Negative testing - exposure

[kal800]

Hi,

Have a concern regarding testing procedure. To determine N+/-x development time I need to have Stouffer tablet somehow projected on my film, then developed in different time related to box time, checked with the transmission densitometer, its readout entered into the spreadsheet and analyzed. I’ve read some materials and there are couple of methods to shoot the tablet, including:

• Putting the tablet atop the light box and make a photo of it with the camera, exposure set by a spot meter on the middle grey step on the tablet. What concerns me, that those LEDs within the box may not have full spectrum covered which negative can be sensitive to, making testing inaccurate.
• Using an enlarger as the light source, putting a negative with the Stouffer tablet in the contact printer. Of course diffused incandescent source has to be filtered to have 5500K daylight, also vigneting has to be taken into consideration, but still I don’t have a clue how long should I expose.
• Putting the same sandwich as in the previous method into the film holder and shoot the white paper in the daylight. Exposure set with spot meter on the paper and moved into zone X.

I’ve got all the gear for all above methods - spot meter, densitometer, enlarger, 4x5 step tablet, LF camera and lightbox.

Please advise which of the procedures will give me most accurate and consistent results? Maybe there are some more of them?

 

[Chuck_P]

For personal film speed testing and N +/- developing times, expose the step tablet onto your 4x5 film; I use the method as described in John P. Schaefer's book "The Ansel Adams Guide - Basic Techniques of Photography Book 2". This is along the lines of your 3rd bullet point in your post.

For paper Range Number testing, use your enlarger to project the step tablet onto your preferred paper; I use the method as described in Steve Anchell's book "The Variable Contrast Printing Manual". I only do the Range Number (RN) testing to determine the contrast grade the paper is yielding relative to the particular filtration that I am giving it. With some papers, changing the filter from, say, #1 to #2 may not provide any change at all in the paper's RN, or there is so little of a change as to be not effective. It helps in not wasting a sheet of paper on an expected change of contrast from a #1 filter to a #2 filter. Instead, you would know that you need to skip to a #3 filter to affect a contrast change. This is along the lines of your 2nd bullet point in your post. You can also do paper speed testing relative to the given filtration being used.

This is a topic that uses a million words to describe things that are pretty simple to do, actually.............so, stand by.

 

[RalphLambrecht]

For personal film speed testing and N +/- developing times, expose the step tablet onto your 4x5 film; I use the method as described in John P. Schaefer's book "The Ansel Adams Guide - Basic Techniques of Photography Book 2". This is along the lines of your 3rd bullet point in your post.

For paper Range Number testing, use your enlarger to project the step tablet onto your preferred paper; I use the method as described in Steve Anchell's book "The Variable Contrast Printing Manual". I only do the Range Number (RN) testing to determine the contrast grade the paper is yielding relative to the particular filtration that I am giving it. With some papers, changing the filter from, say, #1 to #2 may not provide any change at all in the paper's RN, or there is so little of a change as to be not effective. It helps in not wasting a sheet of paper on an expected change of contrast from a #1 filter to a #2 filter. Instead, you would know that you need to skip to a #3 filter to affect a contrast change. This is along the lines of your 2nd bullet point in your post. You can also do paper speed testing relative to the given filtration being used.

This is a topic that uses a million words to describe things that are pretty simple to do, actually.............so, stand by.

Unless you have your enlarging lens in a shutter, photographing, a Stouffer tablet is probably the best idea. Don't worry about the color temperature too much; you're not always photographing in calibrated by daylight either.

 

[Stephen Benskin]

Hi,

Have a concern regarding testing procedure. To determine N+/-x development time I need to have Stouffer tablet somehow projected on my film, then developed in different time related to box time, checked with the transmission densitometer, its readout entered into the spreadsheet and analyzed. I’ve read some materials and there are couple of methods to shoot the tablet, including:

• Putting the tablet atop the light box and make a photo of it with the camera, exposure set by a spot meter on the middle grey step on the tablet. What concerns me, that those LEDs within the box may not have full spectrum covered which negative can be sensitive to, making testing inaccurate.
• Using an enlarger as the light source, putting a negative with the Stouffer tablet in the contact printer. Of course diffused incandescent source has to be filtered to have 5500K daylight, also vigneting has to be taken into consideration, but still I don’t have a clue how long should I expose.
• Putting the same sandwich as in the previous method into the film holder and shoot the white paper in the daylight. Exposure set with spot meter on the paper and moved into zone X.

I’ve got all the gear for all above methods - spot meter, densitometer, enlarger, 4x5 step tablet, LF camera and lightbox.

Please advise which of the procedures will give me most accurate and consistent results? Maybe there are some more of them?

You're asking good questions and doing some critical thinking concerning the various popular testing methodologies. This is more than most people do. Don't ever stop. First off, contacting is the only way to eliminate flare from testing. Flare can be factored in later for determining shooting conditions, but it's impossible to control and will introduce a factor into the test that will skew the results. Any method that uses an optical system between the step tablet and film will introduce flare. Even if the step tablet is carefully masked, the less dense sections will create veiling flare affecting the shadows.

The color temperature of the light source does have an influence on testing results. The 1960 speed standard had to make a small change in the speed equation to compensate for a change in the color temperature of sensitometers from sunlight to daylight. The additional blue added 1/3 stop to the film speed. That's why the constant is 0.80 instead of 1.0. For the DIY testers, an additional factor to consider is the exposure meters. They are calibrated to a specific color temperature. Based on the type of photo cell used and it's spectral bias, the accuracy of the meter will vary based on how far from the calibrated color temperature the color temperature of the light source falls. While these facts are important to maintain a realistic perception of the level of precision possible, there are so many other variables and potential experimental errors influencing the results to worry too much about the color temperature as long as the color temperature is similar to that experienced in normal shooting conditions.

What is perhaps most important is something you didn't mention and that is the accuracy of the method used to determine film speed and development. Most common methodologies make certain assumptions that may or may not be correct or that may work under some circumstances but not others. Many of the techniques assume the speed point is four stops down from the metered exposure point. This does not conform to the ISO standard. What you have is two different testing parameters that will produce different results. While neither may have a negative affect on quality, it does bring into question the accuracy of any one method. The ISO speed point is effectively 3 1/3 stops below the metered exposure point (as a point that many assume differently). This creates an obvious discrepancy of 2/3 stop between the Zone System four stop approach and the ISO method. Along with all the other variables and experimental errors that can influence the speed test, it's better to not test for speed and to assume the ISO speed when using a general developer and either make an adjustment for the Zone System speed or test your personal metering approach in the field and make adjustments then. Ask yourself what does exposing a white piece of paper at Zone X actual produce in the way of exposure. Any method will produce a result but is it the correct one?

This brings us to your goal of determining +/- development. First you need to determine what is the standard or Normal development. Kodak uses CI of 0.56 or 0.58 depending on the group who's writing the data sheets. Contrast Index is a method to determine the film's average gradient or Rise / Run. Run is based off of the subject Luminance range and for Normal that would be the statistically average Luminance range of log 2.20 or 7 1/3 stops. Rise is the LER of the printing paper. Generally this grade 2 using a diffusion enlarger for about a LER of 1.05. Problem is 1.05 / 2.20 is equal to 0.48 and not 0.58.

While the run is based off of the subject Luminance range, it doesn't use the subject Luminance range but the Camera Illuminance range or what the subject Luminance range would be a the film plane and that includes a degree of camera flare. 1.05 / (2.20 - 0.40) = 0.58. Most common testing methods don't consider flare and with apologetically create reasons to rationalize the discrepancy. Generally, they tend to used different values for the negative density range or scene Luminance range or a combination of both.

Next is defining what the pluses or minuses are. Once again, there are so many variables (including personal taste) that any answer will produce acceptable results or results good enough to work with in most cases. It's when the conditions become more extreme that the irregularities begin to have unwanted results. In general, a +1 means compensating for a Luminance range that is one stop or log 0.30 shorter than what is considered normal. And a -1 is the opposite. However, average flare changes with changes in luminance ranges. Here are the results from a few developmental models based on different variables. As you can see, depending on the model the results begin to vary as the Luminance range changes. A +2 Fixed Flare has the same CI as a +3 Variable Flare. The different methods are explained in a paper I wrote. What is Normal?

Since you don't need to test for film speed and you want to contact the step table, using an enlarger is probably the best option of the three methods you've outlined. Using a sensitometer is the best. Contacting in a film holder needs to have a reliable way to ensure good contact. Also lenses have light fall off the further out from the center of the lens. Unless you have a lens with an image circle significantly bigger than the film holder, there's a chance the light is falling off at the exact point where you need the most precision.

Stephen

 

[ic-racer]

One can obtain excellent results using multigrade paper with large format negative that are processed together under the same standard conditions.

 

[Doremus Scudder]

kal800,

I'm going to dumb this discussion down a bit (with apologies to Stephen Benskin ).

Reading Stephen's post points out the many variables in testing that are present and that can lead to differing results. Going Stephen's way requires quite a bit of control of these variables and quite a lot of effort and time spent doing the tests. This is all great if you're looking for quantifiable and scientifically precise results. However, going down that rabbit hole is often not needed to get the results you're after, especially if you are planning on making photographs in the field and not under carefully-controlled lighting conditions.

Additionally, there are a lot of contrast controls at the printing (or post-processing) stage that enable you to make an excellent print from a not-quite-zeroed-in negative.

I'm assuming here, due to your reference to N+ and N- developments, that you're planning on using the Zone System. If that's the case, here are my suggestions:

First, forget the step wedge for dealing with your negatives and opt for a more down-and-dirty approach to determining both your personal E.I. and development schemes. The whole reason for the Zone System was to simplify and make more practical and accessible the science of sensitometry and tone reproduction. Simple and less precise is adequate here.

If you haven't already tested for a personal E.I., simply rate your film 2/3 slower than box speed and go out and make a few identical negatives of an average subject. Find one with a textured shadow that you want in Zone III, a few darker areas that will be textureless, some highlights that you want rendered in Zone VIII and a bright reflection or light source that will render higher than that. Meter the mid tones to and keep careful notes.

Now, develop one of these negatives for your normal time (N) and set about printing it. In the darkroom, use your favorite paper and a middle contrast setting (personally, I like the 2 1/2 setting). Print your negative (I'd enlarge, not contact print) so that the clear rebate of the film is just an almost indistinguishably lighter black than maximum paper black. Develop the print, dry it down and evaluate. If all the Zones are where you wanted them, you've got an E.I. and a good N development time.

If the shadow detail is not what you wanted, e.g., too dark and featureless, then you'll have to rate your film slower and repeat the run. That will more than likely not be the case. But, even if it is, go on to the next step anyway.

If your highlights are not where you wanted them, you'll need to adjust development time. Highlights too dark and dingy? Increase development time. To overexposed and featureless? Reduce development time. Try a 20% increase or reduction and develop your next negative. Print it the same way and make a print. Repeat the process for the third negative if needed, but making a smaller increment of change in your development.

For N+1 development, you do the same thing, except you're now planning for a metered Zone VII to print like a "normal" Zone VIII. Make a few negs and prints and zero in on your N+ development time.

For N-1 development, your target will be to get a metered Zone IX to print like a "normal" Zone VIII.

Use the same method for more extended contractions. Personally, I don't like to develop more than N+1 on the expansion side, using instead the available contrast controls of different paper contrasts, etc. to achieve more contrast if needed. For example, I'll develop N+1 and then use higher contrast settings on my enlarger (or even a #47 blue filter). If I need more contrast than that, I'll switch print developers, use a bit of judicious bleaching or, if really needed, bleach and redevelop the negative (I've done that once in 40+ years).

Keep careful notes in the field and refine your regime as needed. You may find you need to alter your E.I. for contractions, or meter differently in conditions that give lots of flare, etc. Don't hesitate to do this. Still, after all the years of photographing that I've done, I end up rating every film I use 1/3 - 2/3 stop slower than ISO speed (and that only because I use Zone-System metering techniques and place shadows).

Yes, what I'm proposing is not as precise. Nor does it eliminate the flare in the optical systems; on the contrary, it includes it so you don't have to compensate for it later. Yes, it's not as precise, but the window for exposure and development of a negative that you can still produce an excellent print from is larger than many think, especially if you tend to err on the side of overexposure where there's a lot of leeway.

Hope this helps,

Doremus

 

[Stephen Benskin]

Nor does it eliminate the flare in the optical systems; on the contrary, it includes it so you don't have to compensate for it later

It actually doesn't Doremus. But I hope you will explain your reasoning.

 

[Chuck_P]

Taking the ZS approach, the speed point is the ISO rating that yields a 0.1 net negative density (after subtracting film-base + fog density) at Zone I. Flare adds density, right? So why wouldn't any flare that is inherent be accounted for in testing, as long as the speed point of 0.1 net negative density is obtained at Zone I? I'm just asking I'm not being definitive.

 

[gone]

Please advise which of the procedures will give me most accurate and consistent results

Simple. Ditch all that complicated and expensive stuff, it is really crazy to do all that. Bracket your shots on a roll or two and you will know where you like things. Try a few different developers too. In the darkroom, make test strips and/or test prints. Problem(s) solved.

 

[Stephen Benskin]

Taking the ZS approach, the speed point is the ISO rating that yields a 0.1 net negative density (after subtracting film-base + fog density) at Zone I. Flare adds density, right? So why wouldn't any flare that is inherent be accounted for in testing, as long as the speed point of 0.1 net negative density is obtained at Zone I? I'm just asking I'm not being definitive.

You shouldn't make the assumption shooting conditions and testing conditions are the same and that they will yield the same results.

How does flare work?
What are the ZS testing conditions?
What influence would flare have under the ZS testing conditions?

 

[Chuck_P]

You shouldn't make the mistake assuming shooting conditions and testing conditions will yield the same results.

I'm not making that mistake at all....I was hoping you would provide a quick answer to my question. If flare is not accounted for in testing like you say, okay, you're the resident expert and I recognize your standing on the subject, I can't really argue against it. You seem to make alot of it. I can opine that it's influence, then, has seemed, at least from my own experience, not to be much of an influence at all in what I've been able to do......I can equally opine that my "testing" as described by Schaefer in his Book 2, sure had improved the quality of my negatives ten fold. I have no problem encouraging the OP to engage in that method and not get too wrapped up in all these weeds.

 

[albada]

Unless you have a lens with an image circle significantly bigger than the film holder, there's a chance the light is falling off at the exact point where you need the most precision.

That's why I raise the head on the enlarger when contacting a step wedge. By doing that, I'm only using a small central portion of the lens' image-circle. Even then, I use an easel meter to check the middle and ends of where the wedge will be, verifying uniform illumination.

Mark

 

[ic-racer]

As mentioned, if doing the test more than once, a sensitometer will help ensure the step wedges are always exposed the same. Even with good notes, I was never sure the enlarger was set at the exact position with the same lens and mixing box, etc, etc when repeating a step wedge exposure months or years later.

 

[Stephen Benskin]

I'm not making that mistake at all....I was hoping you would provide a quick answer to my question. If flare is not accounted for in testing like you say, okay, you're the resident expert and I recognize your standing on the subject, I can't really argue against it. You seem to make alot of it. I can opine that it's influence, then, has seemed, at least from my own experience, not to be much of an influence at all in what I've been able to do......I can equally opine that my "testing" as described by Schaefer in his Book 2, sure had improved the quality of my negatives ten fold. I have no problem encouraging the OP to engage in that method and not get too wrapped up in all these weeds.

Average camera flare is based on a subject with the statistically average Luminance range. The highlights create a veiling exposure that has a proportionately greater affect on the shadow exposure. A flare factor of 2 means the value of flare is equal to the shadow exposure thus doubling it, as well as reducing the effective Illuminance range. Zone System testing uses a single tone target. There isn't a highlight to produce the flare exposure or a shadow to be affected by it. The target is generally middle gray which is only slightly affected by camera flare even when there is normal flare. As the subject Luminance range is only a single value, practically no flare exists in Zone System testing and if any does exist, it has minimal influence on the results.

If you recall, the OP was asking about the affect of color temperature on film testing. I found this interesting because most people just accept a methodology without question. It's unusual for someone to engage in that level of analysis. I though it important to point out other considerations that will have a greater influence on the results. In addition, it's always a good idea to be aware of the variables. I'm sure we all remember not too long ago how Dunning-Krugger created conspiracy theories accusing manufactures of faking film speeds because Zone System film speeds were the true film speeds.

 

[ic-racer]

What lens gave you a flare factor of 2? Was it wide open or what was the aperture? Wouldn't this information be on the graph? How did you measure it?

 

[kal800]

Hi,

Thanks so much for all your input. I have not expected such fantastic feedback.

In general, to make things more clear, what I expect is to put a second leg in the ZS - I've been tough the Zone System at the very beginning, but since I've been roll film field shooter exclusively I was unable to apply second part of the principle - "develop for highlights". As the result I've had limited tonal range on my negatives which I compensated in the darkroom with the grade knob on my enlarger. I believe paper grades should be applied exclusively for creative reasons, not to correct tonal range, which should be on the negative in the first place. Now when I turned into sheet film, I am finally able to do so.

Also, I'd like to have precise matching of my Analyzer Pro grey scale indicator with the actual developed print. Currently it matches the midtones, but on the both ends of the scale it is not as precise and I still need to use test stripes. I believe careful calibration of the device will make test strips obsolete, or almost obsolete.

Now, being an engineer, I prefer the analytical approach to the procedure, measuring the outcome with the dedicated meter, comparing them to the reference values, putting numbers into the spreadsheet, apply the results, then check if they are satisfactory, if needed fine tune.

@stephen - thanks for the information provided and the paper regarding Normal setting, for sure I'm going to read it thoroughly. Have a question regarding wedge exposure. You suggest to use an enlarger, but I still don't know how to set an exposure. In case of white paper shot, it is clear since I have a spot meter. You mentioned that such approach is OK as soon as I have a lens with an image circle significantly bigger than the holder. My lens (Symmar-S 150/5.6) stepped down to f22 has 210 mm image circle allowing 38x32mm displacement of the lens in case of 4x5. Is it big enough?

Kal800

 

[Bill Burk]

@Chuck_P you asked “Does Zone System testing include flare because it was taken through the same camera and lens that you will use in the end?”

Traditional Zone System testing where you photograph an evenly-lit gray card four stops down creates a low flare situation.

Other test schemes have been devised, so if you mean something else, it might have flare. Taping a step wedge to a window and photographing has a lot of flare. Taping the step wedge to the film in the holder doesn’t have flare.

 

[Chuck_P]

@Chuck_P you asked “Does Zone System testing include flare because it was taken through the same camera and lens that you will use in the end?”

Traditional Zone System testing where you photograph an evenly-lit gray card four stops down creates a low flare situation.

Other test schemes have been devised, so if you mean something else, it might have flare. Taping a step wedge to a window and photographing has a lot of flare. Taping the step wedge to the film in the holder doesn’t have flare.

Where did I ask that question you have placed in quotes?

 

[Bill Burk]

Where did I ask that question you have placed in quotes?

Paraphrase of:
“I was hoping you would provide a quick answer to my question. If flare is not accounted for in testing…”

 

[Chuck_P]

The highlights create a veiling exposure that has a proportionately greater affect on the shadow exposure...............................There isn't a highlight to produce the flare exposure or a shadow to be affected by it.

I don't know if this is 100% correct, honestly, it doesn't matter but this response does makes sense to me and I see more of the issue regarding your claim that flare is not accounted for in ZS testing procedures, thank you. AA indicates that flare is accounted for in the testing he advocated for in The Negative, who was I all those years ago to argue against that, especially when my own negatives improved greatly. If old AA was wrong as wrong can be on that, so be it....................I'm mainly interested in results and testing in that way has paid dividends imo.

 

[kal800]

Have a question regarding sensitometer - I found couple of those - they are dedicated to test X-ray films against 21 step wedge. But it is lit by green or blue LEDs. Is it suitable for our ortho or panchromatic B&W negs?

 

[Stephen Benskin]

Hi,

Thanks so much for all your input. I have not expected such fantastic feedback.

In general, to make things more clear, what I expect is to put a second leg in the ZS - I've been tough the Zone System at the very beginning, but since I've been roll film field shooter exclusively I was unable to apply second part of the principle - "develop for highlights". As the result I've had limited tonal range on my negatives which I compensated in the darkroom with the grade knob on my enlarger. I believe paper grades should be applied exclusively for creative reasons, not to correct tonal range, which should be on the negative in the first place. Now when I turned into sheet film, I am finally able to do so.

Also, I'd like to have precise matching of my Analyzer Pro grey scale indicator with the actual developed print. Currently it matches the midtones, but on the both ends of the scale it is not as precise and I still need to use test stripes. I believe careful calibration of the device will make test strips obsolete, or almost obsolete.

Now, being an engineer, I prefer the analytical approach to the procedure, measuring the outcome with the dedicated meter, comparing them to the reference values, putting numbers into the spreadsheet, apply the results, then check if they are satisfactory, if needed fine tune.

@stephen - thanks for the information provided and the paper regarding Normal setting, for sure I'm going to read it thoroughly. Have a question regarding wedge exposure. You suggest to use an enlarger, but I still don't know how to set an exposure. In case of white paper shot, it is clear since I have a spot meter. You mentioned that such approach is OK as soon as I have a lens with an image circle significantly bigger than the holder. My lens (Symmar-S 150/5.6) stepped down to f22 has 210 mm image circle allowing 38x32mm displacement of the lens in case of 4x5. Is it big enough?

Kal800

Hi Kal,

According to the Google, a Symmar-S 150/5.6 has an maximum image circle of 233mm. To cover a 4x5 negative, the image circle needs to be at least 154mm, so you're good, but that's not to say there won't be some fall off.

The points I made on each of the methods you were considering was to illustrate that no method is without potential problems and no results are definitive. If you are just expanding your interests into tone reproduction, might I suggest Phil Davis' book Beyond the Zone System. It's a good introduction and Davis is factual. Just watch out for the use of Subject Brightness Range. It's an outdate term.

Your question on exposure using an enlarger is also applicable to the third method (Schaefer's?). How do we know what exposure to use? Davis has a good explanation of exposing with an enlarger and to be honest, no method outside of a sensitometer is going to give you anything other than relative film speed. In many case, unless you're careful, the method can lead to a false sense of accuracy. This is why I suggest starting with the ISO and evaluate what EI works best through real world shooting and metering. How you meter and personal taste will have larger influence that any speed difference, real or in error, derived from speed testing.

To determine what the exposure needs to be to create a given exposure at a specific step density, decided on where you want the speed point to fall if the film has a certain speed. I believe Schaefer uses a log density of 2.70. This is good as you want some room to the left for the toe and for higher development. Determine the exposure needed to obtain a density of 0.10 for a given film speed. As the film speed equation is 0.80 / Hm = EI, where Hm is the exposure in mcs or lxs that has a corresponding negative density of 0.10 over Fb+f. To find the lxs for each film speed use 0.80 / EI.

100 = 0.0080 lxs
125 = 0.0064 lxs
400 = 0.0020 lxs
The required exposure would be

. For a 100 speed film, the exposure would be 4 lxs to obtain a value of 0.0080 lxs at the 2.70 density step.

100 = 4 lxs
125 = 3.2 lxs
400 = 1 lxs

Confirming

where Density= 2.70.

100 = 0.0080 lxs
125 = 0.0064 lxs
400 = 0.0020 lxs

The 64 thousand dollar question always comes down to whether the available equipment is capable to achieving this level of precision. If the answer is no, then there will be a level of inaccuracy introduced into the testing.

A camera and meter, as stated in the third method, might be able to achieve something closer to this level of accuracy, even considering all the variables of an optical system, and questions regarding the calibration of the f/stops, shutter speed, and meter. The best possible work around would be to take the meter reading at the film plane, but most people don't have that type of meter.

So what values we have if the exposure is based on a metered target and the exposure is adjusted by opening up five stops form the metered reading? Will it be the same or different from what was previously determined? Exposure at the film plane for Hg is 8/ISO. This is what meters are calibrated for.

100 = 0.080 lxs
125 = 0.064 lxs
400 = 0.020 lxs

Open up 5 stops 25*(8/ISO)

100 = 2.56 lxs
125 = 2.05 lxs
400 = 0.64 lxs

My understanding is that this method is based on the assumption that full film speed is achieved if the film density is at 0.10 over Fb+f at the 2.70 step tablet density and that if it falls else where the film speed is determined by the log-H difference between the two points. We know that the exposure values determined previously would achieve this stated goal, so the question is does the metering a target and opening up five stops achieve the same exposure values? No they don't.

There would be nothing wrong using the different exposure values for Hm mathematically, but that is not how this method works. Under the that assumption that full film speed is achieved when the film density of 0.10 falls at the step tablet density of 2.70, this method will produce different film speeds. So at what step tablet density would these exposures reach the target Hm exposure? Using third method's exposure, the Hm would fall at the step density of 2.50 or Δ 0.20 log-H to the right 2.70 implying a 2/3 stop slower film speed. This is the exact same difference between Zone System and ISO speeds. So this method, in effect. produces Zone System speeds, which is fine, except it doesn't appear to specify this fact. It's an easy fix though. Simply increasing the camera exposure by 2/3 stop, or use the actual values for Hm and do the math.

I feel it's important to question and understand what's involved in the various methods to achieve the best results.

 

[albada]

Also, I'd like to have precise matching of my Analyzer Pro grey scale indicator with the actual developed print. Currently it matches the midtones, but on the both ends of the scale it is not as precise and I still need to use test stripes. I believe careful calibration of the device will make test strips obsolete, or almost obsolete.

I have the same goal as you: eliminate test strips. But I use a DIY controller instead of the Analyzer Pro. Also, I am using a LED head, so I can change green and blue brightness independently, making it possible to set both exposure and contrast by changing LED brightness. In trying to match tones precisely, I discovered two more sources of inaccuracy:

1. Due to the inverse-square law, the 20mm thickness of the easel light-sensor causes light measurements to be too high. My solution is to put a thin sheet of foam under the easel, making it the same thickness as the sensor. Then, I remove the easel when measuring light, putting the sensor on the baseboard. Thus, both sensor and easel are the same distance above the baseboard.
2. Due to developer and fixer, negatives often have a slight blue or pink color, changing the spectrum on the paper compared to the Stouffer wedge used for calibration, thus causing measurements to be inaccurate. My solution is to have green and blue offsets (bias) in the controller to compensate for inaccuracy of both exposure and contrast. These offsets can also compensate for a different developer or old paper.

Now I can match tones precisely. For example, I can tell the controller to place one measurement on zone 2.5 and another measurement on zone 6, and that's how it will print. With no test strip.
You can check for color-cast in a negative by putting it next to a Stouffer transmission wedge on a light-table. By doing that, even a slight color-difference will be visible.
I recently programmed a feature into the controller to compute offsets based on one test-print. I enter the desired and actual tones of two locations, and it computes the offsets.

If you want precise matching, I suggest replacing the tungsten lamp with a LED-head and suitable controller so that you can compensate for contrast-shift.

Mark

 

[Doremus Scudder]

It actually doesn't Doremus. But I hope you will explain your reasoning.

Stephen,

I'll always defer to your expertise, but here's my thinking:

Making in-camera images with a conventional taking lens in "average" lighting and a scene with a SLR that registers as "normal" in Zone System parlance has to be influenced by flare from the optical system. In my case the flare inherent in my spot meter as well as the flare from the taking lens. Hopefully the amount of flare will be "average" as well. In this case, then, shooting conditions and testing conditions are at least similar, the variation coming into play with variations in luminance ranges and distributions in different scenes.

Then, making a "proper proof" with the enlarger instead of making a contact print will include the flare from the enlarging lens.

So, by including the whole tone-reproduction system from meter to taking lens to enlarging lens, I'm also approximating in my tests the flare that's going to happen when making actual photographs in the field. (I say approximating because I'm well-aware that the amount of actual flare will vary according to a number of factors like the distribution of luminances in the subject (not every subject has a "statistically average" luminance range), whether the lens is single or multi-coated or not coated at all, the IC of the lens, whether a lens shade is used, etc., etc.)

And, I've also included other variables like my own idiosyncrasies in metering, my personal visualizations of what tonality each Zone represents, etc.

In a nutshell, I make a test negative and develop and print it in exactly the same manner as I would for any photograph I would in actual practice. The difference being making the print a proper proof, i.e., ensuring that FB+fog density renders very, very close to maximum paper black under viewing light that I consider excellent gallery lighting. With this last, I'm also including my eye's ability to discern differences in dark tones under changing lighting conditions.

We mention the "first excellent print" a lot in discussions like this, but we rarely mention the actual range of tolerances in exposure and contrast gradient that will still yield excellent prints.

The "first excellent print" is predicated on the minimum exposure to get desired shadow values. There's a large window of exposure above that minimum that will still yield excellent prints until the overexposure actually begins to degrade the image by shouldering off the higher-density values or showing too much grain. While I see the value in working with the minimum exposure to get an excellent negative, e.g., being more often able to use optimum f-stops and shutter speeds, I also realize that overexposing a stop or even more, especially with large-format film, will still get the job done and provide a bit of insurance against underexposure errors in tricky situations.

Similarly with development. Just as the contrast controls available with VC papers and a good color head make it possible to make good prints from scenes with a wide spectrum of subject luminance ranges, it also makes it possible to make excellent prints from negatives that are a bit over- or under-developed. I.e., there's a range of possible developments that will still allow for excellent prints.

So, using my more empirical approach to determining personal E.I. and development schemes I can start by simply choosing an E.I. that "should" be close to ideal (in the case of Zone System metering practice, that's 2/3-stop slower than ISO speed) and a development that "should" be close to "normal," go out and make a few identical negatives of a "normal" scene, in which I have clear Zone III and Zone VIII values, develop a negative and print it as a proper proof, and see immediately what adjustments I have to make. Usually the adjustments consist of refining development times since the 2/3-stop slower than ISO speed usually gets me very close to an ideal personal E.I.

Since I have a couple of other identical negatives, I use those to refine the development time. If I need to adjust my E.I., I usually just make a note of that and use the new E.I. in the field, keep notes and refine from there. Doing the same test for expansions and contractions gives me my N+ and N- times.

So, yes, there's a bit of a "black box" approach here: I assume that there is flare at several stages of the system, but don't do anything to eliminate it during testing or compensate for it later. What matters is if the shadow tones I get in the print correspond to the placements I made metering and if the highlight tones fall where they were planned to.

I'd be interested in hearing your thoughts.

Best,

Doremus

 

[Stephen Benskin]

I don't know if this is 100% correct, honestly, it doesn't matter but this response does makes sense to me and I see more of the issue regarding your claim that flare is not accounted for in ZS testing procedures, thank you. AA indicates that flare is accounted for in the testing he advocated for in The Negative, who was I all those years ago to argue against that, especially when my own negatives improved greatly. If old AA was wrong as wrong can be on that, so be it....................I'm mainly interested in results and testing in that way has paid dividends imo.

Before Copernicus, there was a mathematical method based on a geocentric model of the universe that accurately predicted the movement of the planets. It had the some of the planets doing a loop to account for the apparent retrograde movements they made. While it was predictive, it doesn't describe reality. The Sun rises in the east whether or not you believe that the Earth revolves around the Sun or the Sun revolves around the Earth. I want to know how something actually works.

I never said the Zone System doesn't work or that it doesn't help to improve the quality of one's work. My argument is that there are certain misconceptions that exist. The Zone System is a way of visualizing the photographic process. It uses a simplified form of sensitometry and tone reproduction. Therefore it isn't unreasonable to compare and contrast the two. In many cases the differences are less about actuality and more about assumptions. Take the normal negative density range. The Zone System has the normal negative density range in a Zone System test as about a log difference of 1.25 between Zone I and Zone VIII. The goal is to print on a grade 2 paper. And all indications is that negatives produced based on Zone System testing do print on a grade 2 paper. Yet, the LER for a grade 2 paper is based on approximately the same Zone I to Zone VIII range is 1.05. Why the discrepancy. I believe there actually isn't one and it's more about the assumptions.

Zone I to Zone VIII is 7 stops or a log Luminance range of 2.10. The aim Zone NDR is 1.25. This would make the film's average gradient (Rise/Run) 1.25 / 2.21 = 0.59. The CI for normal development according to Kodak is 0.58. Essentially identical. However, if you plug in the 1.05 or the paper LER with the 2.20 of the log subject Luminance range, you get 1.05/2.20 = 0.48 and not 0.58. Kodak also incorporates a value for camera flare. In this case it's 0.40. 1.05 / (2.20 - 0.40) = 0.58. Camera flare effectively reduces the luminance range down to 1.80.

If normal negatives from both approaches have identical average gradients, then the only difference between the two is that one is more accurately describing reality. Just like the difference between the geocentric and heliocentric model.

Here it is graphically. Both use the same luminance range and the same film curve. The one without flare has a NDR of 1.25. The one that incorporates flare has a NDR of 1.05 which matches a paper's grade 2 LER.