Panasonic Lumix DMC GH4 VLog-L Latitude Test
- March 9, 2016
- Shane Hurlbut, ASC
Many of you out there have been strong backers of the Panasonic GH4. I did not personally like what I saw in my initial test a few months back as this camera had qualities and characteristics that I do not like to see in a camera when I am creating a filmic look. It felt very sharp and “video” looking at times. The saturation on the skin tones on our model Monette’s face made her feel plastic and it didn’t feel natural to me.
By Shane Hurlbut, ASC
Today we are testing again. This camera may perform well in other scenarios, but the one scenario that is going to matter the most is when you are shooting a person’s face. The face is unforgiving. What you see is what you get. A camera test on a person’s face is going to give you a foundation of how you can use the technology and where you shouldn’t.
I want this article to just focus on the camera and its performance in the latitude. This is incredibly important to have a solid understanding of what your latitude means and what it does for you. We will have two more articles focusing on:
- IR Pollution
- Back Lighting this camera
- Fill Ratio
- Day ISO Noise
- Night ISO Noise
Shooting in a Log Profile
Panasonic has released an updated profile to the GH4 by creating a log format – V-Log L. What exactly is a “Log” format? You’ve most likely seen CanonLog, RedLogFilm and LogC (Arri Alexa) and even SLog2, SLog3 on Sony cameras. Shooting in a Log format gives you the most to play with in post-production color correction.
A Log image is going to have a grey color overall with limited saturation and contrast, and it will look “washed out.” What you are seeing is the camera telling you that there is a lot of “room to move” and that there is information in the camera that you just cannot see at the moment. When you import the footage and take it into DaVinci Resolve or Adobe Creative Cloud, you have the ability to adjust that footage by adding contrast, color and even moving the black level, midtones and highlights to what you feel is appropriate for the look you want to achieve.
What does this mean in regards to testing the camera’s latitude?
The latitude of a camera means how far overexposed and how far underexposed before you introduce unwanted noise or the camera’s color information begins to “fall apart.” What I mean when I say that it falls apart is that there isn’t enough data in the recorded information for you to “bring back” the image so that it looks good or how you want it to look. Maybe you are looking for a slightly overexposed image on your actor’s face, but how far should you go over? That’s what we are here to see. The idea is that if you overexpose a camera by too many stops, there isn’t enough information recorded on the camera to allow you to bring the highlights back so that you can see the image the way you want it to appear. The opposite would occur in the underexposure. If you go too far under, will there be enough information either to correct the image or to accomplish the look you are attempting?
GH4 V-Log L Latitude Test – Under Exposure
Let’s dive right into this VLog profile on the GH4 in the underexposure. What I want to do is to test the camera to find out which area in the underexposure looks the most filmic. Is it at a perfect -/+ 0, or is it at a -1 stop of underexposure or more? When I tested the Canon 5D Mark II for Act of Valor, I found that -1 stop of underexposure was that camera’s sweet spot. Let’s see what happens in our test with the GH4.
A quick run through of our camera specs for this test:
- Record Quality: 4K UHD 10-Bit External Record on Atomos Shogun
- Lens: 25mm Veydra
- ISO: 800
- K: 3200
- Shutter Angle: 180
- F Stop: 5.6 (on the 25mm Veydra lens)
These settings are the “control group” of our experiment. Just like in chemistry class in high school, these settings will not change, giving us a foundation for our test. The only thing that will change will be our key light. You will see that it starts out at a F5.6, and it will change, but the 25mm Veydra will be set to a F5.6 for the entire test. Only the light level will change.
Let’s take a quick second to also talk about what we are looking for:
- Skin Tone detail on our model Monette’s face
- Highlight control
- Black Level control
- Overall Color/Saturation
- Overall Noise in the image
We did this test with a LUT that I created that has a similar color profile to the one I used for Into the Badlands. I call this one Neutral Day Interior. We’re working on creating more LUTs for the GH4 that will work in various environments, and I feel this LUT works well in a controlled situation where you can dial in the light level without sunlight effecting your image.
One thing I find with these prosumer DSLR cameras is that the saturation needs a slight adjustment to bring out the skin tones and make the image stand out. However, you can end up pushing the saturation too far as there isn’t a lot of room to play with on these cameras, so we opted to keep our level at a balanced tone in saturation. You can see at an exposure value of -/+ 0 level, Monette’s skin looks very nice and filmic, and the overall color looks very good.
You can see in the VLog image on the left that there is a lot more information available to us in this image. We were able to dial in more contrast, there is plenty of room for saturation of her overall, and we have a large amount of control over the black level where we can really dig in there and make the image pop.
To me, this is the sweet spot of the exposure of this camera. You will hear me talk about the overexposure in the video coming up, but -1 stop of exposure is where the beauty in this image lies. Just like the Canon 5D Mark II, this camera loves to be underexposed. So somewhere in -2/3 of a stop to a full stop (-1) is where this camera performs its best.
Monette’s skin comes alive, and it has a more vibrant vitality here. Let’s understand how to underexpose her properly by one stop (-1) with your light meter.
- Camera is set to 800 ISO
- Set your light meter to 1600 ISO, which is -1 stop underexposed or 1280 ISO for -2/3.
When you start lighting, you want to light your scene with your camera set to 800 and your meter set to either 1600 ISO (-1) or 1280 ISO (-2/3), and this will allow you to hit that sweet spot. Since this camera performs much better with less light, you will have more room in post-production to bring up your exposure if needed without losing detail.
Keep in mind that your camera’s lens is set to a F5.6, which is what an 800 ISO setting would read. When you rate your meter at 400 ISO, your light level will tell you to expose the camera at an F4, but you want to leave your lens set at a F5.6, which is one stop under (-1).
For those of you who have a Sekonic L-758Cine-U Light Meter, there are two buttons, one for ISO 1 and one for ISO 2, which allow you to select two different ISOs. You can set your first ISO to 800 ISO, which will give you that -/+ 0 rating, and your second ISO set it either to 1600 ISO (-1 stop) or 1280 ISO (-2/3 stop), which will allow you to see both what the camera settings should be (ISO 1) and what you are lighting to (ISO 2). See the picture below:
One more time, let’s take a look at what your perfect exposure would be at -/+0 and then -1 stop under side-by-side.
Moving on to two stops underexposed, it looks like the graded version is starting to get muddy and smoky in the black level.
When we crank it back up to retain that same IRE value on her skin when our key light was at a F5.6, we start to see a lot of noise. We are also seeing less saturation so with this you’d have to add a small amount of saturation – because as I mentioned before, with this camera, a small amount goes a long way.
Now we are going to push it even further by underexposing by three stops. Another thing I look for when doing these tests is the latitude and how it reacts with the key light. I like to see when the key light becomes so dark that it is hard to see, which shows you the latitude of how much you can push your fill light. When the key light starts turning to your fill light, you’re starting to go into the extremes of your latitude.
When we try to push it back up to -/+0, I’m seeing a lot of digital noise, and the color is really starting to fall apart. Her skin tone with the three stops underexposed doesn’t look natural; it looks like it lacks depth. Three stops under seems to be the breaking point for our camera.
When we go even further and underexpose her by four stops, it is actually looking ok. I feel like I could bring in some fill light and still feel the emotion of the character. There’s just enough detail in there for us to work with it.
Underexposing by five stops would work well for a semi-silhouette look. If you have a nice backlight, like on a street for a night exterior under a sodium vapor and want people to squint to see the details on your character’s face, then five stops down is great.
When grading this back up to -/+0, this camera is definitely broken. The digital noise is colorful and off the wall.
In conclusion of our underexposure latitude test, underexposing by 2/3 to a stop is the sweet spot, and you don’t want to underexpose and then bring it back with the grade because small adjustments make drastic changes. The digital noise of this camera also doesn’t look filmic. It looks digital, and we found that underexposure at four stops is good for barely seeing the emotion on the face of your character and underexposure at five stops is great for a semi-silhouette situation.
Over Exposure Latitude:
In the overexposure test, we are going to look at the very same things we did in the underexposure, but going in the opposite direction by adding more light to Monette and seeing how the camera performs. We found some really interesting things by going into the underexposure, so now let’s find the “cliff” so to speak.
The image still has some slight desaturation in it, and I would put a little more saturation into this V-Log L profile. What I see right away is that Monette’s skin starts to “glow” a little more. The midtones and highlights pop a little more, desaturating the image even more, but overall not bad. We are able to bring the image back to that -/+0 without a problem. Going +1 in exposure is able to be brought back.
We determined that the “sweet spot” of this camera is going into a -1 underexposure area, so we want to see how things will handle when we go +2 stops over now. When coming down from +2 to get to -/+0, you can see that the yellows and browns start to lose detail when we go this far over. The information starts to go pretty quickly here. With some good power windows in DaVinci Resolve and good Luminance Keys, you could bring this information back, but you’re going to have to pinpoint those exact colors and specific areas, which is going to be more work in the end.
You can really see where her skin starts to fall apart when we are +3 stops overexposed. We would have to do some larger power windows here to save the image.
Somewhere between +3 and +4 is where the breaking point of this camera lies. We can see that the camera “clips” in the highlights and there is no longer any information that we would be able to bring back. You can see how Monette’s hair goes yellow and white. This is the breaking point in the overexposure of this camera.
Let’s take last look at the +5 overexposure, where you can really see that the image has fallen apart and we have gone past its breaking point.
Overall Thoughts on the GH4 in V-Log L
The V-Log L boasts that you’re increasing your latitude to twelve stops compared to shooting in the CineLike D profile, which has around ten stops of dynamic range. The V-Log L definitely brings in more dynamic range, but I’m not quite sure that the camera had 10-12 stops. It’s very close, but it most likely falls somewhere around 11-11.5.
The best part about this V-Log L is that it doesn’t feel as “video” in its image. It still leans that way in its color, but the V-Log L gives you a lot more control than the Cinelike D or Cinelike V modes gave you with this camera. There is a lot more flexibility in color control in post as well as limited noise in our controlled latitude test.
In my opinion, this is a much-needed improvement to this camera, and when shooting video with it, the skin quality looks quite nice. This camera paired well with the Veydra Prime lenses that added to this test big time as well.
Remember to rate this camera about -2/3 to -1 stop underexposed to really give yourself the best image quality on this sensor. It gives you a lot of control that way, just like I had when exposing the 5D. These DSLRs just eat light up, so you have to be careful with having too much at times.