The Effect of OBA in Paper and IlluminationLevel on Perceptibility of Printed Colors
A research was conducted to study the perceptibility of color difference of color pairs, caused by OBA differences in paper substrates, and its relationship with quantitative measurement metrics. Based on the psychometric experiments conducted, the results show the utilization of the visual difference index (VDI), from 0 (no difference) to 3 (noticeable difference), to rate 27 color pairs with each pair prepared by the same colorants but different OBA amount in the substrates. The findings indicate that (a) printed colors are affected by the presence of OBA from no difference to noticeable difference, (b) ∆E00 has a stronger linear correlation with visual color difference than ∆E*ab does, (c) there is no significant association between illumination levels and visual color difference. This research introduces the metric, OBA, per ISO 15397 (2013), as the CIE-b* difference in color pairs under M1 and M2 conditions. It also defines ∆OBA as the OBA difference between any color pairs, including substrates. The results show that there is linear correlation (1) between visual difference and ∆E00 which describes the color difference, and (2) between visual difference and ∆OBA which describes the criticalness of M1 lighting to realize the color match.
M1 Simulation by Varying Printing and Proofing Substrates
ICC color management can match color, pixel by pixel, from the source color space to the destination color space. The degree of color match is limited by the repeatability of the device and color management constraints between the source and destination. This research outlines a method whereby printing and proofing can be simulated visually and quantitatively. Major findings indicate that (1) the simulation error at the device level is about 1 ∆E00 at the 95th percentile of the sample distribution; (2) the error at the color management workflow level, except special causes, is about 2 ∆E00 at the 95th percentile of the sample distribution; (3) gamut clipping, due to CIE-b* difference or CIE-L* difference, is a special cause that contributes to proof-to-print mismatch. Avoiding gamut clipping by choosing the proofing substrate close to the white points of the printing paper, but with more “head room,” is a key finding in this study. In addition, we need no fewer than two proofing stocks to choose from. This is because the OBA difference between a proof and a print is an indication of the criticalness of the M1 lighting, i.e., the match becomes more metameric when the OBA difference is high.
Investigations on the rôle of organic matter in plant nutrition
1. As the result of decomposition of green manure in a swamp soil, the coarse fractions (including coarse and fine sand) of the surface layer (first 3 inches) decreased by 11·2 per cent. while the fine ones (silt+clay) increased by 9·8 per cent. in the course of 43 days. The effect was less pronounced in the manured soil maintained at 60 per cent. saturation, while no alteration was to be noticed in the case of the unmanured specimens. 2. Treatment with dilute hydrochloric acid prior to dispersion had no appreciable effect on the estimates of mechanical composition obtained in the different cases. Loss in solution was also comparatively small. 3. The silica-sesquioxide ratio increased slightly as the result of decomposition of green manure in swamp soil. The composition of the fine fractions was also altered, the total percentages of the oxides of iron, aluminium and silicon increasing from 90·5 to 99·3 in the course of 71 days. 4. The practical significance of the above and related observations has been discussed.