Henry Wilhelm Interview
By Chris Maher and Larry Berman
in the November 2003 Shutterbug Magazine

Chris and Larry: Your work as a pioneer in the field of image permanence has shown you both the good and bad about ink jet printers. How can a photographer pick an ink jet printer that they can trust to make prints that will be around for decades?

Henry Wilhelm: The simple answer is to pick a printer for which print permanence data is available for the ink and media combinations used for that printer.

Chris and Larry: Where can that data to be found, and how much credence should someone give to a manufacturer who claims a given expected lifetime of a print?

Henry Wilhelm: I think the important thing is that first the manufacture would describe or at least have available a description in some detail how the tests were done. In the case of HP and Epson, both of those companies have primarily relied on our company (Wilhelm Research) to do the test evaluations and then they make that information available, or steer people to our web site or to publications that are quoting it. Canon, with its initial launch of its photo printer also did that. More recently, Canon has been publishing data generated by them selves that uses similar but not identical test procedures. I think that one important issue here is that the paper itself, particularly with the dye-based inks, can have a significant impact on the permanence of the image, and not only in terms of light stability. In other words, there is not just one single permanence figure for a printer with its ink set.

Chris and Larry: That is an excellent point. It is not just the type of ink that will affect the image stability, but the combination of the ink and paper used. When a manufacturer says that their printers produce prints that will last a certain length of time, one should carefully look at the exact paper and ink combination they used. Is it safe to assume that they always use their own papers with their inks in testing?

Henry Wilhelm: Yes, although manufacturers themselves often will publish data just for their paper that does the best, even though they have additional papers available.

Chris and Larry: So if one reads that a given printer will make a print that will last for a hundred years or more when displayed, one should immediately ask exactly what paper the test was done on. Often that is not stated very clearly. Would it be safe then to believe that, using the exact ink and paper, one can probably achieve the same kind of archival image stability?

Henry Wilhelm: Yes. Most of the quoted numbers have been for exposure to light on long term display. In general, the data have been for prints framed under glass. I think we also need to talk about susceptibility to ozone for prints that may be exposed to ambient atmosphere for long periods of time. Prints that are not framed under glass, for example the classic refrigerator display conditions or prints tacked to the wall in your office, things like that. Especially smaller prints which will never be framed under glass. There is a special concern about porous or microporous papers with dye based inks and greater susceptibility of these papers to ozone. I think from the reader’s standpoint, the simple way to distinguish between porous and microporous and swellable papers is that if the paper package says instant dry. That’s pretty good assurance that it is a microporous type. And if the printer is using dye based inks, which the majority of current desktop photo printers are using, then you can probably assume that your prints on microporous paper probably has a high susceptibility to ozone. You have to be careful there.

Chris and Larry: Tell us a little more about swellable verses microporous papers and what is the squeak test that we’ve heard about?

Henry Wilhelm: Well the squeak test is a simple means of identifying microporous high gloss papers. Just rub your finger across it – if the paper feels like it squeaks and sort of grabs your finger that is caused in part by the papers being so absorbent that they absorb the tiny traces of oil and moisture off your finger which act as a lubricant on smooth surfaces. Nevertheless, I think looking for the designation “instant dry” is a good way to identify microporous paper, and will probably more useful for most people. It is a pretty accurate way to distinguish microporous from swellable.

The swellable ink jet papers use an ink receptive coating on the surface that is more akin to traditional photographic gelatin. In fact, gelatin is one of the polymers frequently used in swellable papers – usually in combination with others. When the ink hits the surface of the print, the image receptive coating literally swells up. In areas of high-density ink coverage it can take a number of minutes, or even longer depending on the ambient humidity and the paper and ink combination, before it actually feels dry to the touch. The ink and its dyes are absorbed into this now swollen layer and then, as the water evaporates, it then shrinks down back to its original surface thickness with the dyes to some degree encapsulated in it. That encapsulation provides a significant amount of protection from the ambient atmospheric gases.

There is a parallel with traditionally photography here. Traditional black and white photographs have an image composed of pure metallic silver, which looks black because its very finely divided filamentary structure absorbs light instead of reflecting it. But if it wasn’t for the protective affect of the gelatin emulsion and the overcoat in which that silver layer resides, black and white photographs in many environments would only last a day or two before the image would become stained or discolored.

Chris and Larry: You have greatly clarified the role of paper in image permanence, can you tell us about pigment versus dyed based inks?

Henry Wilhelm: Traditional color photography has always used dyes in its films and print material, whether it is Ektacolor, Fujicolor, or any kind of type C prints. Even Ilfochrome or Cibachrome are dye based. It actually has not been possible to use pigments in most color photography processes. In the distant past there was tri-color carbro and a few other esoteric processes that used color pigments. But they are very difficult processes, requiring image sized separations in black and white, definitely not something the typical photographer would ever manage to do. But historically, it is interesting to note that the very first photographic color prints, by the French inventor Ducos Du Hauron, back in the late 1870’s, did use pigments to form the image using glass plate separation negatives. One of those prints is in the collection at the George Eastman House.

In a nutshell, dyes are dissolved in the ink vehicle, or dispersed in the image forming layer, at the molecular level itself. Consequently, they are very, very small. Pigments, on the other hand, are insoluble and are much larger particles. As classes of colorants go, pigments certainly have the possibility of having much higher light stability. They are also usually much more resistant to ozone, or gas fading as it’s referred to. Pigments have other advantages as well. They have very little short-term drift. In other words, when you print the image, after just a very quick initial drying phase, the image will change very little over time. For people using color management, making profiles of each paper and ink combinations, that’s a very important consideration. Dye based images tend to drift more. And if you are using a tightly based color management system, then that may create some real difficulties.

Chris and Larry: Earlier you had talked about microporous instant dry papers, and compared them to the swellable encapsulating papers that take a while to dry. Will that longer drying process actually affect how the image looks when it first comes out of the printer compared to when it is totally dry?

Henry Wilhelm: Yes, to some degree it can. But the same problem can occur with some dye-based ink and microporous paper combinations.

Chris and Larry: So you can look at a print when it first comes out of the printer which is just great and a couple of hours or a day later come back and say, “wait a minute, that’s not the same image that I saw before.”

Henry Wilhelm: That would be true. Now, it’s a different kind of change, it’s not fading, normally. But it may shift in color balance somewhat. The density may change slightly and not necessarily uniformly over the density scale.

Chris and Larry: So, one can’t just simply say that a print gets lighter or darker or shifts in a certain color direction.

Henry Wilhelm: No. And it would depend very much on a particular ink set and the paper it’s on. It would be even difficult to generalize. Some are much more stable in this respect than others. With traditional color photography, people could not evaluate color prints until they were completely dry. Papers like Ektacolor or Fujicolor appearance changed rather remarkably in the course of drying so there is certainly no similarity here. However what is different is that in traditional color photography once the print is dry coming out of an RA4 process, then it is highly stable in terms of this short-term drift phenomena. In other words, in weeks or months later it will not change. With a dye based ink jet print that’s not necessarily so, and it partly depends on the environment you’re in. If you are a photographer in Miami, Florida where the humidity is very high this may be a more serious problem. On the other hand pigmented ink systems have very good short term drift behavior. Pigmented ink systems also tend to be waterproof.

Chris and Larry: Could you tell us about the differences between the systems that use four, or six or 7-inks. Is there a difference in the stability or is it simply a tonal issue?

Henry Wilhelm: Well actually, it’s both. Historically the use of dilute magenta and dilute cyan inks would typically cut the light stability or display permanence by a factor of two or even three times. Those inks were more susceptible to fading on exposure to light. Now, with Hewlett Packard’s newest system used in the PhotoSmart and other HP printers using dilute magenta and cyan inks, that is no longer true. In fact, the 6-ink implementation of that is much more stable than the HP 4-ink implementations on HP’s photo papers. That’s a departure.

One thing I’ve learned in this field is to be very careful about universal generalizations. Even if they might be true at one point in history, with new products introduced a few months later they might not be true. I think my previous caveat about light or display permanence of 6-ink systems with dye-based inks is really no longer true.

The rational for using the dilute inks, whether it’s dye based or pigment is to improve smoothness of tone. When you see a printer rated at 1440x720 DPI, those DPI figures or resolution numbers are actually true only at only maximum image density. The only way an inkjet printer can make lighter tones from darker inks is to leave droplets out, or to some degree by varying the droplet size. In an image produced even with a nominally high-resolution printer using only 4-inks, that leaves a feeling of granularity or lack of smoothness to the image. This is especially true of the tonal gradations in lower densities like the highlights in someone’s face, for example.

Chris and Larry: Is that why you can see a dither or some kind of dot pattern in some four color printers?

Henry Wilhelm: It’s a feeling of what I call a granularity or texture that doesn’t have the same smoothness. The use of dilute inks, the magenta and cyan, allows many more dots to be laid down by the printer for the same density and that means there is less white space in the lower densities. In addition, all other things being equal, color saturation is also improved with 6-ink systems because in middle and lower densities there is less desaturation of colors because of the visual mixing of the white space between ink droplets that occurs with 4-ink systems. This is particularly important for portraits or landscapes that have subtle skies. Many types of images benefit greatly from this. And that is why the dilute inks were developed in the first place. It’s better for photographic reproduction. Yellow ink is very low in image contrast, so there really hasn’t been any perceived benefit to having a dilute yellow.

Now with the newest Epson printers, the 2200 and the large format units like the 7600 and the 9600, there is a seventh ink, a dilute black, which gives two benefits. One that in the near neutrals it allows significant replacement of the color inks with black inks through much of the tonal scale. It’s called GCR, or “grey component replacement.” That allows for a more accurate and linear reproduction of the neutral scale. Also, because the black ink, especially in pigments, tend to have higher stability, it can increase the overall stability of most images, especially in terms of color balance shift. It also allows a satisfactory printing of black and white images, which was more difficult before. It also reduces what is called Metamerism or metameric failure, which a color print may look significantly different when viewed under different light sources. For example, daylight verses tungsten halogen verses florescent. You certainly want to minimize that to mimic what human vision does. The use of the dilute black has improved that significantly.

Chris and Larry: What other factors should photographers consider when they choose a printer, paper and ink?

Henry Wilhelm: I think there are several other performance distinctions between dye-basedinks with microporous papers, dye-based inks with swellable papers, pigmented inks with microporous papers, and pigmented inks with swellable papers. One is that at this point in time that there really isn’t really a completely satisfactory high gloss media for pigmented inks. There are certainly satisfactory in terms of image permanence, however they do exhibit what is referred to as differential gloss. In other words, the gloss of the image is to some degree a function the density of the ink. If you look at the reflection of light off the surface of a print, you will notice that. This is something traditional color photographs never had a problem with. The gloss of your Ektacolor or Fujicolor print, if it’s a high gloss surface, looked completely smooth. Dye-based inkjet is capable of printing on high gloss papers, either swellable or micro porous and exhibiting little if any differential gloss. So that’s something to consider.

Microporous papers both with dye-based and with pigmented inks are in general, waterproof once they dry. At least they are for short-term exposure if you should spill water on them. Swellable papers are not. Now of course as photographers we all know it’s not a good idea to get your prints wet no matter what they were made with, but this is a somewhat increased level of vulnerability.

At this point in history it’s difficult to say, overall, which system is better, if, particularly for small prints, what we think of as 4x6 photo finishing prints, where most people seem to prefer high gloss prints. That’s been a tradition, certainly in this country. If that is what your goal is, at this point in inkjet technology you’re pretty much restricted to dye-based inks. And with the microporous or instant dry papers, which have wonderful image quality, very good water resistance, and the instant dry feature, the shortcoming, which is potentially very serious, is susceptibility to ozone or other airborne pollutants. Again, pigmented inksets like those used with the Epson professional photo printers or the Hewlett-Packard large-format printers, in general have better light stability, and good water resistance. But again, from a photographers point of view, one of the biggest drawbacks is the lack of a completely satisfactory high gloss paper. Now for larger prints, this is not so much of a problem for many photographers because they prefer the sort of semi gloss or luster surfaces anyway. So this gets down to a personal preference question, and I think you do see a sort of split in both the printers and the way photographers are using them, that in general people who have use small prints, traditional photo finishing snapshots 3x5 or 4x6’s in general prefer high gloss papers. For those people, dye-based inks may be preferred or even essential in order to get the perfectly smooth high gloss surface.

Chris and Larry: Is lamination a possible solution?

Henry Wilhelm: Lamination can be a very good solution. It’s just that, certainly on the desktop, and even for fairly large-scale use of small prints by photographers, that it’s an extra and potentially expensive step which the laminator itself may cost more than the printer did.

Chris and Larry: Going back to glossy surfaces vs. luster, can it be roughly broken into two camps? The amateurs that are shooting for snapshots and passing prints around to their friends and the professionals that are shooting something that they would like to outlive them as it hangs on a wall somewhere?

Henry Wilhelm: I think that’s a good point. Again drawing the analogy from traditional photography that the wedding/portrait business historically has not used high gloss photography papers, but rather the luster or semi-gloss. And the transition to ink jet with pigmented inks is much easier. It’s the same kind of surface basically that’s been used all along. And once large prints are framed under glass, it’s much harder to see the surface reflections.

Chris and Larry: What about fingerprints?

Henry Wilhelm: Fingerprints also, but I wouldn’t say that inkjet prints are particularly more or less susceptible than traditional photographs were. And I think most photographers have learned to handle their prints reasonably carefully.

Chris and Larry: That’s probably true of serious photographers. Perhaps real amateurs and the friends they hand prints to may not be so careful.

Henry Wilhelm: You mean the home snapshot amateur much less so, and you’re correct. But I think that even the microporous dye-based prints or the swellable high-gloss prints are reasonably resistant to fingerprints, or at leas the immediate evidence of fingerprints. Fingerprints, as far as we can tell with these products, do not have a major impact on ink jet permanence.

Fingerprints certainly did affect the initial types of dye sublimation prints before the manufactures began protecting them with a clear coating after the image layers were in place. Over time the oils from your fingers could cause the dyes to start migrating physically. In the earlier Kodak dye-sub prints, this would manifest itself in the fingerprint becoming visible as a red image. The cyan dye became mobile in that system. The early dye-sub prints were also extremely susceptible to contact with plasticized PVC sleeves such people have in their wallets or PVC notebook pages.

I think all of this shows a parallel to the completely new modes of deterioration such as susceptibility to ozone that are possible in any new imaging technology. Traditional black and white RC prints are another example of this. They suffer from a kind of deterioration in which low-level oxidants are generated by the top polyethylene layer of the paper, especially when framed under glass, which then in turn attack the silver image. That’s a mode of deterioration that did not exist with traditional fiber-based black and white prints.

It’s really easy to forget that the entire inkjet printing field, at the photographic quality level, is a very young field and could be dated to 1994 on the desktop when Epson introduced the first 720 dpi printer. For a field that is less than 10 years old I think that an astonishingly amount of progress has been made.

Chris and Larry: Going back to our discussion of dye vs. pigment, there are actually some affordable desktop pigment inkjet printers now.

Henry Wilhelm: An important part of this whole discussion of pigmented verses dye is that Epson has introduced 4-ink plain paper office printers that do use pigments. The Epson C80 was the first. The Epson C82 is the printer currently on the market. These are reasonably inexpensive, 4-ink systems that use fully pigmented ink sets. They offer the advantage of actually being waterproof on plain paper. That has not previously been possible with dye-based inks. And the light fading stability is the best of any general purpose desktop printer.

Chris and Larry: The Epson C82, from what we’ve seen of it, makes a remarkably nice picture, but it’s not photographic in quality.

Henry Wilhelm: Right, particularly when you get into the low densities, it is not up to the image quality level of the 6-ink or 7-ink photo printers. Now this brings us to the HP printers that can function as either 4-ink or 6-ink printers. The new HP PhotoSmarts, the 7150 the 7350 and the 7550 all have that capability. And so does the HP desktop printer, the 5550, which is a modestly priced office printer. The DeskJet 5550 is sold with a 4-ink configuration. It has a pigmented carbon black black ink. Pigments have long been used on HP printers for the black for printing text, both because of the sharpness of it and the nominal waterproofness of the black ink. Waterproof ink on plain paper is desirable if you’re using it for addressing envelopes that might get wet, or restaurant menus and things like that. That’s one thing people have always liked about laser printers is that their images are waterproof.

With the new HP printers one can simply take out the black cartridge and replacing it with what HP refers to as a photo cartridge that converts it from a 4-ink printer using a pigmented black, to a 6-ink printer using a dye-based black. The reason for changing the black of course, was to for the ability to print on high gloss photo papers. These are the first printers on the market that can switch between four and 6-ink capability. And I think that for particularly the snapshot photographer at home, that’s a significant advantage because it means that one printer can do everything. It’s an excellent plain paper 4-ink printer or you can switch to 6-inks when you want to print high quality long-lasting photographs.

The top of the line new HP PhotoSmart printer, the 7550 actually has all three cartridges in it and it, by the choice of paper, if you pick plain paper it will automatically switch to the 4-ink mode, with carbon black. If you pick one of the photo papers it switches to the 6-ink mode with a dye-based black. Within the industry, I consider that to be an historic development in that for the amateur desktop this will be increasingly be seen as a desirable approach. You only have one printer connected to your computer and it’s only taking up one printer area on your desk, which usually is pretty crowded.

Chris and Larry: Are other manufactures going to follow HP lead?

Henry Wilhelm: Keep in mind that that in the HP printers, the cartridge and head are one in the same. That allows instant change without worrying about residual ink in another head. That made this process easier for HP to do it. Epson has its piezo heads, which are permanently built into the printer, and Canon’s heads are nominally permanent with separate ink tanks. However, there’s nothing that I’m aware of that would prevent those manufacturers from simply switching off the dilute inks when you wanted to print on plain paper. I don’t know if this will happen in the immediate future, but I think it at the amateur home level, that’s a very desirable capability. I think there’s a lot of misunderstanding between the four and 6-ink printers, and a lot of people focus on whichever DPI is the highest, kind of ignoring the much larger difference between four and 6-ink. Lexmark, at this point in time does not have a 6-ink printer option, nor what we consider a high stability photo ink set.

On the level of advanced to professional photographers, it really boils down to Canon, Epson and Hewlett Packard possibilities.

Most of us in the image permanence field, including myself, never really expected to see a 6-ink dye-based photo printer with the level of light stability that HP has achieved with their newest ink set and paper. That was a major breakthrough. I think that there was sort of a foregone conclusion that pigments would be the ultimate answer, and I think that’s not so quite clear now. On the most stable paper combinations, in these cases HP Premium Plus Photo paper, the light stability of prints on display is comparable to the pigmented inks in the UltraChrome inkset currently used by Epson.

Chris and Larry: Now that gets us to the next question, which is about the color gamut or the color range. The consensus has long been that the colors in the pigment sets were not as rich or as vibrant as the dye based ink sets. Is technology changing that?

Henry Wilhelm: The previous pigmented ink sets that the Epson’s used, which was known as the archival ink set and used in the 2000P and the 7500 and 9500 large format machines, was what we considered an extremely high light stability pigmented set. With many types of media it would go past 200 years in our standard display conditions test. Epson came to believe, in part because of the very question you’ve asked about the color gamut of pigment verses dyes, that photographers wanted higher color saturation and larger gamut and sacrificed some of the light stability of the previous set to achieve that. And that’s sort of a classic trade off that color photography’s always dealt with at one level or another, that if you could ignore permanence completely that virtually every system would have a larger gamut and higher saturation than actual systems on the market do.

The initial pigmented sets used by HP on their large format machines, like the 5000 or 5500, are extremely high stability 6-ink systems that are capable of being used for a reasonable length of time, even in outdoor graphics. Epson’s UltraChrome inkset could be thought of as the first pigmented ink set introduced by a major producer designed for indoor use with a reasonable gamut, which takes advantage of the permanence advantage that the pigments have. They also have advantages like short-term color drift, resistance to high-humidity environments and so on. I think we are seeing very interesting developments in the field right now where there are viable pigment systems that most photographers feel have adequate color gamut. If any difference is really noticed with the UltraChrome inkset it’s probably not so much the color gamut as it is maximum density, or the depth of the blacks, which kind of anchors the sense of brilliance of the image.

Chris and Larry: What is the single biggest factor that causes print fading with today’s inkjet printers?

Henry Wilhelm: Especially with any of the dye-based printers, whether it’s Epson, HP or Canon, one really needs to be aware that the choice of paper can have a huge affect on the outcome as far as permanence. It’s not just an image quality question.

An example that we always cite is our tests with Staples Premium Glossy Photo paper. The new HP printers with their ink set and HP Premium Plus Photo Paper received a 73 year rating. The same printer and ink with the Staples paper was rated as lasting only two years on display! It can be that dramatic.

Our company, as a matter of policy, has pretty much stayed away from the image quality questions, leaving that to people like your selves. I will say that it’s a very multi-parameter problem.

Chris and Larry: Optimum print quality is certainly subjective. Experimenting with different ink and paper combinations can yield a rich range of image tones, but can yield unexpected image stability issues. I found I really liked the way Canon printers produced black and white images on Epson heavy weight matt paper, but the images were not very stable.

Henry Wilhelm: Yes, I think a good example of that is if you like the flat matt papers as many photographers do, that if you were to print on Summerset Enhanced using dye-based inks, you can produce absolutely stunning prints with a high d-max. However resulting prints are extremely unstable with dye-based inks on every platform, including the Iris printer. After you make the print and look at it you’ll say great, but six months of display later it may look anything but great. There’s no way to know that out of the box - it gets back to the point where if you don’t have specific information available about the permanence of your ink media combination, you’re potentially going to have a disaster, or something somewhere in between reasonable and disaster.

I think one of the real differences that has developed in photography in the past few years is the ability of the average photographer, including rank amateurs or school kids at home, to have the ability to make their own color prints. That was simply not possible before without a major investment in equipment. Most photographers took their film to a lab. It could have been a mini lab or a higher end professional lab. But the choice of paper usually was not one that the photographer made. They might make a choice of surface, like high gloss, semi gloss or luster, but the paper was the same. Now that has completely changed.

If you walk into CompUSA or Best Buy, there’s a huge shelf full of paper and the end user is now actually choosing and buying paper to make color prints and that never existed before in photography. That’s one of the things that’s become confusing because people have been offered a huge array of different papers at different prices, most of them claiming to be excellent in every respect. You even see it on the Kodak Ultima inkjet papers, which, on the front of the package, says it makes “long-lasting prints” as sort of a general statement.

Certainly one thing I would advise people to be very aware of is that the papers made by Kodak and the other third-party companies -- that is other than the printer manufacturers themselves -- are all advertised, without exception, as being suitable for all printers. It means that in the formulation that they are not optimized for any particular inkset or printer. They are using a “one size fits all” approach and that means that they don’t fit any of them well compared to what the printer manufacturers can do because they design their papers specifically for their inksets.

I think that nowhere is that more evident in HP’s new photo inks and Premium Plus Photo Paper, which is available in both a gloss and matt surface. At this point in history, I would consider that ink and media match to be the most highly engineered match of an ink set to a paper yet in terms of permanence. And it kind of points where I think the field is going. That these are highly specialized products, and particularly with the dye based inks, a proper match between ink and media is critically important.

Contact Us

email Larry Berman - larry@bermanart.com

412-401-8100