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2.5 - 3 stops below 18% gray comment from AC article


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#1 David Edward Keen

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Posted 17 December 2015 - 10:31 AM

From the December issue of AC the article "A Mid-Century Affair" by Iain Stasukevich:

 

"...He lit most of Carol at or around T2.8, with 'shadow detail 2.5-3 stops below 18% gray, and highlights within 2 tops over.'"

 

 

________________________________________________________________________

 

Can someone explain precisely what is meant by this? Is it just saying that there are lots of details to be seen in quite dark areas? My understanding of gray scale is quite a new study, so what are the various things being expressed about the process of using super 16mm, and lighting here? 

 

Where on the gray scale might some scenes in the Godfather part 1 be found, say the scene in the study where Michael Corleone asks his mom about losing one's family? (Mr Coppola apparently was nervous about how dark the shot was)

 

thanks!


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#2 David Mullen ASC

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Posted 17 December 2015 - 12:44 PM

Traditionally cinematographers exposed film for the range visible in the positive print made from the negative, which is narrower than the range that the negative records (which is useful since it allows us flexibility to print up or down).

 

So depending on the print stock, you'd generally find that things plunged to black 5-stops under and burned out to white 5-stops over.  And if using a reflective (spot) meter than caucasian flesh tones were generally about 1-stop over middle gray.

 

Now I don't know in this case what they mean by "highlights within 2-stops over" -- obviously you will have some highlights that are much brighter than 2-stops over middle gray.  So probably they mean skin tones, but 2-stops over is somewhat on the high key side unless you print down, or you are dealing with very pale faces.  But I can definitely see where faces were exposed 1 1/2-stops over 18% grey so maybe that's what they meant by "within" 2-stops.

 

You'll also find that on a print, a shadow detail that is 3-stops down looks fairly dark but visible, whereas 4-stops down starts to cross into the nearly black zone of detail.  So it is not usual for a drama to generally keep fill levels to about 3-stops down for mood but visible shadow information.

 

When doing a D.I. though, you have some flexibility to drag detail out from the wider 14 to 15-stop range of the negative, however at the bottom end there is a lot of grain there (especially so if shooting in Super-16) so you'd be safer sticking to the narrower range typically seen by print stocks, at least in terms of shadow detail.

 

The thing is that final scene brightness is a combination of exposure and printing decisions, so I can't tell you what Gordon Willis' meter readings were on that scene in "Godfather Part II".  I know that Willis was very precise about printing everything at the same light and that he was rating 100 ASA film at 250 ASA with a 1-stop push, so the resulting processed negative was only about 1/3-stop "thin" though the exposure the negative got was 1 1/3-stops under.  So that was his base for everything.  On top of that was the exposure for the scene to get the mood and brightness he wanted.  So maybe for that scene, he kept the faces let's say 2-stops under to make it feel like a dimly-lit room but later regretted that decision (as he himself has said, the way he rated the negative deliberately limited his or the studio's ability to print a scene much brighter without grain problems.)  But I really don't know what the actual exposure was.


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#3 Bill DiPietra

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Posted 17 December 2015 - 01:44 PM

If you haven't learned the Zone System yet, this is a pretty good reference:

 

Zone System Digital Reference Chart.jpg


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#4 David Edward Keen

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Posted 18 December 2015 - 07:08 AM

great info thanks!


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#5 David Edward Keen

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Posted 18 December 2015 - 08:27 AM

[quote name="David Mullen ASC" post="442702" timestamp="1450374248"]

...(which is useful since it allows us flexibility to print up or down).
______________________

What's the meaning of printing up or down?
 
When doing a D.I.
______________________

What's D.I. stand for?

 I know that Willis....was rating 100 ASA film at 250 ASA with a 1-stop push, so the resulting processed negative was only about 1/3-stop "thin" though the exposure the negative got was 1 1/3-stops under.  So that was his base for everything.
_________________________
This means to describe developing time being deliberately a different duration of time than "recommended" for a 100 ASA stock? Isn't that pushing?


BTW, if it's too much to go into here, perhaps a good book(s) recommendation?
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#6 Jay Young

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Posted 18 December 2015 - 08:33 AM

What's the meaning of printing up or down?
 

What's D.I. stand for?


BTW, if it's too much to go into here, perhaps a good book(s) recommendation?

 

When doing a photochemical film print, you can change the value of the print lights which effect color density and contrast. 

 

D.I. stands for Digital Intermediate -  It means scanning the negative and doing all color manipulation in the digital realm.

 

For Books, the ASC Manual comes to mind.  


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#7 Kenny N Suleimanagich

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Posted 18 December 2015 - 10:22 AM

Richard Crudo has a very useful writeup on printer lights which might help you understand how they work. 


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#8 David Mullen ASC

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Posted 18 December 2015 - 10:50 AM

[quote name="David Mullen ASC" post="442702" timestamp="1450374248"]

...(which is useful since it allows us flexibility to print up or down).
______________________

What's the meaning of printing up or down?
 
When doing a D.I.
______________________

What's D.I. stand for?

 I know that Willis....was rating 100 ASA film at 250 ASA with a 1-stop push, so the resulting processed negative was only about 1/3-stop "thin" though the exposure the negative got was 1 1/3-stops under.  So that was his base for everything.
_________________________
This means to describe developing time being deliberately a different duration of time than "recommended" for a 100 ASA stock? Isn't that pushing?
 

 

"Print up" just means make the print brighter/lighter (which requires using lower printer light values, which is confusing).  "Print down" is the opposite.

 

I said "1-stop push" so why are you asking if that is pushing?  Or are you asking what push-processing is?

 

I said "when doing a D.I." (digital intermediate) I meant doing electronic/digital color-correction from a scan of the negative in the comparison to doing a straight photochemical print from the negative.


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#9 Bill DiPietra

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Posted 18 December 2015 - 10:56 AM

 

"Print up" just means make the print brighter/lighter (which requires using lower printer light values, which is confusing).  "Print down" is the opposite.

 

 

A basic still-photography class that includes darkroom time makes all this a lot clearer, since you are the one doing the printing from negatives of different densities.


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#10 David Edward Keen

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Posted 18 December 2015 - 11:03 AM

ah ok. 

 

 

"Print up" just means make the print brighter/lighter (which requires using lower printer light values, which is confusing).  "Print down" is the opposite.

 

I said "1-stop push" so why are you asking if that is pushing?  Or are you asking what push-processing is?

 

I said "when doing a D.I." (digital intermediate) I meant doing electronic/digital color-correction from a scan of the negative in the comparison to doing a straight photochemical print from the negative.

ah ok.

 

Yeah I meant more broadly what is push-processing, but really the words "rating 100 ASA film at 250 ASA with a 1-stop push, so the resulting processed negative was only about 1/3-stop "thin"" 

 

contain a lot of information I don't yet understand. It may be time to take a course.  Though many googled questions come right back to discussions on cinematography.com ! great site!


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#11 John E Clark

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Posted 18 December 2015 - 01:11 PM

 

 

Yeah I meant more broadly what is push-processing, but really the words "rating 100 ASA film at 250 ASA with a 1-stop push, so the resulting processed negative was only about 1/3-stop "thin"" 

 

 

A Film film will have a manufacturer's recommended time in the developer. In some cases, by extending the development time, more 'density' is developed in the negative... this is called 'push processing'. A '1 stop push' would be adding development time such that the resulting density was effectively 'one stop' more.

 

For the given example, with a Film film rated at ASA 100, and a meter set for ASA 250, one is 1 1/3 stop 'under' the recommended exposure.

Hence to compensate for the 1 1/3 stop under exposure, one 'push processes' one stop, and so now one is only 1/3 stop 'under' which may be acceptable for the given situation.

 

There were limits to how much density a film could achieve, the limiting factor being how much silver halide was in the film in the first place.

 

There were also other 'artifacts' of push processing such as more obvious grain, which in the olden days was considered an objectionable feature of Film film and manufacturers took many pains to produce 'fine grain' films. These days it seems 'grain' has been turned into an aesthetic feature...

 

There was another phrase used as well... 'pull processing' which was to reduce the development time, and again the usual reference of a '1 stop pull'...

 

Pull processing was to compensate for 'over exposure', which if developed normally would lead to blocked up highlights.

 

While I have no experience with motion picture print production the terms are similar for stills, which I have years worth of... ok strictly Black and White printing... color was too complex for me...

 

In that mind, one would 'print down' that is make the print image darker, or 'print up' that is make the print image lighter, depending on the creative requirements... or, saving the day from a botched exposure...

 

In the case of stills one could wave 'wands' or 'fingers' between the enlarger and the paper to selectively 'burn in' areas or give less light to 'print up' areas. Call them old fashioned 'power windows'...

 

I think for motion pictures in the Film film days, one had to make masks or mattes that matched frame for frame the negative to yield the same effect, which in many cases would be too costly to produce, especially if the masks had to 'travel' with elements of the shot.


Edited by John E Clark, 18 December 2015 - 01:16 PM.

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#12 David Mullen ASC

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Posted 18 December 2015 - 05:34 PM

Keep in mind that if you rate the film stock as recommended by the manufacturer and process it normally, you end up with a negative of what you could say as having an "average" density.  

 

So if you underexposed and then developed normally, you'd end up with a less dense -- "thinner" -- negative (clearer, lighter, etc.)  Keep in mind that on a negative the clearer, thinner areas with less silver (in b&w) or less dyes (in color) corresponds to the darker areas of the photographic subject.  

 

Push-processing can involve increasing development time or temperature (or change in chemistry I guess) but for motion picture rolls, changing the development time is more common.  You usually can order the amount of pushing in one-stop increments.

 

So in theory, if you underexposed the negative by one-stop and then push-processed it by one-stop, the net effect would be a negative of normal density once processed, instead of a "thin" negative.

 

Now if you want to consistently underexpose everything by one-stop, the easiest thing to do is just set your light meter to a different ISO rating -- so rating 100 ISO film one-stop faster would mean setting your meter to 200 ISO.  Rating the stock two-stops faster, i.e. underexposing it by two-stops, would mean rating 100 ISO at 400 ISO.  So a 250 ISO rating is 1 1/3-stops faster than 100 ISO.


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#13 Alexandre de Tolan

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Posted 19 December 2015 - 07:01 AM

If you haven't learned the Zone System yet, this is a pretty good reference:

 

attachicon.gifZone System Digital Reference Chart.jpg

 

In Ansel Adams words, 18% is mid grey on a "geometric scale of black to white", We know that he was primarily concerned with printing and that Grey cards are all about proper exposure.

 

Seeing things that way we come to find a slight deviation from mid grey on a Zone System depending the purpous of what we are really doing, printing or exposing, since reflectance (print evaluation), and luminance (exposure evaluation using a incident meter) differs by about half a stop. This was noted by Ansel Adams himself and was written in his former manuals as a "K factor". Something that unfortunately editors cut of from future printings.

 

What surprises me (and that's the all point of this post), is to see an imprint of a Grey card between Zone VII and VIII in the image above posted by Bill DiPietra. Of course it all makes sense. If it is of a higher reflectance than caucasian skin we have to open up to properly expose caucasians as we all know (in a reflected metering). Or even seeing that it is 82% RGB, which lets off the remaining 18% reflectance that are associated with meter calibration (that we know now to be off regarding ANSI standards).

 

But my question remains: If all this is correct, how come have Adams referred to 18% being mid grey on a "geometric scale of black to white", hence 50% RGB?


Edited by Alexandre de Tolan, 19 December 2015 - 07:04 AM.

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#14 David Mullen ASC

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Posted 19 December 2015 - 10:26 AM

https://en.wikipedia...iki/Middle_gray

 

It's odd that the chart above doesn't equal the 18% grey card with Zone V...


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#15 Bill DiPietra

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Posted 19 December 2015 - 11:31 AM

https://en.wikipedia...iki/Middle_gray

 

It's odd that the chart above doesn't equal the 18% grey card with Zone V...

 

I found that chart in a Google search, so now that this was brought up, I was curious to find out the answer as well.  So I went to the website where I saw that image.  Since the image is called "Zone System Digital Reference Chart," I kind of had a feeling there might be a slight variance with how film reads 18% gray as opposed to digital.  Take a look at this link to the discussion below and scroll until you see this image:

 

DSLR Zone Chart.jpg

 

Kind of makes sense, but if what they saying is accurate, then according to the initial chart I posted (see below,) that means you'd have to open up another 3 stops on a DSLR than you would with film to get to 18% gray.

 

Zone System Digital Reference Chart.jpg
 
Having never used a DSLR, I have to ask...is this accurate?  Seems like a rather drastic limitation.

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#16 David Edward Keen

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Posted 19 December 2015 - 02:44 PM

https://en.wikipedia...iki/Middle_gray

 

It's odd that the chart above doesn't equal the 18% grey card with Zone V...

i think i've confused a couple terms.

 

Middle gray is 50% gray or 18% gray? (middle being halfway between all black and all white)

 

Is 18% gray the same as saying "18% of this pure white is gray"? 


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#17 David Edward Keen

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Posted 19 December 2015 - 02:45 PM

sorry, "18% of this pure white is black" is what i meant. 

 

i think i've confused a couple terms.

 

Middle gray is 50% gray or 18% gray? (middle being halfway between all black and all white)

 

Is 18% gray the same as saying "18% of this pure white is gray"? 


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#18 Alexandre de Tolan

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Posted 19 December 2015 - 03:10 PM

i think i've confused a couple terms.

 

Middle gray is 50% gray or 18% gray? (middle being halfway between all black and all white)

 

Is 18% gray the same as saying "18% of this pure white is gray"? 

 

According Ansel Adams, middle grey is in the middle of a "geometric scale of black to white" in a printed image. That means 50% grey. 18% does not refer to grey "directly" but to the reflectance properties of a surface. A Kodak grey card reflects 18% of the light which falls upon it. 


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