Do you have a link or reference?
Do you have a link or reference?Turns out there is a fairly simple intensification technique for silver images using dyes! Haist discusses a Leitz formula that uses a Copper Sulphate bleach and dyes like Methylene Blue which gives impressive intensification going by the graphs. If DR5 is using some such process, it's no surprise that he gets impressive DMax. Archival stability is uncertain though.
Do you have a link or reference?
I don't get all that need and urge for intensification and those sparkling DMax figures.
The same Grant & Haist book cited, on volume 2, section reversal, says that densities beyond 2.2 to 2.4 are useless because the human eye can't discern the difference.
what about DMin?When I used to do it, Id get 2.3 in my standard developer with Delta 100, and around 3.0 with one passed of catechol redeveloper. The difference was very significant to look at, especially side by side.
Seems that once the negatives are processed reversal, you can't print them on paper anymore.
I don't get all that need and urge for intensification and those sparkling DMax figures.
The same Grant & Haist book cited, on volume 2, section reversal, says that densities beyond 2.2 to 2.4 are useless because the human eye can't discern the difference.
I don't get all that need and urge for intensification and those sparkling DMax figures.
The same Grant & Haist book cited, on volume 2, section reversal, says that densities beyond 2.2 to 2.4 are useless because the human eye can't discern the difference.
When I used to do it, Id get 2.3 in my standard developer with Delta 100, and around 3.0 with one passed of catechol redeveloper. The difference was very significant to look at, especially side by side.
what about DMin?
And I am saying that if that is what the book says, it isnt correct. dMax beyond 2.4 in transparencies is easily noticeable, its not just a minor difference, it is substantial, and a vast improvement to visual viewing quality of the transparency. 2.4 looks faded when viewed side by side with a high dMax slide, while still being able to simultaneously see the detail in the darkest parts of the slide.
For projecting on a white matte surface, in an average sized room that doesnt have black ceiling/walls etc with a regular light source that may be the case. It will have similar limitations to prints (can be improved a lot with a better light source and eliminating reflections). But it doesnt hold a candle to high dMax slides viewed directly. More dMax means more separation between tones, and you can see much more contrast in shadows, and local areas of the images, as the shadows and any other image portion will occupy a broader contrast range on the slide.You can check the latest edition of Basic Photographic Processes and Materials:
"Although these films are capable of achieving densities over 3.0, the shadows are best reproduced at densities of 2.7 and less."
The tint wouldnt matter, as if you couldnt pick up detail beyond 2.4 you wouldnt be able to see it in the slide warm tone or not. Human eyes are also more sensitive to green than warm tones. Additionally the low light receptors in yours (rods) are monochromatic.
But it doesnt hold a candle to high dMax slides viewed directly.
There exists a wikipedia page for Methylene Blue, and the stated prices for this compound suggest, that DR5 used something else.Turns out there is a fairly simple intensification technique for silver images using dyes! Haist discusses a Leitz formula that uses a Copper Sulphate bleach and dyes like Methylene Blue which gives impressive intensification going by the graphs. If DR5 is using some such process, it's no surprise that he gets impressive DMax. Archival stability is uncertain though.
There exists a wikipedia page for Methylene Blue, and the stated prices for this compound suggest, that DR5 used something else.
I feel it's much simpler than that (judjing from the Dr5 Tecnolab d&d machine display), maybe a simple final toning step (either gold, selenium or whatever)...
I don't get all that need and urge for intensification and those sparkling DMax figures.
The same Grant & Haist book cited, on volume 2, section reversal, says that densities beyond 2.2 to 2.4 are useless because the human eye can't discern the difference.
I employ a 12 bath process, if I include the washing stepsHis german competitor Wehner (schwarzweissdia.de) to own statement employs a 10bath, 20 steps, 2h process.
No.I think this about direct vision of the transparency. In our case though it is about a seeing an image reflected off a screen.
No.
The maximum density of the positive
silver image should be at least 2.0, transmitting only 1/100 of the incident light,
or, preferably, around 2.2 to greater than 2.4. High maximum densities are
not needed because, as H. Verkinderen(8) has pointed out, "by normal pro
jection all density-discrimination for densities exceeding from 2.2 to 2.4 is
lost."
(8) H. Verkinderen, "Reversal Processing," Brit. Kinemat., 13 (2): 37 (1948).
https://archive.org/stream/britishki1213brit/britishki1213brit_djvu.txt
Seems that once the negatives are processed reversal, you can't print them on paper anymore. I have always made positives for display with continuous tone ortho from negatives.
Back in the 1970;saround 1973/4 while at University I went to a lecture by a PhD student from the Birmingham School of Photography (part of Birmingham Polytechnic).. His PhD research project was B&W reversal processing and then reversal prints, his print quality was superb.
His main issue was print process time as he was using Ilfobrom, RC/PE papers hadn't been released, washing times between steps needed much longer than films or RC papers. He also indicated that it wasn't easy needing lots of test strips etc. But it can be done.
Ian
Ian: While high DMax and high contrast are absolutely essential for a good viewing experience of slides, they are more a PITA for printing. I did a few reversal prints of slides using SLIMT but it requires good amount of testing. Would you be able to give more details of the process employed by the PhD student? Did he use contrast reduction masks?
No.
The maximum density of the positive
silver image should be at least 2.0, transmitting only 1/100 of the incident light,
or, preferably, around 2.2 to greater than 2.4. High maximum densities are
not needed because, as H. Verkinderen(8) has pointed out, "by normal pro
jection all density-discrimination for densities exceeding from 2.2 to 2.4 is
lost."
(8) H. Verkinderen, "Reversal Processing," Brit. Kinemat., 13 (2): 37 (1948).
https://archive.org/stream/britishki1213brit/britishki1213brit_djvu.txt
Turns out there is a fairly simple intensification technique for silver images using dyes! Haist discusses a Leitz formula that uses a Copper Sulphate bleach and dyes like Methylene Blue which gives impressive intensification going by the graphs. If DR5 is using some such process, it's no surprise that he gets impressive DMax. Archival stability is uncertain though.
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