Backlight brightness optimization

The following images are from a set of holes at 9 feet into the Ampico 70403 1929 test roll (Ampico B). Mouse-over the images to see the calibration settings (aperture setting and number of diffusers on bottom light). The images should be shown at 100% scale (300 dpi) when the webpage is viewed at 100% size. Click on each image to view the full scan width at the same aperture and diffuser settings.

Apertures 1.0 to 6.0 in 0.5 increments, using 1 diffusion sheet on bottom light, and 250 microsecond exposure. Notice that the holes drop below 100% white at aperture 4.0:

Each diffuser sheet is equivalent to adjusting the back light by about 0.4 aperture units (back-light diffusers do not affect the front-light brightness).

Apertures 1.0 to 6.0 in 0.5 increments, using 2 diffusion sheets on bottom light, and 250 microsecond exposure. Notice that the holes drop below 100% white at aperture 3.5:

Apertures 1.0 to 6.0 in 0.5 increments, using 3 diffusion sheets on bottom light, and 250 microsecond exposure. Notice that the holes drop below 100% white at aperture 3.0:

Apertures 1.0 to 6.0 in 0.5 increments, using 4 diffusion sheets on bottom light, and 250 microsecond exposure. Notice that the holes drop below 100% white at aperture 3.0:

Apertures 1.0 to 6.0 in 0.5 increments, using 5 diffusion sheets on bottom light, and 250 microsecond exposure. Notice that the holes drop below 100% white at aperture 3.0:

Apertures 1.0 to 6.0 in 0.5 increments, using 6 diffusion sheets on bottom light, and 250 microsecond exposure. Notice that the holes drop below 100% white at aperture 3.0:

Apertures 1.0 to 6.0 in 0.5 increments, using 7 diffusion sheets on bottom light, and 250 microsecond exposure. Notice that the holes drop below 100% white at aperture 3.0:

Ordering the images by diffusion sheet count

One to seven diffusion sheets on the back light at aperture 1.0, and a 250 microsecond exposure:

One to seven diffusion sheets on the back light at aperture 1.5, and a 250 microsecond exposure:

One to seven diffusion sheets on the back light at aperture 2.0, and a 250 microsecond exposure:

One to seven diffusion sheets on the back light at aperture 2.5, and a 250 microsecond exposure:

One to seven diffusion sheets on the back light at aperture 3.0, and a 250 microsecond exposure:

One to seven diffusion sheets on the back light at aperture 3.5, and a 250 microsecond exposure:

One to seven diffusion sheets on the back light at aperture 4.0, and a 250 microsecond exposure:

One to seven diffusion sheets on the back light at aperture 4.5, and a 250 microsecond exposure:

One to seven diffusion sheets on the back light at aperture 5.0, and a 250 microsecond exposure:

One to seven diffusion sheets on the back light at aperture 5.5, and a 250 microsecond exposure:

One to seven diffusion sheets on the back light at aperture 6.0, and a 250 microsecond exposure:

Scanning the same holes on a flat-bed scanner

Scanned at 600 and 300 dpi on a flat-bed scanner (with white and black backgrounds):

These represent the best case (at 300 dpi) and better-than-best-case (600 dpi) views of the holes.

Thresholded versions of the above images

Apertures 1.0 to 6.0 in 0.5 increments, using 1 diffusion sheet on bottom light, and 250 microsecond exposure:

Apertures 1.0 to 6.0 in 0.5 increments, using 2 diffusion sheets on bottom light, and 250 microsecond exposure:

Apertures 1.0 to 6.0 in 0.5 increments, using 3 diffusion sheets on bottom light, and 250 microsecond exposure:

Apertures 1.0 to 6.0 in 0.5 increments, using 4 diffusion sheets on bottom light, and 250 microsecond exposure:

Apertures 1.0 to 6.0 in 0.5 increments, using 5 diffusion sheets on bottom light, and 250 microsecond exposure:

Apertures 1.0 to 6.0 in 0.5 increments, using 6 diffusion sheets on bottom light, and 250 microsecond exposure:

Apertures 1.0 to 6.0 in 0.5 increments, using 7 diffusion sheets on bottom light, and 250 microsecond exposure:

Thresholded images organized by diffusion value

One to seven diffusion sheets on the backlight at aperture 1.0, and a 250 microsecond exposure:

One to seven diffusion sheets on the backlight at aperture 1.5, and a 250 microsecond exposure:

One to seven diffusion sheets on the backlight at aperture 2.0, and a 250 microsecond exposure:

One to seven diffusion sheets on the backlight at aperture 2.5, and a 250 microsecond exposure:

One to seven diffusion sheets on the backlight at aperture 3.0, and a 250 microsecond exposure:

One to seven diffusion sheets on the backlight at aperture 3.5, and a 250 microsecond exposure:

One to seven diffusion sheets on the backlight at aperture 4.0, and a 250 microsecond exposure:

One to seven diffusion sheets on the backlight at aperture 4.5, and a 250 microsecond exposure:

One to seven diffusion sheets on the backlight at aperture 5.0, and a 250 microsecond exposure:

One to seven diffusion sheets on the backlight at aperture 5.5, and a 250 microsecond exposure:

One to seven diffusion sheets on the backlight at aperture 6.0, and a 250 microsecond exposure: