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  1. #21

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    I got tired of rolling my home-made tubes in a tub. Bought a used Unitron motor base on eBay, but my grey conduit tubes wouldn't rotate (too small). So, made a sling for each end of tube, and suspend the tube above the motor base. Works fine & don't have to worry about tubes 'walking off' the motor base.
    van Huyck Photo
    "Progress is only a direction, and it's often the wrong direction"

  2. #22

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    Quote Originally Posted by sanking
    All we would need to do is substitute the typical R40 floodlight that is used for printing with AZO with a bulb that puts out a lot of UV light. Given the fact that AZO is much more sensitive than alternative processes the bulb could be fairly low in wattage.
    Sandy - this also leads to the idea that one could, if one can find a set of lights/lamps with a good balance of intensity, make a variable contrast printing setup for the Azo paper.

    Instead of the usual VC setup of using a set of filters with a single lamp, use two lamps for different times or intensity settings. Exactly like the way VC cold light heads work.

    Once the lights are getting close in printing time/speed, it may be possible to make fine adjustments to the overall balance of the lights though filtration. They could be permanently filtered, and then contrast could be adjusted simply by time.

    Kirk - www.keyesphoto.com

  3. #23

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    Quote Originally Posted by Kirk Keyes
    Sandy - this also leads to the idea that one could, if one can find a set of lights/lamps with a good balance of intensity, make a variable contrast printing setup for the Azo paper.

    Instead of the usual VC setup of using a set of filters with a single lamp, use two lamps for different times or intensity settings. Exactly like the way VC cold light heads work.

    Once the lights are getting close in printing time/speed, it may be possible to make fine adjustments to the overall balance of the lights though filtration. They could be permanently filtered, and then contrast could be adjusted simply by time.

    Kirk - www.keyesphoto.com
    I would be very surprised if this would work. The VC materials have two emulsions whereas Azo is a single emulsion material. In other words it either exposes or it doesn't...

    The degree of variation from two light sources to expose Azo through a stained negative are best accomplished with other means. For instance Amidol with water bath would be far more effective to decrease contrast. It is virtually impossible to increase a papers exposure scale past the emulsion characteristics.

  4. #24

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    Quote Originally Posted by Donald Miller
    I would be very surprised if this would work. The VC materials have two emulsions whereas Azo is a single emulsion material. In other words it either exposes or it doesn't...

    The degree of variation from two light sources to expose Azo through a stained negative are best accomplished with other means. For instance Amidol with water bath would be far more effective to decrease contrast. It is virtually impossible to increase a papers exposure scale past the emulsion characteristics.
    Well, you might be surprised, but Sandy has said that he can get two different contrasts out of the Azo by using different light sources. I'm taking his word on that observation. So it only goes to follow that if one varied the light sources, one could control the contrast range of the paper. We don't have to change the contrast of the paper at all, since we are controlling the contrast with the filtration that is inherent in the stained negative.

    And yes, VC paper's have two emulsions, each with different intrinsic contrasts. In fact, Ilford MG IV claims to have 3 emulsions to accomplish the VC properties.

    Sandy's measurements have shown that the PyroCat density increases with decreasing wavelength, i.e. PyroCat has a much greater density in the UV than in the blue or green wavelengths. That density probably increases fairly continuously as the wavelength decreases. Combine this with the spectral characteristic of the Azo paper, and that is what would give us the VC properties of this technique. See this for the spectral properties of Azo. http://www.kodak.com/global/en/profe...009_0106ac.gif
    So we accomplish this either of two ways here -

    1) Pick a light source that is "tunable" so that we can vary the wavelength of the light that goes through the negative, and the negative will have a different contrast range based on the wavelength we "tune" to, or

    2) Vary the amount if light coming from each end of the spectral sensitivity spectrum of the Azo paper. By changing the ratio of these colors of light, we would be making 2 exposures on to the same paper with a negative that had 2 different "contrasts". The combination of those exposures, when properly balanced, could create an exposure of either contrast extreme, or somewhere in the middle.

    I'm not saying it would be easy to do, but it should work...

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

    Donald, I don't mean to say there aren't better ways to control the contrast, I'm just pointing out that here's another way that probably hasn't been tried yet.

  5. #25

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    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?

  6. #26
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    Quote Originally Posted by Donald Miller
    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.
    Gadget Gainer

  7. #27

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    Quote Originally Posted by gainer
    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.
    Last edited by Donald Miller; 04-26-2005 at 12:06 AM. Click to view previous post history.

  8. #28
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    Quote Originally Posted by Kirk Keyes
    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?

  9. #29

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    Quote Originally Posted by c6h6o3
    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

  10. #30

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    Quote Originally Posted by Donald Miller
    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

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