FS7: FS7 MLUT to match Small HD 702

S

spencerbenjamin

Member
Hi all, I've got a weird issue where I'm trying to load LUTs into the FS7 and have the same LUTs available in my new Small HD 702. I started a thread in the support section which has a bit more info:

http://www.dvxuser.com/V6/showthread.php?344103-Small-HD-702-(-amp-502-)-won-t-take-REC-709-LUT

But basically I am able to load some LC709, LC709A LUTs into the Small HD, but when I tried to load LUTs which convert Slog3/S-Gamut3.cine into REC709, the Small HD won't take them.

This morning I thought I'd hit the jackpot as I downloaded some LUTs from the Convergent Design site, and the SLog3 to REC709 LUT loaded up ok on the Small HD.

Then I noticed the zebras on the camera viewfinder (with preset REC709 LUT) and the zebras in the Small HD were in slightly different places. In the viewfinder I have zebras set at 70% with a 10% aperture (ie. 65%-75%). On the Small HD I have zebras set with a min IRE of 65 and a max IRE of 75, so to my thinking this should be the same, and if I have a custom picture in the camera (no MLUT) and the same picture in the Small HD (no LUT) the zebras are in identical places.

I figured I'd take the Convergent Design LUT which worked on the Small HD over to the FS7 and load it as a user MLUT, but the FS7 just says it is 'NG'.

So a few questions I suppose - what could be the specs in the LUTs that won't load on the Small HD and/or FS7? In LUTCalc I created some LUTs which were identical, except the output gamma/gamut is changed in each one, and they all loaded in the Small HD except the REC709.

Has anyone found a LUT which converts SLog3 to REC709 that will work between the FS7 and the Small HD monitor (even the 502?).
 
Killick, you got me thinking, I have loaded LUTs into the FS7 previously, but not for a while and not since the new firmware. So I went back to check, and I realised I had been trying to load the file which starts with '_', which I remember are the wrong files. So I navigated to the correct file (this is the Convergent Designs SLog3 to REC709 LUT) and loaded it ok!. I double checked the small HD had the exact same LUT loaded.

So here's the weird thing. With the same LUT loaded in the camera and the monitor, zebras are still in different spots. Remembering that with an un-LUTted custom picture, the zebras are identical.

So I guess my conclusion is that the camera and the Small HD 702 are applying the same LUT with different results?!
 
That was my first thought regarding the file... I had the same problem when I first tried loading a LUT on the camera and took me a half day to figure out what was going on.

Weird about the zebras on the Small HD though. Are you sending the signal HDMI or SDI? Since both have different LUT output settings maybe the other would register Zebras correctly. Worth a check.
 
I'm cabled via SDI, and definitely no LUT applied to the output, only to viewfinder. Just to be sure, I checked the straight SLog picture in the viewfinder and monitor, and zebras appear in identical places there as well.
 
That is really weird. Try HDMI and see if you're having the same problem. Assuming the monitor is reading the LUT the same as the camera is, then perhaps it is the output signal somehow.
 
Yeah, it's the same with an HDMI output. So I loaded another LUT that both the FS7 & the Small HD can both read, which is a LUT I created in LUTCalc, basically an LC709A with increased colour saturation. And the difference between the two is even more pronounced. There's about a stop's difference between the two, which obviously if I'm going to be using the 702 for critical exposure is not great.

Killick said:
perhaps it is the output signal somehow.
Click to expand...

When there's no LUT's applied, the output signal seems identical. It just seems to me that either the FS7 or the Small HD is applying LUTs incorrectly. If it's the FS7 then it would seem that Doug Jensen has been right all along and we shouldn't expose using a LUT in the viewfinder! If it's the Small HD, that would be a bit disappointing, as in all other respects it seems to be an outstanding monitor.

When I have a bit more time I should be able to get a bit more mathematical about this, and figure out which in incorrect and by how much, but now I have to do some shopping or my family will be eating crackers for dinner (again).
 
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Yeah... math... I think this is the point I tap out of the investigation. Looking forward to hearing your findings though! :)
 
hmmm... I'm intrigued too and interested to find out why... just curious - are they perhaps the "extended" CD luts you are using? Also, wondering if you've turned on sdi1/internal like you were going to burn in the lut - and then output that signal to the Small to see if zebras land where they should?
 
Try to change the LUTs in LUTcalc so that the ones on the fs7 is "Data in - Legal out" and the ones on the monitor is "Data in - Data out"
 
Well, thanks stokstad, at least I can now get a REC709 LUT in the Small HD by changing to 'Legal Out'.

But I was reading another thread which came up where someone was rating the camera at other than 2000, so when they applied a LUT without stop/rating correction it looked different. I checked my camera and sure enough I was rating at ISO 800. I thought, maybe that was the problem all along, changed the camera's ISO to 2000 (which obviously only affects the LUT not the underlying SLog).

And now, the difference between (IRE) 65-75 on each is almost 2 stops?! It seems the application of the LUT on one or the other is WAY out, not just a little bit as I previously thought.

markfpv said:
if you've turned on sdi1/internal like you were going to burn in the lut - and then output that signal to the Small to see if zebras land where they should?
Click to expand...

Hi markfpv, yes if I turn on the MLUT for SDI/Internal output, remove the LUT on the Small HD, zebras are bang on accurate on both.

I'd love to hear from any Small HD 502 users, to see if they have this issue as well.
 
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Hi Spencer,

sorry if I go over anything already covered - I've just noticed this thread.

First off, if you are going to be changing CineEI and want to use a LUT in your external monitor, you have to feed it from an SDI socket with LUTs turned ON and set to S-Log3 (or S-Log2 if you are using that). Just make sure that you are not burning in the LUT!

This ensures that the monitor receives an exposure-adjusted log signal. If you have LUTs turned off it will just be fed the base log recording. That is fine if you are working at native ISO, but as I say, if you change CineEI it will appear too dark or too bright. Alternatively, you can load up your monitor with ISO-adjusted versions of your LUTs, but that could easily get very messy if you start changing CineEI.

However, if you want to flick between camera MLUT and SmallHD MLUT for testing, set the camera to native CineEI and feed the monitor a signal with LUTs OFF.

I think that you have realised that all that is probably the basis of your initial problem. So next...

As for the SmallHD in particular, I don't have direct experience of them so haven't included a preset in LUTCalc, but I did recently hear from Nez / videosoul on the Sony forums telling me that SmallHD had responded to an enquiry by him that the monitor LUT system is designed around 17x17x17 3D LUTs data in / data out, preferably in cube format.

If anyone with a SmallHD wants to try out those settings and let me know if they fit the bill, I would be very welcome; I'm keen to add the preset but want to confirm the setup first.

As for LUTs in the FS7 itself, if you use the 'Sony User 3D MLUT' preset in LUTCalc, that will be correct; the aim should be for the SmallHD to agree with that.

One way that I use of checking the range settings (the bane of my life and the source of most problems relating to LUT consistency) for any gizmo or piece of software is to make a LUT up starting with LC709 gamma. You then set the black level to a readable line on your preferred waveform but above 0% (eg 10% or 25%), then turn on 'Highlight Level', set 'reflected' to 1150 and 'maps to' an IRE level below 100% but corresponding to another line on your waveform (eg 90% or 75%). Make up versions with data in/data out, data in/legal out, legal in/legal out and if you are really keen legal in/data out then try them in the device / software under test. Lenscap on then massively over exposed. With luck only one variation should fall on the expected lines; you let me know which one and I add it as a preset! ;-)

Ben
 
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Ben, thanks so much for your reply. Yeah, I've pretty much covered the first part of your post, at one point I was inadvertantly rating the FS7 at 800ISO, but rather than being the source of my problems with exposure it made it worse.

I will try some of the settings you recommend and get back to you. I know the LUTs I've been generating have been 33x33x33, so that's a start, & I'll check different data/legal range combinations.
 
Ok so... a bit embarrassed I didn't notice this earlier, but also kind of annoyed.

I was just checking the waveform on the Small HD, and realised that it did not change at all when flicking the LUT on and off.

So it's only reading the underlying SLog signal, and as far as I can tell cannot read the post-LUT picture.

But surely the zebras do? I mean, that's the whole point of this setup, surely, that you can have the different pages, one effectively acts as a viewfinder, with zebras (and/or waveform) giving me post-LUT exposure information? and one to show director/client, with a nice LUT but no extraneous info, and another with the base SLog picture so I can see exactly what detail is being recorded?

The zebras only read the underlying signal. So I'm pretty sure this explains the zebras appearing in different places. The FS7 viewfinder applies the zebras to the post-LUT picture. The Small HD doesn't & can't?

Now bear in mind this monitor does not come with a manual or in fact any documentation whatsoever, not even a pdf available on the Small HD website, perhaps if I'd done enough reading of forums somewhere I might have found this out. But you would think this is something that could be pointed out by Small HD somewhere?! Might have saved me 3 days of frustration. Might not have bought it...
 
Just found this on the SmallHD website:
Waveform always reads the raw image (along with every other tool) so you don’t have to fear getting false data from your scopes, zebras or false color.
Click to expand...

So it looks like you just have to work your zebras / waveform from the S-Log3 or S-Log2 values. What does still stand is that if you change CineEI, make sure that the SmallHD is getting a signal from the camera with MLUTs on and set to S-Log3 (or S-Log2). That way the LUTted image on the SmallHD should look as expected, and the waveform and zebra tools will be working from exposure-compensated log, ie you don't need to remember what 18% gray is for every ISO! It'll behave just like a C300mkI in CP Lock with video assist.

Here is a Dropbox link to the 10-bit and %IRE values for various stops in S-Log, S-Log2 and S-Log3 if that helps, and these are the log %IRE values for 0% black, 18% gray and 90% white:
Reflectance 0% 18% 90%
S-Log3 %IRE 3.5 41 61
S-Log2 %IRE 3 32 59
S-Log %IRE 3 38 65

Ben
 
Thanks Ben, that's a very useful link for the Dropbox. I've been doing a little calibrating myself; I generally have zebras to pop slightly (highlights) on caucasian skin, and I've found at S-Log3 zebras at 50-55% closely matches Rec709 zebras @ 70% with 10% aperture (ie 65-75).

The Small HD link you provided specifically refers to the DP7-Pro, which is a different monitor to mine (702) although the same brand. To be honest I didn't think to ask the question before I bought the monitor, so yeah I guess it's all my fault! I was just excited to find a monitor that is daylight-viewable, reasonable colours, good peaking, zebras, nice user interface, the ability to view (and toggle) LUTs, at a reasonable price. It'll still be a great monitor for most of the work I do, and there's some workarounds for the zebras (pre/post LUT), but it would be a nice thing to have a choice.
 
Ben is the man! :D

Ben, can I ask: are there any updates coming?
What I'd love to see is:
- default camera choice (saved after closing LUTcalc)
- auto naming conventions for LUT title if I don't want to give it a custom name (for example combined from settings chosen: minus1stop_slog3_6000K)
- default saving directory with "save" button. So for example you could point it at directory for LUT's in Resolve and then every single new LUT would be generate there by simply pressing "save" (without dialog box).
- white balance and stop correction range generator. When creating a LUT I almost always generate it for at least 5-6 WB settings and same goes for stop correction. I would be so helpful if a range of LUTs with different WB and stops could be generated automatically (by option).
 
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