Comparing JSC and ASU scans of Apollo Hasselblad photographs
Introduction
Multiple sets of scans of the original film photographs taken during the Apollo missions were made. Here I mostly intend to highlight some of the scanning artifacts present in these and especially in the most recent set made in partnership with Arizona State University, in hope that eventually these historic photos are scanned again. Below are described the different sets.
2005 JSC Scans
This set of scans was made circa 2005 by Johnson Space Center. Mercury and Gemini photographs were scanned as well as the Apollo ones as part of the effort.
Mercury and Gemini scans are downloadable from March to the Moon in uncompressed TIF format.
Apollo scans are downloadable from the National Archives Catalog or the Project Apollo Archive account on Flickr, in compressed JPG format.
In the about section of March to the Moon we get this information :
The Mercury and Gemini flight film negatives were scanned with Oxberry 35 mm and 70 mm systems.
The Oxberry systems use the Kodak HR-500 scanner, which incorporates the Kodak KLI-6013 tri-linear line sensor. Dark signal correction and flat-fielding are performed automatically during standard scan operations. Scans are digitized as 8-bit numbers per channel.
The scans are 4410 samples by 4600 lines, and the file sizes are ~58 MB.
A typical unprocessed 2005 JSC scan can be recognized by the lack of contrast and the greenish tint.
The main scanning artifact on these images is the horizontal red streaking that happens when a bright object is in the frame.
2008 JSC Scans
This set is very similar to the aforementioned JSC scans, and was likely made with a similar scanner, apparently around 2008. There are a few differences though.
Some of these are downloadable from NASA’s Gateway to Astronaut Photography of Earth, I’ll take AS08-14-2383 as an example. You can see it here, and you’ll notice that you can download the previously mentioned 2005 JSC scan on there. Up until very recently you could go to the “Download Options” section and select “Request Raw file from camera”. That button has disappeared but the link it would take you to still exists here. On there you have to wait 5 minutes for the file and it should download. What you get is a 189 MB 5700x5800 16-bit TIF file, shown below.
These also have a characteristic scanning artifact, though it is more subtle. In the image below you’ll notice that there is no streaking across bright objects, though if you look closely to the left of the frame, there is a sort of line/separation with blueish light to one side.
ASU Scans
This set was made by Johnson Space Center in partnership with Arizona State University.
It’s unclear exactly when these were scanned. It seems that the project was started in 2007, with scans of photographs taken by the Apollo 15, 16 and 17 Mapping Cameras being progressively published to the Apollo Image Archive from 2010 onward. Panoramic images started getting published soon after.
Hasselblad photographs scans were done and published later to March to the Moon, but I’m not sure when exactly.
In the about section of March to the Moon we get this information :
Apollo scans are acquired with a Leica DSW700 photogrammetric scanner allowing for very high geometric and radiometric fidelity. In addition, the films are scanned at very high spatial resolutions up to 200 pixels/mm (5 microns) and an extended bit depth (14-bit A/D) in order to ensure that as much of the information content of the film is preserved.
The DSW700 was modified from the original 12-bit A/D to a 14-bit A/D because the Moon is a very high-contrast target and the original film is capable of capturing a very wide range of grey scale variation. The combination of small pixels (5 micron) and the 14-bit gray scale results in a very detailed scan and, of course, very large raw scan files.
The real selling point of these is the resolution. It it much higher than that of the 2005 or 2008 JSC scans. But unfortunately, these have many scanning artifacts.
A typical unprocessed color ASU scan looks very dark.
Inversely, a typical B&W negative ASU scan looks very bright.
Comparing JSC & ASU scans
To highlight the scanning artifacts of ASU scans, they are shown next to JSC scans. I mostly used 2005 JSC scans for the comparisons.
Except when stated otherwise, the JSC scans are shown on the left side, and the ASU scans on the right side.
All images have been enhanced (extremely brightened or darkened in some cases) to make artifacts as obvious as possible. Clicking on the images to enlarge them is recommended.
Streaking/Lines - B&W Photos
These streaking artifacts are very common. A few examples are shown here but they are present on most if not all B&W scans.
Underexposure - B&W photos
ASU scans are said to have an extremely good dynamic range. Quoting from March to the Moon’s about page :
the films are scanned at an extended bit depth (14-bit A/D) (16,384 shades of grey) in order to ensure that as much of the information content of the film is preserved.
It is surprising then to find that some JSC scans, which have a lower bit depth — and were downloaded as mere compressed JPG files for this post — manage to actually capture more information in even the darkest parts of the most underexposed photographs.
Glare - Color Photos
Glare is present on every single ASU scan of a color slide, probably introduced during the scanning process itself. It has the same general pattern on each frame, but is still slightly different every time, making it challenging to remove accurately.
It is worth mentioning that ASU provides processed versions on their site that attempt to get rid of this glare by subtracting a fully dark frame (with only the glare on it) from the raw scan. The results vary, it works fairly well on darker photographs where the glare tends to be quite consistent, but it doesn’t work as well on brighter photographs where the glare is more erratic.
it also looks like the Apollo 9 and Apollo 13 photographs were scanned differently, so that the glare is rotated by 180° compared to scans of other missions. This wasn’t taken into account and the same flat-field correction was applied anyway, which ends up with the glare not being properly removed at all.
Streaking/Lines - Color Photos
Very similar to the ones on the B&W negatives mentioned earlier, but this time in color. These are unfortunately very frequent too.
Overexposure - Color Photos
Again, one of the main benefits of the ASU scans is supposed to be the great dynamic range, and again it gets outclassed by the JSC scans. Some of the brightest photographs have regions that are overexposed in the former but not the latter. The two following examples use the 2008 JSC scans for the comparison.
