0-100IRE slog adjustment?

Hunter Hampton

Hunter Hampton

Carbonite Member
Question for you F35 geniuses: Is it possible to adjust the signal through the hdsdi (either PP or whatever) so that in s-log, the hdsdi sends out 0-100IRE instead of the full 0-109IRE? Im just using a prores422 recorder and have a suspicion it might squeeze in a bit more highlight detail if I could do that.

Thanks!
 
Why not switch to Hypergammas? If you're recording to 422, will you really be planning to do much in post?
 
I was hoping to keep some of the same LUTs I've been working with, does the hyper gamma look significantly different than slog?

Edit: based on what I've seen the hypergammas seem to have a "baked" in contrast.
 
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Thats what my recorder records and I like it- If I had the chump change I might get a better recorder!

Ok how about this; How do I tweak picture profiles so that I might make one with slog 0-100IRE? Is there some software needed or is it something you can do in camera? I guess I can use a waveform to measure the clip at 100.
 
If you're using LUTS tht means you're using Davinci. Then why not setting those prores files in davinci to full range?
That's going to be easier than anything else.
 
Mac- correct me if I'm wrong, but if the hdsdi is spitting out 0-255 (0-109IRE), and the prores recorder is recording broadcast safe 16-235, then the only thing your getting back is an illusion of extra range by stretching back to 0-255.

I remember after shooting on the f3 to card (xdcam) and then prores recorder, I've noticed the difference in the range and thought it might be a similar issue with the f35? I haven't really noticed a problem with doing what you said, but Im just curious if there would be a bit extra if you mapped the slog to fit inside broadcast safe. I believe that Log-C on the alexa does just that when shooting prores.

Edit: 10-bit prores values being 64-940 I guess... But you know what I mean
 
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Hunter Hampton said:
Mac- correct me if I'm wrong, but if the hdsdi is spitting out 0-255 (0-109IRE), and the prores recorder is recording broadcast safe 16-235, then the only thing your getting back is an illusion of extra range by stretching back to 0-255.

I remember after shooting on the f3 to card (xdcam) and then prores recorder, I've noticed the difference in the range and thought it might be a similar issue with the f35? I haven't really noticed a problem with doing what you said, but Im just curious if there would be a bit extra if you mapped the slog to fit inside broadcast safe. I believe that Log-C on the alexa does just that when shooting prores.

Edit: 10-bit prores values being 64-940 I guess... But you know what I mean
Click to expand...

As I best understand and recall, it's a codec read-back issue, not a recording issue perse. The recorder is taking the 0-109% values in over SDI, and is feeding all on them into the encoder, and all 0-109% are encoded to the recorded files. Here's the big but.... when you play back a Pro Res file through a quicktime render engine, the decoder/playback clips at 104%. Now, some professional non-linear editors and color correcters should be opening the file without quicktime, decoding it in such a way that the levels can be retrieved, and crushed below 104% before being recompressed into the finished file. And I may have the technicals slightly wrong here. I can't find many good links on this issue right now. I do know if you use the wrong software, the footage will just look crushed.

My thinking was that there is a way in DaVinci to pull these levels back down.

Honestly, I've just been avoiding ProRes for important jobs.
 
Hunter you are correct about Hypergamma 5 looking different than if you were to shoot SLOG and load in one of our standard LUT's. The color is a little down and the contrast is low. I've been messing with the black gamma setting and also boosting the contrast in camera trying to get a setting I could shoot to prores and come out with as little corrections needed as possible. I still can't get footage to "pop" like some examples of Macgregors's Lut's here and still need to play around with the color in final cut.

The DP4 has become a bit of a hassle to use with my F35 because of how it renders the image from the F35. The colors are usually horribly off, if I check my TV Logic 17 image in the F35, I am usually happier with how the colors are rendered. F35 footage looks so much better and I am able to appreciate what it is seeing so much more when I watch it connected HDSDI to a calibrated HDSDI monitor. When I watch it on my laptop, it looks like it needs a lot more correction. After you guys are doing your color correction to footage, is there a secret to preparing footage for web and computer screens in general that will preserve the DR in the footage?
 
I have a weird thought on this as well... I noticed something while shooting today. On 23.98 422 10-bit into the Odyssey 7Q (to DPX) in SLOG my highlights were getting crushed at legal levels. I had read this thread a bit earlier in the day so I messed with some settings. I then found that with some of the hyper gammas, the O7Q was reporting to record to 109IRE as expected. THEN I swapped to 23.98 444 12-bit (maybe 10-bit, I forget, stupidly, but I know it was the 444 setting) back in SLOG and the O7Q THEN reported recording to 109IRE once again.

Does the F35 clip the highlights when recording to 422/444? I attached some screenshots of the readouts. I should have let them blow so you guys could actually see the clipping point, but the first shot is of the 23.98 422, second is with a hyper gamma, still in 23.98 422, and third is with the setting in 23.98 444, you can see it's recording over 100.

Now this is all to DPX, but if this has any relevance on prores, it may be helpful. I too am wondering what happens to footage when recorded in the different settings, and haven't really properly tested yet, but now I want to! I know the first screenshot looks different exposure, which it was, since it was clipping at the top, which I should have illustrated, but i hope you'll trust me hah.

Sorry for the big images.

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Hunter Hampton said:
Mac- correct me if I'm wrong, but if the hdsdi is spitting out 0-255 (0-109IRE), and the prores recorder is recording broadcast safe 16-235, then the only thing your getting back is an illusion of extra range by stretching back to 0-255.

I remember after shooting on the f3 to card (xdcam) and then prores recorder, I've noticed the difference in the range and thought it might be a similar issue with the f35? I haven't really noticed a problem with doing what you said, but Im just curious if there would be a bit extra if you mapped the slog to fit inside broadcast safe. I believe that Log-C on the alexa does just that when shooting prores.

Edit: 10-bit prores values being 64-940 I guess... But you know what I mean
Click to expand...


Your recorder will record full range to prores. Nothing is clipped. But your prores files will only show the limited range In the editing software. The info is there but it's not showing. BUT once you get those prores files in davinci (or scratch or any decent grading suite) you can tell the program that those files are full range (clip settings - data levels). And done. Nothing is clipped.

This is easy to check if you were to record the same image on DPX and prores. They won't match until you switch to full range in davinci. All this was explained ages ago sir!
 
I see that one can make custom gamma curves with the CVP editor software and load it into the F35.
Now I played around with it and you can load a standard Slog preset and adjust the top end from 109% to 100%.
wonder how that would affect the signal at the end of the day?
 
Hunter, there is actually a "white clip" function that you can set in-camera. Never used it before, but you can independently set R, G, and B values on a range from -99 to +99 until you've got the result you want. Sounds like it might take awhile to figure out, but if you want S-log and the 100IRE in camera, might be the way to go.
 
I saw someone post this over in the F5 forum. https://vimeo.com/96746530

I think it would be really cool to get the Macgregor LUT saved as an MLUT on the F35. This would give the option of recording the LUT straight onto prores. All you would have to do is toggle the MLUT button, there is a way to turn off that little MLUT in the corner when it's on.

I guess the question I have, and worth putting some time into learning, is getting the LUT's already developed into CVP editor, from there we can save them onto a memory stick and load them into the F35. I guess the road block is figuring out how to import SLOG into Resolve, color correct, then save that information into CVP editor for creating the MLUT.
 
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