Evaluating the quality of output in epson inkjet
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The study evaluates the print quality output of an Epson Stylus Pro 7900 inkjet printer using design of experiments to analyze the influence of various printing parameters, including dot shape, screen resolution, and paper type on color gamut. Results indicate that the substrate's surface properties significantly impact color reproduction more than dot shape and resolution adjustments. Ultimately, the findings emphasize the necessity of profiling different paper types to achieve consistent and economical print quality.
![IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308
__________________________________________________________________________________________
Volume: 03 Issue: 01 | Jan-2014, Available @ http://www.ijret.org 41
EVALUATING THE QUALITY OF OUTPUT IN EPSON INKJET
PRINTER USING DESIGN OF EXPERIMENT METHOD
Ramakrishna Nayak1
, Prathap Nayak2
, Sandeep Nayak3
, Vinod Kamath4
Manipal, India
Abstract
The print quality in digital printer like Epson Stylus Pro 7900 is influenced by the various printing parameters and among these dot
shape, screen resolution and paper are considered to be the major. The study conducted here was to evaluate the print quality in
terms of the maximum number of color that it can reproduce on two different printing substrates at different dot shapes and
resolutions by maintaining other printing parameters constant. Linearization and profiling of the Epson stylus Pro 7900 printer for
all these combinations were completed using IT8.7-3 CMYK standard test target using Harlequin RIP V8.3 software. Then the color
gamut volumes are analyzed using Taguchi’s Design of experiments in Mini Tab software. This is done to evaluate the significant
parameter that has a major influence on the color gamut. From the result obtained in the project it was concluded that change in the
dot shapes and resolutions have less influence on the color gamut than the substrate’s surface property. The glossy effect of the Epson
proofing commercial 187 GSM paper has shown a significant change in the color gamut in comparison with the other paper
properties and printing attributes. There are different paper substrates available which are mainly made for use in ink jet printer and
since these digital devices are widely used for proofing and by photographers, it is better to take similar type of study to know the
print quality on different paper substrates and making a profile for each paper is a must for achieving a consistent print in more
economic way.
Keywords: Inkjet Printing, Color gamut, design of experiments, Print quality, Paper properties
----------------------------------------------------------------------***-----------------------------------------------------------------------
1. INTRODUCTION
Advancements in digital printing has made it possible to use
inkjet printers to get a high quality print for photography and
proofing work. When we say a four color printing using cyan,
magenta , yellow and black inks, it is not only these color inks
that are involved in reproducing a desired print quality, but
along with that there is a fifth analog color; the paper [1].
Printing on a paper substrate using inkjet process involves a
number of process parameters that one should consider to get
a quality and consistent output. Quality of a print is actually
measured by its color gamut and every printers aim is to get
the optimum print quality by controlling the process variables.
The smoothness and roughness factor of printing paper has a
significant role in producing maximum color gamut[ 2]. When
ink is laid on the paper substrate, the ink will try to penetrate
into the pores of the paper and the vehicle whether it is water
or solvent tries to evaporate or get absorbed and pigment will
settle on the surface. Surface roughness of the paper will affect
the pigment deposition and this also contributes for the
reduction in the color gamut [3].
When inkjet printers are used to produce the proofs for color
matching or photograph printing, it is very difficult to get the
color match in a regular printing or writing paper. For this
reason papers are manufactured especially for inkjet printers.
These papers are coated with different surface sizing materials
to improve their print quality. These coatings make the surface
glossier, smoother and fill the pores of the paper to reproduce
a higher color gamut [4]. Due to these coatings the spreading,
absorption and light reflection of the ink layer will be
improved and that is why a proofing paper will give higher
color gamut than that can be produced in a writing and regular
printing paper [5]. The surface coating is prepared with some
optical brightening agents (OBA) that further improves the
reflection, color gamut, print stability and light fastness on
inkjet coated papers [6].
Most of the ink jet inks are standardized in terms of their
optical and physical properties. So there will not be any such
variations in the ink for a particular manufacturer. But another
major parameter which is of serious concern is the printer
condition and the settings. To bring the printer in a standard
condition or to stabilize it a linearization process is carried out.
With linearization a printer is said to be in a controlled
position. A consistent and good quality print is possible only if
the printer is linearized using some software for each and
every combination of paper and image profile. [7].
Linearization and printing is accomplished using different
raster imaging processing [RIP] tools. Every printer is
supplied with its own RIP software and we can also use some
other third party RIP software also. When different RIP](https://image.slidesharecdn.com/evaluatingthequalityofoutputinepsoninkjet-140808022524-phpapp01/85/Evaluating-the-quality-of-output-in-epson-inkjet-1-320.jpg)
![IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308
__________________________________________________________________________________________
Volume: 03 Issue: 01 | Jan-2014, Available @ http://www.ijret.org 42
software is used the color gamut may vary, especially in case
of RGB platform as each RIP has its own color conversion
algorithms which cannot be controlled by the user. But in
CMYK platform it will not produce much more difference in
color gamut [8].
Linearization is also carried out to understand the maximum
and minimum print density of the printer. These values are
denoted by Dmax and Dmin which provides an idea about the
maximum and minimum ink film thickness that can be
deposited by this printer on a certain paper at particular printer
settings. Dmax and Dmin of inkjet printer depends on the ink
formulations, nozzle settings and the mechanism used for ink
deposition and these values also contribute for increasing
color gamut in the printer [ 9].
Along with linearization of the printer the next most important
print attribute which will affect the quality of color is the
image settings. The resolution, dot shape, screen angles and
the dpi of the image are of most important to get a high quality
image without affecting the clarity of the original image. As
the printer resolution is increased it will produce an image
which will be more like a continuous tone and beyond a
certain limit there will not be any further increase in the color
gamut. So a printer should know the optimum resolution for a
particular dot shape, screen angle, paper, dpi and for the
printer. It is also true that different dot shapes will result in
different amount of dot gain which will be further supported
by the resolution. Screen angle is one which is to be controlled
to get a clear image without any moiré pattern [10].
2. METHODOLOGY
The project “Evaluation of quality of output in Epson inkjet
Printer using Design of experiment method” is carried out
using the following steps. Two types of paper substrates,
Gloss (Epson Proofing commercial 187 GSM) and Matte
(Epson Semi matte proofing paper 90 GSM) with different
optical and physical properties were selected. Optical and
physical properties of the paper substrate were measured using
appropriate testing devices. Epson stylus Pro 7900, inkjet
printer was selected and its initial settings and nozzle checking
were carried out as per the manufacturer’s instructions. post
RIP software is installed in the system to produce the output
through Epson Printer. Two types of dot shapes, round and
elliptical were selected and these dot shapes were printed on
the above said papers with two different resolutions 720×720
and 1440× 1440 maintaining screen angle for CYAN15,
Magenta 75, Yellow 0 and Black 135 degrees. Linearization
and calibration of the Epson ink jet printer is done using the
RIP software for both types of paper at two different
resolutions and dot shapes. Characterisation and
standardisation of the Epson printer was done for two types of
paper at two different resolutions and dot shapes. Test target
IT8.7-3 CMYK(fig 1.) is generated using X-Rite Profile
Maker 5.5 software to evaluate the print quality by measuring
color gamut in the Epson printer. Test target was printed on
two types of papers using post RIP software at two resolutions
and at two types of dot shapes. The color values of printed test
targets were measured using i1iO spectrophotometer in
conjunction with X Rite Profile Maker 5.5 measure tool
software and profile for these measured data were generated
using CHROMIX Color Think Pro software. Color gamut
values[2] were tabulated into MiniTab software for analysing
at three factors and two level experiments using Design of
Experiment method. Subsequently the analysis was made.](https://image.slidesharecdn.com/evaluatingthequalityofoutputinepsoninkjet-140808022524-phpapp01/85/Evaluating-the-quality-of-output-in-epson-inkjet-2-320.jpg)
![IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308
__________________________________________________________________________________________
Volume: 03 Issue: 01 | Jan-2014, Available @ http://www.ijret.org 47
= 0.05, by default. The plot in this experiment shows that term
paper is only significant and dot shape and resolution change
are insignificant.
The Pareto chart displays the absolute value of the effects and
draws a reference line on the chart. Any effect that extends
past this reference line is potentially important. The reference
line corresponds to alpha = 0.05, by default. From the Pareto
graph generated in this experiment shows the paper only as the
significant term.
The DOE analysis says that the change in dot shape from
round to elliptical and resolution from 720 x 720 to 1440x
1440 dpi has not shown any significant changes in comparison
with the change of paper substrate. This is quite obvious due
to the small change in the dot shape from round to elliptical
and due to the higher end resolution that was selected for the
printing. If the dot shapes selected were round and square or
square and elliptical there would have some significant results
on color gamut. Similarly the printer shows similar color
gamut when it is printed using 720 x 720 or 1440x 1440 dpi
resolutions this is due to the fact that both resolutions are of
high end and printing with 720x720 dpi is optimum for paper
substrates. In addition to this when an optimum resolution is
achieved i.e. 720x720 dpi as here further increase in the ink
deposition will not contribute for enhancing color but instead
it will increase the amount of ink deposition and its
consumption which is not economical. The result would have
some significant effect if it printed with 720x720 dpi and
360x360 dpi or other dpi of lower range.
The DOE analysis strongly says here that change from Epson
semi matte proofing paper (90GSM) to Epson proofing
commercial (187 GSM) has a significant change in the color
gamut. When we compare the optical properties of these paper
grades, we can see that opacity, brightness and L a b values of
these papers are somewhat similar with smallest variation. But
when we compare the gloss there is a huge change in their
property. To get the gloss normally paper substrates are coated
and calendared with special treatment during manufacturing.
The glossy surface makes the light to reflect in specular way
and since these surfaces are coated they will not allow ink to
get absorbed into the pores of the fibers and due to these
properties of the coating the pigments of the ink will stay on
paper surface and reflect all the colors resulting in maximum
color gamut.
The residual plot versus Fits and fitted value is expected to
have values uniformly spread above, below and throughout the
length of the zero line then the model is correct on average for
all fitted values. In our experiment due to lack of data we
could see only eight values but they are equally distributed
from zero level so the model is quite fine and it is random in
nature. The Normal Probability plot also expected to have the
residual plots values uniformly aligned with the reference line
to conclude the errors are distributed normally and the
normality of errors assumption is valid. But in our experiment
they are not so aligned and more data might be required to get
clearer picture.
SCOPE FOR FURTHER WORK
In this experiment the two types of dot shapes taken were
having similar curvature and that could be the one reason for
having no significance of the dot shape on the color gamut.
There are so many other dot shapes available in the RIP
software, which have square, line and other shapes and using
such dot shapes similar experiment can be performed to see
whether the dot shape is significant or not. The two resolutions
taken for this experiment are of high end and found no
significant effect on the color gamut. The resolution options
available are vary from printer to printer and similar study can
be conducted to see their significance level.
The entire project is carried at a constant screen angle which is
one of the standards screen angle followed by the printing
industry. Some the printers based on the type of image
whether it is high key or low key pictures screen angle is
changed for individual colors. Further study can be planned
for other industry standard screen angles.
The significant factor that was found in this experiment was
the paper type. The glossy surface of the paper had significant
effect and the color gamut was nearly double when paper is
changed from semi matte surface to glossy surface. This
experiment can also be used by the paper manufacturer to
evaluate the improvements that happens due to the surface
modification of the paper on the color output.
REFERENCES
[1] Bandyopadhyay.S., Jadhavpur University (India),
“Effect of paper properties on print quality of inkjet
printer, proceedings of IS & T s, NIP17, International
Conference on Digital Printing Technology, p 141-144
,(2001)
[2] Chovancova Lovell, V.L , Fleming P.D, “Effect of
optical brightening agents & UV protective coatings on
print stability of the fine art substrates for inkjet”,
Proceedings of the IS & T NIP 22, international
conference on digital printing technologies, Denver,
September 17-22, p 227-230, (2006)
[3] E.Hrehorova, A.Sharma, P.D.Fleming, “Colour
reproduction studies in RGB & CMYK workflows
using inkjet printer drivers & RIP’s”, Proceedings of
the 58th
TAGA annual technical conference (2006)
[4] Isabel M. T. Moutinho,a,* Paulo J. T. Ferreira,b and
Margarida L. Figueiredo F.b (2011) “Paper surface for
inkjet,” BioResources 6(4), 4259-4270.
[5] Livens & Mahy 2002, “Quality managed proofing- the
road to visual consistency”, presented at the 29th](https://image.slidesharecdn.com/evaluatingthequalityofoutputinepsoninkjet-140808022524-phpapp01/85/Evaluating-the-quality-of-output-in-epson-inkjet-7-320.jpg)
![IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308
__________________________________________________________________________________________
Volume: 03 Issue: 01 | Jan-2014, Available @ http://www.ijret.org 48
International IARIGAI Research conference September
8-11, 2002, Switzerland.
[6] Marguerite Doyle, “Measuring the imperfect dot”,
IS&T’s NIP 16, International Conference on Digital
Printing Technologies ,(2000).
[7] Renmei Xu, Paul D Fleming & Alexandra P, “The
effect of inkjet paper roughness on print gloss” ,Journal
of Imaging Science and Technology, vol 49,Issue No 6,
November / December 2005, p 660-665
[8] Trish Wales, “Paper; the fifth color”, IPA bulletin, May
/June ,2008
[9] Torry Pines research, Carlsbad, CA 92009, “Inkjet Print
Image quality considerations”, March 2003,
www.tpr.com
[10] Yu Ju Wu, Pekarovicova, A. and Fleming P. D., "How
Paper Properties Influence color reproduction of digital
proofs for publication gravure”, TAGA, 527- 544
(2007).](https://image.slidesharecdn.com/evaluatingthequalityofoutputinepsoninkjet-140808022524-phpapp01/85/Evaluating-the-quality-of-output-in-epson-inkjet-8-320.jpg)
Evaluating the quality of output in epson inkjet
- 1. IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308 __________________________________________________________________________________________ Volume: 03 Issue: 01 | Jan-2014, Available @ http://www.ijret.org 41 EVALUATING THE QUALITY OF OUTPUT IN EPSON INKJET PRINTER USING DESIGN OF EXPERIMENT METHOD Ramakrishna Nayak1 , Prathap Nayak2 , Sandeep Nayak3 , Vinod Kamath4 Manipal, India Abstract The print quality in digital printer like Epson Stylus Pro 7900 is influenced by the various printing parameters and among these dot shape, screen resolution and paper are considered to be the major. The study conducted here was to evaluate the print quality in terms of the maximum number of color that it can reproduce on two different printing substrates at different dot shapes and resolutions by maintaining other printing parameters constant. Linearization and profiling of the Epson stylus Pro 7900 printer for all these combinations were completed using IT8.7-3 CMYK standard test target using Harlequin RIP V8.3 software. Then the color gamut volumes are analyzed using Taguchi’s Design of experiments in Mini Tab software. This is done to evaluate the significant parameter that has a major influence on the color gamut. From the result obtained in the project it was concluded that change in the dot shapes and resolutions have less influence on the color gamut than the substrate’s surface property. The glossy effect of the Epson proofing commercial 187 GSM paper has shown a significant change in the color gamut in comparison with the other paper properties and printing attributes. There are different paper substrates available which are mainly made for use in ink jet printer and since these digital devices are widely used for proofing and by photographers, it is better to take similar type of study to know the print quality on different paper substrates and making a profile for each paper is a must for achieving a consistent print in more economic way. Keywords: Inkjet Printing, Color gamut, design of experiments, Print quality, Paper properties ----------------------------------------------------------------------***----------------------------------------------------------------------- 1. INTRODUCTION Advancements in digital printing has made it possible to use inkjet printers to get a high quality print for photography and proofing work. When we say a four color printing using cyan, magenta , yellow and black inks, it is not only these color inks that are involved in reproducing a desired print quality, but along with that there is a fifth analog color; the paper [1]. Printing on a paper substrate using inkjet process involves a number of process parameters that one should consider to get a quality and consistent output. Quality of a print is actually measured by its color gamut and every printers aim is to get the optimum print quality by controlling the process variables. The smoothness and roughness factor of printing paper has a significant role in producing maximum color gamut[ 2]. When ink is laid on the paper substrate, the ink will try to penetrate into the pores of the paper and the vehicle whether it is water or solvent tries to evaporate or get absorbed and pigment will settle on the surface. Surface roughness of the paper will affect the pigment deposition and this also contributes for the reduction in the color gamut [3]. When inkjet printers are used to produce the proofs for color matching or photograph printing, it is very difficult to get the color match in a regular printing or writing paper. For this reason papers are manufactured especially for inkjet printers. These papers are coated with different surface sizing materials to improve their print quality. These coatings make the surface glossier, smoother and fill the pores of the paper to reproduce a higher color gamut [4]. Due to these coatings the spreading, absorption and light reflection of the ink layer will be improved and that is why a proofing paper will give higher color gamut than that can be produced in a writing and regular printing paper [5]. The surface coating is prepared with some optical brightening agents (OBA) that further improves the reflection, color gamut, print stability and light fastness on inkjet coated papers [6]. Most of the ink jet inks are standardized in terms of their optical and physical properties. So there will not be any such variations in the ink for a particular manufacturer. But another major parameter which is of serious concern is the printer condition and the settings. To bring the printer in a standard condition or to stabilize it a linearization process is carried out. With linearization a printer is said to be in a controlled position. A consistent and good quality print is possible only if the printer is linearized using some software for each and every combination of paper and image profile. [7]. Linearization and printing is accomplished using different raster imaging processing [RIP] tools. Every printer is supplied with its own RIP software and we can also use some other third party RIP software also. When different RIP
- 2. IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308 __________________________________________________________________________________________ Volume: 03 Issue: 01 | Jan-2014, Available @ http://www.ijret.org 42 software is used the color gamut may vary, especially in case of RGB platform as each RIP has its own color conversion algorithms which cannot be controlled by the user. But in CMYK platform it will not produce much more difference in color gamut [8]. Linearization is also carried out to understand the maximum and minimum print density of the printer. These values are denoted by Dmax and Dmin which provides an idea about the maximum and minimum ink film thickness that can be deposited by this printer on a certain paper at particular printer settings. Dmax and Dmin of inkjet printer depends on the ink formulations, nozzle settings and the mechanism used for ink deposition and these values also contribute for increasing color gamut in the printer [ 9]. Along with linearization of the printer the next most important print attribute which will affect the quality of color is the image settings. The resolution, dot shape, screen angles and the dpi of the image are of most important to get a high quality image without affecting the clarity of the original image. As the printer resolution is increased it will produce an image which will be more like a continuous tone and beyond a certain limit there will not be any further increase in the color gamut. So a printer should know the optimum resolution for a particular dot shape, screen angle, paper, dpi and for the printer. It is also true that different dot shapes will result in different amount of dot gain which will be further supported by the resolution. Screen angle is one which is to be controlled to get a clear image without any moiré pattern [10]. 2. METHODOLOGY The project “Evaluation of quality of output in Epson inkjet Printer using Design of experiment method” is carried out using the following steps. Two types of paper substrates, Gloss (Epson Proofing commercial 187 GSM) and Matte (Epson Semi matte proofing paper 90 GSM) with different optical and physical properties were selected. Optical and physical properties of the paper substrate were measured using appropriate testing devices. Epson stylus Pro 7900, inkjet printer was selected and its initial settings and nozzle checking were carried out as per the manufacturer’s instructions. post RIP software is installed in the system to produce the output through Epson Printer. Two types of dot shapes, round and elliptical were selected and these dot shapes were printed on the above said papers with two different resolutions 720×720 and 1440× 1440 maintaining screen angle for CYAN15, Magenta 75, Yellow 0 and Black 135 degrees. Linearization and calibration of the Epson ink jet printer is done using the RIP software for both types of paper at two different resolutions and dot shapes. Characterisation and standardisation of the Epson printer was done for two types of paper at two different resolutions and dot shapes. Test target IT8.7-3 CMYK(fig 1.) is generated using X-Rite Profile Maker 5.5 software to evaluate the print quality by measuring color gamut in the Epson printer. Test target was printed on two types of papers using post RIP software at two resolutions and at two types of dot shapes. The color values of printed test targets were measured using i1iO spectrophotometer in conjunction with X Rite Profile Maker 5.5 measure tool software and profile for these measured data were generated using CHROMIX Color Think Pro software. Color gamut values[2] were tabulated into MiniTab software for analysing at three factors and two level experiments using Design of Experiment method. Subsequently the analysis was made.
- 3. IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308 __________________________________________________________________________________________ Volume: 03 Issue: 01 | Jan-2014, Available @ http://www.ijret.org 43 Fig 1 IT8.7-3 CMYK i1iO Test target 3. RESEARCH FINDINGS Table 1 Opacity values of two types of paper substrates Paper Name Reflectance (black backing) % Rb Reflectance (White backing) % Rw Reflectance (Paper backing) % Rp Print Opacity ( Rb/Rp) % Opacity Contrast (Rb/Rw) % Averag e Print Opacity % Average Opacity Contrast % Epson Proofing commercial Paper 187 GSM 87.9 93.7 93 94.52 93.81 96.38 95.8390.3 93.1 92.6 97.52 96.99 90.6 93.7 93.3 97.11 96.69 Epson Semi matte Proofing paper 90 GSM 82.4 89.3 86.8 94.93 92.27 94.11 92.4181.8 88.4 87 94.02 92.53 81.6 88.3 87.4 93.36 92.41 Table 2 Brightness and L a b color values of two types of paper substrates Paper Brightness (%) L a b Values Average L Average a Average B Average Epson Semi Matte Proofing paper 90 GSM 83.40 83.63 91.28 90.86 2.86 2.72 -3.69 -3.9583.40 91.35 2.89 -3.76 84.10 89.95 2.42 -4.39 Epson Proofing commercial Paper 187 GSM 88.80 88.80 93.96 94.02 2.00 1.99 -2.75 -2.7388.90 93.98 2.02 -2.81 88.70 94.12 1.96 -2.64
- 4. IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308 __________________________________________________________________________________________ Volume: 03 Issue: 01 | Jan-2014, Available @ http://www.ijret.org 44 Table 3.Gloss values of two types of paper substrates Paper GLOSS Values( GU) 20 Degree 60 Degree 85 Degree Values Average Gloss (20 Degree) Values Average Gloss ( 60 Degree) Values Average Gloss (85 Degree) Epson Semimatte Proofing paper 90 GSM 2 2 3.6 3.60 9.40 9.502 3.6 9.30 2 3.6 9.80 Epson Proofing commercial Paper 187 GSM 15.6 17.8 55.1 55.63 93.80 92.8318.9 55.7 90.60 18.9 56.1 94.10 Table 4 Comparison of color gamut in various combinations of print parameters Name of the paper Dot Shape Resolution Color Gamut (Number of colors) Epson Proofing Commercial(187 GSM) Round 720 x 720 437289 Epson Proofing Commercial(187 GSM) Round 1440x1440 460105 Epson Proofing Commercial(187 GSM) Elliptical 720 x 720 440085 Epson Proofing Commercial(187 GSM) Elliptical 1440x1440 474562 Epson Semi Matte Proofing (90 GSM) Round 720 x 720 265433 Epson Semi Matte Proofing (90 GSM) Round 1440x1440 282805 Epson Semi Matte Proofing (90 GSM) Elliptical 720 x 720 270908 Epson Semi Matte Proofing (90 GSM) Elliptical 1440x1440 285338 Table 5 Factors and levels for Design of experiment Factors Paper type Dot shape Resolution(DPI) Level 1 Epson Semi matte proofing paper (90 GSM) Round 720 x 720 Level 2 Epson Proofing commercial paper (187 GSM) Elliptical 1440 x1440 Table 6 Combination of factors and levels in MiniTab software full factorial design Std order Run Order Center Pt Blocks Paper Type Dot shape Resolution 2 1 1 1 Epson Comm Round 720 7 2 1 1 Semi Matte Elliptical 1440 1 3 1 1 Semi Matte Round 720 3 4 1 1 Semi Matte Elliptical 720 8 5 1 1 Epson Comm Elliptical 1440 5 6 1 1 Semi Matte Round 1440 6 7 1 1 Epson Comm Round 1440 4 8 1 1 Epson Comm Elliptical 720
- 5. IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308 __________________________________________________________________________________________ Volume: 03 Issue: 01 | Jan-2014, Available @ http://www.ijret.org 45 4. ANALYSIS 4.1 Full Factorial Design Factors: 3 Base Designs: 3, 8 Runs: 8 Replicates: 1 Blocks: 1 Center pts (total): 0 All terms are free from aliasing. 4.2 Design Table (randomized) Run A B C 1 + - - 2 - + + 3 - - - 4 - + - 5 + + + 6 - - + 7 + - + 8 + + - Factorial Fit: Color Gamut versus Paper Type, Dot shape, Resolution 4.3 Estimated Effects and Coefficients for Color Gamut (coded units) Term Effect Coef SE Coef T P Constant 364566 1825 199.72 0.003 Paper Type 176889 88445 1825 48.45 0.013 Dot shape 6315 3158 1825 1.73 0.334 Resolution 22274 11137 1825 6.10 0.103 Paper Type*Dot shape 2311 1156 1825 0.63 0.641 Paper Type*Resolution 6373 3186 1825 1.75 0.331 Dot shape*Resolution 2180 1090 1825 0.60 0.657 S = 5162.94 PRESS = 1705980872 R-Sq = 99.96% R-Sq(pred) = 97.33% R-Sq(adj) = 99.71% 4.4 Analysis of Variance for Color Gamut (coded units) Source DF Seq SS Adj SS Adj MS F P Main Effects 3 63651618174 63651618174 21217206058 795.97 0.026 2-Way Interactions 3 101410258 101410258 33803419 1.27 0.560 Residual Error 1 26655951 26655951 26655951 Total 7 63779684384 4.5 Estimated Coefficients for Color Gamut using data in un coded units Term Coef Constant 331155 Paper Type 78885.5 Dot shape -112.00 Resolution 30.9358 Paper Type*Dot shape 1155.63 Paper Type*Resolution 8.85104 Dot shape*Resolution 3.02743 4.6 Least Squares Means for Color Gamut Mean SE Mean 4.7 Paper Type Semi Matte 276121 2581 Epson Comm 453010 2581 4.8 Dot shape Round 361408 2581 Elliptical 367723 2581 4.9 Resolution 720 353429 2581 1440 375703 2581 4.10 Paper Type*Dot shape Semi Matte Round 274119 3651 Epson Comm Round 448697 3651 Semi Matte Elliptical 278123 3651 Epson Comm Elliptical 457324 3651 Mean SE Mean 4.11 Paper Type*Resolution Semi Matte 720 268171 3651 Epson Comm 720 438687 3651 Semi Matte 1440 284072 3651 Epson Comm 1440 467334 3651 4.12 Dot shape*Resolution Round 720 351361 3651 Elliptical 720 355497 3651 Round 1440 371455 3651 Elliptical 1440 379950 3651
- 6. IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308 __________________________________________________________________________________________ Volume: 03 Issue: 01 | Jan-2014, Available @ http://www.ijret.org 46 4.13 Effects Plot for Color Gamut and Pareto for Color Gamut 50403020100 98 95 90 85 80 70 60 50 40 30 20 10 0 Absolute Standardized Effect Percent A Paper Ty pe B Dot shape C Resolution F actor Name Not Significant Significant Effect Type A Half Normal Plot of the Standardized Effects (response is Color Gamut, Alpha = .05) BC AB B AC C A 50403020100 Term Standardized Effect 12.71 A Paper Type B Dot shape C Resolution Factor Name Pareto Chart of the Standardized Effects (response is Color Gamut, Alpha = .05) (a) (b) Fig. 2 (a) Half Normal plot and (b) Pareto Chart of the Standardized effects 4.14 Half Normal Effects Plot and Residual Plots for Color Gamut 50403020100 99 95 90 80 70 60 50 40 30 20 10 5 1 Standardized Effect Percent A Paper Ty pe B Dot shape C Resolution Factor Name Not Significant Significant Effect Type A Normal Plot of the Standardized Effects (response is Color Gamut, Alpha = .05) 500025000-2500-5000 99 90 50 10 1 Residual Percent 500000450000400000350000300000 2000 1000 0 -1000 -2000 Fitted Value Residual 200010000-1000-2000 4 3 2 1 0 Residual Frequency 87654321 2000 1000 0 -1000 -2000 Observation Order Residual Normal Probability Plot Versus Fits Histogram Versus Order Residual Plots for Color Gamut (c) (d) Fig. 3 Normal Plot of the standardised effects and Residual plots for color gamut CONCLUSION FROM THE DESIGN OF EXPERIMENT OUTPUT: The analysis of variance table gives a summary of the main effects and interactions. This shows that Main effects are significant than two way interactions. Effect P-Value Significant* Main Effects 0.026 yes Two-way interactions 0.560 no * significant at alpha = 0.05 After identifying the significant effects (main effect) in the analysis of variance table, the estimated effects and coefficients table shows the p-values associated with each individual model term. The p values indicate that just one main effects paper (p = 0.013) is significant. Paper type has a maximum effect of 176889 on the color gamut and it is significant as p value is below 0.05. Next term that is having highest effect is resolution but it is not significant as its p value is greater than 0.05. In the normal probability plot of the effects, points that do not fall near the line usually signal important effects. Important effects are larger and further from the fitted line than unimportant effects. Unimportant effects tend to be smaller and centered around zero. The normal probability plot uses α
- 7. IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308 __________________________________________________________________________________________ Volume: 03 Issue: 01 | Jan-2014, Available @ http://www.ijret.org 47 = 0.05, by default. The plot in this experiment shows that term paper is only significant and dot shape and resolution change are insignificant. The Pareto chart displays the absolute value of the effects and draws a reference line on the chart. Any effect that extends past this reference line is potentially important. The reference line corresponds to alpha = 0.05, by default. From the Pareto graph generated in this experiment shows the paper only as the significant term. The DOE analysis says that the change in dot shape from round to elliptical and resolution from 720 x 720 to 1440x 1440 dpi has not shown any significant changes in comparison with the change of paper substrate. This is quite obvious due to the small change in the dot shape from round to elliptical and due to the higher end resolution that was selected for the printing. If the dot shapes selected were round and square or square and elliptical there would have some significant results on color gamut. Similarly the printer shows similar color gamut when it is printed using 720 x 720 or 1440x 1440 dpi resolutions this is due to the fact that both resolutions are of high end and printing with 720x720 dpi is optimum for paper substrates. In addition to this when an optimum resolution is achieved i.e. 720x720 dpi as here further increase in the ink deposition will not contribute for enhancing color but instead it will increase the amount of ink deposition and its consumption which is not economical. The result would have some significant effect if it printed with 720x720 dpi and 360x360 dpi or other dpi of lower range. The DOE analysis strongly says here that change from Epson semi matte proofing paper (90GSM) to Epson proofing commercial (187 GSM) has a significant change in the color gamut. When we compare the optical properties of these paper grades, we can see that opacity, brightness and L a b values of these papers are somewhat similar with smallest variation. But when we compare the gloss there is a huge change in their property. To get the gloss normally paper substrates are coated and calendared with special treatment during manufacturing. The glossy surface makes the light to reflect in specular way and since these surfaces are coated they will not allow ink to get absorbed into the pores of the fibers and due to these properties of the coating the pigments of the ink will stay on paper surface and reflect all the colors resulting in maximum color gamut. The residual plot versus Fits and fitted value is expected to have values uniformly spread above, below and throughout the length of the zero line then the model is correct on average for all fitted values. In our experiment due to lack of data we could see only eight values but they are equally distributed from zero level so the model is quite fine and it is random in nature. The Normal Probability plot also expected to have the residual plots values uniformly aligned with the reference line to conclude the errors are distributed normally and the normality of errors assumption is valid. But in our experiment they are not so aligned and more data might be required to get clearer picture. SCOPE FOR FURTHER WORK In this experiment the two types of dot shapes taken were having similar curvature and that could be the one reason for having no significance of the dot shape on the color gamut. There are so many other dot shapes available in the RIP software, which have square, line and other shapes and using such dot shapes similar experiment can be performed to see whether the dot shape is significant or not. The two resolutions taken for this experiment are of high end and found no significant effect on the color gamut. The resolution options available are vary from printer to printer and similar study can be conducted to see their significance level. The entire project is carried at a constant screen angle which is one of the standards screen angle followed by the printing industry. Some the printers based on the type of image whether it is high key or low key pictures screen angle is changed for individual colors. Further study can be planned for other industry standard screen angles. The significant factor that was found in this experiment was the paper type. The glossy surface of the paper had significant effect and the color gamut was nearly double when paper is changed from semi matte surface to glossy surface. This experiment can also be used by the paper manufacturer to evaluate the improvements that happens due to the surface modification of the paper on the color output. REFERENCES [1] Bandyopadhyay.S., Jadhavpur University (India), “Effect of paper properties on print quality of inkjet printer, proceedings of IS & T s, NIP17, International Conference on Digital Printing Technology, p 141-144 ,(2001) [2] Chovancova Lovell, V.L , Fleming P.D, “Effect of optical brightening agents & UV protective coatings on print stability of the fine art substrates for inkjet”, Proceedings of the IS & T NIP 22, international conference on digital printing technologies, Denver, September 17-22, p 227-230, (2006) [3] E.Hrehorova, A.Sharma, P.D.Fleming, “Colour reproduction studies in RGB & CMYK workflows using inkjet printer drivers & RIP’s”, Proceedings of the 58th TAGA annual technical conference (2006) [4] Isabel M. T. Moutinho,a,* Paulo J. T. Ferreira,b and Margarida L. Figueiredo F.b (2011) “Paper surface for inkjet,” BioResources 6(4), 4259-4270. [5] Livens & Mahy 2002, “Quality managed proofing- the road to visual consistency”, presented at the 29th
- 8. IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308 __________________________________________________________________________________________ Volume: 03 Issue: 01 | Jan-2014, Available @ http://www.ijret.org 48 International IARIGAI Research conference September 8-11, 2002, Switzerland. [6] Marguerite Doyle, “Measuring the imperfect dot”, IS&T’s NIP 16, International Conference on Digital Printing Technologies ,(2000). [7] Renmei Xu, Paul D Fleming & Alexandra P, “The effect of inkjet paper roughness on print gloss” ,Journal of Imaging Science and Technology, vol 49,Issue No 6, November / December 2005, p 660-665 [8] Trish Wales, “Paper; the fifth color”, IPA bulletin, May /June ,2008 [9] Torry Pines research, Carlsbad, CA 92009, “Inkjet Print Image quality considerations”, March 2003, www.tpr.com [10] Yu Ju Wu, Pekarovicova, A. and Fleming P. D., "How Paper Properties Influence color reproduction of digital proofs for publication gravure”, TAGA, 527- 544 (2007).