Hi Aram!
As I understand things, "Dayglo" paint works by absorbing UV and re-radiating
it in the visible range, thus giving it "the glow".
If the shot is metered on the sign, it renders properly. But, if we increase
the exposure, to allow for the interior of the tent, the sign is now
overexposed. This, I think, is clear enough.
However, I'd expect it to be washed out, (it is) but that does not explain the
colour shift. Sorry, I can get you a film shot, but you'll have to wait until
next year.
I will send you the original .orf file via private email, once you are home.
(Let me know, will ya?)
Thanks.
David.
--
David Young - Photographer
Logan Lake,BC, CANADA
Webpage: www.furnfeather.net
Photography e-books: http://tinyurl.com/SS2SS-Books
Hi again David. Had some time to read other's posts. Not sure I agree with
all of any. I put your photo into Lightroom and adjusted the exposure. No
matter how I reduced the total exposure, it never shifts the color enough to
give the orange sign seen in your T10 photo. The black always has a color
tint. Not sure what that means, but there is something other than just an
exposure induced color shift, perhaps. And if I use the dropper tool to set
the white balance off the black letters, I still get nowhere close to
orange. I need more time to play, time that I don't have today.
Your observation about UV is worth some thinking. As you mention, camera
sensors are more prone to IR problems than UV. If I read your thoughts
correctly, you are thinking that thre is more UV being sensed from the
fluorescent part of the sign, but I would postulate that there is less UV
from that part of the sign. Given the UV light is uniformly striking the
whole sign, the orange part is "converting" some part of the UV to visible
light. The rest of the scene is not. That should mean there is less UV
striking the sensor from the orange sign than would if it were just a plain
paint.
As I stated in a previous post, too bad there is no film record of the scene
to see if it is a sensor issue or a scene issue.
But I am still thinking. Busy day today as we are planning on leaving for
home tomorrow. Could you send me an undeveloped photo to play with? I
won't have time until I get home, but could be fun.
Aram
Aram Langhans
(Semi) Retired Science Teacher
& Unemployed photographer
"The Human Genome Project has proved Darwin more right than Darwin himself
would ever have dared dream." James D. Watson
-----Original Message-----
From: leicareflex-bounce@xxxxxxxxxxxxx
[mailto:leicareflex-bounce@xxxxxxxxxxxxx] On Behalf Of David Young
Sent: Monday, January 18, 2016 8:03 AM
To: LRflex <leicareflex@xxxxxxxxxxxxx>
Subject: [LRflex] The Sign - more research.
Good Morning, fellow flexers!
As you know, I spent my weekend, selling beer, for charity, at our local
Pond Hockey Tournament. (Photos to follow.)
It all started with a shot I took a shot of two of our volunteers, joking
around, as if they were drinking (the cans were sealed).
But something was very odd with this photo. Take a look.
http://www.furnfeather.net/Look/BeerSign.html
The tent, sky, snow, clothes, faces, etc. are all the right colours.
But the sign appears to be RED lettering on a YELLOW background - at least
on my monitor. (Your mileage may vary.)
So I took a little Olympus T-10 Point & Shoot ($49 when new.) and made some
comparison shots.
First up is the sign, by itself. To me, the sign looks correct , with
BLACK lettering on a flourescent ORANGE background.
http://www.furnfeather.net/Look/sign/Sign-1.html
However, when I backed up, to take the entire tent (as I'd done with the
first, troublesome shot), the camera exposed for the tent's interior. As
with my E-M1, all colours are correct, EXCEPT for the sign, which changes
colours.
http://www.furnfeather.net/Look/sign/Sign-2.html
For a control, I shot the tent, with my E-M1, exposing only for the "Beer
Garden" sign.
http://www.furnfeather.net/Look/sign/Sign-3.html
and the colours are all accurate (if dark) including the sign.
But, when I exposed for the interior, the sign changes colour, again!
http://www.furnfeather.net/Look/sign/Sign-4.html
Now, exact colours may be slightly different, on different monitors (mine is
calibrated) but you should all be able to see the differences.
My question remains ... why?
I can only think that since flourescent paints re-emit UV light in the
visible range, to get that "glow", that when the frame is exposed for the
shadows, the sign becomes over-exposed, creating the colour shift. (It is
IR, not UV that most sensor have problems with.)
But, curiously, this does not appear to be the case with other flourescent
items, such as safety vests.
http://www.furnfeather.net/Look/sign/Sign-5.html
though I admit that this shot is not exposed for shadows. (Sorry, could not
find a better "control", yesterday.)
If anyone has a better idea, I'd love to hear it!
Thanks
David.
PS: Bill: Yes, the beer boxes are red and correct for Budweiser boxes.
Neil: your explanation may come closest to the truth. Thanks to all who
looked and responded to my first plea.
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