TCPglobal - news, views and issues on total cost of printing

Issue #0636/1 - With two technologies contributing to this printer category, we briefly explain the technologies with their differences, features, benefits, advantages and disadvantages.

For reasons of practicality, only two printing technologies are used in portable photo printers – inkjet and dye-sublimation. Within the inkjet category, we find the usual two variants of the inkjet – thermal and piezo.

Of the players in the market, only Epson utilises Piezo inkjet technology while Canon, Hewlett-Packard and Lexmark use thermal inkjet technology and Kodak, Olympus and Sony base their products on dye sublimation technology.

Canon also includes inkjet technology in its range of portable photo printers and is the only manufacturer to work with both technologies in this category.

Dell had a portable photo printer in its line-up for a while, using Kodak’s dye-sublimation technology, but this product has since been dropped.

There are around 35 models to choose from, ranging in price from under £50 to approaching £200, so users must assess their needs before buying.

Prints from this category of printer are 10×15 (4×6). For prints larger than this, an A4 format printer is required.

Print technology – dye-sublimation

Dye sublimation is a kind of hybrid technology:

• Not quite thermal inkjet, ink is placed on the page using heat in the transfer process
• Not quite impact dot matrix, the technology has a finite resolution as if a series of pins were lined up across the page
• Definitely not laser, although some sources will quote it as ‘laser dye-sublimation’

Heat is the catalyst in the process but the ink transfer process is vapour-based. The ink is held on a thin film, from where it is vaporised while the film is in contact with the print media.

Data for each colour is processed individually, similar to a four-pass colour laser printer, and the image of that individual colour placed on the media before the next colour is processed. This means that the media has to pass backwards and forwards under the print head three or four times – once for each colour, CMY(K) – to allow the full colour image to be created.

So, the basic image creation method is identical to all other digital printing technologies in that the image is created from a vast grid of millions of dots of three colours – Cyan, Magenta and Yellow. Black may also be used for highlighting and printing of text but photo printers do not need black inks so the configuration is usually CMY plus a gloss or protective coating.

How it does compare very closely to thermal inkjet technology is in the requirement for a very small point on the imaging array (representing each pixel) to be heated to a very high temperature and potentially cooled again very rapidly in order to print, or not print, the next pixel.

In this instance, the print head is a fixed, full width array (usually 300dpi). So each of those 300 points per inch across the page is individually addressed by the imaging controller and the paper moved under the head to provide the two-dimensional aspect of the image.

Variable intensities of colours within the image are accomplished by varying the temperature of that point in the printhead - the higher the temperature, the more dye is transferred.

Therefore, it is by the rising and falling of the temperature in each heater in the printhead, combined with the movement of the paper under the array that the image is created.

Where the process differs radically from either laser or inkjet technologies is that vapours do not have hard edges so the coloured dyes effectively intermingle on the page to create an image that is continuous in its tonal qualities, giving very smooth tonal gradations.

Print technology – inkjet

For the purposes of introduction, inkjet technology is the process of firing droplets of ink from the nozzles of an inkjet gun (cartridge), often at frequencies of 35,000 droplets per second (from each nozzle).

These droplets create dots on the paper much like the dots printed onto paper by the offset lithography process used in printing of magazines and the like. It is the combination of different coloured dots placed close together (or even overlapping) that create the range of colours we see with our eyes.

However, inkjet printing technology needs no explanation because it is in such common usage. So the following section compares the two technologies in terms of print quality and practicalities of usability

Technologies compared

Dye-sublimation prints tend to be slightly inferior to inkjet prints in some respects but there are certain advantages to the technology.

One of these is the fact that portable photo printers may be used on a very sporadic basis – family weekends, Christmas, holidays and other special occasions when a few prints are required to give to a host or a guest, or perhaps to display on the refrigerator or in a frame on the sideboard.

I’m ashamed to say that my portable photo printer has not printed an image for more than a year – almost entirely because my whole family is so digital that, when glossy photos are printed, they are exclusively for hanging on the wall (in the early stages of teaching several of my sons to drive, I had to remind them that driving a car is an analogue process rather than a digital process like the representation of driving a car in a PlayStation game!!). In the last 12 months, we have had the weddings of two of our four sons – so the photo printers in the family have actually seen some action this year to print out about 60 shots of each wedding for ‘show-off’ albums. But, believe me – that situation is rare and they have been printed at home on A4 printers!

What this means is that my main photo printing comes from testing the printers themselves, including producing prints for psychometric quality testing on a human audience, and printing a small number of larger prints for display purposes!

Now, I do realise that my family is not typical. Many families do print quantities of photographs at 10×15 (4×6) size and their printers will see more regular action than mine.

However, the principal still stands that any portable photo printer runs the risk of sitting unused for months on end. During this period the nozzles in the ink cartridge of an inkjet machine may well dry out and clog up, potentially rendering it useless. In this situation, owners would be well advised to remove the cartridge and protect it in a garage unit when not in regular use, perhaps even attempting to vacuum seal it in a polythene bag.

Dye-sublimation printers, on the other hand, are not susceptible to this danger and can be lifted down from the shelf or out of the drawer at any time for that occasional quick print.

On writing this, I’ve just dug my portable inkjet photo printer carry case out from beneath a mound of other rarely-used items (at least I knew where it was!!), unpacked the printer, plugged it in, switched it on and received a perfect print first time! Well done Mr Manufacturer, no striping, no banding, no lost nozzles – after more than a year’s dormancy. Not what I had expected, I have to confess!

Another advantage of dye-sublimation technology is that the consumables unit is guaranteed to give an exact number of prints – no more and no less. So, owners know exactly where they stand both in terms of number of prints available and cost per print.

On the downside though, is the fact that images do tend to be a little softer than inkjet images both in photographic terms (contrast) and in terms of image sharpness. This is essentially because the dye-sublimation image is a continuous tone image (like a real silver halide photograph) whereas an inkjet printer produces half-tone images (made up of distinct dots that may or may not overlap).

In addition, image permanence of dye-sublimation materials is not as high as the latest inkjet materials.

For instance, Willhelm Labs rates the permanence of the best of Hewlett-Packard’s inkjet materials (Photosmart B9180 professional photo printer) for 230+ years, Epson’s best materials (Stylus Pro 3800, Ultrachrome inks and Somerset Velvet paper with post production PremierArt spray) for 166 years (both mounted under glass).

Speaking of 6×4 portable photo printers specifically, Wilhelm testing puts Epson inkjet materials at 96 years; Hewlett-Packard at 82 years; Canon right down at 41 years and silver halide prints from Fuji, produced at a high street mini-lab, at just 40 years. The best of the dye-sublimation prints are from Kodak with a rating of only 26 years.

Right at the bottom of Wilhelm’s current table are four dye-sublimation printers from Sony, Canon and Olympus, with image permanence ratings of only 4-8 years.

Oh yes, Lexmark’s P315 portable inkjet printer (with No.33 or 35 inkjet cartridges) rates very poorly at 16 years!

Therefore, based on these findings, from the image permanence point of view, Epson’s PictureMate is the best bet, followed by Hewlett-Packard but Lexmark inkjet and all of the dye-sublimation printers should really be avoided.

Looking at it from the angle of Cost of Printing however, the situation changes. Next week’s TCPglobal considers Cost of Printing along with the individual printers’ capabilities.

So far, we have presented the dye-sublimation technology in the light of producing inferior images to inkjet. However, there is also a sense in which the exact opposite is true.

Inkjet printers are dealing with discrete ink droplets and therefore discrete ink dots on the page whereas dye-sublimation is dealing with vaporised dye. Thus, vaporised dyes blend with one another and vapours for individual pixels in the image blend with those around them, whereas ink droplets are captured by the coating of the inkjet photo media.

This results in the sharp, and sometimes harsh dot-based, edges of inkjet images and the soft, indistinct edges of a dye-sublimation image mentioned previously.

These two images show the difference in the way the image is handled between the two technologies. At magnification, the dye-sublimation image looks sharper but at real size, the opposite is, in fact, true.

Now consider the accompanying images below. These are scans from a series of photographs printed on different photo inkjet printers. They illustrate the extent to which the ability of inkjet printers to reproduce the in this image vary hugely.

In the poorest of the images, there is a very visible, and extremely nasty, colour banding in the sky area whereas the better image blend the colours much more smoothly. The fault lies in the image processing of the printer and the ability of the printer to graduate the supply of ink smoothly. Instead, a sudden change in the ink flow causes a harsh and unattractive colour change.

Although I do not have a dye-sublimation print of this image by way of comparison, dye-sublimation printers are capable of producing even smoother tonal gradations than we see in the better of these two images.

Printer supplies

All manufacturers offer photo packs for their portable photo printers, comprising either dye-sublimation ribbons or inkjet cartridges with a specific quantity of glossy media designed to match the yield capability of the ink supply. These packs are great for portable printers because users can be assured of achieving a specific number of prints, giving them a definitive (maximum – in the case of inkjet) cost per print.

They also represent the cheapest way of buying the colour cartridge and media by a large margin!

These packs range in print volume from about 40 prints right up to 200 prints. However, as with laser printer starter toner cartridges, most portable photo printers ship with sample volumes of media even if a full ink cartridge is supplied with the machine.

For instance, the Kodak dye-sublimation machines ship with a 10-photo starter pack while inkjet machines tend to ship with a media sampler pack containing (typically) five sheets. These are fine for the user to experiment with but not enough to be productive with (I wonder why?)

For that reason, in the calculation of Cost of Printing in next week’s TCPglobal, it is assumed that owners will need to buy a photo pack before they can start serious photo printing.

Major features and capabilities

Although photo printing is not exclusively colour, the majority of prints made by consumers are colour and most of the portable photo printer devices are designed specifically to be colour printers.

With both machine technologies, the typical ink configuration is a tri-colour cartridge or ribbon, although Epson utilises both four-ink and five-ink configurations in its machines.

Not many devices are capable of printing true black and white. Canon has a black and white kit available for one of its newest dye-sublimation printers and some of the Hewlett-Packard printers accept the No.100 tri-grey cartridge.

Other printers, with a tri-colour capability only, rely on composite black (the combination of Cyan, Magenta and Yellow) to print black and white images – producing an image that is incapable of having the look and feel of a true black and white print.

So, enthusiasts who require a good black and white printing capability should take extra care in the selection of a printer.

Almost by definition, these printers are all capable of producing borderless prints. Likewise, they are all capable of printing photos from a computer via a USB interface and PictBridge has become a standard feature for direct printing from digital cameras.

Other uses to which some manufacturers may put the PictBridge interface are the connection of a proprietary hard disk drive, for mass storage of images (Olympus), or connection of a CD-R drive for immediate archiving of images onto CD from the memory card (Epson). Some printers even have integrated memory for the (temporary) storage of images (Hewlett-Packard).

These features are designed to allow the printers to be fully functional as photo printers independently of a PC.

Standalone use must be considered to be a major benefit of this class of printer. Some photo enthusiasts may well wish to be involved with digital photography because of the flexibility it offers but specifically not want to own a computer. A standalone printer not only allows them to access photo prints whenever desired but also allows travellers to carry a printer with them on which they can modify images, backup and archive images while on their travels and produce prints on demand. The printer may also enable the digital sharing of images with friends around the world or fellow travellers.

However, not all portable photo printers are fitted with memory card slots for direct printing, rendering those printers considerably less versatile and flexible and also tying the printer to a PC much more closely than those that are fitted with memory card slots.

One other major feature designed to facilitate standalone printing is an LCD preview display to allow images to be selected for printing visually. Many devices also include image processing, formatting and cropping capabilities for which the presence of a preview display is essential.

Although these printers are exclusively 10×15 (4×6) format devices, some have capabilities for printing panoramic images with a maximum width of 10cm but up to 30cm in length (Hewlett-Packard).

On the basis of this assessment, even though dye-sublimation printers do have some image quality and cartridge longevity advantages over inkjet, on balance most users will find the features and capabilities found in the inkjet devices to be more attractive.

I believe this is largely because the inkjet machines are produced by manufacturers whose primary understanding is imaging and printing, whereas the dye-sublimation machines come from stables where cameras and photography are the focus.

Next week we will see how the Cost of Printing affects the equation and draw some conclusions on which devices offer best value for money, combined with flexibility and versatility.

Next week:

1) Portable photo printers – lowest cost

Seven manufacturers are active with portable printers that can be bought for less than £85 but as low as £45. Here we compare the lowest cost machine from each manufacturer

2) Portable photo printers – highest cost

Four of the seven manufacturers also sell a high-end portable photo printer that cannot be found in-store for less than about £110

~End~

This entry was posted on Friday, November 24th, 2006 at 12:03 am and is filed under Hardware, Comparisons, Total Cost of Printing. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.