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Incident meter, how does it work?


Hongji Wu
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It's a stupid question, but i haven't find any satisfying results on the internet, so the idiot starts to ask! :)

 

there's something i don't understand about incident meter:

 

We know that when we use the reading from the spot meter, the measured area will be rendered 18% middle gray regardless of the actual reflectance of the area, so we open up or close down the aperture and get a proper exposure.

 

But when we use an incident meter, which takes an average reading of the incoming light onto the object, we don't have any actual reference or benchmark like 18% grey for it to calculate, how could the meter "know" which part is lighter and which part is darker? I see some people answered "using the reading from an incident meter makes a gray card in the same light settings falls into ZONE V" but i got more confused because it kinda explains nothing...

 

Let me be more specific, E.g. How did incident meter calculate the light distribution on an Caucasian face and gives out a reading that replicates the same tone as we see?

 

there may still be misconceptions and errors in my understanding of zone system or both meters, can some one explain it to me in an easy way? That would be very helpful, thanks! :lol:

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Well basically the meter doesn't give a damn. What'll happen is it'll measure the light coming in and say, ok, to make middle grey fall into middle grey, use this exposure. So on your example, let's take a face flatly lit. Spotting it will give us a reading to make that face middle grey, let's say F4, however we know the face isn't middle grey, it should be 1 stop over, so we'd adjust to F2.8

The incident meter, with the dome taking the place of a face, will instead say, hey, the light here should be F2.8 to expose middle grey at middle grey and therefore the range of exposures on the face will reproduce faithfully. In our flat lit face it'll be 1 stop over middle grey, with proper skin tones. If we have a super high contrast face, well then the over and under exposed areas would be over and under exposed with reguard to middle grey (if the overs were +3 stops, they'd be +3 stops, and the shadows -3 if they actually are -3, let's say).

 

Hope that makes sense.

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Well basically the meter doesn't give a damn. What'll happen is it'll measure the light coming in and say, ok, to make middle grey fall into middle grey, use this exposure. So on your example, let's take a face flatly lit. Spotting it will give us a reading to make that face middle grey, let's say F4, however we know the face isn't middle grey, it should be 1 stop over, so we'd adjust to F2.8

The incident meter, with the dome taking the place of a face, will instead say, hey, the light here should be F2.8 to expose middle grey at middle grey and therefore the range of exposures on the face will reproduce faithfully. In our flat lit face it'll be 1 stop over middle grey, with proper skin tones. If we have a super high contrast face, well then the over and under exposed areas would be over and under exposed with reguard to middle grey (if the overs were +3 stops, they'd be +3 stops, and the shadows -3 if they actually are -3, let's say).

 

Hope that makes sense.

Thank you for your reply Adrian !

 

I seem to understand a little bit more, to put it in my own words:

 

incident meter basically collects the incoming light from all direction and get the data of the intensity, they don't need to know what's a darker gray or a lighter gray because it's changing, but the middle point of 18% gray (which is unchangeable as a fact of the reality) is fixed, and that acted as a baseline of calculation. So as long as the reading of the incident meter makes the camera replicate the mid gray tone from the mid gray tone in the actual scene, other lighter or darker areas falls into its place naturally.

 

Am I correct about that ?

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Yep; the key is, the meter makes it so you're exposing middle grey to fall in middle grey, and the rest will fall where they would fall.

For myself; i tend to use incident metering the most-- saving spot to get an idea of where on the scale other things are in relation to my shooting stop (e.g. incident, and get a T2.8 and check a highlight which is at T11 and know, ok, that's 4 stops over my exposure; but it's a highlight so it's all good).

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Yep; the key is, the meter makes it so you're exposing middle grey to fall in middle grey, and the rest will fall where they would fall.

For myself; i tend to use incident metering the most-- saving spot to get an idea of where on the scale other things are in relation to my shooting stop (e.g. incident, and get a T2.8 and check a highlight which is at T11 and know, ok, that's 4 stops over my exposure; but it's a highlight so it's all good).

thanks again Adrien!

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  • 6 months later...

So as long as the reading of the incident meter makes the camera replicate the mid gray tone from the mid gray tone in the actual scene, other lighter or darker areas falls into its place naturally. Am I correct about that ?

 

Yes and no. There does not have to be a mid gray tone (commonly called the “key” tone) in the scene to expose for. This is a complicated subject. The key tone, or mid gray because it appears in the middle of a photographic gray scale, is the common reference point used by light meters, lab processors, and transfer colorists. A lab processor knows what density his processed emulsion should be to render mid gray and so he is able to adjust his processing accordingly. A transfer colorist, knows gain will reproduce the luminance of mid gray so he is able to set his gain. Simply put it is the reference point to which we peg all other values on the characteristic curve of the film or digital format we are using. Meters are likewise calibrated for mid gray. For example there are basically two types of meters: incident and spot. Incident meters read the light falling on your subject. Spot meters read the light reflecting back from your subject. An incident reading gives you an exposure that after normal processing would render an 18% gray card as 18% gray (a specific density of the film) had you held it in front of the camera in the same light. Incident meters enable you to peg the key tone (18% gray) in this fashion even though there may not be a mid-tone in your scene.

 

A spot meter is then typically used to take reflective readings to see how other objects will expose relative to the key tone that was pegged with the incident meter. The thing to remember about spot meters is that they want to expose everything as mid gray. For instance, if you expose a black piece of paper with the reading of a spot meter it will appear as mid gray after normal processing (not pushed or pulled) – likewise for a white piece of paper. But, if you place an incident meter down on the black piece of paper and expose for the incident reading the black paper will be black, and the white paper will be white, after normal processing because you exposed for the key tone by using the incident reading and thereby pegged the other values (white and black) relative to it. If you don’t have an incident meter, but want to peg the key tone under your subject's key light, an old trick is to take a spot meter reading of the palm of your hand under the key light and open up one full stop. This will give you a close approximation because the average Caucasian flesh tone is one stop more reflective than 18% gray.

 

 

Metering_characteristic_curve.jpg

(The “Characteristic Curve” of a high contrast B&W Reversal emulsion. The object of exposure is to place the contrast range of the scene on the straight line portion of the curve so that the different luminances of objects in the scene are reproduced accurately on the film. Mid gray being the common reference point.)

 

You use the reading from the spot meter to be sure that the object you are metering will be within the exposure range (characteristic curve) of the film stock you are using. If the stock has a nine stop range (five stops over before detail burns out, and four stops under before detail blocks up), and your reading of a dark object is six stops under your key tone, it will not be rendered on the film after it is processed normal (to reproduce mid gray as mid gray).

Metering_Contrast_Exceeds.jpg

(The contrast range of this scene exceeds the film’s exposure range, so when the image is exposed for the light outside the arch (Left Image), detail is lost in the archway. Likewise, if the image is exposed to hold detail in the archway (Right Image), detail is lost outside the arch. Pegging the key tone centers the contrast range of the scene on the straight line portion of the curve such that some detail is lost outside and inside the arch way, but the luminance values of most of the scene are rendered accurately in the middle image.)

 

Since in this situation the contrast range of the scene is beyond the exposure range of the film you have two choices. 1) You can open up and expose for the shadows (over exposing the key tone and blowing out your highlights more in the process) and print down to make mid gray mid gray again. In the end you have the detail in the shadows you want, but in the process you have lost detail in the highlights. Why? Because the contrast range of the scene was beyond the exposure range of the film, and you exposed for shadow detail, you burned out the highlights (no detail) so it is not there when you print down to mid gray. You can't bring it back. Is that bad - not necessarily. It's just another "look."

 

Metering_Scene_Contrast.jpg

(The contrast range of this exterior exceeds the exposure range (flat line portion of the “Characteristic Curve”) so shadow details, in his hair and the black velour under the MacBeth Chip Chart, that fall on the bottom of the ”toe” of the curve “block up” (max density) and detail in that area of the frame is lost. Likewise, highlights like the specular sun on the windshield and the white towel, that fall on the upper end of the “shoulder” of the curve “burn out” (min density) ) and detail in that area of the frame is lost. The object of lighting is to compress the contrast range of the scene so that it fits on the straight line portion of the curve so that the different luminances of objects in the scene are reproduced accurately on the film.)

 

Or, 2) you can throw some light into the shadows to bring the reflective value of the dark object within the exposure range of the film (onto the straight portion of its’ characteristic curve) without changing the exposure of the key tone value (mid gray) or blowing out the highlights. In this fashion you fit the contrast range of your scene into the exposure range of the film emulsion you are using. Of course this is only the starting point. From this “correct” exposure a DP will further manipulate the relationship of the contrast range of a scene to the exposure range of the film stock to create a desired effect. This is old school film exposure theory, but it is a good conceptual frame work for exposing digital video, especially now that you can record "raw" and apply "looks" to the raw data.

 

Metering_Challange.jpg

(Post in this thread the problems in this image and how to fix them)

 

A fun exercise is to shoot a frame with just available light and then think about how you can improve upon it through lighting. For example, identify the problems in the image above and then list how to fix them through lighting and wardrobe.

 

Guy Holt, Gaffer, ScreenLight & Grip, Lighting & Grip Sales and Rentals in Boston

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Guy, you have made an excellent analysis of the principles of exposure. You are right on! I don't think the younger members of our craft truly study "the curve" anymore and relate it to balancing the light. That's ashame. Great post Guy.

 

G

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Guy, you have made an excellent analysis of the principles of exposure. You are right on! I don't think the younger members of our craft truly study "the curve" anymore and relate it to balancing the light. That's ashame. Great post Guy.

 

G

 

I don't know that The Curve, and knowledge about it, realtive to Film film processing is all that beneficial.

 

What I'd like is better 'curves' from digital Camera manufacturers, in the DSLR category, about their sensors, relative to say the IRE display. The latter seems to be taking the place of the H-D curves of film.

 

In the olden days, one could get the Kodak data sheet on the film type one was going to use, then one shoot test shots, develop, and measure the resulting densities...

 

These days, with all the hype about 'high Dynamic Range', often it is any one's guess as to the real response curve of the camera, and further, how much 'post' modification that data can take without producing garbage.

 

Last NAB I went around to several major DSLR brand booths and asked the somewhat simple question of 'how does X determine the ISO values for camera Y'... only the Black Magic camera both had someone 'technically' up, at the booth... I got a range of responses to the question at the other big names ranging from... 'that guy is ill today', or 'that guy isn't at the show'... to 'that may be a question for Japan'...

 

In the olden days... a Kodak or Fuji rep would say... 'we use Standard X'... and if I exposed film, developed it per the Kodak data sheet I'd get 'close' to those lab results.

 

I did contact one of the popular rental houses, by email after the show, and the person said they have setups at their facility and I could bring in cameras or test their rental selection with some charts they have setup.

 

Unfortunately I don't make it to LA all that frequently during the work week...

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Yes and no. There does not have to be a mid gray tone (commonly called the “key” tone) in the scene to expose for. This is a complicated subject. The key tone, or mid gray because it appears in the middle of a photographic gray scale, is the common reference point used by light meters, lab processors, and transfer colorists. A lab processor knows what density his processed emulsion should be to render mid gray and so he is able to adjust his processing accordingly. A transfer colorist, knows gain will reproduce the luminance of mid gray so he is able to set his gain. Simply put it is the reference point to which we peg all other values on the characteristic curve of the film or digital format we are using. Meters are likewise calibrated for mid gray. For example there are basically two types of meters: incident and spot. Incident meters read the light falling on your subject. Spot meters read the light reflecting back from your subject. An incident reading gives you an exposure that after normal processing would render an 18% gray card as 18% gray (a specific density of the film) had you held it in front of the camera in the same light. Incident meters enable you to peg the key tone (18% gray) in this fashion even though there may not be a mid-tone in your scene.

 

A spot meter is then typically used to take reflective readings to see how other objects will expose relative to the key tone that was pegged with the incident meter. The thing to remember about spot meters is that they want to expose everything as mid gray. For instance, if you expose a black piece of paper with the reading of a spot meter it will appear as mid gray after normal processing (not pushed or pulled) – likewise for a white piece of paper. But, if you place an incident meter down on the black piece of paper and expose for the incident reading the black paper will be black, and the white paper will be white, after normal processing because you exposed for the key tone by using the incident reading and thereby pegged the other values (white and black) relative to it. If you don’t have an incident meter, but want to peg the key tone under your subject's key light, an old trick is to take a spot meter reading of the palm of your hand under the key light and open up one full stop. This will give you a close approximation because the average Caucasian flesh tone is one stop more reflective than 18% gray.

 

 

Metering_characteristic_curve.jpg

(The “Characteristic Curve” of a high contrast B&W Reversal emulsion. The object of exposure is to place the contrast range of the scene on the straight line portion of the curve so that the different luminances of objects in the scene are reproduced accurately on the film. Mid gray being the common reference point.)

 

You use the reading from the spot meter to be sure that the object you are metering will be within the exposure range (characteristic curve) of the film stock you are using. If the stock has a nine stop range (five stops over before detail burns out, and four stops under before detail blocks up), and your reading of a dark object is six stops under your key tone, it will not be rendered on the film after it is processed normal (to reproduce mid gray as mid gray).

Metering_Contrast_Exceeds.jpg

(The contrast range of this scene exceeds the film’s exposure range, so when the image is exposed for the light outside the arch (Left Image), detail is lost in the archway. Likewise, if the image is exposed to hold detail in the archway (Right Image), detail is lost outside the arch. Pegging the key tone centers the contrast range of the scene on the straight line portion of the curve such that some detail is lost outside and inside the arch way, but the luminance values of most of the scene are rendered accurately in the middle image.)

 

Since in this situation the contrast range of the scene is beyond the exposure range of the film you have two choices. 1) You can open up and expose for the shadows (over exposing the key tone and blowing out your highlights more in the process) and print down to make mid gray mid gray again. In the end you have the detail in the shadows you want, but in the process you have lost detail in the highlights. Why? Because the contrast range of the scene was beyond the exposure range of the film, and you exposed for shadow detail, you burned out the highlights (no detail) so it is not there when you print down to mid gray. You can't bring it back. Is that bad - not necessarily. It's just another "look."

 

Metering_Scene_Contrast.jpg

(The contrast range of this exterior exceeds the exposure range (flat line portion of the “Characteristic Curve”) so shadow details, in his hair and the black velour under the MacBeth Chip Chart, that fall on the bottom of the ”toe” of the curve “block up” (max density) and detail in that area of the frame is lost. Likewise, highlights like the specular sun on the windshield and the white towel, that fall on the upper end of the “shoulder” of the curve “burn out” (min density) ) and detail in that area of the frame is lost. The object of lighting is to compress the contrast range of the scene so that it fits on the straight line portion of the curve so that the different luminances of objects in the scene are reproduced accurately on the film.)

 

Or, 2) you can throw some light into the shadows to bring the reflective value of the dark object within the exposure range of the film (onto the straight portion of its’ characteristic curve) without changing the exposure of the key tone value (mid gray) or blowing out the highlights. In this fashion you fit the contrast range of your scene into the exposure range of the film emulsion you are using. Of course this is only the starting point. From this “correct” exposure a DP will further manipulate the relationship of the contrast range of a scene to the exposure range of the film stock to create a desired effect. This is old school film exposure theory, but it is a good conceptual frame work for exposing digital video, especially now that you can record "raw" and apply "looks" to the raw data.

 

Metering_Challange.jpg

(Post in this thread the problems in this image and how to fix them)

 

A fun exercise is to shoot a frame with just available light and then think about how you can improve upon it through lighting. For example, identify the problems in the image above and then list how to fix them through lighting and wardrobe.

 

Guy Holt, Gaffer, ScreenLight & Grip, Lighting & Grip Sales and Rentals in Boston

 

I like to imagine that every film stock is as limited as reversal film. That way it FORCES my brain to think hard about nailing something. I just don;t like to allow myslef to be acknowledging lattitude.

 

Negative stocks might have lattitude for miles, yes it might be there, but if you count on it too much, that's when the drunk driving begins. That vehicle starts to move more erratically. Sooner or later you'll hit a guard-rail thinking like that.

 

The funny thing to me is...and I guess this is ironic considering what I just wrote...I follow the incident metering principles mentioned like a hawk, but when it comes to the act of backing it up with a spot meter, and taking it to the next level checking those relative exposures of various sections of a scene etc., I kind of veer off into another direction and do that part based way more on intuition (I have super limited experience, but I already do have a decent grasp on making sure a black is black or a light is light), so it's not that hard to figure out what a scene looks like "by eye" and use your human mind to figure out where to throw a hard or soft light, or bounce or flag something off with an object in the room or whatever. I mean, you can see (at least I can anyway) when a scene is completely going to have a deep set of blacks and blown out highlights. I don't think I want to be dallying around spot-metering for that stuff (because I just accept my creativity on that part - in the sense of a "painting" decision, not so much a "chemistry class" decision, if that makes sense).

 

As for the exercise above...I don't know how you would do it, but I'd throw something over the glass to knock that window down at least two stops and then stick a single 1K above it, aiming downward at 45 degrees to rim their heads and ten bounce it off a white board to fill their faces. I'd also put a "creative" light on the African American gentleman, coming from the right side, and flag it so it does not hit the Caucasian gentle-woman. Then, I'd put some lame incidental room light in front of the man, just so it appears like "something" is justifying the extra burst of brightness onto him (but it wouldn't e strong enough to actually "do" much. Just basically be a prop.

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Oh! One more lighting problem!...that background would turn way too black with that window knocked down (it's already in need of repair), so the folks in the background would need another touch of lighting magic. This I do not know how to do though...because my gut is telling me they HAVE to get it from the direction of that window (simulating the window light) but yeah, there is no room back there, so MAYBE just hide the lights behind the people and tell them to hold still?! Something like this.

Edited by Matthew B Clark
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Or actually...maybe just have something aiming across their faces from the side, as a very soft and generic fill that gives a lot of pop to the table surfaces and comes up to hit their faces and sort of distinghuishes whatever activity they are engaged in (in other words, rims the shapes enough, or basically fills key definitions of "them"). I just don't like how you can't see anything back there right now and it needs some creative slash of light to pick up the action.

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Or actually...maybe just have something aiming across their faces from the side, as a very soft and generic fill that gives a lot of pop to the table surfaces and comes up to hit their faces and sort of distinghuishes whatever activity they are engaged in (in other words, rims the shapes enough, or basically fills key definitions of "them"). I just don't like how you can't see anything back there right now and it needs some creative slash of light to pick up the action.

 

The shot of the woman and man, are from one of several 'shoot outs' organized and presented by "Zacuto" a sales and rental house based in Chicago.

 

I don't recall a shot that 'constrasty', but then it has been a while since I've watched the several shootouts...

 

Here's a link to the shoot out I think this still came from:

 

http://www.zacuto.com/shootout-revenge-2012

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I like to imagine that every film stock is as limited as reversal film. That way it FORCES my brain to think hard about nailing something. I just don;t like to allow myslef to be acknowledging lattitude.

 

Negative stocks might have lattitude for miles, yes it might be there, but if you count on it too much, that's when the drunk driving begins. That vehicle starts to move more erratically. Sooner or later you'll hit a guard-rail thinking like that.

 

Negative stocks did not have 'miles' of latitude, especially when one viewed the final print film to be used.

 

There were effects from 'overexposure', even with processing by reducing development times, which may or may not have interfered with the 'aesthetic' look of the film. Grain was in many cases objectionable. So, underexposing, and 'over developing' led to 'more grain'... aka 'noise'.

 

Perhaps not the same type of 'noise' now found objectionable in digital images, but definitely not something 'Hollywood' looked to present... until the 60's and the 'new wave' of realism, wherein grainy images were considered more 'real' as in 'just like newspaper reportage images of 'real' events'.

 

Most 'movie' films of the classic era had ASA values of 16-50. In the 50's that value began to creap up to 100-200 then in the 70's 500... Black and White movie film seems to have fossilized at 250D/200T for Double X which is still made. (I think faster B&W movie filmes may have been developed, but production has been stopped for years...).

 

Tri-X a popular 'highspeed' still B&W had a ASA of 400, and even then when a 35mm negative was blown up... grain was the most signficant detraction... (It was a really great film for 4x5 shooting...).

 

For me, I rated my Tri-X at 200, and could expect about 2 stops of 'latitiude', by compensating with reduced development times. For 'underexposure', perhaps a stop or 1.5 stops, before 'grain' started to become a problem.

 

I'm sure people who used Double X at the time, probably had about the same 'wiggle' room.

 

Color film... what me shoot color film... hell no...

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Jedediah Ebonezza Clark of 2006, on 10 Jun 2014 - 06:33 AM, said

 

"Negative stocks did not have 'miles' of latitude, especially when one viewed the final print film to be used....

 

Most 'movie' films of the classic era had ASA values of 16-50. In the 50's that value began to creap up to 100-200 then in the 70's 500...

 

For me, I rated my Tri-X at 200, and could expect about 2 stops of 'latitiude', by compensating with reduced development times. For 'underexposure', perhaps a stop or 1.5 stops, before 'grain' started to become a problem...."

 

 

In the quest for uniqueness are you giving new definition to the word "latitude" ?

 

I think most color films in the 70s were shot on 100T stock (5254/47).

Edited by Gregg MacPherson
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In the quest for uniqueness are you giving new definition to the word "latitude" ?

 

I think most color films in the 70s were shot on 100T stock (5254/47).

 

From the wiki on the film use of the word 'latitidue':

 

http://en.wikipedia.org/wiki/Exposure_latitude

 

---

Exposure latitude is the extent to which a light-sensitive material can be overexposed or underexposed and still achieve an acceptable result.

---

and

---

It is not to be confused with dynamic range, the range of light intensities a medium can capture simultaneously.

---

 

As for ISO 500... sure... the point being, that only in the last 30 years has Film film stocks gotten any amount of 'speed' to speak of.

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Jaqueline Elizabeth Clark of 2006, on 10 Jun 2014 - 08:29 AM, said

 

 

"...wiki ...

http://en.wikipedia.org/wiki/Exposure_latitude

 

Exposure latitude is the extent to which a light-sensitive material can be overexposed or underexposed and still achieve an acceptable result.....

it is not to be confused with dynamic range..."

 

 

I think Matthew B Clark can be forgiven for his exageration in saying that negative film has miles of latitude (I think the common assumption was color negative). It's relative, he's excited about it.

 

Not to confuse latitude with dynamic range, but one can't meaningfully separate (decouple) these two (I can't). And how is lattitude meaningfully decoupled from the range of values within a frame. Unless one assumes a range that is generic, which may be a common working practice I guess.

 

Too much wiki...

Edited by Gregg MacPherson
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Not to confuse latitude with dynamic range, but one can't meaningfully separate (decouple) these two (I can't). And how is lattitude meaningfully decoupled from the range of values within a frame. Unless one assumes a range that is generic, which may be a common working practice I guess.

 

Too much wiki...

I think what the troll as trying to say is that latitude should refer to "how much you can mess things up" vs "how much room you have from shadows to highlights" Granted, they are intimately linked but they are different, no doubt. But now that we are in the age of digital, "proper exposure" is meaningless since people don't expose that way...they expose for look. Maybe they always did so latitude is a very fluid concept.

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It's pretty hard core calling someone a troll. Expect comeback before the end.

 

If one imagines the full tonal range of the film, 10 or 13 stops, whatever one thinks, the scene being photographed (frame) may have less range, less stops between the brightest and darkest usefull information. So this scene can be shifted up or down the scale. But it really depends on what can be quite intimate or spiritualized creative intentions, and exactly how things will look at the extreme ends of the dynamic range of the film (tonal range of the film as I put it)

 

So that's me trying to explain it. Guy or one of the working DoPs will explain it better.

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It's pretty hard core calling someone a troll. Expect comeback before the end.

After what he said to you on the other thread, I think he made it clear that he provides very little use to this site at this point. He has shown disrespect in everything from responses to people to the forum rules.

 

I expect retort. But what you know about me, what makes you think that I am not used to it? ;)

 

I mouth off sometimes but I stand by my words and I am truthful about my identity. He just goes on about posting here like he is a regular who isn't disobeying the (almost only) rule this forum has. I say

let Jannard have him.

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Not to confuse latitude with dynamic range, but one can't meaningfully separate (decouple) these two (I can't).

As I understood it. they're related by the range of the scene...

 

Latitude = DR - scene

DR = scene + latitude

 

etc...

 

Actually, or is it:

 

Latitude = (DR - scene)/2

 

...and then that's just viewing it as a simplistic linear model - which we know it isn't (the 'curve').

 

...and then can you be asymmetric? i.e. purposeful under or over exposure.

 

...and then what about extending and compressing the scene via push/pull, is latitude defined as before or after such carry-on.

 

No doubt there are answers to this (or someone pointing out it isn't relevant and/or my logic is at fault).

 

But unless you're processing and trying to do things by the book (which is a viable and often fruity(ful) path for those that way inclined) it doesn't matter (much) anyway, most people use the term in a simplistic and relative sense (that concept, again), as opting for an absolute and correct version will yield different interpretations (see above re. /2 or not for a very basic example) and therefore different results.

 

Not saying it's impossible to communicate all the complexities and caveats in a (very long) post or two, just saying a forum such as this certainly can afford half-arsededness ;) where we can call BS on parts of someones argument, then in turn skirt over complexities of our own (aware or not).

Edited by Chris Millar
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It's pretty hard core calling someone a troll. Expect comeback before the end.

 

If one imagines the full tonal range of the film, 10 or 13 stops, whatever one thinks, the scene being photographed (frame) may have less range, less stops between the brightest and darkest usefull information. So this scene can be shifted up or down the scale. But it really depends on what can be quite intimate or spiritualized creative intentions, and exactly how things will look at the extreme ends of the dynamic range of the film (tonal range of the film as I put it)

 

So that's me trying to explain it. Guy or one of the working DoPs will explain it better.

 

There may be creative reasons for having blank black shadows, blown out highlights, or similar. Making such choices is part of the creative process.

 

But underneath those choices is the knowledge of what the process is capable of. If one is working with a system that has 8 stops of representation capability, and the scene has 8 stops of 'contrast'... then one has 'no latitude' for error. If one has a recording medium of 15 stops, and one has a scene with a contrast of 7 stops... one has 'a lot' of latitude'.

 

But there will be effects of those choices in most cases. It has been my experience with still films that 'over exposure' for Tri-X yields images that begin to have flare in the shadow areas, and that affects my perception of the quality of the image. Now... some people like flare for some situations... ok... so for those situations, the flare is part of the 'creative' effect.

 

I don't think 'moving picture' film behaved significantly different in this regard, and perhaps the movie film photographer did not have the ability to adjust 'easily' for over exposed highlights that I as a still photographer did (such as burning in blown highlights, dodging under exposed areas, etc...). There may have been some adjustment in the print light intensities, perhaps with the creation of a high contrast 'mask', to deal with blown highlights, or alternatively 'preflash' the film stock, so as to ad 'density' in shadow areas to lift the resulting values 'a bit'.

 

But all those things were bandaids on getting an image to a presentable form.

 

But ultimately what happens on the screen, or in the print, is how the image is evaluated, and as far as I can tell, even these days, the output range is about 7-8 stops. If one consideres 'Rec 709' at least some varients, that knocks it down to about 5 stops.

 

One would think that if a DSLR yielded 10 stops of dynamic range, fitting that into 5-6 stops of 'TV' would be fine dandy. But I think one of the problems is that the DSLR was 'engineered' to yield a 'ready for presentation' image, and so the engineering has already taken away a certain amount of 'choice'.

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