Kodak ENDURA Papers User Manual

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ENDURA Papers

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KODAK PROFESSIONAL ENDURA Papers

The following pages discuss light and thermal stability as they apply to Kodak’s newest generation of professional color negative papers, KODAK PROFESSIONAL SUPRA, SUPRA VC Digital, and

LTRA ENDURA and ENDURA Metallic papers.

Since the earliest days of photography, people have wanted to increase the stability and extend the

ongevity of captured images. As the medium

l evolved, ongoing improvements in image stability, as well as the discovery of new challenges to image stability, have been the rule.

The introduction of KODACHROME Film for color movies and slides in the 1930s brought new stability challenges related to color. In 1942, Kodak announced KODACOLOR Film for prints, the world’s first true color negative film. The advancements of color technology into prints allowed color photography to expand rapidly into the professional portrait/social and consumer environments.

It was at this time that Kodak recognized the need for dedicated testing facilities to examine the stability of images. Since then, the company has invested in and expanded its testing capability continuously for over 50 years.

As advances in technology have improved image stability and reduced major concerns, new, more subtle c silver halide-based photographic materials of all manufactur need for more precise measurements of image stabilit have also brought a need for a better understanding of these factors:

•

• how the different uses of images affect

The following pages discuss these factors as they apply to Kodak’s newest generation of prof PROFESSIONAL SUPRA, SUPRA VC Digital, and ULTRA ENDURA and ENDURA Metallic Papers, and will cover the f

oncerns have arisen. In the last 15 years, the

s have improved significantly, creating a

er time periods. New technologies

er long

y o

omplexities of how images on modern

the c photographic print materials fade

e lif

imag

sional color negative papers, KODAK

opics:

wing t

ollo

ow materials are processed and used by finishing

• h

laboratories

• how prints are used and stored by the end-user

• what image stability means today

• the importance of the ways in which image stability is easured and interpreted

Note: In this discussion of image stability, we

ssume that the process conditions in the finishing

a lab meet specifications set by the manufacturer of the photographic material. A process that does not meet specifications can have an impact on image stability that is as large as or larger than any of the variables discussed here.

Philosophy of Product Design

Obviously image stability is a decisive factor in the design of color photographic paper. In fact, it would be possible to design a paper solely to optimize image stability. However, designing and optimizing for a single criterion such as image stability will often degrade other key factors.

During the last 20 years, the design of Kodak silver halide color papers has been driven by a three-prong strategy, coupled with continuous improvement. While a typical Kodak color paper has more than 60 individual design parameters, we follow three major design criteria:

• image quality today

• image quality tomorrow (i.e., print longevity)

• ease of use in the finishing lab

In many instances, trade-offs between the major crit

eria would be possible. For example, excellent

image quality with accurate color and pleasing flesh

eproduction depends on the image dyes formed by

r the paper, so color and flesh reproduction could be

omised t

ompr

c dyes optimized for image stability can be more process-sensitive, which can cause difficulties for the finishing lab.

o achie

ve good dye stability. Similarly,

• objectives in the design of photographic materials

KODAK PROFESSIONAL ENDURA Papers involve no

24°C

years

100

log days

Inverse Kelvin

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.0031

.003.0029.0028.0027

uch trade-offs. Both the dye set used and the

s emulsions and curve shape drive short-term and long-term image quality, as well as ease of handling and processing.

Kodak has supplemented its three-prong design philosophy with continuous improvement between major development programs. Ongoing improvements keep products fresh by adding new technology as it becomes available. Over the last 20 years, we have made a multitude of improvements in image quality and lab operations in addition to image stability.

As the stability of papers improves, the testing

ecomes more complex. Predictions of image

b stability are based on accelerated testing, and the accuracy of predictions depends entirely on generating test data that are low in noise. Figures 1 and 2 show a hypothetical example of two different

apers tested for thermal stability. One paper is

p more stable than the other, but because of time

imitations, both samples were tested for one year.

Figure 1

Four-Point Prediction

—Linear Fit

KODAK PROFESSIONAL ENDURA Papers, however, are truly revolutionary. Made with advanced dye technology, they represent a major leap forward in

Linear Fit

Log Days = 13.04666 + 5229.7488 Inverse Kelvin

image stability and print life without sacrificing image quality, while also enhancing ease of use in the lab

In the professional market, flesh reproduction is the paramount image-quality criterion. In many color papers optimized for image stability, image quality and flesh reproduction suffer. But the three new dyes in KODAK PROFESSIONAL ENDURA Papers have been optimized for excellent image stability without degrading color reproduction or flesh reproduction. SUPRA ENDURA Paper has additional patented technologies specifically designed to optimize flesh reproduction through modifications

es combined with precise curve-

o the imag

e dy

shape control in the emulsions.

Testing Methodology and Modern

aper C

Stabilit major degradation pathways, and includes testing for light fade, thermal fade (degradation due to heat, often referred to as “dark fade”), and base

omponents

y testing of c

olor paper

s focuses on the

igur

enerat

e 1

s four data points based on fade

sho

ed from four high-temperature conditions. The points form a straight line with a high linear correlation coefficient, and the extrapolated prediction of room-temperature performance is 100 years. Given the correlation and the statistically calculated error from this extrapolation, the high

w limit around the predicted 100 years is plus

and lo

he actual performance may be

or minus 40 y

ears. T

as high as 140 years or as low as 60.

degradation. Although we will not discuss the specifics of imag important to understand the major challenges in

e-stabilit

y testing here, it’s

performing the tests correctly and in interpreting

est data.

the t

log days

Inverse Temp

0034.0033.0032

.0031

003.0029.0028.0027

24°C

ears

200

Figure 2

Bivariate Fit of Log Days by Inverse Temp

testing, which predicts a material’s stability over

00 years, is used. Because the test is so highly

1 accelerated and run in such a short time, it cannot detect the impact of ambient ozone. Only after images were displayed in the real environment, which included low levels of ambient ozone, was the

rue stability determined. Then it turned out that

t product stability was measured in weeks, not years.

As Kodak added new resin stabilizers to increase the stability of the paper base, Kodak scientists encountered another example of a test becoming difficult to use because of noise in the data. The then-current accelerated test to measure cracking and crazing of the resin was no longer generating

—Linear Fit

Linear Fit

Figure 2 shows a straight-line extrapolation to 200

years. However, because the paper is more stable than that in Figure 1, only three data points are available. Because of noise, the three points are scattered around the predicted straight line. With only three points and the higher noise, the correlation is lower and the error band is higher. So while the straight-line extrapolation predicts a performance of 200 years, the statistically calculated error is very wide and quite nonlinear. According to the plot, the paper could last as long as 600 y running the test for a longer period of time would

e more precise prediction with less error around the pr

In light-fade testing, using only highly accelerated tests can lead to significant errors because of

ecipr

r we now know that some inkjet materials are highly susceptible to image fading due to very low levels of ambient ozone in the atmosphere. outcome when only high-intensity light-fade

ears or as few as 50. In this example,

entually g

enerate a fourth data point to give a

ediction.

ocity and other external factors. For example,

Consider the

the normal response of cracks that would predict long-term resin stability. Instead of trying to accelerate the test further and risk the creation of even more noisy, possibly erroneous data, Kodak scientists looked to the molecular level for a predictive mechanism. They made measurements of the actual decay of the resin molecules and found that those measurements provided a good correlation to the prediction of long-term resin stability.

In these times when companies, including Kodak, introduce new products at a faster pace, it is tempting to run image-stability tests for shorter times with greater acceleration and noisier data. It would be even worse to use the high end of the statistical noise to promote a product as more stable than it really may be.

t Kodak we do neither. We continue to run highly

A accelerated light- and thermal-fade screening tests, using high light levels and high temperatures.

, we verify the results with less accelerated

How tests by using lower light levels and lower temperatures. Although these tests take significantly longer, often more than a year, the data is much more reliable. We use only this data to support product claims for image stability. We take

xtra time to generate reliable data because

the e

D.E. Bugner, D. K Reciprocity Failure Resulting from the Accelerated Fade of Inkjet Photographic Prints,”

Technology,

opperl, and P

Proceedings of IS&T’s 12th International Symposium on Photofinishing

2002, pp. 54–57.

. Artz, “Further Studies on the Apparent

of our commitment to report image-stability data

ccurately and to maintain integrity and credibility

a with our customers.

These same four degradation mechanisms also

pply to inkjet materials. However, we must also

a consider other mechanisms:

Kodak is very confident in the revolutionary image

tability of KODAK PROFESSIONAL ENDURA

s Papers. To further demonstrate this confidence we commissioned a major study with the Image Permanence Institute at the Rochester Institute of Technology. Through this study, we not only achieved independent substantiation of Kodak’s own internal testing, but learned that in fact our intrnal claims were conservative.

Defining Print Life— Degradation Mechanisms

Defining print life requires information on the mechanisms that degrade prints and which mechanism first becomes limiting. This often requires knowledge of the environment in which the image is stored or displayed, because different degradation mechanisms may outweigh others in different environments.

In silver halide-based color papers, four mechanisms contribute to determining print life:

• degradation of the dyes caused by heat

• degradation of the dyes caused by light

• yellowing of the minimum densities (D-min) due to light or heat

• ambient moisture (relative humidity)

• atmospheric pollutants

• direct water contact

• fingerprinting

A multitude of tests, reports, and conclusions from many sources have described the significant advancements made in inkjet light stability. However, while the thermal stability of most inkjet systems is quite good and very significant improvements in colorant stability due to light exposure have occurred, promotion of products based on light-stability testing is extremely misleading when it ignores the other important degradation mechanisms. To describe print life accurately requires taking all degradation mechanisms int

o account. A material could have excellent light- and thermal-fade performance but poor print life if the colorant stability is poor when exposed to moisture or atmospheric pollutants.

For a more detailed discussion of the degradation mechanisms and image-stability performance of

2,3

Kodak inkjet materials, see the references

below

as well as the technical papers found at:

http://www.kodak.com/eknec/PageQuerier.jhtml?p

q-locale=en_US&pq-path=98#technical_papers

adation of the resin base

degr

•

ample, a resin-based color paper may have

or e

F very high light stability but only mediocre resin

y in the base. It will perf

stabilit

orm very w

ell in tests for light stability. However, if it is stored in an environment where the base degrades faster than

omes

the dy

ellent light stabilit

es, ex

y bec meaningless. In this example, degradation of the resin base is the limiting mechanism.

It is extr

emely important to recognize that the life of the image may not necessarily be limited by the stability of the image dyes. A manufacturer who talks about “dye stability” or “light stability” alone, or who uses only light-fade data to describe the performance of a product, is very likely not

esenting an accurate prediction of print life.

D.E. Bugner and C.E. Romano, “Printing Memories to Last a Lifetime:

standing Imag

Under

ger Magazine, 13(1), 2001, pp. 134–140.

echar

D.E. Bugner and P. Artz, “A Comparison of the Image Stability of Digital Photographic Prints Produced by Various Desktop Output Technologies,” Proceedings of the International Conference on Imaging Science 2002, 2002, pp. 308–310.

e Stabilit

or Ink Jet P

y f

rints,”

+ 9 hidden pages