#55309 - 01/30/03 12:21 AM
Re: Visible light demo
[Re: MW1]
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srs1a
Old, dense-headed hammers are cool. Best nail pounders.
Registered: 08/15/02
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Wow! Super demonstration!!! thank-you MW1.
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#55310 - 01/30/03 05:35 AM
Re: Visible light demo
[Re: srs1a]
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Anonymous
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U DA BOMB MW !
I'm sure this helped a lot of collectors. vwtdi
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#55311 - 01/30/03 01:31 PM
Re: Visible light demo
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Anonymous
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Nice post. As a side note, UV wavelength LEDs have recently been introduced into the marketplace. I haven't obtained one yet, but it could potentially offer a "do it yourself", low cost option if the brightness and uniformity is sufficient for illuminating cards. Currently they're being used for dentistry (catalyst to harden filling material).
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#55312 - 02/08/03 03:14 PM
Re: UV demo
[Re: MW1]
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povertyrow
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Here's the image of a well-known football card illuminated by a high-band UV source in a dimly lit environment.
Interesting. What was used to photograph the UV pic?
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This is THE WATER COOLER. All tremble before its wrath and might! ::oh my::
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#55313 - 02/10/03 03:10 PM
Re: UV demo
[Re: povertyrow]
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MW1
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povertyrow,
I used a Nikon950 with spot metering, no flash, in close-up mode and a slow shutter speed.
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#55314 - 02/11/03 06:21 PM
Re: UV demo
[Re: MW1]
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povertyrow
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I used a Nikon950 with spot metering, no flash, in close-up mode and a slow shutter speed.
OK - lemme back up a bit. Was a pro photographer in the 70's (2 1/4 x2 1/4 and 4x5).
What I mean for this type of photography is:
What light source
What film type?
Any special filters?
Thanks!
_________________________
This is THE WATER COOLER. All tremble before its wrath and might! ::oh my::
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#55315 - 02/13/03 02:58 AM
Re: UV demo
[Re: MW1]
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hammer
Carpal Tunnel
Registered: 11/19/02
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MW, I'm not following you here. Which are the specific areas on the card imaged above, that the blacklight is indicating as redone, altered, or bleached?
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#55316 - 02/13/03 03:32 AM
Re: UV demo
[Re: povertyrow]
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MW1
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What light source?
Good question! I collected 10 different samples of incident light using a standard light meter. Then, using the following equation for irradiance (14.1),
where d represents the diffusiveness of each wall, I was able to derive a value of .05 Watts per meter squared. Hey, I'm only kidding! 
I had the lights off in the room where I took the photograph. Two rooms over -- approximately 50-60 feet away, I had the lights on (standard fluorescent office lighting). There may have also been a small amount of light diffusing through the blinds on the windows.
What film type?
128 MB Lexar High-Speed Compact Flash Card.
Any special filters?
None. Using my medium format (film) camera, however, I would probably throw on a clear filter and a polarizer to get the image to look right -- but I really haven't used anything but digital cameras for over a year now, so who knows. I'm sure you have a better idea about this than I do.
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#55317 - 02/13/03 03:39 AM
Re: UV demo
[Re: hammer]
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MW1
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hammer,
The contrast between light and dark is not as great as it would visually appear in person. Suffice it to say that the darker areas represent "unaltered" portions of the card and lighter areas represent sections of the card where "alterations" have been performed. With the UV source I used, there are also slight graduations in the lightened areas -- probably due to the type of alteration that was done. In my experience, this is fairly typical for most professional grade work.
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#55318 - 02/13/03 03:47 AM
Re: UV demo
[Re: MW1]
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MW1
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Followup:
hammer,
A fair portion of the card has been altered in some fashion (micro-trimmed, chemically treated, re-inked, etc.). With the exception of some interior portions, not a whole lot of the card remains untouched. If I were to take a similar picture of an unaltered 1952 Bowman Large Lansford, the only thing you would see is a darkened image on your screen and a perhaps a slight magenta tint. Hope that helps!
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