Deep Blacks, LONG Range

[Robert]

</span><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (Tom Duffy @ Mar 20 2003, 12:19 PM)</td></tr><tr><td id='QUOTE'>
for very generous exposure (high contrast scene) of APX 100 and Acros (EI 32) I've got much shorter times in Rodinal then I've seen published. With 5 min presoak and developed in a jobo, I got times of 9 min at 68 for APX and 7 min at 68 for Acros. Rodinal was mixed at 1:50 if I did the math right (10ml Rodinal to 500 ml of water).
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Agfa's time for APX 100 in rodinal 1:50 g of 0.55 [Is that gamma? Contrast] is 8 minutes in a rotary tank 20C. I wonder if it's only the english language stuff that's so hard to find.

 

[David Hall]

I could probably do a bunch this weekend and send them out Monday. Why don't you PM me with snail mail if you want one. I will send you an azo print unmounted so you can also see how thin the paper is.

dgh

 

[Michael A. Smith]

When I wrote:

You all should know that there will be a light source coming soon (the patent has been applied for) that will enable one to enlarge on Azo. The light will not be hot, exposure times will be relatively short, and the whole thing will be reasonably priced. "

I hope I did not give the impression that I was coming up with the light source. This is someone els'e invention. No, there is no focus shift. I'm not sure what part of the spectrum is being used. It is a trade secret, at least for now--and even I don't know. Paula and I are just helping to test it.

Michael A. Smith

 

[SkipA]

Michael, it's good to hear that the new light source for enlarging onto Azo will be available sometime soon. Do you know if the light source will be readily adaptable to common 4x5 enlargers? Especially to a Beseler 45?

Skip.

 

[Ed Sukach]

</span><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (glbeas @ Mar 20 2003, 02:15 PM)</td></tr><tr><td id='QUOTE'></span><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (Michael A. Smith @ Mar 20 2003, 06:07 PM)</td></tr><tr><td id='QUOTE'> You all should know that there will be a light source coming soon (the patent has been applied for) that will enable one to enlarge on Azo. </td></tr></table><span class='postcolor'>
...will this be using the visible blue end or the uv spectrum to expose Azo? If it's uv would there be any problems with focus shift like you have with infrared?</td></tr></table><span class='postcolor'>
How would one notice a "focus shift" in the enlarger? - Or would this be switchable from "Ordinary" to "Special for AZO"?

 

[Donald Miller]

I am sure that the new light source must be UV in that Michael related that it is not "hot". Additionally Azo (according to the Kodak spectral sensitivity curve on the material) exposes entirely in the 360-410 nm UV band. This is near band UV or A band in the three band method of classification. This light probably still in the visible spectrum (at least the upper 410nm band would be) that focus shift would not be a consideration.

This new light source is probably useable only on Azo, unless a secondary light source is incorporated into the system.

The "new" Durst 5X7 enlarger which is useable on both Pt-Pd and Azo is designed for UV output. This enlarger is scheduled for 3-03 release. And, once again, useable only for the materials noted.

 

[Eric Rose]

Maybe it uses the same bulbs as tanning beds. I wonder if anyone has ever tried to expose their contact print in a tanning bed just to check it out.

 

[Donald Miller]

I imagine that it would expose, Eric, although I have not tried that myself. I think that the problem that exists, and apparently is being solved by others, is getting enough light intensity to pass through to the easel. The enlarging lens does "choke" things down a bit. I visited with a fellow on another forum and he related that while Azo is very slow (paper speed 6) vs polycontrast (paper speed 150) it is still a lot faster then pt-pd and he had contact printed Azo under his UV printer for pt-pd.

 

[glbeas]

</span><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (Ed Sukach @ Mar 21 2003, 08:51 AM)</td></tr><tr><td id='QUOTE'> </span><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (glbeas @ Mar 20 2003, 02:15 PM)</td></tr><tr><td id='QUOTE'></span><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (Michael A. Smith @ Mar 20 2003, 06:07 PM)</td></tr><tr><td id='QUOTE'> You all should know that there will be a light source coming soon (the patent has been applied for) that will enable one to enlarge on Azo. </td></tr></table><span class='postcolor'>
...will this be using the visible blue end or the uv spectrum to expose Azo? If it's uv would there be any problems with focus shift like you have with infrared?</td></tr></table><span class='postcolor'>
How would one notice a &quot;focus shift&quot; in the enlarger? - Or would this be switchable from &quot;Ordinary&quot; to &quot;Special for AZO&quot;? </td></tr></table><span class='postcolor'>
Same way you notice the focus shift when shooting infrared, it comes out fuzzy!

Focusing in visible light and shooting in a non visible wavelength can give errors if the lens doesn't focus the same at all wavelengths, and most lenses are corrected for visible light.

 

[Ed Sukach]

</span><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (glbeas @ Mar 21 2003, 11:57 AM)</td></tr><tr><td id='QUOTE'>Same way you notice the focus shift when shooting infrared, it comes out fuzzy!

Focusing in visible light and shooting in a non visible wavelength can give errors if the lens doesn't focus the same at all wavelengths, and most lenses are corrected for visible light.</td></tr></table><span class='postcolor'>
Hmmm ...

This is one thing I have been meaning to check out. I have read quite a bit about IR and have wrestled with the focus problem.
"Fuzzy" - I am famliar with.
The last I've read, and I've reconciled it with the optical theory that I know, is that any "focus shift" will be directly proportional (but not linearly) to the wavelength of light in question; and given the IR sensitivity of films like Konica 750, Ilford's SFX, MACO 820 ... and what was that extended red range film from Agfa? ... AND the fact that when using a SLR with a Red #25 or 29 fiter in place, a great deal of the non-affective wavelength will be eliminated, the most common error is to OVER-compensate. With films 'way out there in the IR spectrum, e.g., Kodak's HIE and opaque filters (87's and 89's) - the usual 10% or so, applied *after* focusing IS valid.

In enlarging, a LOT is going to depend on the actual spectrum from the new light source. If my memory of Geometrical Optics serves, there will be relatively less shift with shorter wavelengths. Another factor will lie in the fact that ordinary glasses, including optical glasses used in enlarger lenses, filter out UV rather effectively - See the Hasselbad UV lens with Flouride elements.

So ... If this light source operates in blue-visible- to- near UV, I doubt that there will be much "shift. If it produces light across the visible spectrum to far (or properly "more distant") UV there could be. "Far" UV is not likely - the human eye will flouresce beyond a certain wavelength and that *IS* uncomfortable.

More "complications" for the perfectionists among us -- all the time.

 

[Donald Miller]

I don't know whether this is factual or not...however I have been told this by someone who should know... The El Nikor lenses are among those that have the capability of transmitting the UV spectrum in which Azo paper is exposed. However, I have also been advised that conventional enlarging lenses are fairly effective in blocking UV transmission. There are apparently quartz elements in some of the more exotic optical systems that are most effective in passing UV. In fact metal halide lamps have a quartz envelope in most cases.

 

[Ed Sukach]

</span><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (dnmilikan @ Mar 21 2003, 01:33 PM)</td></tr><tr><td id='QUOTE'> There are apparently quartz elements in some of the more exotic optical systems that are most effective in passing UV. In fact metal halide lamps have a quartz envelope in most cases.</td></tr></table><span class='postcolor'>
The reason for using quatz is that it has a *very* high melting point - much higher than glasses. Halogens, etc., get *hot*.

I can only remember two outstanding attributes of crystalline quartz - It has a very high index of refraction; and it can be made without "inclusions" that would cause the energy from a laser to be "grabbed" - absorbed and converted to heat.... LOTS of heat.

Plastics, generally, are transparent to UV. The only other material I know of with the requisite transparency is "Iceland Spar", otherwise known as "Calcite" or "Fluorite".
Interesting stuff - Calcite is also the only material with two (2) indices of refraction.
That DOES complicate optical design.

BTW - That Hasselblad UV lens is listed at something like $US 10K.

 

[Donald Miller]

Ed,
I was under the distinct impression that acrylic was more resistant to uv transmission then glass. At least that is what my supplier has indicated to me. Am I correct, or have I been misinformed?

At that price, I think that I may have to order a couple of the blad lenses...how many for you?

 

[Ed Sukach]

</span><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (dnmilikan @ Mar 21 2003, 03:34 PM)</td></tr><tr><td id='QUOTE'>&nbsp;
I was under the distinct impression that acrylic was more resistant to uv transmission then glass. At least that is what my supplier has indicated to me. Am I correct, or have I been misinformed?

At that price, I think that I may have to order a couple of the blad lenses...how many for you?</td></tr></table><span class='postcolor'>
Acrylic filters out very little UV by itself. Coatings can be applied to absorb UV - as is done regularly with sunglasses... and some of the acrylic sheeting used to take the place of glass in frames (about double the price and scartches like crazy).

Glass on the other hand - It is pretty futile to try to get a tan in a Greenhouse or a glass- enclosed porch.

 

[Donald Miller]

Ed,
Thank you for clearing that up for me. I understand what you are saying and what the basis for my suppliers claims were. Thanks again.

 

[David Hall]

Well, whatever the light source, I look forward to it and hope it will be practical for us.

dgh

 

[Donald Miller]

David, I agree. The more immediate problem seems to be whether Kodak is going to keep Azo Gr.3 in their product line. I certainly hope that Michael and Paula are able to prevail in their efforts. In lieu of that, maybe the thing that I should be looking toward is putting in a walk in freezer to stock up on the Gr 3.

 

[Aggie]

..

 

[Ole]

</span><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (Ed Sukach @ Mar 21 2003, 02:52 PM)</td></tr><tr><td id='QUOTE'> I can only remember two outstanding attributes of crystalline quartz - It has a very high index of refraction; and it can be made without &quot;inclusions&quot; that would cause the energy from a laser to be &quot;grabbed&quot; - absorbed and converted to heat.... LOTS of heat.

Plastics, generally, are transparent to UV. The only other material I know of with the requisite transparency is &quot;Iceland Spar&quot;, otherwise known as &quot;Calcite&quot; or &quot;Fluorite&quot;.
Interesting stuff - Calcite is also the only material with two (2) indices of refraction.
That DOES complicate optical design.
</td></tr></table><span class='postcolor'>
Ed,

As a geologist I have to protest. "Iceland Spar" is Calcite, calcium carbonate. Fluorite is calcium fluoride; not the same thing at all. Fluorite has only one index of refraction, MOST other minerals - including quartz - have at least two. Calcite has one of the most pronounced differences, giving rise to the double refraction.

What is usually ment by "quartz" in optics is fused silica, a glass with the same chemical composition as quartz. But unlike the mineral, glass (all glasses) has only one index of refraction. Crystalline quartz does funny things to light, like rotating polarized light or splitting it into two beams. Not very useful in (photo-)optics.

Calcite was earlier used to make polarizers for microscopes, I know of no other optical use.

Fluorite has very low dispersion, and has been used in some very expensive lenses.

 

[Ed Sukach]

I can only remember ....

Oh, picky, picky...!!

This just illustrates how *time* can attenuate one's memory. However, this is the first I've heard of *many* minerals having more than one index of refraction... either my training was not that microscopically (pun intended) precise, or the differences between the indices was not pronounced enough to be included .... come to think of it .... they both mean the same...

To the filing cabinet in my darkroom...

Well ... I'm gaining ... The Hasselblad lens I'm thinking of is:

"20134 Zeiss UV-Sonnar CF f/4.3 105mm

A special purpose lens for photography within the ultraviolet spectrum. It is sensitive to radiation from 215 nm to 700 nm (2150 - 7000 A ~with little circle over~ gstroms), i.e. from short-wave ultraviolet to the initial part of the infrared range. The lens can be pre-focused for ultraviolet in visible light without requiring refocusing for use in the UV range."

I've seen more information about the construction of this lens ... typically - I can't (#$@%@#$) find it. Never can, when I NEED it.

As far as quartz/ fused quartz - I did a lot of work in physical optics - Spectrophotometry, Optical QC, - and a LOT of Interfereometry ... most of the optical flats we used were "Fused Quartz", (much more durable than glass) and minor defects, e.g. "seeds" (bubbles) and whatnot were not uncommon, and had no effect of the operation. I did a LOT of calibration, optical polygons and the like - Autocollimators, Theodolites ...
Ah, Theodolites ... a sort of "super transit" with, commonly, 40x telescopes over optically read scales. I worked in Cambridge, Massachusetts - a lively avant-garde College town... and I had a set up on the sixth floor, where I would check "Infinity focus" by training the telescope on certain windows....

Crystalline quartz components were used - and necessary - in laser optical testing - for Modulation Transfer Functions - precisely for their *absence* of what would be minor defects in ordinary optical bench testing.

I remember one "Commercial" use for Crystalline quartz - in cylindrical form. It was used to convert a laser beam (of xDiameter) to a one meter - or so - *line*.

 

[fingel]

I just had a thought after reading all of the comments on UV enlarging lights for AZO. How are you supposed to work with this light source without going blind? Isn't UV light very bad for your vision?I know I wouldn't want to be looking through a grain magnifier at a UV light source, unless they build in some kind of removable UV blocking focusing filter. Anyway that is just a thought.

 

[Eric Rose]

It is also a major contributor to skin cancer.

 

[Donald Miller]

There are three different designations of UV emission. The primary health hazard lies below the near band which is required to expose Azo and Pt-pd prints. The far band is particularly nasty stuff, from what I understand. Obviously caution is still in order even with the near band but the hazard is not as great as is commonly attributed.

 

[Nige]

</span><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (Ed Sukach @ Mar 25 2003, 01:15 AM)</td></tr><tr><td id='QUOTE'> and I had a set up on the sixth floor, where I would check &quot;Infinity focus&quot; by training the telescope on certain windows....

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A good and practical use!

 

[Eric Rose]

</span><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (Nige @ Mar 24 2003, 02:44 PM)</td></tr><tr><td id='QUOTE'> </span><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (Ed Sukach @ Mar 25 2003, 01:15 AM)</td></tr><tr><td id='QUOTE'> and I had a set up on the sixth floor, where I would check &quot;Infinity focus&quot; by training the telescope on certain windows....

</td></tr></table><span class='postcolor'>
A good and practical use!

</td></tr></table><span class='postcolor'>
Especially at night when ....... LOL