Capture and organize RGB triplets

Before you start

Check camera alignment, focus, film flatness, and stray light first. Use independently controlled red, green, and blue lights or suitable separation filters.

Steps

1. Keep film and camera still and capture a test group

   Keep the film still through all three exposures, with lens, magnification, focus, and holder fixed. When changing filters, watch for camera movement, focus changes, or image shifts. Capture a test R, G, B group and compare the same edges at the center and corners under magnification. Check alignment before capturing the roll.

2. Fix camera exposure and set each light’s intensity

   This workflow requires the same shutter speed, ISO, aperture, and camera gain for all three exposures, with automatic exposure and Auto ISO disabled. Balance the signals by adjusting each light’s intensity during setup. Their intensities need not be equal, but use the chosen settings for the whole roll and chart. The app does not use EXIF to compensate for exposure differences between the three captures.

3. Check exposure and sharpness in each record

   Inspect each source, not just the combined brightness. Check for clipping within useful film, adequate signal in dense regions, and consistent sharpness. Look for noise in a weak channel, lighting bands, and flare. Composition and CCM cannot restore clipped or blurred measurements. Repeat the tested illumination recipe throughout the roll.

4. Example: combining three grayscale records

   This example uses monochrome-camera files rgb_7.tiff (R), rgb_8.tiff (G), and rgb_9.tiff (B). Each is a 6464 × 4852, 16-bit, single-channel TIFF, so a grayscale appearance is normal. The images below show the three sources and their composite. Web previews have only display encoding and resizing applied, without separate channel stretches. The composite has no CCM or negative conversion yet and remains negative.

   

   

   

   

5. Capture each frame in R → G → B order

   Ordinary import groups consecutive sorted files in threes: first R, then G, then B. Complete the triplet before advancing the film. The following names are illustrative only; numeric role prefixes enforce sorting and do not designate a sample.

   Correct ordering example: six sources produce two frames

   Logical frame	R: first	G: second	B: third
   Frame 1	0001_01_R.dng	0001_02_G.dng	0001_03_B.dng
   Frame 2	0002_01_R.dng	0002_02_G.dng	0002_03_B.dng

6. Check filenames and groups

   Use zero-padded consecutive numbers so that every sorted group runs R, G, B. Suffixes _R, _G, _B alone may sort as B, G, R, and the app should not be expected to pair files across separate color folders. Leave tests, duplicates, and incomplete groups out of the import and check that each group shows the same frame. A multiple of three can still contain wrong groups; one missing file can shift later grouping. Back up originals before reorganizing or renaming them.

7. Capture a separate CCM chart group

   Capture the transmission chart once under each of the same R/G/B light settings, camera parameters, and input policy. Keep these files separate from ordinary film frames. One White-lit chart is not a substitute for three spectral chart records. This device-CCM task differs from a Color Chart originally photographed on the film.