Category: labnotes

Newton Rings

Posted on Posted in da net, labnotes, the Lab

Newton rings are those colored irregular circles you may see when two smooth surfaces are in contact. Film touching glass is the situation most lab workers ask about. The common advice is to use anti-newton ring glass in the negative carrier. Alternate methods: control humidity (to around 40%) — use a spray such as odorless hairspray, use oil carrier, use talc powder.

So, disrupt the surface by making one of them less smooth. That’s the general idea; workable if you are using only one piece of film, however, in a mask stack you will have more than a single piece of film. These two sheets of film may have newton rings if placed back to back, or if one has a smooth emulsion layer. 40 years ago in labs we didn’t see this with Sep Neg type 1 (or 2) and Pan Masking film because Kodak had solved it with design of the emulsion. Now only Kodak Professional Tri-X 320 has the surface tooth; there for retouching — this film isn’t the best solution for masks or separations, alas.

Some possible products, or items to use to cut down on Newton rings. AN glass is available widely. It isn’t rare although reading the forums it seems to be lost and gone.

Some chemicals used in those anti-newton cans of the past: cerium oxide; STAYBELLITE ESTER.

Offset press powder consists of vegetable starch.

One supplier: https://stargraphicsupplies.com/categories/pressroom-supplies/spray-powder.html

Or, try SX 2001 Scannex Anti-Newton spray from: http://www.aztek.com/Products/Aztek%20Imaging%20-%20Scanning%20Supplies(main).htm

There is a patent on using spray to control newton rings which offers some advice along with a description of the problem. https://patents.google.com/patent/US4575398A/en

Darkroom Word Badges

Posted on Posted in babl, labnotes, minimum daily requirement, overnight notes, the Lab

the circle of craft, in which mastery gets you – nothing. Like old man in speedo; like strutting around the wading pool wearing a snorkel. Doing it the difficult way doesn’t make you better at the hard stuff.

Words come together over time as people try to say something meaningful about something new. We start with existing words, then alter them, or just use them differently. A recent example, wrong to me, but not to the lab selling the printing service. They call a C-Print from a laser printer “continuous tone” — what they think the C means. To me, C meant type C, a Kodak product from 70 years ago. Their sales group used the “chromogenic” print from the research department to brand their color printing paper. Today those papers are RA-4, after the chemical process. I’ve also heard people think C meant chemical. Time is timeless, meanings aren’t.

The need to distinguish is a driver in this pushing of meaning – molding distinctions as some new method manages to breath. Users may introduce a word. Labs have to route work to the group with that skill, so we have quick-print, machine-print vs. hand-print.

In the photolab printing has moved from contact, to projection, and enlargement. Kodak’s enlargers were Projection Printers until moves (cinema) dominated the market. Making “projection prints” didn’t make sense there; they projected prints onto a screen for Saturday’s popcorn crowds. In the 90s distinction was made in film labs between prints made using an optical printer or a digital printer. Kodak supplied emulsions to them as well as color paper for commercial and private darkroom printing. Addressing the exposure differences between incandescent, and LED/Laser lights meant devising an emulsion that could be printed in two different manners. From a piece of film in an enlarger, or from a digital output using and LED or Laser system.

Kodak literature lifted the terminology from the film world: optical, digital. An optical print or a digital print. The first publications put optical in quotes; by 2003 the quotes had been dropped. The word had changed, it burst out of quotes and was born as an Optical Print.

“There are two major differences between optical and digital printer balancing procedures. Optical printers typically are balanced on one density point; a gray target on a standard portrait (often known as a “Shirley”) negative. A typical balance is approximately 0.80 red, 0.80 green, and 0.80 blue. Digital printers typically balance on multiple density points ranging from just above the D-min of the paper to the D-max. Because of these multiple balance points, the printer can adjust for a straight line response if the process varies from normal aim through most of the density range.”