12% subject looks right printed to match 18% gray card

Bill Burk · Apr 13, 2016

When making a black and white print of a normal scene from a normal negative, 12% in the subject might look right on a print when it is printed lighter than real life.

I am saying you may expect 12% to match the standard 18% gray card.

It's easy to understand why.

Your print can only go from white to black.

In a normal outdoor scene with mixed lighting conditions, some things are in the main light and some things are in the shade.

The things in the main light might range from white to black.

If you take something that was black in the main light, and print it black on the print, then you haven't left any room for things in the shade to look darker.

When you leave room for things in the shade to look darker, then the black thing in the main light won't be black any longer it will be a dark medium gray. This lifts up the dark medium grays accordingly and something that started out as 12% in the original scene winds up lighter on the print.

I have found that 12% from the subject arrives at approximately 18% on the print.

I am not trying to be precise. The target I used includes a 12.7% sample because it fits the Sekonic Exposure Profile Target series of grays. Whether we are talking 12%, 12.5%, 12.7% isn't my point.

If I were to relate this in Zone System terms, I am saying you should expect Zone IV in the subject to approximately match an 18% gray card when you compare the card to the print.

There's room for interpretation of course, but one thing is certain: 18% doesn't print as 18% unless you increase the contrast significantly. You would do that if you were shooting copy work. But most of the time you are not doing copy work.

Here is an example of what I am talking about. Exposure target next to a print that includes a photograph of the exposure target. You can see the 12.7% chip on the photograph (the darkest of the middle row of 7 grays) matches pretty closely to the 18% (the boundary area and the middle of the middle row of 7 grays) of the gray card setup next to the print.

Doremus Scudder · Apr 14, 2016

Bill,

You're missing the point of the Zone System. It's a visualization tool primarily and only loosely connected to sensitometric tone reproduction. The fact that any measured luminance ends up at any particular print value is arbitrary. There really are no fixed Zones in the subject. Your arranging of tones to get a pleasing result for a scene with both shaded and directly lit subjects is just your "visualization" at work. Knowing that a "middle grey" in the light should often be rendered at higher than Zone V in the final print when there are lots of shaded areas that need to be rendered with detail is just part of the process of learning to visualize. Doing the "place the shadow and see where everything else falls" exercise allows a practiced eye to do exactly what you've done before the shutter is released.

It takes time and practice to know where you want print values to be (or where they are going to end up no matter what you do...). Plus, we really only have limited control with exposure and development; the relative tone distribution stays much the same, just the overall range is somewhat adjustable. Darkroom manipulations give us more controls, but still, we're largely stuck with the limitations of the medium. Knowing how those work and what we can expect from the controls available to us is the purpose of visualization. It doesn't matter to me what reflectance a certain important subject elements have; I arrive at an exposure and development scheme that gives me final print values that I hope will make an expressive print, working within the limits of the medium, of course.

Snow is white, but I like shaded snow in Zone V or maybe V+ on bright sunny days. Dark subjects in bright sunlight get rendered way brighter in a scene in which the interest is largely in the shadowed areas than if the scene had no shadows. Conversely, I'll let light areas in shaded parts of a scene go really dark if I want to emphasize separation in a lit area of the scene. The trade-off is dictated by the limited reflectance range of the final print.

Best,

Doremus

RalphLambrecht · Apr 14, 2016

Doremus Scudder said:
Bill,

You're missing the point of the Zone System. It's a visualization tool primarily and only loosely connected to sensitometric tone reproduction. The fact that any measured luminance ends up at any particular print value is arbitrary. There really are no fixed Zones in the subject. Your arranging of tones to get a pleasing result for a scene with both shaded and directly lit subjects is just your "visualization" at work. Knowing that a "middle grey" in the light should often be rendered at higher than Zone V in the final print when there are lots of shaded areas that need to be rendered with detail is just part of the process of learning to visualize. Doing the "place the shadow and see where everything else falls" exercise allows a practiced eye to do exactly what you've done before the shutter is released.

It takes time and practice to know where you want print values to be (or where they are going to end up no matter what you do...). Plus, we really only have limited control with exposure and development; the relative tone distribution stays much the same, just the overall range is somewhat adjustable. Darkroom manipulations give us more controls, but still, we're largely stuck with the limitations of the medium. Knowing how those work and what we can expect from the controls available to us is the purpose of visualization. It doesn't matter to me what reflectance a certain important subject elements have; I arrive at an exposure and development scheme that gives me final print values that I hope will make an expressive print, working within the limits of the medium, of course.

Snow is white, but I like shaded snow in Zone V or maybe V+ on bright sunny days. Dark subjects in bright sunlight get rendered way brighter in a scene in which the interest is largely in the shadowed areas than if the scene had no shadows. Conversely, I'll let light areas in shaded parts of a scene go really dark if I want to emphasize separation in a lit area of the scene. The trade-off is dictated by the limited reflectance range of the final print.

Best,

Doremus

exactly!

Bill Burk · Apr 14, 2016

Doremus Scudder said:
Dark subjects in bright sunlight get rendered way brighter in a scene in which the interest is largely in the shadowed areas than if the scene had no shadows. Conversely, I'll let light areas in shaded parts of a scene go really dark if I want to emphasize separation in a lit area of the scene. The trade-off is dictated by the limited reflectance range of the final print.

Placing things where they aren't expected to fall is one of the things that keeps me enthusiastic about the Zone System. It gives you the working vocabulary to imagine a gray stone embedded in a rock wall is the moon at night over a stormy sea (Minor White's Moon and Wall Encrustations).

And it's not Zone IV that comes up to Zone V in the print... (When I wrote that I was translating to densities and mentally added a step .15 instead of a stop .30 to gray .74 - it's only a half stop lift in tone value).

It might be better to say from my example that the middle scale of grays in the exposure target are ALL Zone V and ANY one of those could be shown in the print as a match to an 18% gray card.

But it is important for the beginner to know that Zone V is supposed to lift up about a half Zone in a full scale Normal scene. We had a new Zone System user recently think he got his film speed wrong because of not knowing that.

Bill Burk · Apr 14, 2016

@Fraunhofer,

Is this relevant to you? When comparing your print to gray card, I am showing that Zone V should be a little lifted in value from the gray card in a straight print because you are leaving room for deeper shadows, so the middle grays have to fall somewhat higher. So don't try too hard to hit Zone V to match gray card... allow it to come up in value just a bit.

markbarendt · Apr 14, 2016

Bill, you make a great point that the zone system provides a vocabulary, I think that's it's biggest strength, what I think what Doremus and Ralph are getting at though is that specific standards/numbers are a bit of a distraction from visualizing.

For example it's not always about a straight print, if one factors in some burn and dodge the general relationships from scene to paper evaporate.

Stephen Benskin · Apr 14, 2016

Bill is working with tone reproduction based on the metered exposure. It helps to understand the standard approach before playing with the variables.

One thing he is showing is how an 18% gray card can be metered with a meter calibrated to 12% and still produce a print with around 18% gray. Maybe this is one of the reasons people believe in 18% gray even though the meter is calibrated 1/2 stop lower.

DREW WILEY · Apr 14, 2016

Here we go again. I wish Damien Hirst would just design a gray card. That way we would have a bunch of real expensive polka dots to choose from.

Fraunhofer · Apr 14, 2016

Bill Burk said:
@Fraunhofer,

Is this relevant to you? When comparing your print to gray card, I am showing that Zone V should be a little lifted in value from the gray card in a straight print because you are leaving room for deeper shadows, so the middle grays have to fall somewhat higher. So don't try too hard to hit Zone V to match gray card... allow it to come up in value just a bit.

Not sure, 12% vs 18% is just 1/2 a stop and my problem was at least one full stop, and I believe related to the fact that I initially only used zone 0 to determine the print time.

On the main issue, here: I thought the difference between 12% and 18% comes from diffuse reflection from a flat vs spherical surface. Usually diffuse reflection is understood as reflected intensity depends on the cosine of the angle relative to the normal vector on the surface. Thus, the shape of the surface matters a lot for the total amount of reflected light, even if they are the very same color/ gray.

Bill Burk · Apr 15, 2016

DREW WILEY said:
Here we go again. I wish Damien Hirst would just design a gray card. That way we would have a bunch of real expensive polka dots to choose from.

Maybe a gray skull.

Bill Burk · Apr 15, 2016

Fraunhofer said:
Not sure, 12% vs 18% is just 1/2 a stop and my problem was at least one full stop, and I believe related to the fact that I initially only used zone 0 to determine the print time.

On the main issue, here: I thought the difference between 12% and 18% comes from diffuse reflection from a flat vs spherical surface. Usually diffuse reflection is understood as reflected intensity depends on the cosine of the angle relative to the normal vector on the surface. Thus, the shape of the surface matters a lot for the total amount of reflected light, even if they are the very same color/ gray.

I'm confident you're on the way to solving your speed issue.

You might be right about the angle of the card changing the reflected light. I found variations in density readings while I read my negatives, from side to side and top to bottom on the same frame. This might be because of the angle the card is turned. I'd recommend shooting the gray card flat with the camera aimed perpendicular to the card.

wiltw · Apr 15, 2016

Bill Burk said:
I'm confident you're on the way to solving your speed issue.

You might be right about the angle of the card changing the reflected light. I found variations in density readings while I read my negatives, from side to side and top to bottom on the same frame. This might be because of the angle the card is turned. I'd recommend shooting the gray card flat with the camera aimed perpendicular to the card.

See this... (there was a url link here which no longer exists)

Bill Burk · Apr 15, 2016

@wiltw you make an important point relevant to this discussion.

The obvious effect demonstrated by your experiment is that the 18% gray card value changes significantly at different angles the card is held.

If you meter and shoot the same card I think the angle the card is held should cancel out (In terms of exposure and the meter calibration 12% versus 18% discussions).

But it does not cancel out for any one picture with the rest of the picture (In terms of tone relation within the shot). In my picture with the dog the card is held 1/3 horizontally and vertically towards the sun.

I suppose if I held the card perpendicular to the camera 18% would have printed closer to 18%. The relation of tones between white and black would still be compressed on the card. But white on the card would also come down and would probably no longer be my key.

Diapositivo · Apr 15, 2016

wiltw shows that the brightness of a flat surface is very dependent on the angle with which it is illuminated.
In his multiple shots, he keeps the exposure equal, keeps the light source steady, and varies the angle of the grey card relative to the light source. That clearly shows how important is the relation between subject, subject shape, and light source.

But it any case, if he had made the same test changing exposure at each shot, and following the "spot" measurement on the flat grey card for each shot, he would have had the same tone for the grey card (IMHO always correctly rendered as 18% grey because I do believe that's how reflected light meters are calibrated) in each shot, with different exposure values i.e. different general appearance of the rest of the image.

[It should also be noticed that if the angle between light source and subject is kept equal, the reflectivity and the exposure does not vary (if not minimally) by varying the subject - camera angle. If he had kept the grey card fixed and made half a circle in front of it, he would have obtained the same exposure, insofar as the grey card approximates a Lambertian surface, i.e. a surface which reflects light in all directions in the same way].

Light meters are not calibrated to 18% grey "cards" (or a shade of grey "cards"). They are illuminated to a certain degree of reflectance of the subject (let's say 18%). An 18% grey cat ("Kodacat"), an 18% grey pullover over a person, an 18% skin.
By focusing on the use of a grey card (and the mistakes and complications induced by its flat shape) it's easy to lose sight of the fact that a grey card has an "anomalous" shape which leads us to logical mistakes in its use when we are confronted with a three-dimensional subject. We should think light meters as being calibrated on 18% grey pullovers or 18% grey skin, 18% cats, 18% grey stuff IMHO.

Or we should use grey cubes, grey spheres, so that we can see, at every moment, the different brightness of the various faces of the cube and infer the different brightness on the different "faces" of the subject. The spot light meter gives us the middle-grey placement of the face that we meter.

Bill Burk · Apr 15, 2016

It's true, I ran this test looking for the effective exposure meter calibration point. And I did wind up with a lot of data I could share, but when I have confirmation I'll open another thread to talk about the calibration information I found.

But in this thread I think my picture shows something obvious. Something easy to understand. Something that is so uncontroversial that it was worth getting out right away. Something we can discuss easily.

I'm not showing the small change of exposure due to meter calibration.

I'm showing overall distortion of tones that you get when you try to fit a normal (or longer) scale subject onto print paper. This is that illusion of reality that you get with black and white photography. The tones are distorted but they look real.

Exposure-wise... The spot and incident readings really were different from each other, but in this shot I used the gray card reading as-is. The result is a 1/6 stop underexposed negative (according to my interpretation of the standards), though I would have preferred this negative to have had a whole stop more exposure.

But in this illustration my underexposure was compensated by the negative-positive print making process.

My 12% would have lifted to 18% in the print even if I had exposed a stop more, because I was intent on making the white strip look good and the dog look good on the same print.

RalphLambrecht · Apr 15, 2016

Bill Burk said:
When making a black and white print of a normal scene from a normal negative, 12% in the subject might look right on a print when it is printed lighter than real life.

I am saying you may expect 12% to match the standard 18% gray card.

It's easy to understand why.

Your print can only go from white to black.

In a normal outdoor scene with mixed lighting conditions, some things are in the main light and some things are in the shade.

The things in the main light might range from white to black.

If you take something that was black in the main light, and print it black on the print, then you haven't left any room for things in the shade to look darker.

When you leave room for things in the shade to look darker, then the black thing in the main light won't be black any longer it will be a dark medium gray. This lifts up the dark medium grays accordingly and something that started out as 12% in the original scene winds up lighter on the print.

I have found that 12% from the subject arrives at approximately 18% on the print.

I am not trying to be precise. The target I used includes a 12.7% sample because it fits the Sekonic Exposure Profile Target series of grays. Whether we are talking 12%, 12.5%, 12.7% isn't my point.

If I were to relate this in Zone System terms, I am saying you should expect Zone IV in the subject to approximately match an 18% gray card when you compare the card to the print.

There's room for interpretation of course, but one thing is certain: 18% doesn't print as 18% unless you increase the contrast significantly. You would do that if you were shooting copy work. But most of the time you are not doing copy work.

Here is an example of what I am talking about. Exposure target next to a print that includes a photograph of the exposure target. You can see the 12.7% chip on the photograph (the darkest of the middle row of 7 grays) matches pretty closely to the 18% (the boundary area and the middle of the middle row of 7 grays) of the gray card setup next to the print.
Interesting design of the test card.You may be on to something here
View attachment 154549

Old-N-Feeble · Apr 15, 2016

Uh-oh... more 12 percent, 18 percent, gray card mayhem.

Everybody run for your lives!!!!!

Stephen Benskin · Apr 15, 2016

Old-N-Feeble said:
Uh-oh... more 12 percent, 18 percent, gray card mayhem.

Everybody run for your lives!!!!!

Except Bill took the time to run some field tests. Personally, I think this would be a good opportunity to have a discussing about testing methods and their effectiveness. Just because someone ran and test and got a result doesn't prove anything. What are the variables that can influence the results? For me the picture of the target with the dog seems to have more contrast than normal. How would this effect the results?

cliveh · Apr 15, 2016

What on earth are you all talking about? Just look at the final image.

Stephen Benskin · Apr 15, 2016

cliveh said:
What on earth are you all talking about? Just look at the final image.

Experimental error and the like. We don't really know about went into the test. Just to start with the basics. What was the film, how was it developed? What was the exposure placement on the film. What is the paper, grade, and LER?

Old-N-Feeble · Apr 15, 2016

cliveh said:
What on earth are you all talking about? Just look at the final image.

I was referring to recent threads on very similar subjects in which bright ideas were quickly tossed to the dark side. There was so much discourse that enlightening facts and logic were buried deeply in the murky abyss of anger and egocentrics.

Bill Burk · Apr 15, 2016

Sorry, I'll be out this weekend camping. Sure there is experimental error and there are things that look like they might be real trends. There are a few things I would do differently when I repeat the test. I relied a lot on the OM-4 spot open aperture metering linkage being accurate over the full range including partial f/stops for a few shots. Other shots I am more confident in because I used electromechanical shutter speed settings and full click stops. I added an 0.1 ND filter when handheld meter indicated a third stop such as 11.3 was required. I'd also like to hit 0.62 with development because I only got 0.5. This is TMAX 100 in D-76 1:1 but the developer was old.

RobC · Apr 16, 2016

Why consider what any percentage is? Just view subject, engage brain, choose a target print tone, then meter and expose to put it on that tone. Colour reproduction really doesn't come into it except in very rare cases where you want actual colour or tone reproduction to be literal. The vast majority of the time you don't want that. Or at least I don't but I suppose if you are working on some mis-guided belief that is what you should be doing then you are doomed to dis-appointment or least, unexpressive prints.

paul ron · Apr 17, 2016

Bill Burk said:
When making a black and white print of a normal scene from a normal negative, 12% in the subject might look right on a print when it is printed lighter than real life.

I am saying you may expect 12% to match the standard 18% gray card.

It's easy to understand why.

Your print can only go from white to black.

In a normal outdoor scene with mixed lighting conditions, some things are in the main light and some things are in the shade.

The things in the main light might range from white to black.

If you take something that was black in the main light, and print it black on the print, then you haven't left any room for things in the shade to look darker.

When you leave room for things in the shade to look darker, then the black thing in the main light won't be black any longer it will be a dark medium gray. This lifts up the dark medium grays accordingly and something that started out as 12% in the original scene winds up lighter on the print.

I have found that 12% from the subject arrives at approximately 18% on the print.

I am not trying to be precise. The target I used includes a 12.7% sample because it fits the Sekonic Exposure Profile Target series of grays. Whether we are talking 12%, 12.5%, 12.7% isn't my point.

If I were to relate this in Zone System terms, I am saying you should expect Zone IV in the subject to approximately match an 18% gray card when you compare the card to the print.

There's room for interpretation of course, but one thing is certain: 18% doesn't print as 18% unless you increase the contrast significantly. You would do that if you were shooting copy work. But most of the time you are not doing copy work.

Here is an example of what I am talking about. Exposure target next to a print that includes a photograph of the exposure target. You can see the 12.7% chip on the photograph (the darkest of the middle row of 7 grays) matches pretty closely to the 18% (the boundary area and the middle of the middle row of 7 grays) of the gray card setup next to the print.

View attachment 154549

thanks for the info

RobC · Apr 17, 2016

Bill Burk said:
though I would have preferred this negative to have had a whole stop more exposure.

But I told you in earlier topic that middle of film curve for ISO standard is 8% reflection. So 18% card is a stop and a tad too light. As usual topic got diverted into nonsense about flare and other pointless stuff.

You develop to ISO standard as far as I know. That is tailored to 7 1/3 stop SBR. Midlle of that is 3 2/3 stops.

so units of reflected light for each zone starting at zone 0 of 1/2 a unit...

0=1/2
1=1
2=2
3=4
3.66=7
4=8
5=16
6=32
7=64
7.33=85
8=128

7/(85/100) = 8 (rounded)

So midpoint of 7 1/3 stop range is 8% reflectance AND NOT 18%.

18% reflectance is a stop and a tad brighter than 8% so would underexpose by a stop. This of course assumes that printing your neg would print the midpoint at same reflectance as middle which is actually 8% reflectance and not 18%.

See following for what MIDDLE actually means: (there was a url link here which no longer exists)

The whole point of zone system is about placing any subject tone on a tone of your choosing in the print. It isn't about reproducing reflectance values in the subject to be the same in the print, not as far as I'm concerned. i.e. its about making creative choices at the taking stage and not painting by numbers.

12% subject looks right printed to match 18% gray card

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