Do ALL LOG Profiles Require / Benefit From Significant Overexposure?

[Mark Romero 2]

Do other LOG profiles (aside from SLOG) benefit from significant overexposure (plus 2 stops), or is SLOG the only one that is really noisy if it isn't overexposed?

Curtis Judd suggested about one stop over for Panasonic V Log. Some people on other forums said that with the GH5 you don't really need to overexpose any more.

Anyone heard anything about N-Log yet regarding overexposure?

Do the actual Pro Log S profiles used in EOSHD Pro Log 3 and Pro Log 4 require 2 stops of overexposure? (sorry, Andrew, if I am dipping in to the secret sauce too deeply)

Shooting in SLOG is just such a frustrating experience on my Sony a6500.

[Mako Sports]

I believe so because with shooting log you are try to protect the shadows.

Exactly why log is almost never recommended for low light situations.

In regards to your a6500, shooting log is a LOT easier with an external monitor because you get access to a waveform monitor.

[KnightsFan]

This is something I've always wondered about, but to me it seems like manufacturers pretty much lie with ISO ratings. If you have to "overexpose" by two stops, doesn't that mean the ISO rating is off by two stops?

[ND64]

1 hour ago, KnightsFan said:

This is something I've always wondered about, but to me it seems like manufacturers pretty much lie with ISO ratings. If you have to "overexpose" by two stops, doesn't that mean the ISO rating is off by two stops?

I think the overexpose is not the right term here. Exposure is light, filtered by time, filtered by aperture. Period. ISO has nothing to do with that.   But, basically you use higher ISO to "underexpose" and get equal brightness of normally exposed image (which is important for action photographers, they can use higher shutter speed without the image "look" darker). So in case of log, they don't tell you to overexpose, they just ask you to Not Underexpose! 

[kye]

It depends on the camera.

High end cinematographers always test the optimal level of exposure when they are about to film with a new camera. The answer of where each camera looks nicest with skin tones and DR is always different from camera to camera. For some it is underexposing, and others it is overexposing.

However this is with cinema cameras and you are talking about prosumer mirrorless.

The real question is perhaps "How do I get good results on a budget 8-bit camera shooting log?"

[Jimmy]

I actually find protecting the highlights better for F-log (if shooting at 800 in decent, high contrast light). Probably 1-2 very clean stops in the shadows. 

Best thing to do is just run your own tests though.

[jonpais]

Log curves lift the lower and middle parts of dynamic range higher up where most of the bit depth is located so you have more shadow detail to play with without clipping highlights. When exposing S-Log2, the footage looks flat and washed out. Watching some grading tutorials, you’ll see that all log clips have the same milky desaturated appearance. It has not been overexposed so much as properly exposed. If underexposed, you’re losing the benefits of shooting log. I believe all log profiles work pretty much the same way.

Samples

[Robert Collins]

49 minutes ago, jonpais said:

Log curves lift the lower and middle parts of dynamic range higher up where most of the bit depth is located so you have more shadow detail to play with without clipping highlights. When exposing S-Log2, the footage looks flat and washed out. Watching some grading tutorials, you’ll see that all log clips have the same milky desaturated appearance. It has not been overexposed so much as properly exposed. If underexposed, you’re losing the benefits of shooting log. I believe all log profiles work pretty much the same way.

Samples

Actually SLog on Sony cameras is something of a special case. While the camera says it is recording at 'iso800' it is in fact recording at base iso 'iso100' so footage is bound to be underexposed irrespective of the underlying log curve.. You can see this by analysing the underlying metadata.

Supposedly Panasonic cameras do something fairly similar but with only a one stop difference.

[jonpais]

@Robert Collins Interesting. hehe

I think you're right, because I exposed for his shirt with zebras at 100+ and the scopes show it's quite a bit lower! omg

 

 

[Robert Collins]

7 minutes ago, jonpais said:

@Robert Collins Interesting. hehe

I think you're right, because I exposed for his shirt at 100+ and the scopes show it's quite a bit lower! omg

 

If you think about it - a camera (as in say the A7iii) which has a base iso of 100, why would it really choose to shoot SLOG at an iso of 800 (lets forget about the dual iso bit for the moment)? If it did so, it would effectively reduce dynamic range by close to 3 stops and increase noise by close to 3 stops. The answer is it doesnt record slog at iso 800 but at iso 100 and therefore you have to 'overexpose' to 'expose' correctly by +2EV+.

(I think the situation is pretty similar with the Panasonic GH5. Its native iso is 200 but it records log showing iso at 400. Something like that.)

Why Sony does this I really dont have a clue - someone suggested it was something to do with maintaining compatibility with cinema cameras which have a higher inherent base iso.

[seanzzxx]

It's because using the term ISO is relatively tricky in an age of digital photography:

 

Quote

"Why can't I use ISO 100 in Log mode?" The answer is that a log gamma curve is so flat that it requires very little light to achieve middle grey, which means it's considered a high ISO. Strictly speaking, though, you can't really calculate an ISO value for log at all, since the standard is based on a different colorspace and gamma. It's a similar story for Raw.

 

[MattH]

Log is forced under exposure.  Thats how it works.  Thats why it says iso800 when its really iso100.  Its a lower iso pushed to a higher average brightness, but it says iso800 to make you expose lower.  Thats how you get more highlight latitude.  How else could you get it?  It cant be magiced up from nowhere.

So if three stops of extra latitude is too much and you'd rather have just two with cleaner shadows then, sure, over expose a stop in log.

But if you're over exposing by two stops (definitely 3) you may as well just shoot in normal gamma because you are throwing away everything log gives you anyway.

[jonpais]

That was... entertaining?

[Deadcode]

21 minutes ago, MattH said:

Log is forced under exposure.  Thats how it works.  Thats why it says iso800 when its really iso100.  Its a lower iso pushed to a higher average brightness, but it says iso800 to make you expose lower.  Thats how you get more highlight latitude.  How else could you get it?  It cant be magiced up from nowhere.

So if three stops of extra latitude is too much and you'd rather have just two with cleaner shadows then, sure, over expose a stop in log.

But if you're over exposing by two stops (definitely 3) you may as well just shoot in normal gamma because you are throwing away everything log gives you anyway.

With +2 stop overexposure, you still have around 12 EV dynamic range, and each stop represented about the same amount of luminance levels.

If you are shooting regular gamma, not each stop has the same amount of luma data which can cause limitation in colorgraing.

I tested extensively Cine4 (0EV) against SLOG2 +2EV which represents the same amount of dynamic range, but the low end of the Cine4 is heavily compressed compared to SLOG2. If you lift your shadows Cine4 falls in to pieces. Of course with regular grading both looks good and very close to each other.

My conclusion after tons of testing: expose for the highlights in wide DR scene, using SLOG2 for best looking image, and always expose for the skintones when using Cine4, and let the highlights clip, if necessary to get out of camera nice results.

[Robert Collins]

55 minutes ago, MattH said:

 Thats how you get more highlight latitude.  How else could you get it?  It cant be magiced up from nowhere.

It is a little more complicated than that and there is a little bit of magic going on.

Here is a video about how Lightroom maps tonal values for stills but it demonstrates the principle.

https://topdownvideos.com/training/tone-mapping/

[Mark Romero 2]

2 hours ago, Deadcode said:

With +2 stop overexposure, you still have around 12 EV dynamic range, and each stop represented about the same amount of luminance levels.

If you are shooting regular gamma, not each stop has the same amount of luma data which can cause limitation in colorgraing.

I tested extensively Cine4 (0EV) against SLOG2 +2EV which represents the same amount of dynamic range, but the low end of the Cine4 is heavily compressed compared to SLOG2. If you lift your shadows Cine4 falls in to pieces. Of course with regular grading both looks good and very close to each other.

My conclusion after tons of testing: expose for the highlights in wide DR scene, using SLOG2 for best looking image, and always expose for the skintones when using Cine4, and let the highlights clip, if necessary to get out of camera nice results.

Thank you for the input.

I can understand your findings. I guess the sadness for me is that the highlight rolloff of Cine4 is... how should we say it... pretty bad... So having the hghlights clip is pretty upsetting to me.

Your testing seems to confirm my (rather haphazard) comparisons between Cine4 and Slog 2. There is not a whole lot more DR in a SLOG2 shot that has been overexposed by two stops. It seems that the main benefit in this case is that SLOG2 gives a less harsh rolloff though.

All other things being equal, in regards to skin tones, would you say that Cine4 at 0 EV gives better skin tones than SLOG2 at around +2 after grading? Or are they about equal? You said with regular grading they both look about equal, so i am assuming that also refers to skin tones being on par with each other when exposed optimally. (I haven't been able to test on skin tones really.)

3 hours ago, MattH said:

But if you're over exposing by two stops (definitely 3) you may as well just shoot in normal gamma because you are throwing away everything log gives you anyway.

Yes, that is definitely a concern. Cine4 is much easier to use in the field (on an a6500) but the rolloff is nasty. Even using in-camera LUT (I don't know what sony calls it exactly... gamma assist???) when shooting SLOG2 the issue is that they recommend switching OUT of SLOG when doing your white balance, which is really difficult on a gimbal with the tiny buttons on an a6500.

 

8 hours ago, kye said:

It depends on the camera.

High end cinematographers always test the optimal level of exposure when they are about to film with a new camera. The answer of where each camera looks nicest with skin tones and DR is always different from camera to camera. For some it is underexposing, and others it is overexposing.

However this is with cinema cameras and you are talking about prosumer mirrorless.

The real question is perhaps "How do I get good results on a budget 8-bit camera shooting log?" 

Thanks for your input.

I think the "real question" for me, though, is maybe more along the lines of, "is it worth it to step up from a budget 8-bit camera if I want to shoot log / get more dynamic range"?

Admittedly, I did only allude to prosumer cameras. Hopefully that won't dissuade people from sharing findings about some of the more affordable cine cameras though.

11 hours ago, Mako Sports said:

I believe so because with shooting log you are try to protect the shadows.

Exactly why log is almost never recommended for low light situations.

In regards to your a6500, shooting log is a LOT easier with an external monitor because you get access to a waveform monitor.

Yes, wave forms or false color would make it a lot easier, I believe, as would just having a larger, brighter, more detailed screen. (The screen on the a6500 is pretty useless).

[Mark Romero 2]

One more question for everyone: How does the HLG profiles of the 3rd Gen Sony mirrorless cameras (a7 III, a7R III) fit in to all this? I understand that 1) It isn't really supposed to be for grading, and that it is is supposed to be for "out of camera" footage that will be shown on HD TVs, but is there a benefit when shooting for (eventual) Rec.709 distribution like youtube?

For example: If shooting HLG and then editing on a Rec. 709 timeline, can I at least get the same 12 stops of DR that Cine4 at 0EV or SLOG2 at +2 provide without having the nasty Cine4 rolloff and without having to deal with the SLOG2 workflow?

I really have only seen the videos comparing SLOG2 with HLG by the one guy Scott Jeschke and they don't seem really conclusive to me (maybe I missed it).

HLG 3 seems a lot nicer than the STANDARD / oicture profiles off:

 

But not really sure about head-to-head with SLOG2

[seanzzxx]

21 minutes ago, Mark Romero 2 said:

All other things being equal, in regards to skin tones, would you say that Cine4 at 0 EV gives better skin tones than SLOG2 at around +2 after grading? Or are they about equal? You said with regular grading they both look about equal, so i am assuming that also refers to skin tones being on par with each other when exposed optimally. (I haven't been able to test on skin tones really.)

The reason I stopped shooting Slog was the fact that by overexposing by two stops the skin tones get really pasty and thin most of the times. I much rather have good skintones than some extra dynamic range, however I agree with you on the fact that the Cine curves have terrible highlight roll off.

[Mark Romero 2]

2 minutes ago, seanzzxx said:

The reason I stopped shooting Slog was the fact that by overexposing by two stops the skin tones get really pasty and thin most of the times. I much rather have good skintones than some extra dynamic range, however I agree with you on the fact that the Cine curves have terrible highlight roll off.

Thank you for the input. Have you had a chance to try the HLG profiles?

[jonpais]

Switch out of S-Log while doing white balance? LMAO