Why does this picture has a greenish cast?
pixels
look and give me your opinions. Picture was taken with an Olympus C-
2500L, P Mode, Centre-weighted metering. It was taken in the late
afternoon at a seaside when the sun was about to go down.
http://pages.intnet.mu/ali/sandplay(2).jpg
Gordon R. Frey
"pixels" <jetc...@enotify.com> wrote in message
news:MPG.13fbe4a5a...@west.usenetserver.com...
Well the sun was setting.... refraction of the suns light though the
atmosphere will give you the red sun sets but at one point the light will be
green, and I've hear it called the green flash.
Gordon
LKRZ
>look and give me your opinions. Picture was taken with an Olympus C-
>2500L, P Mode, Centre-weighted metering. It was taken in the late
>afternoon at a seaside when the sun was about to go down.
>http://pages.intnet.mu/ali/sandplay(2).jpg
Variation on Oly blue.
Digital cameras, Olys in particular it seems, have problems getting colors
right at twilight.
This is, fortunately, very easy to fix if you've got a imaging program that
does layers.
Put the eyedropper on the sea and to get the green-grey color.
Now open the color wheel and go to the OPPOSITE color on the wheel (in this
case a light violet/grey).
Add a top layer to the photo.
Flood fill the layer with the color above.
Set layer to Dodge and adjust transparency.
I tried this with your photo using Paint Shop Pro. Result was excellent.
LKRZ
>taken at a slightly different angle and here there is no geen cast.
I think it's the angle that matters. I don't know technically what does it, but
I know that I usually have to do what I described to photos I take at twilight
if I have to shoot toward the sun, with the definition of twilight varying by
how far north or south I am and the time of year.
It must be certain parts of the spectrum that have to hit in certain ways that
do it.
Fortunately, it is very easy to fix.
An example of the Oly Blues is here
http://albums.photopoint.com/j/AlbumIndex?u=31200&a=1256897
Mike Russell
Color balance algorithms operate on the image data, and the algorithms are
proprietary. They can produce interesting and unpredictable effects. The
camera's computer probably took a look at the orange reflections from the
wave surfaces, decided the boss wouldn't want a picture that red, and
ordered up a big serving of green for you.
Try setting color balance to Daylight next time and you'll get something
much closer to reality, until like me you forget and leave it that way
indoors. Then you'll get agent orange instead of the green berets but at
least you'll know the reason.
"pixels" <jetc...@enotify.com> wrote in message
news:MPG.13fc03485...@east.usenetserver.com...
> In article <20000809145301...@ng-cc1.aol.com>, lk...@aol.com
> says...
> Thanks for your help. It did work wonders on the picture but I'll have to
> disagree with you as regards to the problem being inherent to the
> Olympus. Here is another shot I took seconds after the one above. It is
> taken at a slightly different angle and here there is no geen cast. I
> tend to believe that it had to do with the quality of light falling on
> the CCD. Then I may be wrong also!
>
> http://pages.intnet.mu/ali/sandplay3.jpg
>
pixels
Charlie Brown
<fre...@aracnet.com> wrote:
>
>"pixels" <jetc...@enotify.com> wrote in message
>news:MPG.13fbe4a5a...@west.usenetserver.com...
>> Just wondering why this picure has a greenish cast over it? Please have a
>> look and give me your opinions. Picture was taken with an Olympus C-
>> 2500L, P Mode, Centre-weighted metering. It was taken in the late
>> afternoon at a seaside when the sun was about to go down.
>> http://pages.intnet.mu/ali/sandplay(2).jpg
>>
>
>Well the sun was setting.... refraction of the suns light though the
>atmosphere will give you the red sun sets but at one point the light will be
>green, and I've hear it called the green flash.
>
>Gordon
As I understand it, "green flash" is a small "glow" above a setting
sun, just before the sun actually sets.
It's usually seen over water, since that gives the viewer the longest
distance through the atmosphere; I believe the green flash is caused
by diffraction of the light through moisture in the air, which must be
just the right amount, and in the right place. It's green because of a
mixture of the yellow light from the sun and the blue of the normal
sky.
At least it sounds good.
The green flash isn't strong enough to color the landscape, so it
won't cause a green tint to a photograph.
I've only seen a green flash once, in Sept. of last year, from Key
West.
Charlie Brown
wrote:
>In article <20000809145301...@ng-cc1.aol.com>, lk...@aol.com
>says...
>> >Just wondering why this picure has a greenish cast over it? Please have a
>> >look and give me your opinions. Picture was taken with an Olympus C-
>> >2500L, P Mode, Centre-weighted metering. It was taken in the late
>> >afternoon at a seaside when the sun was about to go down.
>> >http://pages.intnet.mu/ali/sandplay(2).jpg
>>
>> Variation on Oly blue.
>> Digital cameras, Olys in particular it seems, have problems getting colors
>> right at twilight.
>> This is, fortunately, very easy to fix if you've got a imaging program that
>> does layers.
>> Put the eyedropper on the sea and to get the green-grey color.
>> Now open the color wheel and go to the OPPOSITE color on the wheel (in this
>> case a light violet/grey).
>> Add a top layer to the photo.
>> Flood fill the layer with the color above.
>> Set layer to Dodge and adjust transparency.
>> I tried this with your photo using Paint Shop Pro. Result was excellent.
>>
>>
>Thanks for your help. It did work wonders on the picture but I'll have to
>disagree with you as regards to the problem being inherent to the
>Olympus. Here is another shot I took seconds after the one above. It is
>taken at a slightly different angle and here there is no geen cast. I
>tend to believe that it had to do with the quality of light falling on
>the CCD. Then I may be wrong also!
>
>http://pages.intnet.mu/ali/sandplay3.jpg
Sandplay2 is shot with the sun directly above the subject, while
sandplay3 is taken with the sun further to the right of the subject.
I've noticed with both my olys (600L & C-3030) that shooting into the
sun (or, as here, towards the sun, but without the sun in the shot)
will sometimes result in color casts to the shot. And not always the
same color, for me.
Andrew T. Young
>
> On Wed, 9 Aug 2000 11:42:06 -0700, "Gordon R. Frey"
> <fre...@aracnet.com> wrote:
>
> >> Just wondering why this picure has a greenish cast over it? Please have a
> >> look and give me your opinions. Picture was taken with an Olympus C-
> >> 2500L, P Mode, Centre-weighted metering. It was taken in the late
> >> afternoon at a seaside when the sun was about to go down.
> >> http://pages.intnet.mu/ali/sandplay(2).jpg
I was unable to reach this picture -- "file not found" -- but the following one
shows considerable shadows, which means the Sun was still several degrees above
the horizon. This rules out the green-flash explanation proposed below.
> >Well the sun was setting.... refraction of the suns light though the
> >atmosphere will give you the red sun sets but at one point the light will be
> >green, and I've hear it called the green flash.
> >
> >Gordon
>
> As I understand it, "green flash" is a small "glow" above a setting
> sun, just before the sun actually sets.
Well, that's one kind. There are others. Take a look at the pictures at
to see some examples.
> It's usually seen over water, since that gives the viewer the longest
> distance through the atmosphere; I believe the green flash is caused
> by diffraction of the light through moisture in the air, which must be
> just the right amount, and in the right place. It's green because of a
> mixture of the yellow light from the sun and the blue of the normal
> sky.
Ouch! Well, almost everything in that paragraph is wrong.
Green flashes are indeed usually seen over water; but that has nothing to do
with the "longest distance through the atmosphere". Rather, it has to do with
(a) the apparent horizon being below eye level, which allows the mirages that
produce green flashes to be visible; and (b) water has high heat capacity, so
it's usually at a *different* temperature from the overlying air -- the
requirement to make mirages.
Flashes have nothing to do with diffraction; the process involved is REfraction
in the atmosphere. Whater vapor plays a very small part, in absorbing some of
the yellow and orange light; but note that flashes have been seen in polar
regions, where water vapor is pretty scarce.
The business about blue + yellow makes green is true only in subtractive color
mixing; that doesn't apply here. Anyway, the setting Sun is red-orange or red,
not yellow.
> At least it sounds good.
> The green flash isn't strong enough to color the landscape, so it
> won't cause a green tint to a photograph.
Actually, there *are* rare flashes bright enough to color a landscape -- though
I don't know of any photographs of one.
> I've only seen a green flash once, in Sept. of last year, from Key
> West.
Well, I've seen over a hundred. They are worth looking for, and photographing.
I have some advice on how to see and photograph them on the page mentioned
above.
OK, let's try to answer the original question. The CCDs used in digital
cameras have enormous infrared sensitivity. Commercial cameras have some
filtration to suppress this, which is effective when the Sun is high. But when
the Sun is close to the horison, the atmosphere (here comes that long air path,
legitimately, at last) acts as a deep red filter that transmits almost all the
near-IR. If the Sun, or the reddish aureole around it, is sensed by the
system, the huge IR signal might upset the color balance. How much, and which
way, would depend on the IR transmissions of the color-separation filters.
I think the experiences of others here with color shifts in low-Sun photographs
support this interpretation. The green cast is probably an artifact of the
camera.
--
Andrew T. Young
a...@mintaka.sdsu.edu