RGB retains color channels
Use RGB when colored stamps, diagrams or annotations matter. Grayscale records luminance and reduces the number of samples, but distinct colors can become similar shades.
One bit is a deliberate reduction
Every pixel becomes black or white. Thresholding can erase faint pencil marks or fill small gaps in text. Compare faint and dense regions before choosing the final threshold.
Compression is a separate choice
Deflate preserves the pixels after rendering and thresholding. It does not reverse information removed by a color-depth decision. The report names the actual codec rather than assuming every TIFF uses the same format.
Compare one difficult page in each mode
Select a page that includes your smallest text and any faint marks you need to preserve. Export it in RGB, grayscale and monochrome at the same DPI. Inspect the three actual TIFF files in the receiving viewer. Keep the mode that preserves the necessary information; file size alone should not decide whether a faint pencil annotation is discarded.
RGB keeps three color channels. Grayscale removes color while preserving multiple intensity levels. Monochrome applies a threshold to produce one-bit black or white pixels. A light blue stamp that is readable in RGB can become weak in grayscale and vanish at an unsuitable monochrome threshold. This is an intentional conversion choice, not a reversible display filter.
For example, a clean black-text letter may work well in monochrome, while an invoice with a pale watermark and colored approval stamp may need grayscale or RGB. Export separate jobs if the documents have different needs. The original PDFs remain unchanged, so keep them available when a recipient later requests a different color mode.
This encoder does not provide CMYK separations, color-managed ICC output, LZW or CCITT Group 4. Do not select monochrome expecting a fax-system-specific Group 4 file: pixel depth and compression are separate properties. If an import system specifies a required compression tag, verify that requirement against the supported Deflate or uncompressed output before sending files.