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|We're not post-Newtonian. We're anti-Newton.|
|Scanning 6x12 with the Sprintscan 120 or Artixscan 120TF|
The Polaroid Sprintscan 120 (and its clone the Microtek Artixscan 120TF) presents an opportunity and two challenges. The opportunity is a 6x24 scanning aperture in even the standard medium format carrier. This allows you to scan really long negative strips or really long negatives. The challenges are keeping film flat and scanning a big frame consistently and conveniently. If you have Silverfast 6.5 (or up), the following is a fairly simple way to address this.
First, get a glass carrier. Forget the one that Polaroid and Microtek sold. It has too many dust surfaces and is so much wider than a 120 filmstrip that you will have misaligned strips (yes, it has little template thingies, but they are fairly pointless). It is also exceptionally difficult to clean. Instead, call up Focal Point in Florida (they actually made Polaroid's original glass carrier) and have them make you a 3mm anti-newton glass that replaces the top plate of the normal 120 carrier.* If you sub a glass for the original top, the film will smash perfectly flat without needing any bottom glass (if you have used Durst enlargers, this is the same trick where you take a glass carrier and swap out the bottom glass for a negative plate). When you scan, you will get the negative plus up to 2mm of black on all four sides (assuming that the cut ends have some margin around the actual image - and your camera is closer to 50mm frame heights than 55mm).
* Note that if this is cut correctly, it will not be able to slide. To remove the glass, you will need to pry it up using one of the cutouts along the side and a wooden barbecue skewer or other similar tool. Note also that the "dull" side of the glass goes down on the negative (you can see which side is which by looking at a reflection of a light on the glass.
Second, load up the carrier. Make sure that the negative is positioned in the bottom part of the carrier such that the film "margin" is visible in the leading edge and top and bottom edges of the carrier (you may not get top or bottom, depending on your camera - you definitely get both with a Noblex). This will assure that you get your black border (so long as you did not cut your negatives into the image). To better align the negative, drop it into the carrier, turn the carrier so the short dimension is up-and-down,and then shake it until then negative strip squares with the channel in the carrier.
Third, boot up Silverfast. I am sorry to say that this does not work with Vuescan due to Vuescan's apparent constant desire to reset exposure between frames no matter how you set it. Set Silverfast for the following:
Fourth, do a prescan of both frames in the filmstrip function, select both frames, and do a prescan of the first frame. Now hit the "auto exposure" button (looks like a camera shutter). This will set the exposure such to get a black and a white. You only need to do this exposure correction once per roll of film (or even for numerous rolls shot and developed roughly equally). You do not need to do the filmstrip part again ever.
Finally, do a 1-2 batch scan. At this point, you are covered for future editing and can use Photomerge on Photoshop to merge your work (you will probably have to downsample to 2000 dpi to get any type of speed on most machines). For advanced productivity, pull the scans into Lightroom, enlarge the slide viewer mode until only two frames fit, and then you can see the pieces side by side (note, for the "flipped" scans, be sure you are looking at the correct halves. Exposure bracketing can lead to confusing results at first.
The easiest way to correct the exposure is with the white/black eyedroppers in Photoshop's Levels function, though Lightroom's tools are very easy.
Why does all of this work?
First, you have eliminated 2 annoying dust surfaces on a bottom glass and created a carrier that will keep things flat and in place. Periodically clean the AN glass. I recommend an Ilford Antistaticum. If you fingerprint the glass, I would recommend using Stoner Chemical's aerosol Invisible Glass, which is available at auto parts stores (it also works fantastically on household glass). You can wipe it off with a paper towel, and then follow up with your Antistaticum.
Second, using the green channel for b/w means that only one CCD line will be used, making the scan go 3x faster and eliminating the "focus banding" you sometimes see with the Sprintscan and other scanners (this is related in part to "stitching" that occurs when the scanner goes back and forth to position each of the R, G and B lines on the same position). In addition, green should be the sharpest color for non-APO optics used in scanners. If scanners are in fact apochromatic, it doesn't matter which color you use.
Third, you have set up an exposure regime that will maximize your ability to merge the two halves (or really, left 3/4 and right 1/4) of the 6x12 image. You can do most of the other steps with Vuescan, but you really have to go to heroics to lock it down.
Finally, you have used overlapping frames to get around the limitations of using the Polaroid with a Silverfast program that does not respect the hardware framing and is not easily adjusted.
Hopefully, that helps.
Disclaimer: all of this is at your own risk.