What is this thing called Middle Gray?
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- เผยแพร่เมื่อ 3 มิ.ย. 2024
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Everybody talks about Middle Gray but nobody does anything about it! Let's focus on demystify middle gray.
Make sure you check out our Video on the Science of Exposure and Metering:
• The Science of Exposur...
It's nice to see someone not only explain this without botching it, but also explain the math of why it is.
Wow, I actually almost understood this one. Usually the technical videos go way over my head.
Is that an 18% gray suit jacket ?
Wow! А remnant of Knowledge in the age of "influencers" who hit the rec button before they understand what they're talking about. Thank you!
Your humour is exactly like mine, that is why I watch Your videos with curiosity !
I think I'm too early for the arguing photo nerds. I'll come back later.
So basically what you’re saying is that Middle Gray is a Gray area?
Okay you win the internet.
Well you set the tone for this comment section.
Take a shot every time he says middle grey
2 rolls of film or so..
Oh, you meant a shot a liquor. Too early. Coffee?
Take a drink or a photo?
Great stuff as always, guys! I really appreciate this follow-up to the exposure video.
fantastic, still very valuable 5 years later, thank you!
I watched this video when it came out, and watched it again today. Hope life's treating you well my friend 🌱✌🏻
Great little explanation. Also I absolutely love your set.
Good topic. I learned about what I know as "neutral grey" through my learning of film makeup. It is used for the sake of highlights and shadows.
I think this is the best video on 18 % grey
Another great afternoon nap video! Thanks!
Thank you for the refresher. It's been a long time since cinematography class! :)
Amazing video as always
Love it! Thanks mate, as always!
Is great! Thank you for such a good explanation.
That fake ending was great! Funny and informative.
00:40 I was expecting the Vsauce music to start there...
John sit on your coat tail to keep it from riding up.
This tip is from the movie 'Broadcast News' :)
Good one!
Ah i have been looking for this since a long time
Thank you!
Love it!
Very good
Wow. Thanks much.
"What the FACEBOOK is middle gray?" XD
careful now... don't want to have the kids hear you swearing!
Filmmaker IQ I understand. Love your videos. I'm working on VFX for a student film, and your videos help.
What the Facebook needs to be a thing. Can we make FilmmakerIQ into a meme?
upvoted for the joke at 0:34 alone lol
This explains it WAY better than "50 shades of gray"
Very inspiring video series. Can you reccomend a textbook that covers this and more theory of digital image processing?
honestly, not really. You have to cull a lot of information from a lot of sources - there might be a book but that contains all this but it might be frankly too technical to be readable.
Thank you for posting. Here is a question: Middle grey vs incident meter? Incident meter gives a reading with dome on pointing at sun gives you a reading of say f5.6 That would be middle grey right? Point the incident light meter dome at camera and shade it from the sun and that gives you middle grey in the shadows.. then pick either end depending upon subject or split the difference or use bounce/fill to fill in shadows to drop the difference between (say on a human face) bright side to dark side. I've tried for a year to get good exposure with grey cards with my 4K camera and spot metering/histograms etc. I gave up and picked up a Sekonic 308 XU incident cine meter.. shooting log 400 ISO pointing dome at the sun I get great over all exposure. (Just wateched your video on BMPCC4K dual ISO) and thinking I should revisit my method and switch daylight log footage to (JVC LS-300 J-LOG) back up to ISO 800 or what ever the chart showed as middle grey in middle or at least more stops above middle grey since theri log profile is at least similar... The putting the 18% grey card at an angle is impresise and not what I learned in college, not that college was right correct about many things.. it wasn't. Grey card slight adjustment left/right/up/down would yield 2-3 stops change easily, hence I LOVE my incident cine meter. Thinking of getting top end Sekonic meter in 2019. So back to my question (I lost somewhere in my rambling at 6:30am with 1 cup of coffee...) Best method? Shoot incident using incident cine meter but have a grey card in shot off center from camera/light so that it you have a in camera reference? Or shoot with grey card metering in waveform and drop 1/2 or 1 stop from what you read in camera? Most log cameras seem to say to put middle grey in LOG between 35-40% reflective. (ok what angle of card.... ) Anyway I find the incident light meter to be more straight forward and repeatable than the grey card. Would you agree?
Yep I'm in favor of incidence metering over spot metering.
thank you.
I have a couple of questions on a topic that I don't think is taught in film classes, what are movie completion dates? and what are the differences of movie completion dates vs. movie release dates?
Well, I don't think I've ever heard of the term "completion date" - there's an old editor's adage - a film is never done, it's only abandoned.
There's such a thing as a "Picture Lock" which means the picture is locked and moves to a different part of finishing... so I imagine a completion date is when the film is totally all done and finished. Then the release date is just the date that it first goes on sale at the movie theaters or via streaming/TV
The movie completion date is the date the movie was completed.
The movie release date is the date the movie was released.
The difference between them is measured in days.
I stopped at 0:37. I don't need more information. And I know the soundeffect from 1:27 from redlettermedia. At 3:55 I noticed your fantastic telephone on your desk. Does it work?
Anyway, a great video as always.
The phone may still actually work but I would need to wire it for modern phone jacks.
So now, should I tilt the grey card and how much and which grey card is that anyway and then what Should I do about the exposure setting ?
This is great knowledge, you sound like you understand some of all this. lol .
The idea is to angle the gray card partly so it doesn't glare - this is for 18% gray cards. If you shoot it straight on flat - you should increase the exposure by 1/2 or 1/3rd stop if you're metering with your camera's meter.
Now if you get a 12% or 13% gray card, then you just go with the settings you're given by your camera.
But... if you've been exposing with 18% gray and it works for you - just go with it. Middle gray is incredibly subjective.
Here's another article from a cinematographer that demonstrates some of these very slight differences: www.ryanewalters.com/Blog/blog.php?id=3551583675371023276
Thank you John, your explanation and reference very helpful.
I think I understood it. Mid grey gives you enough "highlight reserves" to shift an image in post either towards black or white. Thats why SLOG3 is the perfect ballance for post prodcution. The image seems to be flat, but you have a "50/50" (of course not 50, as we learned in the video, but just ot make it more easy to understand) ballance to shift the image the way you want. So basically SLOG-3 records in the mid grey range. Am I correct or fully wrong? :D
I wouldn't call SLOG3 any better than any of the other log formulations. If you want to get more complicated, look up my video on dynamic range.
I wish youre my science teacher
Where have u been all my life
It is an IQ!
You are either exactly correct... or not exactly correct. Either way, I don't care. This is one ass-kicking video. Great job!
Probably enjoyed the humor of second 42 too much. Nerd laughed pretty hard can't lie
Lol. I made this video with my comment xD
Yep ;)
I work in colour science and I have to tell you that you are somewhat off the mark. You make it sound like "18%" is just a convention based on the Lab colour space. First, you have to differentiate between radiometric and photometric light measurements. Light is either measured as a physical phenomenon independent of human viewers, in which case we call the measurements "radiometric"; or it is measured according to the standard perception of the human visual system, in which case we call the measurements "photometric".
Object brightness can thus be measured either as a radiometric quantity, in which case we'd measure its "radiance" in watt per steradian per square meter; or as a photometric (perceptual) quantity, in which case we'd measure its "luminance" in candela per square meter (aka 'nits'). The difference between the two is that in the case of radiant intensity we add together the contributions of every wavelength of light in the source's spectrum, whereas for luminous (i.e. photometric) intensity the contribution of each wavelength is weighted by the "standard luminosity function".
This standard luminosity function is a standardized model of the way the human eye is sensitive to various radiant wavelength - it is the characteristic spectral response of the human eye. The standard luminosity function looks like a bell curve centred on ~570 nanometers of wavelength for relatively bright light (so-called 'photopic' light, perceived by the retina's cone cells), and shifted to ~500 nanometers for relatively dim light (so-called 'scotopic' light, perceived by the retina's rod cells).
When you measured the brightness of grey patches in your video, your exposure meter was converting the radiometric measurements of wide spectrum reflected photon energy into the photometric quantity of luminance (with a reading in candelas per square meter). In essence, your meter was "looking" at the grey patches through a green-sensitive bandpass filter (that's what the standard luminosity function is). As it comes to the conversion of this reading into reflectance (or transmittance) values, and how we get to the standard "18%" value for the middle grey patch, we use another function, which you are correct in stating that it was first suggested by Albert Munsell in 1905.
Throughout the 20th century, the mathematical description of this function has been refined, but it essentially has always been a cube-root function that plots object luminance versus lightness perception, and normalized between 0 and 100%, in what is called 'relative luminance'. Munsell called this dimension of colour perception, the "Value" of a colour (along with its "Hue" and its "Chroma" aka, saturation) and by the mid-1930s the plot of this function by itself (void of hue and chroma), the "neutral value scale". By the end of the 1950s, Kodak scientists refined Munsell's neutral scale model into the "Lightness" scale, denoted "L*" (pronounced "L-star"), and by 1976, the Commission Internationale de l'Éclairage standardized the "CIELAB" colour space, that enhanced Richard Hunter's "Lab" colour model by using Glasser and Wyszecki's cube-root model in place of Hunter's square-root.
Thus, the CIELAB model uses the L*a*b* notation (with asterisks), and the L* function has since then represented the most practical and stable representation of a "perceptually uniform" visual scale of lightness, in spite of much more complex "colour appearance models" having come into existence since the late 1970s (models that take into account various perceptual effects such as simultaneous contrast, saturation-dependent brightness perception, and so forth). It IS safe and accurate to state today, that in general as it concerns relative luminance (that is, as per the CIE XYZ model, Luminance - denoted "Y" - normalized between 0 and 100, the latter value representing diffuse white, and not considering specular highlights), the L* function represents the perceptually-uniform scale of lightness, computable directly from radiometric and photometric measurements.
You incorrectly stated that the "L'" in CIELAB corresponds to "Luminance", whereas in fact it corresponds to "Lightness", a totally different metric. As you were nonetheless accurate to point out, when computing this function, it so happens that when an object reflects 18.42% of its incident illumination, one will obtain an L* value of 50, spank in the middle of the Lightness scale. This is valid throughout the luminance range that the human visual system can cope with, it goes without saying.
The fudge factors used by Ansel Adams in the 1930s (some of which have unfortunately made their way into exposure meters) were based on empirical methods at a time these functions were not in existence. In the days of black and white silver halide photography, the golden rule was "expose for the shadows, develop for the highlights", so a modicum of overexposure was deemed preferable, to obtain a dense negative (silver halide emulsions don't suffer from quantization issues like digital imagers do), which you could then either under-develop ("pull process") and tone to achieve excellent contrast effects.
Adams was a master of these techniques, all of which he documented in his books about the Zone System which is concerned with both exposure and negative development. But Adams was not a champion of colour photography - it's a well-known fact in contrast, that colour negative film in the motion picture industry always looked better when under-exposed. It's also a well-known fact that antiquated standards such as ANSI PH3.49 1971, which was quickly superseded by ISO 2720-1974, contain ludicrous mathematics and dubious fudge factors such as the infamous "K" constant used by exposure meter manufacturers. Simply stating that "Aha ! ANSI PH3.49 defines middle grey as 12.8%" has zero scientific value.
It IS because serious engineers abide by the proper math, that colour science in the context of digital imaging produces consistent results and much better handling of colour and exposure than was the case 50 years ago. Two last points in the context of the new wave of HDR imaging: The beauty of the L* function is that it defines the Just Noticeable Difference (JND) in lightness that can be perceived. The JND, also referred to as the Delta-E (a metric those who calibrate devices will recognize) corresponds uniformly to 1% of the L* function. So each 1% step along the L*, represents the smallest increment in lightness that can be perceived.
In parallel, Peter Barten published a series of seminal papers from 1992 onward, about the contrast sensitivity of human vision. The Barten model complements the L* scale to define the just noticeable difference in contrast. Whereas scientists and engineers used the L* function to define the proper amount of digital encoding resolution required to represent relative luminance without quantization artifacts (i.e 'banding'), in recent years engineers used Barten's model to define the proper way to encode high dynamic range scenes that extend beyond diffuse white (relative luminance) and into the specular domain.
What the Barten model helped engineers with, is decide how few bits (code values) could be used, and according to what mathematical distribution (the so-called "opto-electronic transfer function" or EOTF), to encode very wide dynamic range (0 to 10,000 nits) without viewers seeing quantization errors. This led to both the HDR Hybrid Log-Gamma and Perceptual Quantizer standards that are in use today. In HDR PQ, when properly exposed, your 18% grey card reads... 50 nits.
Thanks for the write up! I think this comment is a bit longer than my entire script ;) still I appreciate the real detail of handling the color science you guys do because frankly it's just mostly Greek to me.
Phil Pan Damn lol You Came With It..... You got props
WTF
Where can I find more of this stuff? Thx @ Phil Pan for taking the time to comment!
@filmmaker IQ: nevertheless great channel! I love your effort, trying to break down those difficult and tech nerdy concepts in somehow more digestible filmmaker educational content. Keep up the good work and Thank you so much
Nerd alert! 😀
I just noticed he looks like a chubbier Hideaki Anno.
Does nobody ask about your 18% Grey card. Is the card still 18% Grey in the sun? Or in the shadows? In dark? Or in light? I'm thinking it would be misleading to judge from a card when you don't know what grey your card is given the lighting conditions
You're misunderstanding the point of 18% gray. Yes it is 18% gray under the sun, shadow, dark and light - it is suppose to be 18% gray regardless of whatever lighting condition you are in.
@@FilmmakerIQ ?? (This is getting interesting)
When the sun shines on my card, doesn't make it brighter? (= makes the card whiter than middle grey?)
Oh, did I mention. I wish to capture my scene exactly as I see it. Hope this piece of info helps to understand my point
Everything is relative. You expose differently when in a bright situation than you do in a dark situation. The point of the 18% gray card is it's middle gray whether you're in the sun or inside in the dark.
If you're in the sun and your 18% gray card is brighter than middle gray - you're overexposed - so you have to pull back the exposure so that your graycard is back to being middle gray.
WTF is gray ?
Google it
It's candles not ken dolls. As in the light dissipated by a single candle, which is the basis of that scale.
If you want to be pretentious, use lumins.
Who the Facebook is talking about candles?
CANDLES... not can-dells.
I never said "Candles"... I said Candelas.
Well, I just learned something. I stand corrected. My apologies.
Is it just me, or is this video underexposed? Maybe the the cinematographer used the wrong gray?
It's you