Exposing/developing for Azo/Platinum

[gainer]

Kirk Keyes wrote :

"You may be right, water baths may work better. But then how do you increase the contrast with a water bath?"

Kirk,

Apparently you failed to read what I wrote earlier in which I stated that it is virtually impossible to increase the contrast of a fixed grade photographic paper beyond the emulsion characteristics. The only reasons that uv light increases contrast with Azo is that Azo is quite sensitive to this portion of the spectrum and also because of the actinic quality of Pyrocat stain. If one used a non staining developer in lieu of pyrocat then there would be no difference in the contrast of Azo between uv lamps and the conventional floods that most of us use.

By the way, I visited your website...It seems that most of your work is in color which is very nice. However I saw only two images portrayed as black and white. Do you have additional black and white images? Do you use Pyrocat developer? Do you contact print on Azo? Have you ever used this material?

The artifact is not in the emulsion of the paper. If the density of the dye layer of the film varies with the light by which it is measured, so will the contrast. This variation of contrast is not in the emulsion of the paper except to the extent that it is sensitive to a range of wavelength and the contrast that you would and in fact do measure by filtering your densitometer over various portins of the bandwidth of the paper varies. Changing the color of the light by which you expose AZO will not change its contrast, but it will change the effective contrast of the negative.

Kirk and I have different opinions about some things and different experiences with others. Your statement about the variability of the contrast of AZO was much too dogmatic and not well enough thought out to allow you to question Kirk's knowledge in the manner you chose to do so. Sorry, but I had to say this.

 

[Donald Miller]

The artifact is not in the emulsion of the paper. If the density of the dye layer of the film varies with the light by which it is measured, so will the contrast. This variation of contrast is not in the emulsion of the paper except to the extent that it is sensitive to a range of wavelength and the contrast that you would and in fact do measure by filtering your densitometer over various portins of the bandwidth of the paper varies. Changing the color of the light by which you expose AZO will not change its contrast, but it will change the effective contrast of the negative.

Kirk and I have different opinions about some things and different experiences with others. Your statement about the variability of the contrast of AZO was much too dogmatic and not well enough thought out to allow you to question Kirk's knowledge in the manner you chose to do so. Sorry, but I had to say this.

Gainer,

I appreciate your post.

I see nothing that you stated as being materially different then what I stated. I stated that the stain of Pyrocat was highly actinic to UV transmission. That would seem to indicate that this effect was the determining factor in an increase of contrast obtained in the use of uva for exposure. It is not the emulsion of the paper that determines the contrast but rather the qualities of the negative that determine this.

Given a negative density range which remains consistant the contrast of the paper will not alter for differing light sources provided the differing light sources are all within the spectral response of the paper's emulsion. This is true if no actinic proportional stain exists on the camera negative. That is what I stated throughout. Perhaps I didn't state this clearly enough. So where do your issues for contention arise with what I said?.

Perhaps my questioning Kirk's qualifications to speak to the subject bothers you. I find nothing wrong with that. I think that you will agree that it is typical of most new scientific claims that the basis for those claims be examined. That would tend to include the qualifications of the person making those claims.

 

[c6h6o3]

You may be right, water baths may work better. But then how do you increase the contrast with a water bath?

I have a negative, and it's of a picture I absolutely love, that is just too thin to print acceptably on grade 3 Azo. If I could increase contrast about 1/2 stop I'd have a stunning print, but I have yet to make a print that is visually arresting enough to deserve a place in my body of work. At this point my only option is to print it on VC enlarging paper and crank up the contrast.

So Sandy, if you were to fabricate such an Azo VC device, what lamps would you use and where would you get them?

 

[sanking]

I have a negative, and it's of a picture I absolutely love, that is just too thin to print acceptably on grade 3 Azo. If I could increase contrast about 1/2 stop I'd have a stunning print, but I have yet to make a print that is visually arresting enough to deserve a place in my body of work. At this point my only option is to print it on VC enlarging paper and crank up the contrast.

So Sandy, if you were to fabricate such an Azo VC device, what lamps would you use and where would you get them?

I am not positive how to go about this right now. What I found in one test was that exposure with a UV bank of BLB (Black Light Blue bulbs), which peak at about 360 nm and cut off virtually all light above about 420 nm, resulted in a significant increase in effective printing contrast when compared to use of the R40 flood that is often used in exposing AZO. However, the exposures were so short as to be impractical for real work so I am looking at alternative types of BLB devices, including the type (both fluorescent and incandescent) that screw into regular sockets.

It does seem logical to me that if the difference in contrast between UV and visible light is as great as I observed in the initial test, and assuming the results of my test can be repeated by others, some type of effective variable contrast light could perhaps be devised using varying proportions of UV and visible light.

The anticipated next step in my own work will be to acquire one of the 13 watt BLB screw-in fluorescent tubes and test it in the same fixture and at the same height at which I use the R40 flood. With any look I will have some report on this later in the week.

Sandy

 

[sanking]

Kirk Keyes wrote :

The only reasons that uv light increases contrast with Azo is that Azo is quite sensitive to this portion of the spectrum and also because of the actinic quality of Pyrocat stain. If one used a non staining developer in lieu of pyrocat then there would be no difference in the contrast of Azo between uv lamps and the conventional floods that most of us use.

Donald,

However, in the test I conducted, from which I want to emphasize I draw only preliminary conclusions, the difference in contrast resulted not from the use of a stained negative but from a regular Stouffer test strip. I have yet to test a stained negative with AZO and UV light, but plan to do so soon.

Sandy

 

[Donald Miller]

Donald,

However, in the test I conducted, from which I want to emphasize I draw only preliminary conclusions, the difference in contrast resulted not from the use of a stained negative but from a regular Stouffer test strip. I have yet to test a stained negative with AZO and UV light, but plan to do so soon.

Sandy

Sandy, I guess I failed to recognize the full implications of your tests. Sorry for any misunderstandings that arose from my failure to comprehend.

 

[Donald Miller]

I am not positive how to go about this right now. What I found in one test was that exposure with a UV bank of BLB (Black Light Blue bulbs), which peak at about 360 nm and cut off virtually all light above about 420 nm, resulted in a significant increase in effective printing contrast when compared to use of the R40 flood that is often used in exposing AZO. However, the exposures were so short as to be impractical for real work so I am looking at alternative types of BLB devices, including the type (both fluorescent and incandescent) that screw into regular sockets.

It does seem logical to me that if the difference in contrast between UV and visible light is as great as I observed in the initial test, and assuming the results of my test can be repeated by others, some type of effective variable contrast light could perhaps be devised using varying proportions of UV and visible light.

The anticipated next step in my own work will be to acquire one of the 13 watt BLB screw-in fluorescent tubes and test it in the same fixture and at the same height at which I use the R40 flood. With any look I will have some report on this later in the week.

Sandy

Sandy,

I have been giving further thought to the increase in contrast that you reportd. My first impression was that this was due to the proportional stain from a Pyrocat stained negative. I could readily understand how that would occur because of the actinic properties of that stain.

On further consideration after becoming fully aware of your exposure being through a Stouffer step wedge I became confused. I can think of only one of two possible conditions that need to be in place for this reported increase in contrast to occur.

The first is that UVA does alter the exposure scale of the paper. The second is that UVA is not affected by neutral density in the same way that visible spectrum light is.

As I view the spectral sensity of grade two Azo as published by Kodak it seems that Azo is most sensitive at 350 nm and tails off to 450 nm. Would you think that this increased sensitivity would alter the characteristic curve of the emulsion? The curve appears to be linear from an approximate dmin density of .10 at 2.0 lux seconds of exposure to dmax density of appr. 2.0 at 3.0 lux seconds of exposure. How do you relate increased sensitivity to an altered characteristic curve? Do your reflective densitometric readings coincide with the published data from Kodak?

If an altered characteristic curve is not the cause of increased contrast, that would appear to leave the possibility that UVA is not affected by neutral density in the same manner that light above 450 nm is. I find no where in my research that anyone reports this variance in transmissivity. Perhaps you are aware of a source that reports this variance. I would appreciate learning of the source if it exists.

To what do you attribute this increase in contrast? Considering the possibility of a variance in transmissivity how would one determine if this is in fact occurring?

 

[sanking]

Sandy,

I have been giving further thought to the increase in contrast that you reported. My first impression was that this was due to the proportional stain from a Pyrocat stained negative. I could readily understand how that would occur because of the actinic properties of that stain.

On further consideration after becoming fully aware of your exposure being through a Stouffer step wedge I became confused. I can think of only one of two possible conditions that need to be in place for this reported increase in contrast to occur.

To what do you attribute this increase in contrast? Considering the possibility of a variance in transmissivity how would one determine if this is in fact occurring?

Donald,

First I want to make it very clear that I have not done enough work with this to know for sure that exposing with primarily UVA light does indeed increase contrast, or if so, in what circumstances. I know that I observed an increase in contrast in some previous tests in trying to make digital negatives with the white Pictorico material. Because of the opacity of this material I wound up having to expose it with a NuArc 26-1k because exposures were very long the R40 lamp. And I definitely saw an increase in contrast when exposing with the UV bank of BLB tubes. Whether or not I can repeat the tests with light sources that work in more real time remains to be seen. It is possible, for example, that the extremely short exposures necessary with these very powerful UV light sources, which are designed for printing alternative processes, not AZO, are somehow distorting the characteristic curve.

However, assuming that I have not made some kind of mistake in my testing the most likely explanation in my opinion is that the silver chloride AZO emulsion gives more contrast when exposed with UV light than with visible light. I have not read any research on this but it would not surprise me if it were so. Other processes, including carbon, gum bichromate, kallitype and Pt./Pd. vary in both sensitivity and in the shape of the characteristic curve depending on the peak wavelength of the exposing light.

The curious thing, however, is that the increase in contrast that I observed with AZO is the opposite of what we would expect with the alternative processes I mentioned above, where radiation of longer rather than shorter wave length increases contrast. So, rather than being surprised that there is a difference in contrast I am surprised that the result was in the direction of more contrast rather than less.

Sandy

 

[Donald Miller]

Donald,

First I want to make it very clear that I have not done enough work with this to know for sure that exposing with primarily UVA light does indeed increase contrast, or if so, in what circumstances. I know that I observed an increase in contrast in some previous tests in trying to make digital negatives with the white Pictorico material. Because of the opacity of this material I wound up having to expose it with a NuArc 26-1k because exposures were very long the R40 lamp. And I definitely saw an increase in contrast when exposing with the UV bank of BLB tubes. Whether or not I can repeat the tests with light sources that work in more real time remains to be seen. It is possible, for example, that the extremely short exposures necessary with these very powerful UV light sources, which are designed for printing alternative processes, not AZO, are somehow distorting the characteristic curve.

However, assuming that I have not made some kind of mistake in my testing the most likely explanation in my opinion is that the silver chloride AZO emulsion gives more contrast when exposed with UV light than with visible light. I have not read any research on this but it would not surprise me if it were so. Other processes, including carbon, gum bichromate, kallitype and Pt./Pd. vary in both sensitivity and in the shape of the characteristic curve depending on the peak wavelength of the exposing light.

The curious thing, however, is that the increase in contrast that I observed with AZO is the opposite of what we would expect with the alternative processes I mentioned above, where radiation of longer rather than shorter wave length increases contrast. So, rather than being surprised that there is a difference in contrast I am surprised that the result was in the direction of more contrast rather than less.

Sandy

Sandy,

I would strongly suspect that exposing a camera negative developed in Pyrocat would exhibit increased contrast when exposed to UVA. In fact my peliminary work in which I used a negative with those characteristics seemed to indicate that to me.

I am surprised, as I have indicated, that neutral density would exhibit that increase.

By the way and off the subject somewhat, I posted on the Azo forum that I have tried UV LEDs as a possibly light source and I found those to be unsuitable in my experience.

 

[sanking]

Sandy,

I would strongly suspect that exposing a camera negative developed in Pyrocat would exhibit increased contrast when exposed to UVA. In fact my peliminary work in which I used a negative with those characteristics seemed to indicate that to me.

Donald,

There is no doubt about that. The actinic stain of a Pyrocat-HD negative can dramatically increase the effective printing contrat of a negative with UV sensitive processes. For example, a negative with an effective printing density range of 0.16 - 1.40 in visible light on graded silver papers will have an effective denisty range of about 0.25 - 2.20 using UV light with alteranative processses.

Sandy

 

[Kirk Keyes]

[...] the difference in contrast resulted not from the use of a stained negative but from a regular Stouffer test strip. I have yet to test a stained negative with AZO and UV light, but plan to do so soon.

Now that IS really interesting! I had assumed as well that you were discussing the use of a stained negative.

Well, that's OK. BY the way, there is a property of photographic materials that is called the "gamma/lambda" effect. Gamma (and Gradient) can be affected by the predominant color of the light used in the exposure. Of course this effect depends on the emulsion type, but in general for panchromatic films, blue and ultraviolet light will produce a lower gamma than white light, and red light will produce a higher gamma. This is also known, understandably, as the "gradient/wavelength" effect.

This effect is typically small, but I have a book the book ("Sensitometry for Photographers" by Jack Eggleston) that shows a graph of this and at exposures made with blue light (400 nm) the gamma is 0.59 and with red light (650 nm) the gamma is 0.72. That's a bit of change there!

But that seems to be the reverse of your situation here, correct?

I seem to remember that last summer we had a big, long thread covering various aspects of UV and visible light, printing, densitometery, sensitometry, and a few other things, and Sandy pointed out that his Stouffer step wedge read lower contrast with his Gretag D-200 II densitometer in UV mode than in Blue (or was it Vis?). It wasn't a big difference between the readings on the densitometer if I remember correctly, but maybe the light source is stronger in UV than the densitometer readings were, and there is more density in those wavelengths.

Anyway, my proposal to use a stained negative to make a VC effect with AZO and properly selected light sources should work.

 

[Kirk Keyes]

Sandy, at one point you had asked Stouffer about the UV density of their product - did they ever get back to you on this?

 

[noseoil]

I wonder if this isn't why I have found that negatives which print well on grade 2 fiber have too much contrast for grade 2 azo. I know that conventional wisdom is to have more contrast in a negative for azo, but I have to reduce development to work with azo. Seems backwards with every conventional wisdom I have heard, read and been told, but the prints show things differently.

Must be the actinic properties of pyro negatives for azo printing which causes these seemingly upside down results for me (ABC, PMK & Pyrocat). Anyone else use a negative and try a contact print on grade 2 fiber and grade 2 azo? Which one shows more contrast?

 

[sanking]

BY the way, there is a property of photographic materials that is called the "gamma/lambda" effect. Gamma (and Gradient) can be affected by the predominant color of the light used in the exposure. Of course this effect depends on the emulsion type, but in general for panchromatic films, blue and ultraviolet light will produce a lower gamma than white light, and red light will produce a higher gamma. This is also known, understandably, as the "gradient/wavelength" effect.

This effect is typically small, but I have a book the book ("Sensitometry for Photographers" by Jack Eggleston) that shows a graph of this and at exposures made with blue light (400 nm) the gamma is 0.59 and with red light (650 nm) the gamma is 0.72. That's a bit of change there!

But that seems to be the reverse of your situation here, correct?

Yes, what Eggleton shows is the opposite of what I observed in printing AZO #2, with both the NuArc 26-1K and a bank of BLB fluorescent tubes. But, the decrease in gamma he notes with shorter wave length light is consistent with my observations for carbon, kallitype and Pt/Pd. So I am very anxious to do some more side by side comparisons with a UV-A light source that more closely approximates the R40 flood in exposure time. As I mentioned, I have ordered a 13 watt screw-in BLB fluorescent that can hopefully be used with more realistic exposure times. Not many folks are going to like exposures of 1/100 of a second.

Sandy

 

[sanking]

Sandy, at one point you had asked Stouffer about the UV density of their product - did they ever get back to you on this?

Well, yes and no. They got back to me with the information that they do not consider UV transmission densities in determining tolerances. In fact, although one of the persons I spoke with indicated they have a UV denstiometer at the site I got the impression that it had not been used for a very long time.

Sandy

 

[Kirk Keyes]

By the way, I visited your website...It seems that most of your work is in color which is very nice. However I saw only two images portrayed as black and white. Do you have additional black and white images? Do you use Pyrocat developer? Do you contact print on Azo? Have you ever used this material?

(And in reply to Partick)Perhaps my questioning Kirk's qualifications to speak to the subject bothers you. I find nothing wrong with that. I think that you will agree that it is typical of most new scientific claims that the basis for those claims be examined. That would tend to include the qualifications of the person making those claims.

Donald, thanks for your kind comments on the photos on my web site: www.keyesphoto.com (in case anyone missed it.) I hope you enjoyed looking at them!

Since you asked about my "qualifications", he's my reply:

I do have more photos in B&W. I made the web site in 1998 and unfortunately, I have not made many updates to it since then. I made it to coincide with a photo show at the time, and as I was focusing on printing color work more than B&W at the time, I chose not to include more B&W images. Were two images out of a dozen insufficient to demonstrate to you that I can make a reasonable B&W print? And does that matter?

I have not developed any negatives with PyroCat-HD. I have recently gotten around to purchasing the chemicals needed to prepare it. I intend to do that this summer. I've been using PMK at various times for more than a decade now. Does it matter?

I do not use Azo, as I prefer to make enlargements. And if I were making lots of contacts, I think I would stick with my usual paper, Ilford Multigrade IV, as I would probably still want to tweak the relative contrast levels in the print. I have never used Azo. Does it matter?

Perhaps my questioning Kirk's qualifications to speak to the subject bothers you.

I found those questions to be a rather interesting way to determine my qualifications. Must I have touched Azo before I can understand it's properties? I say no. Actually, I do have to say that I've touched several prints made on Azo by other photographers, and I can't say that it is a magic bullet to perfection.

As I asked in another thread, just how does someone's competence as a photographer really directly relate to my understanding of the properties and science behind photographic materials and processes? And how does someone's undertanding of the science of a process always relate to the ability to make a work of art? I don't think it is as close a relationship as you seem to think. You seem to immediately questions a person's skill as a photographer when you have a disagreement with some technical viewpoint that they have made. I don't think this is the right way to go about that...

But Donald, if you like, I would be happy to send you a B&W print to keep and you may then examine it first-hand. Perhaps you would like to reciprocate with a print for me?

If you would like to really like to hear what my qualifications are, here is some background info - I have a Bachelor's of Science degree in Chemistry, and I've been employed as an analytical chemist for nearly 20 years now, with 8 of those years as a Group Leader and Supervisor for the department. I also studied physics for a couple of years at Reed College before I dropped out. (I didn't tune in while I was there, and I didn't turn on, so all that was left for me to do was drop out!)

For nealy all of that time, I've specialized in wet chemistry analytical techniques. One of the main tools used in that field is the spectrophotometer, where you measure the absorbance/transmittance of light through various reactions at various wavelengths.

Photographically, I've been doing photography for over 25 years, and in the last several of years, I've been playing around with studying the effect of the stain on VC materials, as well as the actual properties of the stain.

I hope you will find that those are sufficient qualifications for me to state the idea that I did. In the future, I suggest that you ask about a person's experience with the studies of chemistry, physics, and materials science, instead of if they have made more than two B&W prints.

Oh, and by the way Donald - what are your qualifications?

To everyone else following this thread, I appologize for this diversion.

 

[Kirk Keyes]

So I am very anxious to do some more side by side comparisons with a UV-A light source that more closely approximates the R40 flood in exposure time.Sandy

I'm anxious too - it's an interesting observation!

Kirk

 

[Donald Miller]

Kirk, Thanks for your response and I don't want to divert this thread from the far more important considerations that it began with. You did pose some questions and while your thoughts were lengthy, I will for the purposes of brevity try to keep my responses more concise.

Donald, thanks for your kind comments on the photos on my web site: www.keyesphoto.com (in case anyone missed it.) I hope you enjoyed looking at them!

Since you asked about my "qualifications", he's my reply:

Apparently you read words that I didn't write...I did not ask you for qualifications. I asked you for your experience in a very specific realm

I do have more photos in B&W. I made the web site in 1998 and unfortunately, I have not made many updates to it since then. I made it to coincide with a photo show at the time, and as I was focusing on printing color work more than B&W at the time, I chose not to include more B&W images. Were two images out of a dozen insufficient to demonstrate to you that I can make a reasonable B&W print? And does that matter?

Yes, I think that it does. I have found in my experience that Azo and contact printing from Pyrocat developed negatives is far different from enlarging. Obviously normally one speaks about what they know about As you are well aware, a website is a poor representation of an actual print. I would reserve judgement until I see an actual print.


I have not developed any negatives with PyroCat-HD. I have recently gotten around to purchasing the chemicals needed to prepare it. I intend to do that this summer. I've been using PMK at various times for more than a decade now. Does it matter?


Yes, I think that it makes a large difference. PMK and Pyrocat exhibit far different stain colors and the effects on printing are quite a lot different. This has been addressed by a number of noted photographers.


I do not use Azo, as I prefer to make enlargements. And if I were making lots of contacts, I think I would stick with my usual paper, Ilford Multigrade IV, as I would probably still want to tweak the relative contrast levels in the print. I have never used Azo. Does it matter?

Obviously, yes, the materials are no where near the same.


Perhaps my questioning Kirk's qualifications to speak to the subject bothers you

Your response to this indicates a propensity that you seem to evidence...my comment was not directed to you.

I found those questions to be a rather interesting way to determine my qualifications. Must I have touched Azo before I can understand it's properties? I say no. Actually, I do have to say that I've touched several prints made on Azo by other photographers, and I can't say that it is a magic bullet to perfection.


You once again are entitled to your opinion. My experience differs quite drastically from yours.

As I asked in another thread, just how does someone's competence as a photographer really directly relate to my understanding of the properties and science behind photographic materials and processes? And how does someone's undertanding of the science of a process always relate to the ability to make a work of art? I don't think it is as close a relationship as you seem to think. You seem to immediately questions a person's skill as a photographer when you have a disagreement with some technical viewpoint that they have made. I don't think this is the right way to go about that...

You are entitled to your opinion. I reserve the right to mine.

But Donald, if you like, I would be happy to send you a B&W print to keep and you may then examine it first-hand. Perhaps you would like to reciprocate with a print for me?

That may prove interesting. My prints are fairly expensive...how do you propose that this be done. I would want my print returned.

If you would like to really like to hear what my qualifications are, here is some background info - I have a Bachelor's of Science degree in Chemistry, and I've been employed as an analytical chemist for nearly 20 years now, with 8 of those years as a Group Leader and Supervisor for the department. I also studied physics for a couple of years at Reed College before I dropped out. (I didn't tune in while I was there, and I didn't turn on, so all that was left for me to do was drop out!)

For nealy all of that time, I've specialized in wet chemistry analytical techniques. One of the main tools used in that field is the spectrophotometer, where you measure the absorbance/transmittance of light through various reactions at various wavelengths.

Photographically, I've been doing photography for over 25 years, and in the last several of years, I've been playing around with studying the effect of the stain on VC materials, as well as the actual properties of the stain.

I hope you will find that those are sufficient qualifications for me to state the idea that I did. In the future, I suggest that you ask about a person's experience with the studies of chemistry, physics, and materials science, instead of if they have made more than two B&W prints.

Now that you have impressed yourself are you happy?


Oh, and by the way Donald - what are your qualifications?

Obviously you are equating a scientific background with the ability to produce a quality photographic print. While I will not denegrate technical knowledge, I do not share your apparent belief. My photographic experience is quite a bit longer then yours. But then I am quite a lot older. I work exclusively in black and white. I have owned and used large format cameras in the following formats: 4X5, 8X10, and 12X20. As Fred Picker once commented about another photographer..."He knows how to hang them on the wall"

To everyone else following this thread, I appologize for this diversion.

To all of you that chose to read this trash...I apologize for this diversion. I promise that Kirk will go back on my ignore list so that these interchanges will cease.

 

[gainer]

Gainer,


Given a negative density range which remains consistant the contrast of the paper will not alter for differing light sources provided the differing light sources are all within the spectral response of the paper's emulsion. This is true if no actinic proportional stain exists on the camera negative. That is what I stated throughout. Perhaps I didn't state this clearly enough. So where do your issues for contention arise with what I said?.

Perhaps my questioning Kirk's qualifications to speak to the subject bothers you. I find nothing wrong with that. I think that you will agree that it is typical of most new scientific claims that the basis for those claims be examined. That would tend to include the qualifications of the person making those claims.

However, if the measured contrast of a negative depends on the spectrum of the light by which it is measured, then this vatiation can be used to vary the contrast of prints made on any material that is sensitive to at least part of the region in which the measured contrast of the negative is variable. This would require the use of narrow band, or at least sharply cut off high and low pass filters in the printing, but these are within current technology. Thus, the variation of contrast with AZO is possible. The fact that the idea that this variation would be possible arose after Sandy King observed that variations in measured contrast within the sensitivity bandwidth of AZO led me to think that you took , or should have taken, that into account when you stated that "the contrast of the paper will not alter for differing light sources provided the differing light sources are all within the spectral response of the paper's emulsion."

There are ways of finding about a person's background and experience without snide comparisons. When "Cold fusion" was announced, many others tried to repeat the experiments without success. If you believe that the contrast of AZO or any other normally fixed contrast paper cannot be affected by the color of light within its sensitivity range, I will agree with you so long as you restrict your statement to tests you have tried, or announce it as speculation based on pertinent experience. Your statement as it appeared was too dogmatic.

 

[Kirk Keyes]

Obviously you are equating a scientific background with the ability to produce a quality photographic print. While I will not denegrate technical knowledge, I do not share your apparent belief.

Donald, you seem to have completely misunderstood what I was trying to say. I do NOT equate "a scientific background with the ability to produce a quality photographic print." It appears that we DO agree on that.

But you seem to feel that the ability to create a nice print is proof of the understanding of the scientific principles behind the process. And that one must use something before they can have an understand that something. I disagree with both of those ideas. I'm sorry you did not understand that from my post. I tried to be lengthy to better convey those ideas, but I guess you missed that point!

You did "question" my "qualifications" - see the post you made to Patrick. So I responded to that.

Anyway, I'm up for a personal print short-time exchange if you are truly interested, and I can return your print if you like. Since you've not posted your "qualifications" other than saying you've been at it longer than I, I guess I have to go by your print. I really would like to see one. Send me a PM and we can proceed. I promise to treat it with care.

And as far as the "ignore list" thing goes - that's fine with me. It's your choice.

Again, I apologize to the rest.

 

[Kirk Keyes]

However, if the measured contrast of a negative depends on the spectrum of the light by which it is measured, then this vatiation can be used to vary the contrast of prints made on any material that is sensitive to at least part of the region in which the measured contrast of the negative is variable.

Yes - we could think of it as a "spectrally variable contrast film" which will change contrast on a single grade paper as the color of the light source changes, as opposed to a film being printed onto a "spectrally variable contrast paper". At least while talking about a stained neg model.

 

[Donald Miller]

Gainer,

I guess that Kirk and you suffer from the same affliction. By that I mean that you both respond to matters that don't involve you or to comments that weren't directed at you. In your case this began with your first comment in this thread.

Maybe you ought to check your dog to make sure he is in the fight.

 

[gainer]

Gainer,

I guess that Kirk and you suffer from the same affliction. By that I mean that you both respond to matters that don't involve you or to comments that weren't directed at you. In your case this began with your first comment in this thread.

Maybe you ought to check your dog to make sure he is in the fight.

If the fight is about whether being able to make an excellent print qualifies one to pontificate about the physics of emulsions, you have not presented an argument for the affirmative. There are and have been too many famous photographers who would not think of themselves as qualified photographic research technicians. That is like saying that the aeronautical engineers who contributed to the design of air and space vehicles must be pilots. That is very far from the truth. Our test pilots at NACA-NASA were graduate engineers, but our engineers were seldom pilots. I used to joke with my friends in other fields that the reason I was not a pilot was because I was an aeronautical engineer and knew too much about airplanes.

Should one be able to look at a display of your valuable prints and draw the conclusion that they represent a man who obviously knows all about Pyrocat HD and AZO and ultraviolet light and all things technical? I would not want that to represent the value of my photographs. It certainly does not present any sort of credential that would prompt me to hire you as a photographic researcer.

 

[Donald Miller]

Gainer,

I guess that we will just need to agree to disagree...My photographic efforts are directed to the end of making photographs that are worthy of display. By that I mean technically well executed images as well as artisticly fulfilling. That would tend to encompass not duplicating sandstone images and slot canyon images that have been done ad nauseum.

I don't give a damn about space shuttles, lunar flight or any of that other irrelavent crap that you seem to pump yourself up with. But then again what the hell, someone may be impressed. I assure you that I am not...so save this for those who might be immature enough to be impressed.

Speaking of pontificating and being dogmatic...have you ever in your extensive experience encountered the aspect of psychological projection? If you have, I encourage you to revisit the subject. If you haven't then I suggest that it may prove interesting reading.

 

[sanking]

Well, today I received the 13-watt screw-in BLB tube and made some comparison tests with a 65-watt RH40 flood light on AZO #2 using both Stouffer step wedges and stained negative step wedges. The results, which I have just finished plotting, are very interesting, and just go to show that no matter what one might theorize or hypothesize, reality has a strange way of kicking sand in your face.

Probably will not have time today to post comparative data re: the curves but I will throw out this piece of information. Exposing AZO #2 with a light source rich in UV-A radiation is extremely efficient. In actual comparison tests of the 13-watt BLB screw-in tube and a 65-watt RH40 flood, used in the same housing and at the same distance from the printing frame, the 13-watt BLB tube proved to be almost two full stops faster in printing speed than the 65-watt RH40 bulb, when contact printing a Stouffer step wedge.

Sandy