Methods of evaluation the neutrality of ND filters

Citation

• Authors: ZHANG Yongxi, JIN Xiu, YANG Wenhua, MA Jing, WANG Ruisheng
• Article Title: Methods of evaluation the neutrality of ND filters
• Journal Name: Optical Instruments (translation)
• Year of Publication: 2013
• Volume and Issue Number: 35(5)
• Page Numbers: 85-88
• Doi:10.3969/j.issn.1005-5630.2013.05.019.

Keywords

• 密度滤光片 / density filter
• 滤光片 / filter
• 光密度 / optical density
• 中性度 / neutrality
• 归一化 / normalization
• 标准中性度 / standard neutrality
• 光谱曲线 / spectral curve
• 透射率 / transmittance
• 波长 / wavelength
• 光能衰减 / light energy attenuation

Brief

This article [ZHANG Yongxi, JIN Xiu, YANG Wenhua, MA Jing, WANG Ruisheng. Methods of evaluation the neutrality of ND filters [J]. Optical Instruments, 2013, 35(5): 85-88. doi:10.3969/j.issn.1005-5630.2013.05.019] proposes a normalization method for comparing the neutrality of neutral density filters based on their spectral curves, introduces a definition and calculation method for standard neutrality, and offers a formula for evaluating neutrality in arbitrary wavelength ranges.

Summary

This article discusses the importance of neutrality for neutral density filters and points out the limitations of existing descriptive methods. To enable quantitative evaluation, the authors propose a normalization method for comparing neutrality based on spectral curves. They introduce a definition and a simple calculation method for "standard neutrality" specifically for the visible wavelength range (400-700nm). Furthermore, the article offers a formula for calculating neutrality in arbitrary wavelength ranges, although it notes that comparability might be limited due to differing ranges. The overall goal is to establish quantifiable metrics for the neutrality of neutral density filters for both standard and non-standard products.

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