Notes on Digital Imaging

When viewing our digital collections there are some media biases that might affect true representation of specimens:

1. Moiré Patterning

Reducing image size for web presentation can sometimes result in resizing artifacts also known as Moiré patterns. These patterns are a form of aliasing resulting from the undersampling of complex patterns. Aliasing refers to the phenomenon of a new pattern arising from the original. In wings, Moiré patterns appear when the parallel barbs in feathers are undersampled when images are reduced in size. The Moiré patterns are not apparent in full resolution or properly resized images and do not naturally occur in the wings. Below are two pictures of a Wilson's Warbler wing: the left photo is affected by Moiré patterning and the right one is properly reduced in size.


The image at left has been resized to include Moiré Patterning, the right is resized correctly (click for detail)

Some pictures, such as this warbler, have been saved at a size that exhibits Moiré patterns. Images in the database may be thumbnailed at a size that results in Moiré patterning. If you see patterns, use the “zoom and pan” from the top bar to view the image at a different percentage. The patterns often show at 33% and 66% and usually only on the smaller wings.

2. Color/Contrast Exaggeration

Many of the images in the database have, through digital processing, become slightly exaggerated in color and hue. Contrast, particularly black and bright white, may be more extreme than is natural. We endeavor to bring you the best representation available by continuing to modify and correct our photographic procedures.

3. Differences in monitors

In general, images on PC monitors will appear darker than on a Mac because the default brightness (gamma) differs. PCs have a default gamma of 2.2 vs. 1.8 on Macs. The images in the original wing collection were created on a Mac while the new images in the database were created on a PC. This accounts for some differences in brightness. In addition, monitor profiles and age will influence hue and saturation of colors.

4. Photographic setup

From Jan-May 2006 images in the database were taken with a Nikon CoolPix 990 on a stand,with direct light from two angled 250W incandescent bulbs and white balance was set to incandescent. Images were shot on manual settings to maximize F-stop. Shutter speed was usually 1/30 or 1/60. The intent was to maximize depth of field (F7-9) with the bright light so the entire wing would be in focus. The result tended to exaggerate the blacks and whites. In June 2006 we altered the setup to a Panasonic Lumix DMC-FZ30PP with indirect light.

5. Disclaimer

The only way to truly see a specimen is to view it first hand. For more information about visiting the museum, borrowing specimens, or obtained high resolution images from the Slater Museum, please contact: Or, visit your local natural history museum.