How to scan a glass negative?

BB
Posted By
Bill_Brammer
Oct 12, 2003
Views
1245
Replies
13
Status
Closed
I have an old silver glass negative that I want to scan? Any advice? Do you know if a regular flatbed scanner will damage the negative? The size of the negative is 4×5 inches.
EI
Ed Ingold
Oct 12, 2003
Is this a negative, or a tintype? The image on the latter is probably too light to scan.

Any flatbed scanner with a transparency adapter should work. Resolution is not a major issue with 4×5 negatives because of its size. 300 dpi in the final print size is normally all that is required. An Epson 2450 (or 3200) would be an inexpensive choice of scanners.

You don’t want to put the emulsion in direct contact with the glass bed, because it might get scratched. Putting any flat surface in direct contact will also result in Newton’s rings, which are hard to remove later. Make a mask which will support the negative at the edges, off the glass. Focus should not be a problem up to 0.5mm (1.5mm for the Epson 2450).

Software is an issue. Epson software doesn’t work well for photographic-quality scanning. Most people use SilverFast AI or Vuescan.

Scan at full bit-depth, which is 14 bits/channel for the Epson 2450. 8-bit scans do not have sufficient resolution for B&W, and will look contrasty and posterized. It helps to combine multiple scans to reduce noise in the dense areas. SilverFast has a multiple-scan option.

Some people have better luck scanning as a positive, then using Photoshop to invert the image. Scanning in RGB then converting to gray scale in Photoshop sometimes works better than scanning directly in gray scale. wrote in message
I have an old silver glass negative that I want to scan? Any advice? Do
you know if a regular flatbed scanner will damage the negative? The size of the negative is 4×5 inches.
L
LenHewitt
Oct 12, 2003
Bill,

Any flatbed with a transparency adapter should be fine.
BB
Bill_Brammer
Oct 12, 2003
What is a transparency adaptor?
MM
Mac_McDougald
Oct 12, 2003
Additional light source from the top.
And no, you can’t very well "make" one.
Turns off bottom light, only top one used.
Sofware/firmware designed to work with it also, to calibrate exposure/color balance, reverse color negs to neutralize orange mask, etc.

Mac
DJ
dennis_johnson
Oct 13, 2003
Depending on the negative’s density, you can sometimes get a useable scan on a standard flatbed scanner. Be sure to place the emulsion side of the negative facing the scanner glass. The worry I would have with a glass negative is that you might scratch the scanner glass.
Another issue that crops up – even using a transparency adaptor – is the air gap between the two glass surfaces creating a moire pattern in the scan.
There are various gooey or wet ways to fill the air gap and cure the moire problem, but I’m no expert in that area. Others here are more familiar with the procedure and will likely come forward.
RH
r_harvey
Oct 13, 2003
Emulsion down, for better focus, then flop the image to make it right-reading. Try little shims at the edges, made of film or (maybe) tape, to very slightly separate the negative from the bed.
PH
Photo_Help
Oct 13, 2003
Dennis,

The "air gap" shouldn’t create a moire pattern. I would set the edges on thin cardboard to prevent contact with the glass as r_harvey has suggested.
LH
Lawrence_Hudetz
Oct 13, 2003
Glass plate negs are usually dense and sometimes contrasty. They are designed for printing with transmitted light, and if you try to scan as reflective copy, highlights will tend to block up. The tonal scale is also skewed. I have tried to scan my 8×10 negs that way, and even thin negs don’t scan well.

Better, make a contact print of the neg and scan that. Be sure that your print is fairly flat in scale. You can pick up contrast later. The print is an intermediary, so don’t worry if it doesn’t look good.
DJ
dennis_johnson
Oct 13, 2003
Photo Help,

Moire patterns are indeed caused by the minute gap between the two surfaces. I called it an "air gap", but meant it in the sense that the gap is perhaps a few molecules of separation, and slight variances in the degree of contact between the two surfaces will cause the interference pattern to appear. If the gap is made larger, as by your technique, the interence patterns do not occur, but you run the risk of losing focus as the scanned element is farther from the scanner surface. I don’t know the focal depth of your scanner, but mine is limited.
LH
Lawrence_Hudetz
Oct 13, 2003
And with moire in mind, do not make a glossy print!
PH
Photo_Help
Oct 13, 2003
dennis,

You said it yourself. It is the contact interference, not the "air gap", that causes the pattern. Raising the negative a millimeter or two is not going to make a bit of difference with regard to the focal depth of the scanner.
JS
John_Slate
Oct 13, 2003
Not moire… the pattern from the thin "air gap" is referred to as "Newton Rings" and is, as suggested above, due to "thin film interference", where the two reflective surfaces (the bottom of the negative and the scanner glass) cancel out (nodal points) discreet wavelengths of light at particular gap widths. They are typically multicolored due to the different parts of the spectrum being cancelled out. The pattern one sees in an oil slick on water is just such a pattern.

Scanner operators have been solving that problem 2 ways for years:

1- Oil mounting

2- Newton Ring powder which is incredibly finely ground glass which diffuses the pattern without harming the image.

Or the wider air gap should work too…
DJ
dennis_johnson
Oct 14, 2003
Yeah…what he said!

🙂

Related Discussion Topics

Nice and short text about related topics in discussion sections