FADGI Exhibit Images

A FADGI device level target which is a gray rectangle around the size of printer paper that displays gray slant edges in the center and corners, many colored circles and black dots throughout. This screenshot has numbers superimposed on the colorful circles representing Delta E values measured, most are under 5 but several teal and teal adjacent colors are over 10.

Delta E Value Measurements from a Flatbed Scanner

The higher Delta E values that are higher numbers and visible on the teal and near-teal color circles suggest those colors are not as accurately represented in this digital image file as the other colors, which all measure favorably toward 3 or 4-star FADGI standards.

Screenshot of a Windows Operating System and Book Pavilion scanning software for a Plustek Opticbook A300 scanner where the previous scan of the FADGI device level target is visible in an open window to the left, which has many circles of colors and values and is around the physical size 8 x 11in, and appears very dark. The settings for the new scan are visible in the window to the right, with adjustments turned off where possible, and a preview of the new scan shows a much more accurate view of the target.

Comparison Screenshot of a Too-Dark Scans Improved with New Scanning Settings

As targets are a consistent item and we know what it should look like when scanned accurately, it can be a helpful quick tool to confirm when equipment isn't performing as desired. In this instance, scans were looking too dark but it wasn't obvious the added contrast was problematic on all materials. The target and FADGI testing here is helpful in diagnosing baseline performance, and led to exploring simple adjustments to improve accuracy with collaborators who do their own digitization work in the library.

A plot line graph where the aim is an even diagonal dashed line from the upper lefthand corner to the bottom righthand corner, and the data points are slightly lower from that, but remain more linear and are not super curved, illustrating an image that will appear slightly dark but overall with even contrast to the original item. The x-axis goes from lightest lights to darkest darks on the patches of the target, and the y-axis represents the estimated lightness value measured from the test image.

Tonescale Graph from Scanner with Improved Accuracy

The Tonescale graph improved with adjusted settings on the flatbed scanner (exposure accuracy, how light/dark it looks... just a little darker than ideal here overall except in the darkest darks). The visualization of the data makes it easier to pinpoint the issue and illustrate the improvements.

A plot line graph where the aim is an even diagonal dashed line from the upper lefthand corner to the bottom righthand corner, and the data points curve downward from that, illustrating increased contrast measured in the midtones of the target image resulting in an image that will appear overly dark all but in the lightest lights. This may be advantageous for certain text files that are scanned for access and readability purposes to make them more legible, in certain cases, but that is not the aim in FADGI compliant, or preservation scanning practices and does not give a true representation of what the physical item looks like. The x-axis goes from lightest lights to darkest darks on the patches of the target, and the y-axis represents the estimated lightness value measured from the test image.

Tonescale Graph from Scanner with dark scans

Here's an example from the testing results from our software. You can see where a neutral reproduction would be (the dotted line) and the curved line is the rendering that the settings on the scanner are producing. The dip represents the darkness we're seeing.

Yellow, green and black coloring of a zoomed in view of the body of the fish with dark spots and texture of the fish's skin visible in the illustration. The bottom view shows more detail in the darkest darks.

Detail Comparison of two versions of the Fish's Body

The bottom image shows more contrast while the upper image appears flatter, and has less visible detail in the darks.

Yellow, green and black coloring of a zoomed in view of the top of the fishes, including a partial fin view, skin texture and scales in the illustrated painting. The left window in the screenshot has the fish positioned slightly lower than the right. The right view shows more detail in the darkest darks. The detail is most visible around two scales near the top of the fish.

Detail Comparison of two versions of the Fish's Upper Fin

The right image shows more contrast while the left image appears flatter, and has less visible detail in the darks.

Two images of the same painting of a fish, catfish looking fish, compared with one on top of the other. The fish's dark spots are richer and darker on the bottom than the top. The fish has whiskers and a deep green coloring, it is long with rounded fins and tail and a light belly. The fish is facing left and is painted on cream colored paper.

Screenshot comparing two variants processed slightly differently of the Ameiurus nebulosus fish from Funk ACES collection Illustrations for The Fishes of Illinois: painting, 1892-1913.

Screenshot depicting the differences in the darkest darks from a fully FADGI compliant image (lighter) and one that is 10% off (darker, showing more variation in detail and texture).

Two graphs, one titled Horizontal and the other Vertical, showing colorful lines representing aims for files measuring 2 star (orange), 3 star (yellow) and 4 star (green) in FADGI standards. The line is smooth, mostly linear from upper lefthand corner (Amplitude of 1 on the y-axis) to the Nyquist Freq dashed light to the bottom right of the graph at the 600dpi mark of the x-axis.

Spatial Frequency Response (SFR) Curve Graphs

Lightness Tab selected, the graph shows horizontal and vertical gray slant lines measured favorably, reaching past 250 dots per inch (dpi) resolving at 50% amplitude and past 550dpi at 10%, toward the highest effective resolution Nyquist Frequency aim for an image captured at 605dpi.