In Electrophotography printing technique with liquid toners, large quantities of ink are deposited on photoreceptor. Voltage variations during the development phase (ΔV=200V) will directly influence the thickness of ink layer on photoreceptor. Optimal reproduction is achieved when smallest image elements (screen dots) have smallest possible diameter, and respectively higher optical density. Suitable method for reproduction analysis is based on spectrophotometric measurement of halftones and on optical densitometry. By adjusting the voltage during development (II. phase) will allow largest manipulation of color (ΔE RR = 10.01). Optimal results are achieved with voltage of -125 V. Under this conditions, average printed screen element had average diameter of 56.9 μm and a maximum reflectance of R=33.50%. Variation of voltage on other two developing devices affect only slightly the color reproduction (ΔE DEV =1.26; ΔE SQU =0.94.) and have lower impact on the size of screen elements (Δd DEV =8.1 μm; Δd SQU =4.1 μm).

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Abstract The importance of accurate identification of the edge spread function for the paper-ink system is closely related with the possibility of separating mechanical and optical dot gain. Our approach is based on the precise fit of the edge spread function, ESF. Namely, all of the research so far incorporates symmetric ESF, in contrast to the research reported so far, in which only the symmetric ESF has been considered¸ which is not realistic, due to the presence of dot gain. This approach, based on image analysis, allows us to identify uniquely the domain of impact of each contribution. Six different paper-ink systems are analyzed and discussed, and all of them show a satisfactory correlation with the proposed model.

The ultimate goal of each production process is to optimize all the subprocesses leading to the high quality final product. Within the printing process, dot gain is identified as one of the most important variables to control because of the extremely negative impact to middle tone contrast and the overall reproduction. Dot gain consists of two components, mechanical and optical dot gain, as a result of two different contributions. This article proposes a model for separately analyzing components of dot gain for electrophotography prints using gradient method, where the impact of printing technique and paper type will be examined. It is shown that mechanical dot gain for electrophotography prints can be satisfactorily approximated with Gaussian, whilst optical dot gain is once again confirmed to have the form of a Lorentzian.

The objective of this work was to establish the relationship between the calculated subsurface scattered-photon distribution and the mathematical quantity known as point-spread function (PSF). Photon distribution of subsurface scattered light was calculated using the Monte Carlo method developed for describing reflectance and opacity of paper and of images printed on paper. The obtained normalized photon distribution made it possible to separate optical and mechanical components of dot gain for the paper-ink system. In the presented method of obtaining the reflectance profile of a screen element, the PSF convolves with a modelled reflectance profile of that element. It was found that the PSF can be better approximated by means of the Lorentzian function when compared to the Gaussian profile that was used in the past research on this topic.