questions about gray scales

mitch brown · Dec 12, 2006

i was just trying to print a gray scale for reference and have been unable to following the method i was told which has led me to wonder. if your film speed is correct and development times are correct should you be able to print a zone 1 thru 10 gray scale using your min time for max black?
thanks
mitchel

Donald Miller · Dec 12, 2006

It would seem that you should be able to do so...unfortunately this takes no account for the characteristic curves of either the film or the paper. These characteristic curves are not linear.

dancqu · Dec 12, 2006

wager123 said:
...able to print a zone 1 thru 10 gray
scale using your min time for max
black? mitchel

I think not. Each zone represents one full
stop. Film will go 10 or more stops but
paper, maybe five. Dan

cowanw · Dec 12, 2006

dancqu said:
I think not. Each zone represents one full
stop. Film will go 10 or more stops but
paper, maybe five. Dan

But the paper will still go from blank white to total black with as many steps in between as you choose. Any text on the subject of zones will show a picture representing the classic zones. The doubling or halving of exposure of light is a construct of the measuring device be it a light meter, film,paper or a photoelectric cell. Each has a level of total exposure and no exposure. The number of steps is arbitrary.
Bill

dancqu · Dec 12, 2006

cowanw said:
The number of steps is arbitrary.
Bill

I think you have step tablet images in mind.
Partial stops. Dan

Photo Engineer · Dec 12, 2006

A typical step wedge in the classic sense has 21 steps, each separated by 0.15 Log E or 1/2 stop. The zone system adopted a step wedge of 0.3 log E or 1 stop steps for convenience.

The curve is an "S" shaped curve and the slope of the curve is the contrast. This is true for paper or film.

The grade 2 papers have a contrast of about 2.5 and the film has a contrast of about 0.6. To get print contrast multiply film contrast * paper contrast and you get about 1.5 for a grade 2 paper, not including toe and shoulder.

PE

Nicholas Lindan · Dec 12, 2006

wager123 said:
i was just trying to print a gray scale for reference

There are several gray scales, which are you trying to make:

o A print with equal reflection OD steps
o A print with equal Zone System steps*
o A set of prints from negative frames exposed at 1-stop (or other)
equal intervals

* Densities at 0.05, 0.12, 0.47, 0.70, 1.00, 1.32, 1.60, 1.90, 2.10
reflection OD

cowanw · Dec 12, 2006

dancqu said:
I think you have step tablet images in mind.
Partial stops. Dan

Thank you so much for being the first responder to a post of mine. This was just my 7th post and I was feeling like a thread ender.
Yes, this would be a step tablet; I think that is what I was trying to say. In printing one can only print a step tablet. Exposure 'zones' only exist in the mind's eye, since they cannot be printed in their entirety, but must be represented or interpreted (or compressed or expanded) with the chosen medium.
Bill

Photo Engineer · Dec 12, 2006

We called them wedges or tablets. It was interchangable.

PE

mitch brown · Dec 13, 2006

i was trying to get a set of prints from neg frames exposed at 1 stop equal intervals using min time for max black.
mitch

noseoil · Dec 13, 2006

My "Stouffer" printed step table is a simple spread of zones 1 - 9 (or mostly black to paper white, more or less). This is not a scientifically printed test strip, but does give enough information to see what's happening on a print. I use mine for print evaluation, also for film tests, to check an exposure and development for film density and contrast. While it may be a good idea to be able to print one, the $12 I spent a few years ago has been a good investment for purposes of evaluation. tim

Photo Engineer · Dec 13, 2006

wager123 said:
i was trying to get a set of prints from neg frames exposed at 1 stop equal intervals using min time for max black.
mitch

If you get one good print from a negative at say f11/12", then a negative exposed 1 stop over will print just about identical at f8/12" and a negative exposed 1 stop under will print just about identical at f16/12".

This (just about identical) I use is due to the fact that the shape of the curve changes in the negative as you go up and down the scale, compressing data in the highlights or the shadows, and changing details there.

I used changes in the enlarger lens opening above, because changes in time may involve reciprocity failure in the print material which will change speed or change contrast.

The best way to do this experiment on-easel is by means of f stop variations, not time. I have done this in color and posted the results here and on Photo Net.

PE

Nicholas Lindan · Dec 13, 2006

wager123 said:
i was trying to get a set of prints from neg frames exposed at 1 stop equal intervals using min time for max black.
mitch

You should not have much trouble. I am assuming you have taken a series of a dozen pictures of a grey test card with the middle of the series being exposed at what your meter reads and subsequent exposures made at one stop intervals with higher and lower exposures.

Method 1:

This gives you a grey scale that starts off at black and is useful if you use a spot meter and 'meter for the shadows and develop for the highlights'. For normal film and paper the frame exposed at 5 stops below the meter reading should be only a very little bit darker than clear film.

o Using a clear bit of film [such as the leader or between frames] make a test strip at 0.2 stop intervals, or at, say, 8, 10, 12, 14, 16, 18, 20 seconds if you don't have an F-Stop timer. Adjust times and or f-stop so there are at least 3 very black strips when examining the print in the fixer.

o Finish and dry the print and find the time that gives a black strip such that it can't be told from the next blackest strip when looked at under bright light.

o Make prints from the remaining negatives at the same time and f-stop.

That should be it. Find what makes blank film print black and use that for all the zone-test negatives you have.

Method 2:

This gives you a grey scale centered at 18% grey, use this if you meter with the camera's meter or use an incident or hand-held light meter.

o Take the negative exposed at the meter reading and make a test strip as above.

o Fix and dry the print and find the strip that matches the 18% grey test card.

o Make prints from the other negatives at the same enlarger time and f-stop.

The two methods produce grey scales that are pretty much the same. The reason for the two methods is to be able to compare the results from different films, developing times, EI's and paper contrast grades. When comparing grey scales you need one point where they all have the same tone: some like black, some like grey.

Nicholas Lindan · Dec 13, 2006

I should add that matching to an 18% grey card is a lot more accurate than finding max black. The problem with matching at 18% is that you may not have a max black or max white in your set of prints.

If you match at the nominal exposure/18% grey card picture/18% print tone and:

o You reach max black before the test negative density is just about clear - which should be ~5 stops under the meter reading - then you are: overexposing; overdeveloping; or using paper that is too contrasty for the negative.

o You never reach max black then you are: underexposing; underdeveloping; or using paper that is not contrasty enough.

o You reach max white too early - less than 4 stops from the meter reading for normal film/paper/development - then you are; overexposing; overdeveloping; or using paper that is too contrasty.

o You never reach pure white then: you are underexposing; underdeveloping; using paper that is not contrasty enough.

mitch brown · Dec 13, 2006

that what i did and they don't come out right . the scale is way to light for the zones. why is this happened? i have done a film speed and a developer test.
mitch

Chuck_P · Dec 13, 2006

I use the minimum exposure for max black (MEMB) through the FB+F because that is how I evaluate my proof sheets and it really gives your eyeball a good training. Therefore, that is how I arrive at my personal EI and "normal" development time for my process. I have the MEMB for a standard 5x7 print and 8x10 print for the quick and dirty straight print as it tells you loads about the acutal densities on your negative-----I don't see the need to expose the paper beyond the time it is needed to reach Zone 0 when evaluating a straight print.

I have found that the key to using the max black method is to make dam sure that you get that max black time right---otherwise, you will not be able to make the needed inferences about your development times when evaluating the upper end of the printed scale. Either way that you choose to standardize is okay,it seems, but remain consistent, as that is the key to evaluating your process when you choose to change a variable. I have produced a very nice gray scale using the MEMB.

I knew that I had done something right, when the MEMB from a Zone V negative produced a Zone V print value that correctly matched the gray card. And, a Zone I negative produced a Zone I print value that showed "slight tonality but no texture"; and, a Zone VIII negative
that produced a Zone VIII print value that was "very light, with some slight texture.." And all the other negatives of the scale printed with accurate descriptions so that I could safely say that the dynamic and textural ranges of the scale were adequately produced.

It is definitely an empiricle way to do it, but one that totally suffices when you don't have access to an expensive densitometer. Be prepared to go through some paper as I found it was well worth it to do so. I would be willing to bet that my negative densities are pretty darn close to the recommended ones for a diffusion enlarger light source.

Just be consistent in which ever method you choose.

Regards
Chuck

Rick Jones · Dec 14, 2006

Printing a gray scale

"My scale is way too light for the zones. Why?" I believe Chuck has you on the right track. Determing an accurate minimum time for max black is the first key to producing a truly representative gray scale. For example, if your time is too short prints from your zone exposures will be lighter than planned. If you developed the film too long prints from your negatives exposed Z5 thru Z9 will be too light. Working out a MTMB can reveal all kinds of problems in your system:timer inconsistencies from print to print, light output inconsistencies from your enlarger, print processing inconsistencies due to changes in processing time and temperatures. The list goes on and on. A small 4X5 print developed after being exposed to room light would make a useful point of comparison when printing negatives exposed to the low zones. Your Z0 print should match that density with the Z1 print showing just slightly less density. So, nail that MTMB , if possible to the nearest second or better, and you should be able to print a gray scale that will reveal any shortcomings in your speed and development tests. My Z1 print show only the very slightest density difference when compared to my print exposed to room light. My Z9 negatives print as paper base white. Others may want PBW to show at Z10.

Nicholas Lindan · Dec 14, 2006

wager123 said:
that what i did and they don't come out right . the scale is way to light for the zones. why is this happened? i have done a film speed and a developer test.
mitch

So exposing clear film is making a nice black but the subsequent prints are all too light [?].

The film is overexposed, and may also be overdeveloped. Make a new test roll of a grey card, start at 7 stops below the meter reading of the card and go to 7 stops over the meter reading this time. The first few negatives should be completely blank.

If there are more than 10 negatives between almost-but-not-quite completely blank negative [black print] and the first pure white print then the film is overdeveloped.

The above applies for normal EI, normal development and normal #2 paper.

Saganich · Dec 14, 2006

I've found that what I thought was max black wasn't close and am supprised over and over when I measure the density (film and paper) and realize how much blacker I can go. Often as a final step in printing I measure my blacks and highlights only to find I'm not where I want to be. In other words I can't trust my eyes during printing. In all cases only after a print is on a wall do I realize the blacks weren't black enough or the highlights weren't crisp enough. I've found that it becomes the difference between a good print and a great one. Like the other folks I use a Stouffer 10 step wedge (transmission and reflection) along with an old Mcbeth densitometer to measure (especially on prints) those blacks and highlights.

Chris

Allen Friday · Dec 14, 2006

Chris,

One trick to make sure that you are getting maximum black while printing is to have some samples of maximum black handy for comparison. Just fully expose a few sheets of paper to the light and fully develop and fix. When you get ready to print, cut a small square from the paper and put it in water, so you don't have any "wet up" issues. When you view the wet print, put the known maximum black sample next to the print for comparison. I also do this with plain white samples to compare the highlights, from an unexposed but fully fixed sheet of paper.

Nicholas Lindan · Dec 14, 2006

Saganich said:
I've found that what I thought was max black wasn't close and am supprised over and over when I measure the density (film and paper) and realize how much blacker I can go. Chris

Max black is not a very good standard tone because it is:

1) Hard to judge by eye - there simply isn't enough light...

2) Hard to measure with a densitomer - there isn't much signal and the effects of stray light and dust on prints can really knock readings for a loop

3) Radically effected on prints by the surface finish, lighting conditions (specular, diffuse), dry/wet state of the paper, toning, drying techniques

4) Max black is -past- the shoulder on the HD curve where tiny changes in density can result in large changes in exposure if max black is used to determine 'max black at min time' exposure time.

Talking about blacks above 2.0OD is a discussion of surface finish, ferrotyping expertise, toning and densitometer optics.

The max black concept has some value when it comes to making contact sheets - but that is only because it is easy to do and it is 'good enough' for a cursory examination of an image.

A fine print should never [almost never] get to max black. When the shoulder of the curve is approached the shadow detail in the print is lost. For low contrast grades the maximum density on a print shouldn't be above 2.0, for high contrast grades one shouldn't go above 1.9. If a deeper black is desired then it should be acheived by toning.

The same applies to highlights, getting below ~0.12 results in drastic loss of highlight detail. It is best to expose so specular highlights are at 0.15 and then use bleach to lower them to dead white.

Middle grey, Zone V, 18% grey is the tone to use for matching prints by eye and setting exposure. Detailed highlites at ZVII 0.27OD and detailed shadows at ZIII 1.32 OD are the densities to use for determining paper contrast (and setting exposure if a good enlarging meter is available).

As usual, exceptions abound.

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