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What Makes Middle Gray, Middle Gray?


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Stop picking on Master Adams.. hey did he not <em>invent</em> sensiometry, microdots, defined the concept of gamma, set the tone to inspire the development of the world wide web and ... oops.. no that was Goldberg.. oh right.. did he not invent chewing gum??? No wait.. that was the photographer Thomas Adams and not Ansel.. wait.. was not Ansel Adams that guy who taught at an arts-and-crafts school in Pasadena to be the poster child of a Sierra Club and a generation of tree huggers... Right.. that's the guy that drove around the west with a big camera in his trunk.. and about the only thing he invented was himself.. no wait.. no.. was that not Fred Picker?? And he's the one that convinced a guy that knew someone that once worked for Kodak that he knew more about film than anyone since George Eastman and to make the grey card in his image..
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<i>White and neutral grey cards were used in the copying industry well prior to WW2.</i></p>

 

No on disputes that. The question is how did they gray card come to be 18% rather than 12% (or some other value). Many (not all) have attributed that to the influence of Adams, so that it aligned exactly on Zone 5 of his Zone System (or the Zone System he adapted if you are so inclined to believe that). That is not to say that Adams� idea was original or that he was alone in this opinion that 18% should be used.

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<i>18% reflection is the middle of a log 1.5 range (5 stops)</i>

<p>

Yes, I said it or corrected it, but if you are using it as support for Zone V and that Zone V is in the middle of a ten stop range, how can it be 18% which is based on a five stop range?

<p>

I don't think you need to use bold type to emphasis your point. I'm simple asking you to elaborate on something you said, not to reiterate it louder. I believe a person only really knows something if you can come at it from a number of directions. Otherwise, it's just dogma.

<p>

<i>that corresponds to about Zone 4.5, and Adams thought it would be more useful to make it exactly Zone V and adjust the film speed accordingly</i>

<p>

I have never read anything where Adams said that. If he really knew that 12% was the average reflectance, why did he supposedly lobby Kodak for 18%? Was he just selfishly attempting to impose upon the unknowing public his personal vision of how photography should work instead of how he knew it really worked?

<p>

Yes, 12% would equal Zone 4.5 if you think about Zone V as being 18%. If you wish to support this statement, show proof. What's the source, otherwise I have to regard it as revisionist history.

<p>

I'm reading some circular logic in these posts. Middle gray is Zone V, Zone V is 18%, therefore middle gray is 18%. This kind of thinking is very common. In fact, there are a number of such stumbling blocks to rational thought. My favorite is the need for the brain to find causal relationships even though it is very bad at it. For example, the Aristotelian theory held that an object falls to the ground when dropped because it longed to be with the Earth. Newton changed that, but he was actually accused of incorporating magical explanations into his theory of gravity (invisible force).

<p>

Let's get back to the question of middle gray and away from ZS dogma.

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The question at hand is not whether it's 12% or 18% but rather why use a middle value to establish exposure rather than shadows or highlights.

 

It seems that using a middle value applies best to the following situations:

 

1) Use of an exposure meter that can only measure the average illumination (incident meter or averaging reflectance meter).

 

2) The subject matter and/or illumination is relatively consistant.

 

3) The exposure guidelines must produce reasonably acceptabe results with a wide range of materials, processes, illumination conditions, and subject matter.

 

So, Mr. Benskin, what is your theory or will we have to wait for the article?

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Steven, I used bold because I needed 3 different fonts to show 1) my original response (italics), 2) you questions about my original response (normal text) and then 3) my final reply (bold). I used bold to distinguish my comments from yours.

 

Based on the thread you started concerning the Sunny 16 rule, I don't think you have enough understanding of photographic principles to understand these concepts, including the concept of middle gray. So I doubt that any further explanation would be satisfactory to you. I hope you don't take personal offense at that, but I don't know any other way to say it.

 

Regarding my providing proof and citing references regarding Ansel Adams' participation in this history of this issue, I don�t care whether you believe it or not. Also, I don't consider my comments to be revisionist history since no one has produced any compelling theory that I am revising. But someone asked, and I gave one story that has been told about these events, but I admitted that not everyone may agree about the accuracy of such history (usually because they don�t like Ansel Adams).

 

Personally, I really don't think it matters "why" or "who" anyway, especially in terms of making photographs. If you test to create your own personal film speed, the choice of 12% or 18% is irrelevant.

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Most all Kodak literature uses the more complex world of real data. This is sensitometry data and curves; instead of the more amateurish "Zone system". A curve has real numbers; DlogE data for each point. Zones is for those who dont have Engineering backgrounds; and want/demand a simplified model. The Zone system is like a football announcer reducing the playing field to 10 zones of 10 yards each; to water down the data. Thus the announcer might call the 0 to 10 yard area Zone 1 of "Riverdale High"; instead of the 7 yard line of "Riverdale High". He might call the grey :) area "mid zone" or the ball in the 45 home to 45 away side. Some zone "people" understand density; and the DlogE curve; others throw out "Zone XYZ" and dont have a clue what they are talking about.
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I suppose the punchline will come in the form of four quadrant curves. :-)

 

A wide-view sensor can do nothing else but average the brightness of a scene into a single "pixel". So, going about this in the most round about way possible, I opened a few "average" scenes, scanned from E6 color transparencies, in Photoshop and resized them to a single pixel. The unsurprising result is they all have a CIE L* value of close to 50. CIE L* 50 corresponds very closely to two stops above B+F on my Stouffer 21-step wedge, step (5) on the 4x5 wedge.

 

I'm not sure what this means. A B&W neg developed to a CI of 2:3 would yield a DR of 1.2 for a brightness range of 1.8, centered on the one tone that renders the same in the print, on the negative, and was so in the real scene. I don't know if it's a happy coincidence, or if the procedures I learned along the way took this into account, or if the meter's response to 18% or 12% allowed this to happen.

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D Poinsett, I kind of changed how I was going to particpate in this thread. I went from looking for a consensus to using the Socratic method in an attempt to tease out more discourse.

<p>

<i>So, Mr. Benskin, what is your theory or will we have to wait for the article?</i>

<p>

Even if I was a quick writer, the magazines aren't in any hurry to publish article on theory. I've been waiting over 1 1/2 years on one.

<p>

Let me just say that I have already expressed some of the ideas on other threads and will probably do so in the future. For me, the idea of middle gray breaks down into three areas:

<p>

Psychophysical and perceptual

<p>

Physical and Camera Image

<p>

Meter Calibration

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Dear Mark,

 

Be careful when you accuse anyone of knowing less than yourself, or of lacking the knowledge of basic sensitometry to understand your explanations. Be doubly careful when accusing Stephen of this. He generally asks questions like this because he knows so much more than most people that he is questioning not the equations or the rules, but the assumptions on which they are based. He knows a great deal more than I -- for a quick summary of my ignorance on the subject, read my book 'Perfect Exposure' (David & Charles/Amphoto), especially Chapter 6 -- and I would be surprised if he does not know rather more than you.

 

Cheers,

 

Roger (www.rogerandfrances.com)

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O.K. D Poinsett, just to prove I'm not being coy, below is the proof for average reflectance. If anybody is wondering, yes, it is based on the camera image and not the original scene. Like I indicated in a previous post, what we want to call middle gray depends on the situation. It's different for each of the three areas I listed. This is just one under average conditions.<div>0081Yq-17641484.jpg.b26ba7a0837a3e06691ac6522afa10cc.jpg</div>
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From the opening post of this thread:

<p>

<i><u>I�m working on an article about middle gray</u>, and I was hoping to get a general consensus on a concept. <u>I have my own theory so this is just a survey</u>, and would appreciate any thoughts.</i>

<p>

Maybe it's just me, but I don't think this is misleading. How about the graph? Is it direct enough? It's kind of quiet now.

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Let's take the camera image concept a step further. If flare has an influence of the placement of the average reflectance, where do you think the point of average reflectance fell back in the days before uncoated lenses? The flare factor was about a stop higher than today. That would make the average reflectance point shift 1/2 stop. Isn't 18% 1/2 stop lighter than 12%?

 

Below is another proof that makes things even more interesting. If you take into consideration the whole processes, the characteristics of the film and the paper work to influence the final placement of any tone in relation to the original scene. For more information on this subject see the Overexposure - Anecdotal vs Objective Analysis thread. It's the idea of Tone Reproduction Theory. The reproduction curve graphs the relationship between the resulting reflection densities in the print which have been shifted and changed by the photographic process against the original scene. That said, this example doesn't have a reproduction curve. It consists of only a three quadrant tone reproduction curve.

 

The proof illustrates that depending on the film and paper characteristics, a point of 12% reflectance in the original scene can produce an 18% reflectance in the print. So, we can meter an 18% gray card and exposure the gray card which will fall as if it were 12% reflectance, but with the right combination of film and paper, it will reproduce as 18%. Could this perhaps cause some people to argue for the validity of 18% as the meter's calibration value? Is it possible that this will cause people to make the wrong conclusion because they are basing it on anecdotal evidence and not Tone Reproduction Theory?

 

It gets even more interesting. Food for thought.<div>0081id-17643584.thumb.jpg.35ea8dce1aa2acf20867b23fd7550b26.jpg</div>

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Well, see, once in a while it does freeze in hell, since I happen to be in agreement with Hicks. Mark, you have no idea of the depth of knowledge Stephen has on sensitometry and photographic reproduction. He is using a very old didactic technique, which is to ask a question for which he already knows the answer to demonstrate his point, I am told Aristotle used to do this..:-)<p>

 

I usually do not participate in his threads because I have little to add. Calling him ignorant just shows how little you understand and your inability to comprehend his questions. As a chemist I am comfortable both with the theory and practice of spectrometric techniques, yet if I have a question on sensitometry that I dont understand, Stephen would be the person I would go to for answers.

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Thanks for posting the graphs. Unlike some others, I have considered your inquiry into this matter well intented and for the purpose of furthering our collective understanding, yours included.

 

In the latest image, the graphic representation of flare on the darkest portion of the photo is quite evident. This is an area where our perception is most challenged to distinguish tonal differences and it's easy to see how the flare works further against us.

 

I haven't figured out the scale shift between the top and bottom of the the camera/flare graph. Perhaps you could explain. The rest makes perfect sense.

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Jorge, I believe you meant Socrates, not Aristotle. The real problem is that whatever Steven knows about sensitometry, he knows little of the Socratic method for arriving at the truth.

 

Socrates often asked questions of those who claimed to know truth, while claiming ignorance himself. In Socrates case, his questions not only showed that people usually did not know what they were talking about, but his questions led people to the truth.

 

If you follow the text of Steven posts carefully, his questions don't lead anywhere. Those who treated his questions as genuine (like me) where deceived in to wasting our time trying to help someone who pretended (disingenuously) that he did not understand.

 

Some people who know Steven outside the boundaries of this thread start with the conclusion that Steven is knowledgeable about sensitometry, and then try to justify his posts on this (and the Sunny 16) thread. Close examination of the text of his posts, and his own admissions, reveal that he was just trolling.

 

If Steven has a point to make, I would like to hear it without the deception and the feigned ignorance. As I said, if someone wants to pretend ignorance within the confines of there posts, don�t blame me and others from calling him ignorant.

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D., I'm sorry, how do you like to be addressed?

<p>

<i>I haven't figured out the scale shift between the top and bottom of the the camera/flare graph.</i>

<p>

I'm not sure what you are asking. The term scale shift is throwing me. Are you asking about the values on the X and Y axis?

<p>

<i>it's easy to see how the flare works further against us.</i>

<p>

Flare does play a very large roll in the photographic process and it is almost never covered in popular literature. Flare in many ways is our friend, but it is also a monkey wrench. The knee jerk reaction is to think of flare as detrimental. Tone reproduction theory indicates otherwise.

<p>

This is somewhat off topic, but without flare the camera image would be the diagonal line. Notice how the shadow falls further down into the film's toe? Without flare, film speed would be at least a stop slower. Processing times would also be shorter (producing even lower film speeds). Ansel Adams never figured flare into his testing procedures. The average reflectance would be 9%. 80% of flare is produced by the subject. It has a tendency to increase as the luminance range increases and decreases as the luminance range decreases. Let's not even get into the compensating effects this has on the apparent scene's luminance range and processing.

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I've had it with you Mark. I've posted my proof. Show us how much you know. Prove me wrong. I'd be surprised if you could even explain my proof. And drop the Socrates argument already. This isn't a philosophy forum. Show me what you know about photography. Come on Mark, give me an intelligent argument that doesn't include Zone System dogma. Argue the topic at hand, and drop your petty crap.

<p>

Once again for the hard of head. <b> I said at the start of the thread that I was writing an article and that I had a theory and was only looking for a consensus.</B> If you feel that people writing articles are inherently stupid, then I can see where I tricked you. Otherwise, the fault is yours for not reading the original post, or the reiterated post, or my last post on the Sunny 16 thread carefully enough.

<p>

What I can't understand is that we have argued issues before. How can you not remember that? Do you not look at the people's names? Do you not take into consideration who you are talking to?

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Predictions about this thread (also includes Sunny 16 thread):</p>

 

1. This thread will be the final blow to conventional B&W photography. After reading these posts, most newbies and moderately experienced photographers (of which there are many lurkers on this forum and do not post) will permanently make the move to digital with auto-exposure cameras.</p>

2. Sales of 18% gray cards will plummet, and they will not longer be manufactured.</p>

3. For the few people who stick with conventional B&W photography, this thread will completely discourage newbies from learning about sensitometry, and forever wipe away the last vestiges of the Zone System, and most people will just use auto-exposure cameras.

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I misread the numerical log scales at the top and bottom of the camera/flare graph. I thought they were slightly shifted from each other but I see that they are the same.

 

I had never thought of the advantages of flare, only that it reduces contrast. I will have to ponder its possibly advantageous effect on tone reproduction. I have thought that a film with a shorter toe (straighter line) would help increase local contrast in shadow detail without any tonal cost to the rest of the image. Hmm...

 

The "beneficial" effect of flare on film speed and development time are of less value to me though I have to admit I hadn't thought about it before either.

 

Can you say more about the effect of flare on tone reproduction or point to another resources? It seems like it would just flatten the shadows more than anything. The only possible advantage I can currently think of is that it would move the shadows up the scale where we can better distinguish tonal separation. But it also seems that this would be offset by lower contrast. Perhaps there is a net perceptual gain.

 

(P.S. I have no significant preferences in how you address me but thank you for asking.)

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Flare is an integral part of the determination of film speed, but that is a topic for another day.

<p>

<i>Can you say more about the effect of flare on tone reproduction or point to another resources? It seems like it would just flatten the shadows more than anything. The only possible advantage I can currently think of is that it would move the shadows up the scale where we can better distinguish tonal separation. But it also seems that this would be offset by lower contrast. Perhaps there is a net perceptual gain.</i>

<p>

Long question, short reply. There's a lot to talk about here. The Overprocessed - anecdotal vs Objective Analysis thread deals with it to some degree. I would also be more than willing to discuss it on a different thread if you want to post it. That way, it will get the attention it deserves.

<p>

And thanks for sticking with traditional photography.

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