As mentioned above, the hypered TP-2415 used in the Schmidt camera is developed for 11 minutes in D-19 developer at 68F. The 103aO spectroscopic film image of the Pleiades was developed in MWP-2, a specialty developer invented just for astronomical applications. But since 103a films are no longer manufactured, there is little point in further discussion of how they are developed. For ease of handling, the individual Schmidt camera exposures are mounted in cardboard 35 mm slide mounts. Most enlarger manufactures produce film holders which accept 2 X 2-inch slides. For regular pictorial presentation, the resulting negatives are printed on Kodak grade 5 paper using an Omega B-22 enlarger.
Kodak strongly cautions that TP-2415 should be developed carefully, with little excess agitation, or the edge of the film next to the spirals of the steel developing reel will overdevelop. I have about 300 TP-2415 negatives taken with the Schmidt camera which bear testimony to to the validity of Kodak's caution. All have a dense stripe of overdevelopment next to the sprocket holes. Over time, I have simply become used to this effect because of the extremely contrasty development needed by astronomical images. Print dodging and burning to eliminate these overdeveloped stripes has become routine and no evidence of them shows on most prints.
The images shown on this Web page were digitized by Kodak using a Photo CD. They were flat scans with no image processing done in the "Base 16" format, resulting in 2048 X 3072 pixel image recorded in Kodak .PCD file format. A Photo CD can hold up to 100 separate 35 mm images in Base 16 format. When the Schmidt images came back from Kodak, I immediately realized I made a mistake in not specifying that all negatives (each mounted in a slide mount) should be scanned backwards. The Schmidt mirror optics everses the image on the negative and thus all the CD scans were reversed, making it necessary to invert every one of them while doing the image processing.
Both Adobe Photoshop 3.0 and LVIEW were used to covert the CD scans into the .JPG images shown here. The Photo CD stores all images, even those in black and white, as color images. The first task was to convert the scans to Photoshop .PSD format and save them as 256-step grayscale images. This reduces the file size to about one-half or less that of the original 16 megabytes in the .PCD format. The next task was to turn around the inverted Schmidt images, then orient them with north in the proper direction. The contrast and brightness was then adjusted to maximize the faint nebular detail. Further processing involved burning in the overdeveloped edges of the negatives. Since the images were more than 2,000 pixels in width, Photoshop's custom brush palate came in handy to create an image dodging and burning spot that was 999 pixels (the maximum allowed) in width to quickly adjust the overall density of the image. The smaller default brushes were used to clean up smaller areas of special interest. Once proper image density was achieved, scratches and film defects were eliminated with Photoshop's pencil options. At this point, the image was basically ready for presentation. In some cases, the processed image benefitted from further contrast enhancement once the image density had been adjusted to get rid of the pesky overdeveloped edges. The completed .PSD format image was then cropped to the point of interest in the image, just as a negative would be in an enlarger. The "keeper" was then saved as a .GIF file on a 100 MB ZIP disk for portability between computers.
To convert the processed .GIF image to .JPG format for display here, the shareware program LVIEW was employed to resize the image to fit an SVGA monitor screen, then save it in .JPG format. An example of the image file sizes involved can be seen with the scene of the Rho-Ophiuchi complex. It began as a 2048 X 3072-pixel 16MB .PCD file, then was converted and cropped to a 1,600 X 2000 pixel 3 MB .PSD file. This in turn was converted to an 894 K 256-shade grayscale .GIF. The .GIF was reduced in size to 616 X 768 pixels and saved as a 147 K .JPG for full screen SVGA display on this Web site.
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