How to Scan Glass Plate Negatives

Please look at the picture full-size against a grey background.

The picture (right) “Netham Trees”  is a Lith process all done in Lightroom.

The subject of this post is in response to a query by Lynn Buckley about my last post on retouching old photos.

Lynn’s query was about the scanning of glass plate negatives. The scanning of Negatives that are going to be enlarged is different to scanning a photo to be printed at the same size.

The first thing to say is – think about all the possible uses for the pictures that will be created from the scans.

  • Will you want to make prints that are bigger than the negative?
  • Will prints be printed on an Inkjet printer or by a professional printing press?
  • Will the scans only be used for pictures on the web?
  • Will the pictures be projected digitally?
  • A combination of print and web/projected?

I use an Epson V750 Flat bed Scanner in the Professional Mode this gives me complete control. I guess all Scanners have a basic mode if you are not sure what you are doing.

If your Scanner has dust and scratch reduction software built-in do NOT use it on silver based ie glass negatives. The software will think the grain that makes up the picture is dust and do very odd things.

If your scanner allows you to crop the picture before the final scan that’s a good idea.

If you can do a preview scan it is a good idea.

I would scan the Glass negatives in 16 bit Greyscale mode.

A less contrasty scan is better than a scan that has too much contrast. Contrast can always added later.

As a general rule its better to do a high-resolution scan and have a larger file than to make a small low resolution scan and then try to make a big picture. You can go down but not up in size.

Be aware of dust on the Scanner platter & Negative, attention to detail with save time later.

Example 1

The scanning resolution Pixels per inch (ppi) must always be at least the number of the printing resolution (dots per inch) dpi

Say for example you what to make a 12×12″ print from a 6x6cm(2 1/4″) Glass negs you have from an ink jet printer. The scan will need to collect and provide enough information to print the created file at 240 dpi (dots per inch).

Therefore the absolute minimum scanning resolution required is 240 ppi without enlargement.

You need enough pixels to print 12″ from a 2 1/4″ Negative. Therefore 12″ divided by 2 1/4″ is a 5.3 times enlargement. 5.3 x 240 dpi of the final print gives 1272 ppi to take the enlargement in to account.

The nearest scanner resolution is 1200 ppi.

Depending on the quality and detail of the glass negative I would probably opt to scan at 2400 or 3200 ppi. Obviously the more detailed the scan the larger the file.

Example 2

Say some of the scans will end up in a book at say 8″ square. A professional printer will always ask for files at 300 ppi.

You need enough pixels to print 8″ from a 2 1/4″ Negative. Therefore 8″ divided by 2 1/4″ is a 3,55 times enlargement. 3.55 x 300 dpi of the final print gives 1066 ppi to take the enlargement in to account.

Depending on the quality and detail of the glass negative I would probably opt to scan at 1200 or 2000 ppi.

Example 3

Say you are only ever going to use these scans for the web or digital projection.

All Computer monitors have a resolution of 72 dpi there is no need to make highly detailed scans in this case.

You need to decide how big you picture will appear on the screen for my blog the pictures are 800 px on the long side. If you are going to project them the standard width is 1400 px.

I use Lightroom all the time. To get the pictures in sRGB at the right size and resolution I use the Export feature of Lightroom. Lightroom when Exporting a file will make a copy, resize it, correct the resolution and then put the copy file where you told it to. Of course you can make a saved pre-set so all the exporting is done with one click.

Hopefully this has been of some help, as scanning is a thing I do very little of.

A big hello to all the new followers of my little blog this week.

(c) Andy Beel FRPS 2012

www.andybeelfrps.co.uk

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4 responses to How to Scan Glass Plate Negatives

  1. Lynn Buckley says:

    Andy, thank you very much! This is excellent and just what I needed to know. I have 250 glass plate negatives to digitise for an exhibition. This information gives me the confidence to get started. Really appreciate this!

    Like

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