems to think that will take too much time or processing or something. Since my relationship with this client is online-only, I don't really have the luxury of digging into workflow and color science.

Do I just shoot with 709 and make sure I get the exposure right? Or is there a different gamma I should be considering?
 
your client is wrong, but you can't tell them that.

Just shoot with LC709A baked in and expose it for middle grey... or sure just use a hyper gamma if you don't mind the look of custom mode.

what would this world be without crazy clients...
 
ProfessorU said:
I have a client who is asking for me to shoot on the FS7 in a LUT that doesn't need much grading, but isn't log. Their impression is that there is some magical gamma I can apply to make the footage look great coming out of the camera and still give them dynamic range to change it if they don't like it.

Now I don't understand why anyone wouldn't just shoot S-log3 and then apply a 709 over the top of it to get exactly this, but he seems to think that will take too much time or processing or something. Since my relationship with this client is online-only, I don't really have the luxury of digging into workflow and color science.

Do I just shoot with 709 and make sure I get the exposure right? Or is there a different gamma I should be considering?
Click to expand...

The Sony issued LUT .. "Slog3 to 709" should do this (create a 709 ready image)

(not LC709 or LC709a which are Low Contrast and designed to be a base point to grade from)

This is the 'magical gamma'.. Sony made it for you.

Absolutely it is sensible to shoot log and apply a single LUT.. this protects both you the operator, and them the client.

1) If exposure and WB are correct the client can colour (normalise) the shoot with one click - easy workflow for client.
2) if you mis expose (or WB) the image is simple to rescue
3) if you have a DR scene beyond the 709 DR the image can be rescued
4) if the client later wants to take the project further with the application of a 'look', or match the shots with another shoot on another camera, then the data is there to do this.

If you LutBake or shoot 709/cinegamma options 2/3/4 become complex or impossible.

What a sensible client. Thier approach is far from 'wrong' it is 100% right.

Now your bit.
You need to work out exactly the exposure (2000ISO) that works with the LUT, and you need to shoot avoiding mixed (off axis) light and correctly select one of the three WB options.
You should light so your ratios work with this LUT.
Should you not be able to avoid off axis lighting shoot a grey card to make correction simple for the client.

If you have a decent monitor with the LUT applied exposure should be easy.. WSYIWYG

If you want to take it one step further you could consider taking this LUT and modifying it to work with 1000ISO, this will give you a cleaner file, you would need to then pass this LUT to the client. If you use a homebrew LUT I would suggest getting the title of that LUT on the clapboard if you use it or at least shoot the details of the LUT and where it can be got from on the first shot. I would only use an offspeed homebrew LUT after consultation with the client as it may interfere with (1) if this is a many camera/location shoot.

S
 
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I've shot for a few clients that have had the same hurdle in their mind.
If you're using CineEI, choose a LUT you like or custom make your own, and burn it in when shooting (just make sure you don't drop the ball on the exposure ;) heh).

I've been shooting weddings this way and its been great so far (the guys I shoot for have no time to colour anything, so I have to deliver a good image straight out of camera). I may tweak this LUT a bit more to be a bit more contrasty, but it worked well.
burntin.jpg
 
chappelldigital said:
I've shot for a few clients that have had the same hurdle in their mind.
If you're using CineEI, choose a LUT you like or custom make your own, and burn it in when shooting (just make sure you don't drop the ball on the exposure ;) heh).

I've been shooting weddings this way and its been great so far (the guys I shoot for have no time to colour anything, so I have to deliver a good image straight out of camera). I may tweak this LUT a bit more to be a bit more contrasty, but it worked well.
View attachment 111440
Click to expand...
All of this is a bit co fusing to me. I always assumed a LUT was for viewing only and that it did not effect the actual recoding.
Land...what about projects which depend a lot on available light acquisition?
 
allenfacemire said:
All of this is a bit co fusing to me. I always assumed a LUT was for viewing only and that it did not effect the actual recoding.
Land...what about projects which depend a lot on available light acquisition?
Click to expand...

In CineEi mode you have a choice to either load a LUT for viewing while recording SLog3 or to bake it in at the time of recording.

Both are valid choices but obviously shooting SLog3 and applying a LUT in post gives you much more wriggle room in post sometimes baking in a nicely handcrafted LUT gives a good balance of post flexibility and being able to send it out the door straight from the camera. I reckon most people can build a better LUT than all of the Custom Mode Hypergammas which is another reason to burn a LUT rather than use Sony's ugly gamma curves.
 
Nirv said:
obviously shooting SLog3 and applying a LUT in post gives you much more wriggle room
Click to expand...

+1 on that. If I'm doing the post (or I know the company I'm shooting for will do the post work) then I'll shoot without burning in the LUT... In those cases the LUT is just to view a nicer image on the screen to help expose etc.
 
aalleexx said:
when viewing the lut on camera, do you expose differently as to when viewing the image without the lut?
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Yes.

A custom LUT may have different ire values for grey and 90% white the the 'usual' rec709 values. Take note of these numbers when you build the LUT and set your zebras to these levels or judge them on the waveform. Some of my LUTs have their 90% white around 75-80 to maintain a nice white roll off.

When the LUT is off you're just seeing the SLog3 levels.
 
You expose based on what you are seeing with the LUT

If you set EI @ 500, you'll see a much darker image in the VF with the LUT. You expose based on what you see with the LUT active. The internal recording is 2000 ISO still, and will look overexposed when viewed with no LUT.

As plainly as possible (I had a hard time wrapping my head around this):

If your scene bright, you can lower your EI, for example to 500. With the LUT active, what you'll see in the viewfinder will be what you would expect if using a lower ISO.
Your shot is still recorded @ 2000 ISO and will look over exposed when you watch it back with no LUT.
In post, you pull the levels down (so it matches what you could see @ 500EI).
This will give you less dynamic range than the 14 stops, and will give you a cleaner image as the darks (which you recorded @ 2000 ISO), you'll be dropping down to where you want, so there will be less noise.

The LUT basically acts as an 'assist' to help you overexpose and underexpose the image.... letting you decide where to keep most of your image's dynamic range.
Overexposing (lower EI) means you're preserving the shadows and losing dynamic range in the highlights
Underexposing (higher EI) means you're preserving the highlights, and losing dynamic range in the shadows.
 
so what do you guys do when shooting slog? do you expose with slog, check the LUT to make sure it looks good, then go back to slog then record?
 
aalleexx, usually when I shoot Slog, I monitor in Slog, with Slog waveforms, and then use a Gratical HD to see what it looks like with a LUT applied, including those waveforms. It's a nice to be able to see both, and I can also use the SDI out to go to a client monitor with at least normalish contrast.

I'm looking at the note from my client right now. "Please use a profile that requires some but not not total colour."
 
The FS7 has a few quirks that make recording in log and monitoring in REC709 not super easy. You basically have to give up waveforms, which for me makes it impractical. I spent my first year with the camera just learning to use and monitor in Slog3, and then when I added the Gratical HD to my kit, am really enjoying being able to see both.

The worst thing ever is when you have to send a flat look to the client monitor and then the client LIKES that look. I absolutely hate that the FS7 forced me into situations like that before I had a viewfinder or monitor with LUT support.
 
Pro Tip:

If you are shooting Slog and monitoring with a custom or REC709 VF LUT and you want to quickly see Slog waveform just press the S&Q button, voila. I find a quick check of Slog waveform for clipping before rolling is all I need.

It's virtually impossible to screw up exposure on the stock FS7.
 
chappelldigital said:
You can record SLOG3, monitor a LUT and have the waveform up at the same time.
Click to expand...

I know, but the waveform only displays the LUT output not the underlying SLog3 signal, if you want to see the SLog3 waveform pressing the S&Q button for a quick peek is a nifty workaround.
 
Nice!
Good to know!

You can also map a custom key to "High/Low Key" switch back and forth between the high and low ends of Slog in the VF, I believe I got that from Doug Jensen's tips.
Can't recall if it gives you the WFM or not... but its useful to have a peek at whats under your LUT
 
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