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Hexavalent
06-27-2013, 06:17 PM
What is "summer speed" emulsion?

wildbillbugman
06-27-2013, 09:08 PM
Do it be about Donna or Susann? Susann, I hear was really fast back in "The Day".

dwross
06-27-2013, 09:14 PM
I am guessing you are referencing post #38 (??) "...ASA 100 (summer speed) ortho ("X2Ag")..." I can see how that was confusing. I meant that the emulsion is ASA 100 in the summer, assuming full sun, mid-day, and a high energy developer. That's the thing with pre-modern emulsions. It is meaningless to assign a speed to them without specifying the shooting conditions. Every photography book published in the late 1880's and early 1900's had a chart of latitudes and times of year with numbers like filter factors to estimate exposure compensation (i.e. "speed"). Since the emulsions see very little beyond UV, the higher the UV, the "faster" the emulsion. "x2Ag" is around ASA 25 at Christmas time.

Hexavalent
06-27-2013, 09:26 PM
Thanks,

I figured it was in regard to "colour-blind".

Summer speed is probably mid-winter here in Ottawa :)

Personally, I'd prefer to go panchro and not have to worry.


I am guessing you are referencing post #38 (??) "...ASA 100 (summer speed) ortho ("X2Ag")..." I can see how that was confusing. I meant that the emulsion is ASA 100 in the summer, assuming full sun, mid-day, and a high energy developer. That's the thing with pre-modern emulsions. It is meaningless to assign a speed to them without specifying the shooting conditions. Every photography book published in the late 1880's and early 1900's had a chart of latitudes and times of year with numbers like filter factors to estimate exposure compensation (i.e. "speed"). Since the emulsions see very little beyond UV, the higher the UV, the "faster" the emulsion. "x2Ag" is around ASA 25 at Christmas time.

Photo Engineer
06-27-2013, 10:35 PM
But the ideal is no such thing as summer speed. The speed should be the same all year round. That is my goal and that is the goal of the ANSI standards committee. If you do it right, the speeds do not vary with the seasons.

Oh dear. Someone has something wrong here.

PE

dwross
06-27-2013, 10:49 PM
Panchromatic emulsion is indeed a very fine goal. Best luck to both of us (and all other serious cooks). I'm almost there. I hope the same for you. I will be proud to use my own pan film, but I'll still make and use colorblind, and also ortho. They all have their own personalities and uses.

kb3lms
06-28-2013, 10:15 AM
How DO you make an emulsion be the same speed all your round? Do you desensitize it to UV?

Pachromatic would be great, except you have to coat it in the dark, right? I'm not that good!

Photo Engineer
06-28-2013, 11:00 AM
Yes, most commercial films today are overcoated with a UV blocker.

And no, I don't like to coat in total darkness either. I've worked in a black lab too many times to know it is not easy and therefore I commonly work in safelight conditions with, at most, ortho films.

PE

Hexavalent
06-28-2013, 11:54 AM
As an aside, if you want to see some truly bizarre color->grey rendering, try some short IR imagesetter film - it's UV/blue and red/IR sensitive, with a green blindness. (It does require some tricks just to get the focussing right).

wildbillbugman
06-28-2013, 12:43 PM
You do not have to work in a Black Room. A Cheap (~$200) generation 1 IR manacle takes a bit of adjustment. But I use one all the time. Worst part is- distorted depth perception.
Denise- Not to be cynical, but "almost there" can be much longer than "halfway there". You and I are working with different systems. But I hope that, once you get "There" you will publish info on TLF.
Ian, If you know the dye system of IR imagesetter, just add some erythrosine and you have a panchro emulsion. No?

Hexavalent
06-28-2013, 12:50 PM
Hi Bill,

I though of treating some imagesetter film with dye, but there's no practical way to get the goods into the film. It's designed for very rapid processing (under 1 minute), and as such the existing dyes, anti-halo etc., wash out if one tries to soak it in erythrosine (or other) solution.
Imagesetter film doesn't make a very good camera film, but it does make a very durable film base if it's fixed and washed :)

lunarcaustic
01-17-2014, 04:38 AM
Can anyone confirm that participants will actually coat, expose, and print plates during the 2014 Handmade Gelatin Dry Plate Making Workshop?
The course description indicates that students will make a silver bromide emulsion suitable for plates to be used in the camera but does not mention the experience of coating, photographing, and printing. Is this a separate workshop?

The 2013 workshop looked most interesting.

Regards,

George

Photo Engineer
01-17-2014, 02:00 PM
George, they did all of it in previous workshops. From start to finish.

PE

lunarcaustic
01-17-2014, 06:06 PM
Thank you.

By the way I purchased your book and DVD's - I'm Hooked! I first developed film and enlarged photos in 1970. In 2010 I purchased a Crown Graphic on Ebay and rejoined the hobby. I really missed the hobby for all of those years. As a Chemical Engineer the topic of VAg and the science behind it is interesting. I have found several patents, applications and papers from RIT that describe the process. I have also read all of your posts on this site. I have even obtained the Computer programs Kodak once used to control the reaction - fascinating stuff.

I hope to make the August Workshop. My wife suggested it as a Christmas gift.


Regards,
George

Photo Engineer
01-17-2014, 06:36 PM
What is the name of the conputer program? Just curious as there were several due to having some computers obsoleted. They also differed according to scale.

There was also a set of programs that allowed for the design of emulsions in the office which then wrote code for the various computers.

Thanks for buying the book and DVD. I hope it works out well for you. The RIT papers are not as "deep" as the patents. I suggest some of the patents in the book by Lin et al. And Judd et. al. In some of them they are co-inventors.

PE

rwhb12
01-18-2014, 06:32 AM
80361

Russ

lunarcaustic
01-18-2014, 08:29 AM
The computer code that provided the most complete information of how the process worked is titled “COMPSELECT”. From this reference, the RIT papers, and other patents, I was able to cobble together the parameters for controlling the Crystal Habit from CubicCubo-octahedralOctahedralTabular. The targets were given for the initial potassium bromide concentration, temperature, along with the minimum and maximum bromide concentration breakpoints for each crystal habit zone. The formulas for the Nernst and Debye Huckle equations were embedded as well. The code also contained two-point calibration checks for the silver billet electrode. From all of this I was able to extract enough information to gain an understanding for controlling the silver ion concentration during the precipitation by modulating the salt and silver jet flow rates under PID control and ramp segments. The evolution of this process from the art of making silver halide emulsions to the science of making them is interesting.

George

Photo Engineer
01-22-2014, 02:52 PM
George, much of the details and references are also in my book, as you know.

COMPSELECT was written in QNX and so would have to have a bit of translation. It was replaced by MERLIN. Also, there were programs for the Taylor, Siemens and WDPF computers.

There are patents on the Debye Huckle and Nernst equations. Lots of detail.

BTW, click on the title of a workshop in the GEH list and you get an expanded description of the course.

PE

Photo Engineer
01-22-2014, 06:26 PM
George, I can find no on-line reference to COMPSELECT.

PE

lunarcaustic
01-24-2014, 05:52 AM
Ron,

This program is written in BASIC. It contains routines for selecting the Halide type: Br, I, and Cl and allows the user to enter a make with up to 15 segments in the flow-profile with holds.

It has ability to pre-heat the z-batch and utilizes both shallow and deep temperature sensors. It also has routines for storage and retrieval of the various “makes” should you want to repeat a particular flow profile. There are also subroutines for VAg calibration whereby the silver billet, triple junction reference and temperature probes are immersed in standard solutions and checked for proper operation.

There are detailed error routines for detecting any drift along with suggested possible causes such as noisy signals caused by faulty connections, plugged junctions, leakage rate of the salt bridge solution and poorly platted silver electrodes. It offers corrective actions to replate the silver billet electrode, and replace the lower bridge junction. This combined with the RIT papers and your many posts on VAg have given me a clear understanding of the topic. All-in-all, it lays out the details necessary to construct a working system migrated to todays programming languages and single-board microcontrollers.

On a related thread you mention the need for higher purity silver for the electrodes and importance of the uniformity of plating. I purchased two lengths of high purity silver rod, diam. 7.0 mm, 99.99%, Sigma-Aldrich item number 26,562-4 (10 grams = 25 mm or 40 grams = 100 mm) for fabricating the silver Billet electrodes. I am planning to round-off and polish the end of the rod to achieve a "bullet" geometry and mount it in the end of a Teflon rod prior to plating. I hoping this smooth-surface geometry will improve the uniformity of plating over wire-type electrodes.

George