After spending so much time making cameras, film holders and sundry other crap, the irony of taping a negative to a plain piece of glass for scanning is not lost on me. Glass does work surprisingly well considering the minimal expense and effort, but I’ve missed working in the shop so thought I would try to come up with a decent carrier for my Epson scanner. I though about modifying a standard enlarger negative carrier, but in my experience those need the tension supplied by the closing of the negative staging on the enlarger itself to keep them closed and flat. Not to mention good ones are difficult to find and expensive in the 5×7 format.
Frugal, but fairly effective. The negative is taped to the glass with low-tack drafting tape, which is reusable for a half-dozen scans or so, and is sticky enough to stretch the negative taut, but not sticky enough to leave any residue on the negatives. 5″x7″ film size is permanently masked off on opposite side of glass from negative with Rubylith tape. The assembly as shown above is flipped onto scanner bed so that negative is on the bottom of glass, facing the scanner’s optics. The 4mm thickness of the rubber feet was blind luck- they perfectly position the negative at the factory-set focal plane of the V700’s lens.
The sweet spot of my scanner’s lens is 1/8″ of an inch above the scanner’s glass platen- a dimension which seems to qualify a variety of materials. But most of the reasonably-priced choices aren’t very flat. There is precision ground 1/4″ aluminum plate available at about $45 per square foot from McMaster Carr, but the milling required for the inside aperture as well as a rabbet to hold the negative at the exact height seems like a little too much effort. Plus I need a way to hold the negative taut instead of just laying it in a frame where it would sag.
Instead of using plate material, I doubled up some locally available 1/8″ non-anodized aluminum bar stock . The corners are lap-jointed with a 3/32″ margin on the inside to support the negative. I checked the stock for flatness on a stone slab before cutting the parts, sometimes they get a little beat up in the hardware store bins.
A simple frame isn’t a terribly exciting project, but since there is only 3/32″ on each side to support the negative it has to be pretty accurate. I thought about brazing the frame but worried a bead would interfere with the tiny margins, or that heat might warp the metal. I’ve not had good luck with epoxies, but to be fair I probably haven’t tried the most appropriate ones. I decided to just screw the parts together so the frame can be taken apart for adjustment or modification if needed.
A piece of 1/4″ plywood cut to the exact O.D. of 5×7 film, along with a rabbet cut to the O.D. of the actual image area, really helps to size the parts exactly and to keep the assembly square. Rabbeted plywood strips screwed to a 3/4″ plywood base keep the parts tight together while drilling all the pilot holes. A few 3/4″ plywood battens were also screwed across the top to prevent parts from lifting out of the frame during drilling.
Test fit. Since it’s only 1/8″ thick on the bottom, I used 6-32 x 1/4″ undercut flathead screws to maximize the thread.
It’s pretty flat, no room for a .005″ feeler gauge around the perimeter, but I briefly lapped the bottom with silicone carbide on float glass just to say I did. I reused the inside jig to keep even pressure on the center of the frame when grinding. The only thing that mars the smooth flat surface of the aluminum during fabrication is the little swarf blossoms that come from drilling and tapping, but those can be sliced away easily with a razor blade.
The long side pieces float- I cut some slots perpendicular to the edge so the negative can be pulled taut before being tightened down. Scoring a line on the underside of each of the floating pieces with a utility knife creates a very fine burr that grabs the margin of the negative securely without damaging it.
Due to the limited depth under the scanner lid when closed, I cut the hub off of oversized thumb nuts and ground them flat. The head on these is only 1/8″ thick. The 6-32 thread on these nuts stops at the head, but once the hub is lopped off it’s easy to tap the head for 8-32 thread without reaming out the hole. It won’t cut to full thread depth, but it’s good enough for such a light duty use. (McMaster used to have a 8/32 version of these nuts that are fully threaded, but can’t seem to find them anymore. They also have ready-made black oxide wheel nuts, but they are almost 1/4″ thick.) The nuts tighten down onto studs that are tapped and secured with red thread-lock into the underlying frame. The final assembly is 3/8″ thick, which barely fits in my scanner. The Epson does have an adjustable lid for scanning thick media like open books, but for frequent use this would require shimming the hinge posts and lid rests to avoid damage, and I would rather not have to change stuff around when switching to reflective scan mode. But as it is the carrier doesn’t touch the light source glass, which is recessed up in the lid.
The carrier is somewhat heavy and the frame is so low-profile that it really needs something to hold onto- otherwise I’ll eventually drop it and shatter the scanner glass. The scanner’s depth is too thin to add fixed handles to this, so I made some swivel handles out of a lone heavy gauge stainless steel coat hanger. It was an odd thing to find, almost providential, this bright burly thing slumming with the anemic and deformed hangers in the back of the closet. The existing neck bends on the hanger were perfect for one side of each piece so I made a simple jig out of plywood and screws to mirror that bend. Although I’m still not sure how I will attach these to the frame.
The parts were scuffed sanded with 180 grit for better paint adhesion, washed with soap and hot water, dried, wiped down with denatured alcohol, and dried again prior to painting. Rustoleum ‘Painter’s Touch’ flat black spray paint is pretty decent- it levels well and dries fast. We’ll see how durable it is. I should just get a kit to anodize aluminum, but haven’t gotten around to it.
After the paint cures the bottom of the frame will be covered with a .005″ UHWM film to protect the scanner glass. I may use some on the bottom of the floating frame pieces and thumb nuts as well to protect the paint. It has high tack adhesive backing so it’s easy to apply. Update- ended up removing this film from the bottom of the frame, scans are sharper without it.
Paint seems dry enough this morning so went ahead an applied the UHMW film to the bottom and finished up the handles.
For the handles, just made a few low-profile battens and drilled holes in the end for the swivels. Good enough.
Easy to load, and the negative doesn’t deform or buckle, even over long scan times under a warm lamp.
Forgot I needed to cut a new calibration strip since I won’t be using the Epson ‘Film Area Guide’ any more- a chintzy plastic frame that needs to be placed on the scanner platen to use the higher resolution area that’s towards the middle of the scan path. I made a much smaller version out of some 1/16″ Garolite. See update below.
First test- new carrier on left, glass-tape method on right. 100% crop at 2400 ppi (for scale, full image with zoom cursor at top right of screen shot). Scans processed identically in photoshop. The new carrier appears to be sharper, but will run a few more scans to be sure. (For full-size view, right click on image and click “View Image” from menu.)
A few more scan tests, properly done this time. I’m embarrassed to admit I’ve been using the wrong setup for my scans. I had it exactly backwards- the ‘Film Holder’ mode is used for the higher rez lens, not ‘Film Guide’ mode. The result was so much better I did another scan with each method- new carrier on left, glass carrier on right. Both were processed identically, all sharpening turned off on the scanner and none applied in PS. Pretty close, but I detect some ghosting on the glass carrier- might be a slight hall of mirrors effect.