How many ML of D-76 powder do I mix with how many ML of water.

Scales are cheap these days, at least the "gem" style ones available on eBay. And I've checked the calibration of the two I've bought, and they were right on. No excuse not to own a couple scales these days. Get one that goes to 100 g and one to 1000g.

Cute... What - no images of Cartman dressed as Hitler to portray the dogma being espoused here?

Nicholas Lindan said:

It does not diminish the created work if a photographer gets the results he likes by measuring out chemicals as a pinch of this, a dash of that and half a handful of the other.

Don't trivialize the art -

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No one is arguing to trivialize the art of photography. If one wishes to practice it as one would when mixing magic potions, then by all means they should do so.

It's just that when one gest results that are not to one's own expectations or satisfaction, then where does one go? You've fulfilled your desire to work to the level of technical complexity you want in your work. Fine.

Nicholas, I'm sure you've noticed how many posts are from people having issues with their photographic art, needs, and desires, and how many of those issues have a technical component to them? And how perhaps a better understanding of the technical side of photography is needed to solve these issues? There's certainly a lot of that going around here. In fact, most people seem to like the level of technical expertise here at APUG.

And you don't have to be up to date in the latest modifications to latent image theory or any other of the many highly technical aspects of photography as a science, but having an understanding and practicing good darkroom practices sure can help make you a better photographer.

It's a lot like using a darkroom meter. Absolutely no need for it, but they sure can make your life a lot easier. (And I've got one of your meters and I love it!) Same thing with using repeatable methods in your darkroom. Certainly, you can be as sloppy as you want, but your life may be a lot easier if you follow more precise and repeatable techniques.

That's really the only arguement being made here.

Thanks Kirk, you said it much better than I did.

I would like to add something.

I address my answers, in part, based on PMs and E-mail from APUG and Photo Net members. I have gotten about 2000 PMs and E-mails in 3 years just from APUG members alone. I have gotten up to 20 E-mail messages in one day from people asking for help. They are virtually all technical issues. The few exceptions relate to my offers for old film that I'm giving away or miscellaneous items. I answer every E-mail and PM.

So a lot goes on behind the scenes that push me in the direction I go. Apologies if it seems to be beating a dead horse to some of you, but I do have a reason. I have been sensitized by the tenor of those notes, pleas for help if you will. Pleas to revive or maintain a dying science - we call it analog photography. Lets not beat it to death.

PE

Wirelessly posted (BlackBerry 8300: BlackBerry8300/4.5.0.55 Profile/MIDP-2.0 Configuration/CLDC-1.1 VendorID/102)

PE--that wasn't aimed at you. Just trying to inject a little humor into this thing.

We are very fortunate to have you here to answer all of these crazy questions.

Nick

Nick;

After 32 years in research at EK, I'm not that thin skinned. I understood. The generic tenor of the thread prompted my response not your post. Thanks though.

PE

gainer said:

Of course lab work should be done to the best available precision, but it is equally a part of this lab work to establish tolerances. These tolerances in measurement will in fact be determined in a systematic determination of the optimum.

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Patrick, well said. The only thing I would add is the word "appropriate" right after "available".

Hummm, It is interesting to consider that in their method of mixing the chemicals for us, Kodak could have already used up that margin of tolerance, therefore there could be much less (remaining) tolerance than we might expect!

Ray

Photo Engineer said:

Patrick;

I believe that I dispelled your assumptions about how powder chemicals are made. They are not made by the method you describe, but by the method I tried to explain.

I guess we will have to go with your methodology and use a teaspoon of silver nitrate, a half cup of food gelatin and a tablespoon of table salt in one half saucepan of tap water on the stove to make our emulsions in the future.

And I'm glad that you, a human factors and mechanical engineer are sharing your extensive knowledge of photographic engineering and chemistry with us all. I will not be returning the favor in human factors or other engineering fields as I deem myself untrained and not competent in these areas.

PE

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You do not know my complete educational background. I started in chemical engineering. I went through analytical chemistry and chemical engineering lab before switching to aeronautical engineering. At NACA-NASA I was assigned photographic tasks and I studied quite thoroughly in order to perform them. That, and your own background, are beside the point. If I make an erroneous statement, it will be in spite of, not because of my education. I try to make it a habit not to make statements I cannot back up by controlled tests. I never went to music school either, and had only a handful of private lessons on the oboe, but became first chair oboist of the Norfolk Symphony and the Peninsula Symphony and the Colonial Williamsburg Governor' Palace Orchestra. A number of my photographs were hung in Chrysler Museum.

According to Aristotle, the argument from authority is the weakest form of argument.

Photo Engineer said:

Patrick;


I guess we will have to go with your methodology and use a teaspoon of silver nitrate, a half cup of food gelatin and a tablespoon of table salt in one half saucepan of tap water on the stove to make our emulsions in the future.

PE

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You didn't even read my methodology. I said nothing about emulsion making. I said that for research purposes, the most accurate means of measurement and the purest ingredients ought to be used. Measurable criteria for success of the experiments must be established before experiments begin. A properly scheduled set of experiments should allow one to establish not only the optimum composition but tolerable deviations from the optimum, if there are such.

My recommended methodology does not begin and end with slap dash measurements. I don't remember seeing where you made it clear that Kodak does not use the method of dividing up a large batch of mixed powders that most of us did not recommend. You did say they were working on more dependable methods of sizing and coating particles to make that method usable in the large, but that would seem to make dividing up a 5 liter package reasonable for the end user.

As to the size of a teaspoon, look at the medicine plunger-type medicine syringes that are sold in most drug stores and you will see calibrations in both ml and teaspoons. The teaspoon mark coincides with the 5 ml mark.

Photo Engineer said:

Yes, art is important as well as science.

I am trying to explain something that people seem to be missing though. Photo system engineers are a vanishing breed. I am trying to teach correct methods for future practitioners of analog photography so that someday in the future you do not have to reinvent the wheel so to speak.


PE

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At our recent visit to the Ilford factory, we noticed that the workforce, and certainly the senior factory management, seemed to be largely made up of older (I can say that, with great respect...being grey-haired myself ) and more experienced people.
Bearing in mind that Ilford is arguable one of the top B&W manufacturers in the world (they're aren't many others now anyway!) , there must be a vast store of skills, knowledge and experience there. And, like the rest of us, everyone will be wanting to retire some time in the future......
I can see exactly what PE is saying here.

Weight or volume?

I would have thought that Kitchen measuring spoons and cups made with modern injection moulding methods would be very consistent for measuring components and even the most sophisticated weighing scales will need recalibrating from time to time.
Kodak and Ilford AFAIK now have their chemicals pre-packaged by an independant company. I haven`t found any information yet as to whether the developers packaged in dry-form are measured by weight or volume.

Kodak formulas are measured by weight using strain guages on the equipment just like small electronic scales that we see on the internet for sale. They are very sensitive. Even the liquids are measured by weight due to the difficulty inherent in measuring some of the viscous chemicals.

Those who take my workshop have seen me demonstrate this! It is very hard to measure volume in the dark, but a hooded safelight over a balance is perfect when it comes to measuring out stuff in the dark.

I hope to have more on this in a little while, but consider this:

A formula calls for 25 g/l Na2SO3 (anh) and you have only Na2SO3.H2O. I have been asked many times, how much of the hydrate can replace the anhydrous. This is easy to do, but if you are worried about this, can you really accurately measure the difference using a volumetric measure, and if you cannot, is the difference important to you? This is a very practical problem that I keep answering over and over and can be applied to sulfite, hypo, carbonate, borate and other salts that come in varying states of hydration.

PE

Patrick;

Yes, I know, you took a few chemical engineering courses. I took a few classes in aeronautical engineering while studying to go into the USAF, and I even "flew" a military jet for a few minutes. That does not qualify me as either a pilot or a person who could design or give advice to an aeronautical engineer or pilot.

I gave advice to two of the first astronauts - on photography!

PE

Photo Engineer said:

Kodak formulas are measured by weight using strain guages on the equipment just like small electronic scales that we see on the internet for sale. They are very sensitive. "Even the liquids are measured by weight" due to the difficulty inherent in measuring some of the viscous chemicals.


PE

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Thanks for clarifying the "weighing" method used.

I have not seen any requirement that one posting a formula here must qualify as a Photographic Engineer. I have seen "Professional Engineers", with a certificate to prove it, who made the rest of us say "Oh Yeah. He's been to see the Wizard alright."

Engineering was the major. The minor was some branch of engineering. One of our professors used to say "Engineers can do anything."

Keith Tapscott. said:

Thanks for clarifying the "weighing" method used.

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I would like to clarify and expand on my previous post.

Some initial operations use weighed samples. The weight is used to calibrate the solid dispenser by using a screw adjusted vernier just as on a powder dispenser in shell reloading.

In high speed operation, some mixed or milled materials are dispensed volumetrically by using these very carefully calibrated volumetric powder dispensers.

The same is true of some non-viscous liquids which are dispensed by volume. For example, water can be dispensed by volume. TEA cannot be dispensed by volume.

You must also consider that if temperature varies, volume varies, particularly with liquids although solids vary as well. Weight does not vary.

So, all of this is taken into consideration for making a given formulation at EK.

PE