How is photography done for output to high-quality spot color presses?

Question

High-quality printing processes are capable of generating a much greater dynamic range in color, saturation, specularity and other characteristics than is possible for a camera to capture.

For example, National Geographic uses special, customized rotogravure presses with customized inks capable of printing metallized and iridescent colors. Before the digital age in 1977 there was the famous issue on Egypt featuring photographs of the hoard from King Tut's tomb:

How do photographers for such high-quality outputs capture images in a way that supports full use of these printers?

There is no "spot-colour press." A spot colour is simply an ink, toner, varnish (a colourless ink), etc. that can be used in any printing press. — Stan, Aug 16 '17 at 0:54

Alan Marcus · Accepted Answer · 2017-08-15 21:51:56Z

Rotogravure is the highest quality ink on paper imaging process. Indeed, this is choice of fine art reproduction. Spectacular it is but it cannot exceed what the camera can do. The Kodachrome film of yesteryear was the film of choice.

Technically a well exposed slide film, viewed on a light box or projected on a screen has a dynamic range that excesses 256:1. That’s 8 f-stops or more. The same film image printed on high quality glossy photo paper has a dynamic range of about 64:1 that’s about 6 f-stops. If printed on a nonglossy paper the dynamic rage drops to about 32:1 or less, that’s 5 f-stops.

Let me add, I am certain that a modern digital camera has exceeded the dynamic range of Kodachrome.

That being said, the stunning attractiveness of slide film and projected images pale when applied to paper. We view prints on paper by reflected light. An external lamp near the observer plays on the image. The light transverses the dye and hits a white paper base. The base reflects the light back through the dye to the observer’s eye. The point is, the light makes two transits through a photographic print. The photo print is limited to three subtractive primaries, cyan (blue-green) magenta (red-blue) and yellow. The Rotogravure adds a black as a key color to adjust for inaccuracies in the color of the dye. They should make black when superimposed but this has never been achieved. Additionally unlike pure photography, the Rotogravure process allows for more colors to be added to enhance. Again it’s the best of the ink on paper process perhaps only matched by the photographic dye transfer process which was also exquisite.

Hold on to your hat, this is a moving target and technology marches on.

So are you saying that there's no need to do anything special because a digital camera can capture a greater dynamic range than the print can produce? — user1118321, Aug 16 '17 at 3:50
@ user 1118321 -- Not so fast! A modern digital can have a dynamic range that will exceed film. The caveats: a. acquired skill b. worthy camera and lens c. appropriate lighting d. artistic skills e. steady hand or suitable support f. commendable subject matter g. exceptional luck. — Alan Marcus, Aug 16 '17 at 4:06

Stan · Accepted Answer · 2017-08-20 21:06:15Z

The bulk of (aesthetic and non-commercial) photographers do not work to support reproduction. They are subjective and take artistic license. Often their creations are original works not tailored for reproduction, per se.

Printers must strive to faithfully reproduce the captured original; however, any reproduction always contains less information than the original. The goal is to produce a reasonable facsimile consistently.
Edit: Commercial photographers who shoot work solely for reproduction try to work with conventional materials within limits of the reproduction process (print and display).
The National Geographic cover you show is such an example.
The workflow is:
1.) The photographer (technical, archival, etc.) attempts to capture as much of the subject as practical. Various kinds of equipment and techniques are involved. Camera, lens, lighting, environment, and many other factors are involved to capture detail of the original within the capability of the recording medium.

Edit: Ideally, all conditions are controlled to pull the photograph into the more limited dynamic range of the chosen reproduction process. Studio photographers, say, must adjust lighting ratios to keep the contrast within the more limited range of halftone printing to be an effective part of their job. Commercial photographers must always keep the ultimate use of their product as part of their technical requirements.
This means… Printing presses can reproduce only approximately a 4-stop range as measured at the image plane. (This might translate to a subject luminance range greater than that; 5 stops, say.) If your record is greater, you must compress the range, somehow, lose the highlights, or the shadows. There are many concessions. Therefore, even though you're capable of reproducing a very large density range, common sense tells you to record only information that can be reproduced on press.

The good people at Quadgraphics have a download there entitled: How To Create and Supply Digital Images; among other prepress tools.

Then…
2.) an attempt is made to reproduce the recording as faithfully as possible using known techniques, materials, and processes. The print process is chosen for the printed material (substrate) which determines the preparation of the materials for the process (pre-press).

Some visual effects such as a good approximation of colour can be recorded, some can be approximated such as the appearance of texture, some rely on optical effects and cultural cues to simulate reality such as perspective and depth. Metallic, Iridescence, and opalescence are a few of examples that still cannot be automated fully for reproduction; but, can be synthesized with foils, flocking, and laminations.

The magic happens in the application of spot colours, varnishes, and inks normally out-of-gamut in the 4-colour-process (4-C).

It is the printing materials used that determine the saturation, not the press. Fluorescent Da-Glo™ ink when lit by UV light is one example.

The dynamic range of most any camera exceeds the dynamic range of a printed reproduction.

There are four different flavours of printing. Offset, relief, gravure, and screen. Each has its pros, cons, and concessions to price and quality for a given job.

It's not over. Reproduction lags creation.

With the advent of wavefront photography (Litro) and new multi-lens image recording (Light Inc.) techniques, experiments are still underway to reproduce the results. Lenticular printing introduces other challenges to optimal image preparation.

Rafael · Accepted Answer · 2017-08-22 16:58:29Z

For example, National Geographic uses special, customized rotogravure presses with customized inks capable of printing metalized and iridescent colors. Before the digital age in 1977 there was the famous issue on Egypt featuring photographs of the hoard from King Tut's tomb.

Well, I am sorry to disappoint you. I went to my old collection and that has no special inks to reproduce metalized or iridescent colors. It is a standard 4 color separation print. (Click to enlarge)

I must say, the print is a bit "low quality" compared to today's standards. The lineature is bigger than the used today and the colors (probably washed out due time) are a bit dull.

(There is a small white space inside each dot of ink on the print, probably this is an indication of some type of flexography used, not rotogravure. I am not sure, this is an assumption)

High-quality printing processes are capable of generating a much greater dynamic range in color, saturation, specularity and other characteristics than is possible for a camera to capture.

No. All this premises are wrong. Not even in today's printing process is true, unless you use a special ink like a fluorescent one that has special capabilities like converting UV light to visible one, no.

Specularity is not about a standard color reproduction but an additional coat you can put over your print to give it a glossy finish.

Yes, you can tweak a file to make it more saturated, contrasted and colorful than the original one, then use a good quality ink on a good quality paper on a good quality machine, but in general terms, any print process has lesser gamut than any RGB one.

https://www.google.com/search?q=rgb+vs+cmyk+color+space&source=lnms&tbm=isch&sa=X&ved=0ahUKEwj1lJHPn-vVAhXJ5iYKHcsUDeMQ_AUICigB&biw=1920&bih=1012

There was a system that used additional Green and Orange inks called Hexachrome, that gave an additional push to this color ranges, but it is not used anymore.