Proofing continues to be a challenge for the flexographic printing industry. In part one of this series, analog proofing pros and cons were discussed. This article will deal with the three types of digital proofs: remote, soft and hard proofing.

There are two basic configurations for remote proofing. The first is where a color-managed device is installed at a customer's site, allowing the customer to generate his own proofs. The second is where a color-managed device is installed at another facility. Both locations would be connected electronically using LAN, WAN, or FTP. The file is "dropped" into a hot folder, routed and ripped using third-party software, and then automatically output on a proofer.

These methods can greatly reduce the production cycle and some systems can even be color-managed using the internet. The downside is that it can be hard to control multiple monitors and output devices at offsite locations. Remote proofing requires extremely close coordination between sites, and third-party software and services can get pricey.

A soft proof is an RGB image displayed on a monitor. This can vary from a customer viewing and annotating a PDF file, to third-party vendors that allow multiple collaborators to simultaneously view a file in real time. They're generally used as quality-control proofs.

The advantages of this method include the elimination of days from the production cycle and use as a tool for the initial art stages. The data generated can be color-managed and sophisticated systems can use high resolution streaming data.

Cons are that color calibration between monitors can be difficult. The methodology is based on additive color theory (light) rather than subtractive (printing) color theory. There is no hard copy to follow. Also, a monitor can reproduce millions of colors, whereas printing can only reproduce thousands.

There are three types of hard proofing: laser ablation, drop-on-demand inkjet and continuous inkjet.

Laser ablation: A laser blasts away tiny spots of actual ink pigment from an ink sheet directly to the substrate (Latran Technologies Prediction) or dyes from a donor sheet to a receptor sheet (Kodak Approval). It is most always used as a contract or profiled contract color proof. The proof can show dots and PMS, and spot colors can be simulated. Ink/dyes can be put on the customer's substrate, and densities can be varied (with Approval). Fixed densities (with Prediction) are necessary to meet multiple color standards (SWOP, FIRST, Eurocolor, GRACol, Pantone Hexachrome). The downside is that standard inks are based on SWOP (litho) standards, and equipment and consumables can be expensive.

Drop-on-demand inkjet: Small drops of ink are dropped on the paper depending on the need for color. This is mainly used for concept proofs, often called "scatters." This method is fairly inexpensive, both for the equipment and the consumables. It has large output capabilities and is an excellent remote-proofing device. Strikes against this method are that it is dimensionally unstable and there is inconsistent color between multiple devices. Detail is not rendered well and proof appearance can be grainier than continuous.

Continuous inkjet: Charged particles of ink are continuously sprayed by a nozzle, deflected in flight and routed to a waste tank. Uncharged particles of ink continue onto the substrate. This is used as a profiled contract proof. This method offers excellent color reproduction and calculated overprints. It is easy to color manage and like devices can reproduce very similar results. Customer substrate can also be simulated. Cons are that the equipment is moderately expensive, as are the consumables. It has a limited color gamut due to its CMYK print engine. Because the proof is similar to 150-175 line screen, at times more detail will be in the highlights than are achievable on press.

The choice of method or methods to use depends on a few things.

1. Intent. Is the proof for color or just for position?
2. Does the proof need to show dots?
3. Is cost or time an issue?

There is often the need for multiple types of proofs to aid in the approval process, and those used will depend on the players involved. When all is said and done, the proof must be able to match what the press can do. It is only with this mindset that the flexographic process will become more predictable and continue to gain in profitability.

Steve Utschig, Consulting Technical Editor, 920/735-4882, utschig@foxvalleytech.com