Volume 48, No 3, 2026, Pages 595-614
Download full text in PDFComparative Optical Roughness Measurement of Mild Steel Ship Plates Using a Microscope
and DSLR Imaging
Authors:
Eko Sasmito Hadi 
,
Muhammad Raaflie Caesar Putra Hadi ,
Muhammad Luqman Hakim ,
M. Dafa Maziya ,
J. Jamari
DOI: 10.24874/ti.2205.05.26.07
Received: 4 May 2026
Revised: 1 June 2026
Accepted: 6 July 2026
Published: 15 September 2026
Abstract:
Surface roughness of ship plates is an important surface parameter because it influences coating condition, fouling development, hydrodynamic resistance, and maintenance decisions. However, this study does not directly measure friction, wear, lubrication, or tribological performance. Instead, it evaluates optical roughness measurement as a supporting method for roughness-based surface inspection of marine steel surfaces. This study compares two non-contact optical imaging systems, a metallurgical microscope and a DSLR camera, for estimating the roughness parameters Ra and Rz of mild steel ship plates. Validation was performed using eight ISO 2632 reference surfaces with certified Ra values ranging from 0.05 to 0.40 µm. Roughness values were processed using Gwyddion and ImageJ, and the DSLR system was evaluated at five camera–surface distances of 1, 2, 3, 4, and 5 cm. All tested configurations achieved validation accuracy above 91% for both Ra and Rz. The microscope showed the highest overall agreement with the certified reference values, while Gwyddion yielded results closer to the certified reference values than ImageJ. In the DSLR workflow, measurement accuracy decreased with increasing camera–surface distance, underscoring the importance of controlled imaging geometry. An application to a mild steel plate showed that both systems could detect small differences in roughness, although the microscope resolved local surface features more clearly. These results indicate that calibrated optical imaging can support the assessment of roughness on fine mild steel surfaces under controlled conditions. However, because the validation range was limited to fine reference surfaces, further validation is required before applying the workflow to blasted, corroded, coated, or fouled ship surfaces. DSLR imaging may be useful as a screening-level approach, but its reliability depends on controlled distance, illumination, focus, exposure, and calibration.
Keywords:
Surface roughness, Optical roughness measurement, Non-contact metrology, Surface characterization, Mild steel ship plates
