Gemini 444 F3 and S Log

[Alister Chapman]

When shooting S-Log you will have two outputs, the 4:2:2 or 4:4:4 S-Log on the A-B SDi outputs plus the monitor output which can be switched between S-Log and S-Log + LUT. Recordings to SxS cards will be S-Log + LUT.

You won't have the normal gamma options when using S-Log, S-Log is an extreme type of gamma curve.

The best way to think of a LUT is as a preset color correction, curves filter or brightness/contrast filter. You could switch LUT's from scene to scene. The LUT converts the S-Log to Rec-709 as that is what your monitor will normally be calibrated for, but you must remember that the LUT is over 12 stops and making it fit into the 7 - 8 stops of Rec 709. So, some picture information is getting discarded and some will be compressed. By how much depends on the LUT, but it means that the image is a compromise. Arguably, grading the S-Log creates a compromise image as again we are making the 12+ stops of the camera look good on a 7 stop display (or film-out). But in the edit suite or grading suite you have the ability to take the specific parts of each image that you want and adjust them precisely the way you want.

I believe user LUT's will have to be created on a PC and then uploaded to the camera in the same way as they are with the F35 etc, but I'm not sure about this.

[Doug Jensen]

QUOTE: "You won't have the normal gamma options when using S-Log, S-Log is an extreme type of gamma curve."

And that, in a nut shell, is exactly the reason why you cannot shoot excellent REC709 and S-LOG simultaneously with the camera. You've got to decide which direction you're going to go with your workflow before you begin shooting. I cannot wait to put hypergammas up against S-LOG and see what the real difference is.

[Leonard Levy]

Thanks once again Alister.

I'm wondering though, since the SxS will be recording S-Log + LUT why you were skeptical that the SxS recording would have the wrong exposure? Shouldn't the LUT be based on the S-Log exposure and while limited in DR still be placed pretty much in the center of the exposure?

If one would generally use a LUT for for lighting and monitoring then shouldn't the exposure match the S-Log?

Also - in the Las Vegas tests were they recording the LUT onto the SxS cards? - again why was the exposure off ?

[Nate Weaver]

Originally Posted by Leonard Levy

Also - in the Las Vegas tests were they recording the LUT onto the SxS cards? - again why was the exposure off ?

Likely because they were monitoring while shooting with the LUT off, and exposing for 800asa.

I think what Sony wants you to do is monitor with a Rec 709 LUT at 800 ASA, and then your resulting S-Log will basically be a stop under, which is really ok given the noise level of the camera.

THEN, the guy who colored it (Tom Wong) didn't apply a LUT to bring the exposure up to match what they would have seen if they had monitored while shooting with a LUT. Make sense? Even if he did, it would have been trivial to bring exposure back down again.

So the deal is, if you are going to want SxS to match the S-Log, you're going to have to roll your own LUT to do so (not hard, if you know a colorist or good DIT). Unless Sony already make one for you when the new deal ships (they are talking about 4 LUTs internally avail, so when there's more choices maybe one that matches exposure will be one of them)

After all this, you might be asking, why wouldnt they do this already?

The answer is to underexpose (save highlights) in S-Log, and give the colorist more to play with.

[Doug Jensen]

The question is, can you use Hypergamma as part of the LUT that is recorded to the SxS card while you are shooting with S-LOG? If the answer is no, then you will NEVER be able to get optimal picture quality on the SxS card and the S-LOG recorder at the same time. Period. In my opinion, the use of Hypergammas is a required element of a decent picture profile that will create great looking images with no grading.

So, you're going to have to choose your workflow before you start shooting. You aren't going to be able to straddle the fence and decide which way to go later. Note that Sony always describes the SxS files as "proxy" files, not as an alternative format for finishing. If you choose to go with S-LOG, you are committed at that point, or else you must accept the fact that you have compromised what you could have gotten instead.

[Leonard Levy]

Nate ,

I'm not sure I follow what you're saying about the L:as Vegas test was exposed - obviously it would be great if someone from that crew would chime in.
If they used Rec 709 to monitor while shooting then the SxS card shouldn't have been overexposed. Perhaps they just used a meter to expose at 800 ASA? I can't recall if this was described on the test posts.

Seems that the SxS footage should have been underexposed not overexposed if S-Log was rated at 1600 and Rec 709 at 800. Are those ASA's Sony specs?

[Alister Chapman]

Those are Sony figures.

When shooting S-Log you would expose for 1600 ISO as this is what the camera becomes rated at. The S-Log + LUT output would also be 1600 ISO, just with reduced dynamic range.

The amount of underexposure of the S-Log material compared to the S-Log + LUT output or monitoring will depend on the LUT used and whether the LUT is simply ignoring anything beyond the normal Rec-709 range or shifting the range further up the S-Log curve.

[Leonard Levy]

Sounds like its all speculation till we see the final LUT's in practice though I'm still curious about how they did the Las Vegas shoot.
Have you seen them Alister?

[Alister Chapman]

All that's floating around at the moment is a beta of the S-Log firmware. I don't believe this has all the options implemented.

[Leonard Levy]

Thanks for the info. Have a good time at you LA seminars.

BTW Is there anyplace to rent a Hurricane in LA? ( for use in San Francisco tho.)