Demystifying N-Log ISO, Exposure, and Noise

[Horshack]

I've just published a video follow-up to my N-Log ISO Deep Dive thread. This is the first part of a series, where I hope to take the mystique out of log video and make it as understandable and approachable to use as regular video. Topics covered:

• 0:00 - Introduction
• 0:37 - Photography exposure analogy
• 1:32 - Log ISO vs Sensor ISO
• 3:35 - Why Log uses a higher native ISO
• 7:07 - ISOs above native ISO
• 9:52 - ISOs below native ISO
• 10:33 - Why Log has more noise
• 12:16 - How Expanded ISOs work
• 17:50 - Overexposing Log (ETTR)
• 19:31 - Additional Technical Details
• 20:38 - Conclusion

While this video uses N-Log for its examples, the material covers all camera log formats and is not specific to N-Log.

 

[AZ Indie]

Great info and quite well-done video!

 

[ClintGryke]

Really excellent video thanks Horshack. I found out most of the practical side of working with (Nikon) log video by trial and error myself. It would have been incredibly useful to have had this video to refer to when learning, as it explains everything I wanted to know at just the right level. This will become a reference for a lot of people. Looking forward to the next one.

 

[nemesix]

This is the best explanation of how log video works that I've ever seen, great video!!!

You mentioned that in your opinion the sensor of the Z6iii should really have a native log ISO lower than 800 - could you elaborate on why that is, and if the Z8/Z9 have the same issue?

 

[j_photo]

Super. Thanks

 

[Kamil Z]

This video truly provides unique information and tips I haven't found anywhere else. Thank you for that!

 

[Geomaticsman]

Excellent video. The challenges of shooting Nlog is why I choose not to and instead record in H265 using Nikons flat profile. Noise is much better controlled and videos are easier to grade, though you have to expose correctly. The extra dynamic range provided by Nlog just isn't worth the extra effort when grading IMO...especially since Nikons LUTs leave so much to be desired including the new Red LUTs - cinematic but of little use for documentaries.

--
Garfield
My amateur videos :~)

 

[Suntan]

Excellent video. The challenges of shooting Nlog is why I choose not to and instead record in H265 using Nikons flat profile. Noise is much better controlled and videos are easier to grade, though you have to expose correctly. The extra dynamic range provided by Nlog just isn't worth the extra effort when grading IMO...especially since Nikons LUTs leave so much to be desired including the new Red LUTs - cinematic but of little use for documentaries.

 

[24Peter]

Bravo Horshack! Thanks for "in-lighten-ing" us!

 

[ArchipiX]

Great Work! This is very helpful.

 

[Horshack]

Really excellent video thanks Horshack. I found out most of the practical side of working with (Nikon) log video by trial and error myself. It would have been incredibly useful to have had this video to refer to when learning, as it explains everything I wanted to know at just the right level. This will become a reference for a lot of people. Looking forward to the next one.

Thanks Clint, I appreciate that.

 

[Horshack]

This is the best explanation of how log video works that I've ever seen, great video!!!

You mentioned that in your opinion the sensor of the Z6iii should really have a native log ISO lower than 800 - could you elaborate on why that is, and if the Z8/Z9 have the same issue?

Thanks. It's because the Z6 III's DR is a bit lower and with some qualitative shadow issues (flickering), which makes it less amenable to the deeper underexposure of log ISO 800.

 

[Horshack]

Excellent video. The challenges of shooting Nlog is why I choose not to and instead record in H265 using Nikons flat profile. Noise is much better controlled and videos are easier to grade, though you have to expose correctly. The extra dynamic range provided by Nlog just isn't worth the extra effort when grading IMO...especially since Nikons LUTs leave so much to be desired including the new Red LUTs - cinematic but of little use for documentaries.

Interesting. I recently made the mistake of recording half the shots of a project on STD and the other half in my regular N Log. The STD shots were so much more hassle to grade and make look right compared to the N log.

I've never used Nikon's luts. It is so much more straightforward to just use color management in Resolve.

One issue with matching SDR vs N-Log footage is the SDR footage has Nikon's 'standard' picture profile color baked into the video, whereas the CST's in NLEs will not, which makes it very challenging to intercut SDR and N-Log footage with CSTs. Nikon's LUTs incorporate the same picture profile characteristics as the SDR modes so they are one option for intercuting, although like you I prefer to use CST's instead.

 

[Suntan]

All I really want to know is how to easily/quickly reduce the screen/EVF display levels when intentionally ettr for scenes that won't have bright highlights.

When almost everything in the display is white, it can be hard to frame/track the subject.

 

[Tom Stites]

If not already doing so, you might try with "View Assist" turned on. I use it to assist with viewing the WFM display, I find it helps considerably in many scenarios.

Cheers!

 

[Tom Stites]

Excellent video. The challenges of shooting Nlog is why I choose not to and instead record in H265 using Nikons flat profile. Noise is much better controlled and videos are easier to grade, though you have to expose correctly. The extra dynamic range provided by Nlog just isn't worth the extra effort when grading IMO...especially since Nikons LUTs leave so much to be desired including the new Red LUTs - cinematic but of little use for documentaries.

Interesting. I recently made the mistake of recording half the shots of a project on STD and the other half in my regular N Log. The STD shots were so much more hassle to grade and make look right compared to the N log.

I've never used Nikon's luts. It is so much more straightforward to just use color management in Resolve.

One issue with matching SDR vs N-Log footage is the SDR footage has Nikon's 'standard' picture profile color baked into the video, whereas the CST's in NLEs will not, which makes it very challenging to intercut SDR and N-Log footage with CSTs. Nikon's LUTs incorporate the same picture profile characteristics as the SDR modes so they are one option for intercuting, although like you I prefer to use CST's instead.

A second issue you run into when mixing SDR with Nlog or HLG in compressed formats is that SDR is in Rec.709 color space and the other two are in BT.2020 and BT.2100, respectively.

If I'm mixing clips from other sources, it would typically be from my iPhone 15 Pro Max, a DJI Mavic 2 Pro or DJI Osmo Action 5 Pro, all of which have log modes and in the case of the iPhone and Action 5, HDR modes, as well.

As much of a pain as it can be, I am pretty much shooting everything in NRaw in NLog or in H.265 10bit HLG. SDR is only used for impromptu shots when I might not have an ND filter handy or time to put it on. If something is destined primarily for YT or Vimeo, I export to HLG Rec.2100 and let them worry about dealing with the Rec.709 feed for those not viewing on an HDR display or device. Also easy enough to create a second timeline in Resolve with different Color Management settings to export a Rec.709 version...tweaks are often minimal from the HLG graded version.

This mess is slowly getting sorted, but it's been quite the slog over the last number of years. No wonder it's a challenge for those just dipping their toes into video.

Cheers!

 

[Horshack]

All I really want to know is how to easily/quickly reduce the screen/EVF display levels when intentionally ettr for scenes that won't have bright highlights.

When almost everything in the display is white, it can be hard to frame/track the subject.

This can be done on cameras that support user-installable LUTs, which unfortunately Nikon doesn't support as of today. Panasonic supports them though, originally only for the log-assist Rec.709 preview but now also for the baked-in footage as well (starting with the S5 II/IIx and S9). For these cameras I have developed ETTR LUTs that do exactly what you're asking - they reduce the exposure in EV increments in V-Log space, which allows a constant brightness for the log-assist preview adjusted for ETTR. I'll be covering this in the next video of my series, which covers exposing tips in the field and adjusting in post.

 

[Horshack]

Excellent video. The challenges of shooting Nlog is why I choose not to and instead record in H265 using Nikons flat profile. Noise is much better controlled and videos are easier to grade, though you have to expose correctly. The extra dynamic range provided by Nlog just isn't worth the extra effort when grading IMO...especially since Nikons LUTs leave so much to be desired including the new Red LUTs - cinematic but of little use for documentaries.

Interesting. I recently made the mistake of recording half the shots of a project on STD and the other half in my regular N Log. The STD shots were so much more hassle to grade and make look right compared to the N log.

I've never used Nikon's luts. It is so much more straightforward to just use color management in Resolve.

One issue with matching SDR vs N-Log footage is the SDR footage has Nikon's 'standard' picture profile color baked into the video, whereas the CST's in NLEs will not, which makes it very challenging to intercut SDR and N-Log footage with CSTs. Nikon's LUTs incorporate the same picture profile characteristics as the SDR modes so they are one option for intercuting, although like you I prefer to use CST's instead.

A second issue you run into when mixing SDR with Nlog or HLG in compressed formats is that SDR is in Rec.709 color space and the other two are in BT.2020 and BT.2100, respectively.

This shouldn't be an issue for SDR <-> N-Log because the gamut can be mathematically converted from BT.2020 to Rec.709 via a CST, the output of which should closely match footage shot natively in Rec.709. (although I'd have to analyze it to be sure)