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So you want to print onto inkjet photopaper? Great! As wide-format inkjet printer manufacturers have improved output quality, many users want to take advantage of higher-resolution printers, archival inks, and more realistic color to produce extremely high quality prints on photopaper. But which paper do you choose? With all of the options available to professionals and consumers alike, it's easy to either feel like a kid in a candy store or like a lost soul in a maze. With different base papers, thicknesses, brands, coatings, and gloss levels, you might feel like the lost soul. This article will shed some light on the key differentiators between coated photopaper grades so you can make the right choice.
There are many criteria that can be used to select a photopaper for any given application. The list below reflects the most important criteria often used when building a varied portfolio of photopaper products or when selecting the right product for the application.
Brands
Choose a brand and a reputable supplier that you can trust to provide a dependable offering of the products you regularly use. This will ensure consistency in base papers, coatings and performance.
You can choose the same brand as the printer you purchased, a brand not affiliated with a printer, or traditional analog brands. All will likely have a portfolio of products ranging from inexpensive to premium. To determine which is the best choice for your application, look beyond the brand to the paper specifications.
Not all brand owners are media manufacturers, but they rely on the actual manufacturer to produce high quality materials. Most of the traditional analog photographic consumables manufacturers also manufacture digital inkjet products to their own specifications. Many of the inkjet printer manufacturers' brands (OEM) are typically designed to work optimally in their equipment, but are not necessarily guaranteed to work in other manufacturers' printers. Also available is a large assortment of non-OEM product compatible with a wide range of printer makes and models.
Gloss Levels
The best way to check if a photopaper meets your desired gloss level is to get a sample and print it. If that isn't possible, look for a gloss number that many reliable inkjet suppliers will publish on specification sheets. Typically the higher the number, the glossier the sheet. However, not all gloss numbers are created equally. Some gloss levels are recorded at 60 degrees, some at 85 degrees, etc. The degree is the angle of the light source in relation to the horizontal base paper; 60° is the standard reference measurement angle for gloss as described in ISO2813 and ASTM D253. So when comparing numbers it is best to ensure the units of measure are consistent.
While this way of gauging gloss is consistent on paper, to the human eye the end-result print may not always look the way the numbers might suggest. For example, a microporous—or instant dry—photopaper with a gloss level of 45 may appear as glossy as a non-microporous photopaper product with a gloss level of 70. In this case, the different coatings can affect how the gloss finish looks so it's important to understand all the components of the media. More on microporous photopaper later in this article.
Another caveat is that some products change gloss once printed. This is not a desirable effect and is called "differential gloss" because the image turns out to be more or less glossy than the white, unprinted background. If gloss levels are critical to you or your customers, always get a sample roll and print it before making any final judgements and know that the amount of ink you apply can affect the final gloss of the print.
Standard Gloss Definitions
- Glossy. The holy grail of the inkjet paper community,this level is defined as equivalent to silver halide (traditional photopaper) gloss photos. Though the two technologies are dissimilar in the application of color, inkjet photopaper manufacturers are coming quite close to achieving the goal. Not all inkjet photopapers will attain the same gloss result. Print a sample to see if the end result will produce glare or reflections if displayed under direct lighting.
- Semi-Gloss / Luster. This finish delivers a lower gloss level typically achieved by adding some matting agent to the coating. The finish can also be achieved by using a base paper with a less-smooth coating, or one that starts with lower gloss level. A semi-gloss finish helps to cut down on glare when the image is displayed under direct lighting.
- Semi-Matte. The finish appears as a slight gloss verging on a matte sheet. This is usually achieved by adding more pigment to the inkjet receiver coating. There is virtually no glare to this finish but it may sacrifice some color gamut versus higher gloss products.
- Matte. This is visually similar to a matte paper but still on a photographic base paper. It can handle heavier ink loads than standard matte papers without paper cockling.
Calipers and Grammage
Inkjet photographic papers are available in a wide range of calipers or thicknesses. Caliper is typically measured in mils where 1 mil = 0.001 inches. Most photopapers range from 5 mils to 10 mils in thickness with 10 mils often being the choice for portraits or unmounted photo-reproductions. The thinner grades are typically used when paper heft and stiffness are not a required premium.
Occasionally the basis weight of the paper is used to differentiate various photopaper offerings, and the unit of measure is typically expressed in grams per square meter (gsm). The gsm is measured by weighing one square meter of photopaper and reporting its weight in grams. Basis weights ranging from 150gsm to over 300gsm are common. However, the relationship between caliper and basis weight is not linear. Some papers with higher basis weights can actually be thinner than their lower basis weight counterparts.
Ink Compatibility and Universal Media
Some media are designed to work with specific printer and ink sets, and others are promoted as "universal," or the ability to work with most or all printers and ink sets. First, let's define "work." It means different things to different people. Paper suppliers express it in terms of product compatibility. Most users will concur that a paper product works when:
- the inks dry quickly enough to handle and finish in seconds or minutes, not hours
- it has excellent image/dot resolution and broad color gamut
- the colors don't bleed into one another when the maximum recommended amount of ink is applied
- the prints will last over a pre-defined amount of time
No one media works to the same standard with all printers and inks, but it should work well across multiple printer platforms with different ink sets. Generally, matte products and microporous products tend to work more universally across printer and ink platforms. Always test before you buy, as all universal media are not alike.
Microporous Coating
Microporous photopapers refer to the inkjet receiver coating applied to the photopaper base. A microporous coating is constructed with millions of microscopic pores that enable the inks to absorb into the open spaces in the coating. These spaces promote rapid ink drying, improve ink smudge resistance and enable greater compatibility with a wide range of inkjet inks. More photopapers are being produced with this coating as they work extremely well with the UV stable water-based pigmented ink sets that deliver excellent print longevity. A downside to these coatings is that if printed with most dye-based inks, the media must be immediately laminated or the image will fade quickly even if it's not exposed to light. While immediate laminating is an option for professional print providers, it is not always practical for many shops that do not own laminating equipment.
Resin Coated Paper
Most of the premium inkjet photopapers use the same base papers as those used in the traditional analog photo industry. These papers are constructed of a high quality cellulose paper sealed with a water insoluble resin on one or both sides. This resin coated (RC) base provides added stiffness, flatness, and a moisture barrier to prevent problems later in coating or imaging. These base papers are then overcoated with other value-added layers including inkjet imaging layers.
RC papers cost more than other non-RC options, but they are well worth the price. They excel at jobs requiring heavy ink loads because they won't cockle, ensuring easy handling and finishing. The ink will stay in the inkjet coat layer, which retains image density and color pop. RC papers also provide the highest gloss levels as most high gloss photopaper is typically on an RC base.
Other Base Papers
Many non-RC grades have base papers that are cast-coated or highly calendared, producing finished inkjet grades with only semi-gloss or semi-matte finishes. These paper products have difficulty holding heavy ink loads without base paper distortion or image show-through. However, the price point is attractive. These base papers cost less, resulting in a lower overall product price/performance position. They can be a great value if a high gloss isn't needed or the job doesn't require heavy ink loads.
Proofing Grades
Although many papers can pass as proofing grades, jobs that demand ultimate color stability and consistency require a different paper construction than those created for appealing photo displays. The variables that cause color instability and inconsistency are myriad, so this segment will focus on a few photopaper-related causes.
Optical Brighteners
Many base papers and coatings contain optical brighteners (OB) that help produce a paper with a blue-white finish. This color is more appealing to the eye than a yellow-white finish and is in demand for most photo applications. The downside is their tendency to fade over time resulting in a color shift in the whitepoint of the paper. Lower amounts of traditional OBs mean less color shift over time. Some products are available without OBs and can often be the best choice if color shift is a key concern. All OBs are not created equally, and there are next-generation designs available that shift more gradually over time. Ask your supplier or contact the media manufacturer about this if you are unsure.
Product Specifications
For tight tolerance proofing applications, ask your supplier or the manufacturer for base color and image color performance specifications. The manufacturing process and specifications used to make and coat these papers varies from manufacturer to manufacturer.
Media Coating / Ink Interactions
If color consistency is important, check the product specifications for specific ink set mentions. Not only will the ink chemistry impact image stability, but its interaction with the coating on the photopaper will have an effect as well.
Sizes
Although this seems too simple to mention, not all photopapers are available in standard sizes. This seems to be most often true with products that are designed to fit specific printers. For example, many 44-inch products that are designed for Epson printers won't fit on a 42-inch HP printer, even if a supplier claims the product is universal. If you don't see the size you want in the product you prefer, ask your supplier if it can be special-ordered. Often enough, customer requests drive these sizes to eventually become standards, so don't be shy about speaking up.
With all of the choices available today, it can be a confusing to obtain the right product that meets your needs. If you're not getting the results you want on the paper you have, switching papers is not always the first answer as you may be jumping from the frying pan into the fire. The media is just one leg of the stool. Ink, printers, RIPs, profiles, printing environment, and post-processing can all play a critical role in the level of printing success on photopapers. If you're not sure which media to use, choose a reputable, knowledgeable media supplier that can help you navigate the maze.
Dan Halkyard is Director of Wide Format Supplies Marketing for Océ Imaging Supplies. He is responsible for all wide format media including display graphics, reprographics, and CAD product lines. For additional information, visit www.oceusa.com/imagingsupplies.
author: DAN HALKYARD