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Old 10th Mar 2021, 12:55 pm   #1
ronbryan
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Default How should a tuning dial glass be scanned?

I had a GEC BC563 AM/FM radio with a tuning dial glass broken at one end that had been glued with the broken bits misaligned. These dials are not very well retained and can fall out when dismantling the set - there is even a warning of this in the service manual, should you read it before dismantling!

I cleaned off the old glue, stuck it together with glass superglue and touched in the break lines with Tamiya model paint, but decided it would be a good idea to scan it and edit the image with Photoshop to disguise the cracks in case the repair failed in future.

The question is how should it be scanned so that a replacement could be made? With my Canon 8400F A4 scanner, if you put the scale directly on the scanner bed glass, you end up scanning the internals of the scanner through the clear portions of the scale. If you line the bed of the scanner with white paper, the scale calibration does not show up. Equally, if you line the bed of the scanner with black paper, unsurprisingly the clear sections scan as black, so are not transparent. Is there a way round this problem?


Ron
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Old 10th Mar 2021, 3:47 pm   #2
paulsherwin
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Default Re: How should a tuning dial glass be scanned?

You need to scan against a white background, which will cause any transparent areas to scan as white. White doesn't print on a conventional consumer printer, so any version printed on film will be transparent again.

Of course, this means that any areas of the scale which actually *are* white will become transparent too. If this is a problem, then you will need to manipulate the colours in software to produce a good printable image. As an example, you could scan against light blue, then change all the white text to black, then change all the light blue to white. You will need to experiment.

If you really do need to print white, you will need to pay a commercial print shop to do it.
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Old 11th Mar 2021, 9:28 am   #3
ronbryan
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Default Re: How should a tuning dial glass be scanned?

Thanks for the helpful suggestions, Paul. I'll do some experiments and see what I can achieve.

Ron
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Old 11th Mar 2021, 10:03 am   #4
Radio Wrangler
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Default Re: How should a tuning dial glass be scanned?

As you're going to photoshop the scanned image, you can scan against any background not white and not that greeny-beige. This will give you some contrast and you can grab the respective areas by colour. You can then recolour the white, beigy-green and transparent areas any colour you want.

As Paul said, domestic printers don't do white ink, that just comes out as transparent. Photographic transparancies are no better. Printers also don't have transparent ink so you cannot print anything which segregates white from transparent. both are not-ink in terms of printing.

You can get opaque white or translucent white on a print done on plastic film by hand painting white paint on the reverse side, so that transparent areas become white.

Printer colours rely on the whiteness of paper. Try to print them on top of any other colour (or lack of colour) and results will be very odd. You may have to paint on a white background behind those greeny-beige areas to make them work.

This leaves the problem that you still can't print white on a transparent background. Worse, even if you decide to go for an off-white colour, then that still relies on being over a white substrate in the mind of the colour management system of the printer.

The damaged bits will need hand-editing anyway to restore them.

You could split the coloured areas off as layers from photoshop and send them out to a silk-screen printing firm, but that could be extensive.

I think you've got something which is outside the capability of what printers aimed at white paper can do.

Some redesign of the panel might get you round it... black outlines for the white characters, perhaps?

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Old 12th Mar 2021, 2:55 pm   #5
Michael Maurice
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Default Re: How should a tuning dial glass be scanned?

Ron, I have had this work done a few times. I will phone you a bit later.
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Old 12th Mar 2021, 5:31 pm   #6
Restoration73
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Default Re: How should a tuning dial glass be scanned?

I could not get a good scan of a Pye glass, so I opened the scanner lid and illuminated it
with a LED lamp from above. The result was very close to the original.
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Old 18th Mar 2021, 7:46 pm   #7
robreddog
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Default Re: How should a tuning dial glass be scanned?

took a picture of mine and then opened it in paint (or simular program), i did this with mine, got some perspex cut to size and printed the dial out on a waterslide transfer, i needed 2 x a4 sheets but they joined up pretty well.
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Old 19th Mar 2021, 9:03 am   #8
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Default Re: How should a tuning dial glass be scanned?

This is a job for a top light scanner as used for scanning film transparencies. So the lid off with an LED light above is the way to go
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