Cross Rendered Proofing



This article discusses the application of modern dye based inkjet printers as accurate proofing devices for other print processes such as CMYK offset printing or laser based Print on Demand (POD) processes.

If you're considering having a book or calendar printed, either a high volume run done on a traditional press, or a low volume run from one of the new Print On Demand services (like Lulu.com, for example), then this article will show you how to preview and edit your work for that print process.

We discuss hardware selection and the three steps required to achieve accurate colour proofs.

Note: This is a basic to medium level discussion of cross rendered proofing. As always there are more complex ways of doing things, but this method should generally provide very useful proofs with very little effort and expense. If you find this article interesting, you might also find Simulating Traditional Processes with Cross Rendered Proofing interesting as well.

Introduction

The modern dye based inkjet printer is a near ideal device for inexpensively simulating other print processes, due to it's versatility with different media, extremely wide colour gamut, stability in terms of colour output, and cost of running. When set up properly it can provide proofs that are very accurate to the final output, with a fairly simple process.

While an inkjet printer is not as cheap to run as laser based devices (such as the Fuji Xerox Phaser devices which are often used in this context), the print quality, and therefore proof accuracy, on offer from inkjets is much higher. In many environments, it will make sense to have two proofing devices - a cheap-to-run laser printer, for proofing of layouts and the proofing of very long documents, and an inkjet printer for final colour accurate proofing.

Note: I am discussing the production of proofs for your own benefit in this article - not what is known as a 'contract proof'. A contract proof is one produced by your printing company that you agree to. A contract proof then constitutes a binding agreement between you and your printing company as to what the final output will look like. The proofs we discuss here are perhaps better termed 'guide prints' that you can use to simulate the final printing process as you develop your work. However, many printing companies can't (or won't) provide contract proofs, and so then this is perhaps the next best possibility of getting some idea of what your final output will look like.

Selecting an inkjet to use as a proofing device

The key qualities you need from an inkjet printer that you wish to use as a proofing device are:

  • Wide colour gamut - this allows you to simulate the entire gamut of your final output device, and have some room to spare.
  • Versatility with media - so you can proof for a variety of final output media.
  • Speed - you will want your inkjet print to be relatively quick, waiting 30 minutes for a full page print is often simply not practical.
  • Size - this refers to how large the printer can print. For most users, an A3+ proof is about as big as you every really need in practice, even if the final output will in fact be bigger.
  • Relatively cheap to run - of course if the proofs cost you a few dollars but save you thousands by preventing you from making a more costly mistake downstream in the process, then they are well and truly worth it!

The key qualities you don't need in a proofing device are:

  • Pigment inks - since these are simply proofs, it makes sense to use cheaper dye based inks that have a wider colour gamut and significantly better print quality. The one exception to this rule is if you want to very do high quality black and white proofing, in which case you will need a pigment ink printer with a specialist black and white printing mode such as the Epson SureColor P800.

The two major players in the inkjet market are unquestionably Epson and Canon. HP also have some nice printers but they are a very small player in the Australian market in comparison to the other two.

Epson pretty much abandoned the dye based inkjet printer market several years ago. In this time, Canon have become the clear leaders in this field, and their range of printers are very fast, cheap to run, work with a huge variety of media, and have a colour gamut that is unparalleled by the pigment ink printers popular in the fine art market.

The three things you require to produce an accurate proof

To achieve an accurate proof for a printing process requires the following three things:

  1. A properly calibrated high quality monitor for initial soft proofing on screen.
  2. Knowledge of the final printing process in relation to measured ICC profiles and printing standards.
  3. A properly profiled inkjet printer using paper stock that is a good match for the final output stock

More details on these three things to the left.

There are a number of articles you can read about colour accurate monitors, monitor calibration and calibrators, so have a read of the articles below to give you an overall understanding on this topic.

Monitor Selection and Monitor Calibration

Once you have a high quality, colour accurate monitor, you will be able to accurately soft proof your final output on screen before making any prints at all. This is great, but no real substitute for an actual hard proof. We have some notes on soft proofing in Using ICC Output Profiles.

Although this discusses soft proofing with a custom RGB inkjet profile, the process is the same if you are soft proofing using a CMYK profile or a printing standard. Simply go into Proof Setup in Photoshop, choose your ICC profile or printing standard, and follow the instructions in those notes to perform a basic or advanced soft proof.

Accurate knowledge of your final print process

To create an accurate proof of a final print process, you need to have some understanding of the process and the final output stock that will be used.

You will need to discuss this with the company doing your printing. Presses and POD (Print On Demand) machines are generally run in one of two ways.

1. The printer can supply you with an accurate ICC profile that is a true measurement of their device's behaviour on the actual output stock - this is the ideal scenario, but it's very rare to see this in practice with presses, although increasingly more common with POD systems.

If they supply you with an ICC profile, then you can follow these instructions to install and use the profile.

2. They will be able to identify to you what printing standard they are printing to - it will have a name such as 'US Web Coated SWOP' or 'Euroscale uncoated' or FOGRA 39 Coated, or similar. These are installed with Photoshop by default. Your printer may alternatively give you a disk with a '.CSF' file on it that you can load into Photoshop.

Either way, once you have accurate knowledge of the final print process (and assuming your printing company actually achieves this colour in practice), then you are well on your way. If your printer can not give you either of these things (an ICC profile or the name of a printing standard), then it's a very bad sign and may be a good idea to look into using another printer who does.

Setting up your inkjet as a proofing device

The final step is a custom ICC printer profile for your inkjet printer on a stock that is as close as possible to your final output stock.

You should consider the following characteristics when choosing a proofing stock - the goal of course is getting the closest possible match to the final output stock:

  • Surface qualities (matte, gloss, semi-gloss etc)
  • Weight and thickness of the stock
  • And most importantly - colour and brightness of the stock.

Brightness is typically expressed in ISO terms (eg. ISO 87), and the colour can be judged pretty well by eye, although for best results you will want to match the presence or absence of optical brighteners in the two stocks. You can measure (and therefore match) the colour of paper white using a spectrophotometer. We are also able to do this for you if required.

All that said, the proofing process itself (see below) will compensate to a large extent of difference in the proofing stock and the output stock, however the proofing stock should be at least as bright as the final output stock. Ink can be used to make a bright stock duller, but it can not be used to make a dull stock brighter.

A classic proofing stock is Epson Archival Matte paper. It's cheap, has great print quality, and is a very bright white. At 180 gsm, it is similar in weight to many stocks used in high quality books etc. Canson PhotoSatin is a very effective proofing stock for satin output.

Once you have chosen your proofing stock, you must then have an accurate custom profile made for your printer and this stock. Full details of this process can be found below.

The process involves making a special print on your printer (carefully following the instructions) and sending that in to us. From this we can create an accurate colour map of your specific printer on this specific stock. We email this back to you in the form of an ICC profile with instructions, and you plug this into Photoshop and follow the process below to achieve your accurate proof prints.

You can of course use the profile both for proofing another printing process and also for simply making very high quality, colour accurate prints on your chosen stock.

SKU Price (inc) Qty.
Custom Black and White Printer Profile Custom Black and White Printer Profile
$50
Custom RBG Printer Profile Custom RBG Printer Profile
$50

Putting the pieces together - Absolute Colorimetric Proofing

The final proofing process is fairly simple. Firstly, you can leave your files in whatever form they are currently in - RGB/CMYK etc makes no difference. There is no need to do a conversion when making the proof, Photoshop can automatically do this for you 'on the fly'.

At this stage, your monitor should be properly calibrated, and you should have a custom ICC profile for your printer and proofing stock. If not, read the notes above and sort these things out first, or you won't get very far with the notes below.

Stage One - Basic Soft Proofing

Follow the instructions for soft proofing as given above and soft proof the final print process (ie. set up a soft proof using either the ICC profile you have been given by your printer of by choosing the ICC profile for the print standard they have specified such as FOGRA39).

At first, try a basic soft proof (i.e. do not simulate the paper colour or ink black). This will show you colour shifts but not density/contrast. Prepare to be dismayed. CMYK processes can be less than wonderful and particularly with reproduction of primary, saturated Red, Green and Blue colours. The inks used are Cyan, Magenta, Yellow and Black and although these colours reproduce very well, the opposite colours (RGB) can be difficult.

You can edit your image with this soft proof turned on, to try and correct any shifts in colour. However you are now working within the boundaries of a specific print process, so it may simply not be possible to achieve the colours you hope for. Remember - it's usually more important to be convincing with colour than technically accurate.

Stage Two - Advanced Soft Proofing

Now, go back in to Proof Setup and turn on advanced soft proofing - tick the simulate paper colour and ink black boxes. You will now see a pretty dramatic shift in the contrast of your image. The soft proofing notes explain this in greater detail, but be aware that simulating a low contrast print on a high contrast monitor is very difficult for the eye to get used to. You should really just use this view to look specifically at difficult areas within your image - deep shadows, very high highlights, very saturated colours etc, to see if these areas are holding detail and remaining as smooth as you need them to be.

Don't be alarmed by the sudden drop in contrast - the final print, when viewed as a print under any normal conditions, will not look as weak and wishy washy as the on-screen proof probably does.

Again, you can edit your image with this proof view on to try and get your image into a better state for printing with this process. That said, you may be better off making a hard proof at this stage as the advanced soft proof view can fool you into thinking you have a problem which may not actually be a problem in the final print. This type of screen view is generally a lot less forgiving than the actual print.

Stage Three - Making a hard proof

This process is known as cross rendered proofing. It's pretty simple to set up.

The screenshot below is from Photoshop's 'Print With Preview' command (from CS2 but the process is exactly the same in CC).

The following points are important:

  • The document profile should have whatever colour space your image is currently in
  • You should select 'Proof' below this as you're not doing a straight print of the file, but a proof print of a print process
  • We let Photoshop Determine Colours
  • We choose the custom ICC profile for our printer plus proofing stock
  • Under Proof Setup Preset we choose 'Current Custom Setup' which uses the same settings we set up above in the Advanced Soft Proof section.
  • We tick 'Simulate Paper Colour' so that Photoshop will use ink to simulate the paper colour of the final output stock if necessary.

Now, hit print. Make sure you set the settings in the printer driver into the exact state required for your custom ICC profile (as per the instructions which came with your profile).

The proof print you will now receive from your printer should now accurately reflect the final print process.

Exactly how accurate this really is comes down to how accurate your ICC profile for your printer is (if made by us it will be very accurate) - and how accurately the actual printer you are proofing for matches the icc profile/print standard they print to. But it should be at least an excellent guide if you're working with a quality printer.