High dynamic range tone mapping for confocal microscopy images

High Dynamic Range (HDR) can capture a much wider range of luminance levels and, therefore, more scene details than Standard Dynamic Range (SDR), making it an important technology in microscopy. However, HDR is not compatible with SDR displays, which remain the most widely used. To bridge this gap, tone mapping operators (TMOs) are employed to convert HDR images into an SDR format. This study evaluates the performance of eight TMOs on HDR confocal microscopy images. The results indicate that existing TMOs frequently introduce artefacts due to the low signal-to-noise ratio (SNR) and the sparse, or out-of-focus, structures typically found in confocal microscopy images. Although some TMOs improve local contrast, sharpness, or noise characteristics, none consistently outperform the linearly compressed HDR images used as a baseline. Based on these findings, key requirements for a confocal microscopy-specific TMO are identified, specifically the need for TMOs that are compatible with grayscale data, robust to a low signal-to-noise ratio (SNR), and have the ability to preserve the high contrast between background and microscopic structures inherent to confocal imaging.