fluorescent lights

Paul Ciszek wrote:
In article ,
RichD wrote:
I have to do some camera work under indoor
fluorescent light. It's bright, no flash needed,
but I'd like to know what adjustments to
ameliorate color distortion.

What happens if you shoot under fluorescent lights with a shutter speed
faster than 1/100 of a second? Wouldn't the flicker of the lights do
weird things to exposure?


They change levels more than tungsten lamps, but the phosphor has
persistence, which limits decay.

Greg

Savageduck wrote:
On 2012-09-20 09:12:40 -0700, Wolfgang Weisselberg
said:
Savageduck wrote:
On 2012-09-19 14:25:23 -0700, Mort said:
Eric Stevens wrote:
On Wed, 19 Sep 2012 12:30:51 -0700 (PDT), RichD

I have to do some camera work under indoor
fluorescent light. It's bright, no flash needed,
but I'd like to know what adjustments to
ameliorate color distortion.
[...]
Some cameras have built-in fluorescent tube correction factors that can
be turned on. Take test pix with the various correction factors, then
see which please you.

Better; Shoot RAW. Adjust WB temperature and tint/hue in ACR.

Best; Shoot a RAW calibration/reference shot with a WhiBal card under
the Fluorescent light. Set WB in ACR.
http://michaeltapesdesign.com/whibal.html
Take a look at some of the videos.

That's not best.

In my World, since I actually have a WhiBal Card with me, it is best.

If the fluorescent light is weak in some colours, but not in
the sum of all colours as seen by the broadband filters of
the camera, your white balance card will show OK.

You didn't look at any of the videos did you?
What do you mean, "your white balance card will show OK"?

The WhiBal card is not going to "show" anything. It is going to be
present in the reference shot, under the light in the shooting
environment. Then it is used as a target for setting the WB in ACR or
whatever SW you are using for RAW processing.

"Best" would be to shoot a colour calibration target
and use that to create a camera+light(+lens+ISO+contrast
curve+saturation+...) specific profile, which you then use to
correct the "wrong" colours out of your camera into the colours
as they should be in sunlight (or whatever light situation you'd
like to emulate).

Perhaps, perhaps not.


One such system (with limitations) was
http://www.nexi.com/239
for Bibble 4.

-Wolfgang

In that case, perhaps not, since I do not use Bibble 4, and the
installed ClairePRO plug-in, and I don't happen to have a Gretag Mabeth
ColorChecker handy.

Therefore for me, using a WhiBal card, and a reference shot to set the
WB for the batch of shots shot under the same light, is the best
solution. It fixes 99% of the WB+colorcast problems without becoming
too anal over the problem.

Now and then I like exploring a photographic problem in as much detail
as I can manage with the kit to hand or not too difficult or expensive
to acquire. That's what gives me the skills to improve the technical
image quality I can coax out of the kit I have, or be able to get
shots of acceptable quality in very difficult conditions.

I'm impressed by how often the camera's auto white balance gets it
good enough, which I guess is 95% of the time. I guess a white balance
card used to set the camera's white balance covers 99%. The problem is
that seriously anal colour accuracy is quite often what is required in
a paying shoot, such as photographing a painting for an artist's or
gallery's portfolio. It might be why they're paying me to do the shot
rather use their iPhone or ask their friend with the big expensive
camera.

That's why I've now started keeping a Gretag Macbeth colour chart
handy in my gear bag. I'm not yet using it to do the tedious process
of setting up colour profiles. I just bung it into a shot when I'm
curious about possible colour problems. Data collection. There's an
interesting residuum of special cases where the white balance is spot
on, but some of the colours quite definitely aren't. Clearly there is
sometimes more than one solution to the problem of getting the white
balance card to to be white in the camera image.

--
Chris Malcolm

On 2012-09-26 04:32:00 -0700, Chris Malcolm said:

Savageduck wrote:
On 2012-09-20 09:12:40 -0700, Wolfgang Weisselberg
said:
Savageduck wrote:
On 2012-09-19 14:25:23 -0700, Mort said:
Eric Stevens wrote:
On Wed, 19 Sep 2012 12:30:51 -0700 (PDT), RichD

I have to do some camera work under indoor
fluorescent light. It's bright, no flash needed,
but I'd like to know what adjustments to
ameliorate color distortion.
[...]
Some cameras have built-in fluorescent tube correction factors that can
be turned on. Take test pix with the various correction factors, then
see which please you.

Better; Shoot RAW. Adjust WB temperature and tint/hue in ACR.

Best; Shoot a RAW calibration/reference shot with a WhiBal card under
the Fluorescent light. Set WB in ACR.
http://michaeltapesdesign.com/whibal.html
Take a look at some of the videos.

That's not best.

In my World, since I actually have a WhiBal Card with me, it is best.

If the fluorescent light is weak in some colours, but not in
the sum of all colours as seen by the broadband filters of
the camera, your white balance card will show OK.

You didn't look at any of the videos did you?
What do you mean, "your white balance card will show OK"?

The WhiBal card is not going to "show" anything. It is going to be
present in the reference shot, under the light in the shooting
environment. Then it is used as a target for setting the WB in ACR or
whatever SW you are using for RAW processing.

"Best" would be to shoot a colour calibration target
and use that to create a camera+light(+lens+ISO+contrast
curve+saturation+...) specific profile, which you then use to
correct the "wrong" colours out of your camera into the colours
as they should be in sunlight (or whatever light situation you'd
like to emulate).

Perhaps, perhaps not.


One such system (with limitations) was
http://www.nexi.com/239
for Bibble 4.

-Wolfgang

In that case, perhaps not, since I do not use Bibble 4, and the
installed ClairePRO plug-in, and I don't happen to have a Gretag Mabeth
ColorChecker handy.

Therefore for me, using a WhiBal card, and a reference shot to set the
WB for the batch of shots shot under the same light, is the best
solution. It fixes 99% of the WB+colorcast problems without becoming
too anal over the problem.

Now and then I like exploring a photographic problem in as much detail
as I can manage with the kit to hand or not too difficult or expensive
to acquire. That's what gives me the skills to improve the technical
image quality I can coax out of the kit I have, or be able to get
shots of acceptable quality in very difficult conditions.

I'm impressed by how often the camera's auto white balance gets it
good enough, which I guess is 95% of the time. I guess a white balance
card used to set the camera's white balance covers 99%. The problem is
that seriously anal colour accuracy is quite often what is required in
a paying shoot, such as photographing a painting for an artist's or
gallery's portfolio. It might be why they're paying me to do the shot
rather use their iPhone or ask their friend with the big expensive
camera.

That's why I've now started keeping a Gretag Macbeth colour chart
handy in my gear bag. I'm not yet using it to do the tedious process
of setting up colour profiles. I just bung it into a shot when I'm
curious about possible colour problems. Data collection. There's an
interesting residuum of special cases where the white balance is spot
on, but some of the colours quite definitely aren't. Clearly there is
sometimes more than one solution to the problem of getting the white
balance card to to be white in the camera image.

....and that makes sense. Perhaps one of these days I might add add a
GMC card to my bag. For now I actually have my WhiBal card with me to
give me a calibrated grey point for WB, and black & white point targets.

--
Regards,

Savageduck

Chris Malcolm wrote:
Savageduck wrote:
On 2012-09-20 09:12:40 -0700, Wolfgang Weisselberg

"Best" would be to shoot a colour calibration target
and use that to create a camera+light(+lens+ISO+contrast
curve+saturation+...) specific profile, which you then use to
correct the "wrong" colours out of your camera into the colours
as they should be in sunlight (or whatever light situation you'd
like to emulate).
[...]
One such system (with limitations) was
http://www.nexi.com/239
for Bibble 4.
[...]
Therefore for me, using a WhiBal card, and a reference shot to set the
WB for the batch of shots shot under the same light, is the best
solution. It fixes 99% of the WB+colorcast problems without becoming
too anal over the problem.

[...]
I'm impressed by how often the camera's auto white balance gets it
good enough, which I guess is 95% of the time.

Good enough for what?

There's a difference between "it looks OK", "it looks
realistic" and "it's as exact a copy as one can make it,
colourwise included".

I guess a white balance
card used to set the camera's white balance covers 99%.

Hmmm ... the "looks OK" part, yes. Which often *is* enough.

The problem is
that seriously anal colour accuracy is quite often what is required in
a paying shoot, such as photographing a painting for an artist's or
gallery's portfolio. It might be why they're paying me to do the shot
rather use their iPhone or ask their friend with the big expensive
camera.

Maybe ...

That's why I've now started keeping a Gretag Macbeth colour chart
handy in my gear bag. I'm not yet using it to do the tedious process
of setting up colour profiles. I just bung it into a shot when I'm
curious about possible colour problems. Data collection. There's an
interesting residuum of special cases where the white balance is spot
on, but some of the colours quite definitely aren't. Clearly there is
sometimes more than one solution to the problem of getting the white
balance card to to be white in the camera image.

Yep. WB can only boost really broad swaths of colour: the red
sensor filter's curve, the green and/or the blue one.

-Wolfgang

On 2012.09.22 01:12 , Gary Eickmeier wrote:
Alan Browne wrote:
On 2012.09.20 15:12 , Paul Ciszek wrote:
In article
,
RichD wrote:
I have to do some camera work under indoor
fluorescent light. It's bright, no flash needed,
but I'd like to know what adjustments to
ameliorate color distortion.

What happens if you shoot under fluorescent lights with a shutter
speed faster than 1/100 of a second? Wouldn't the flicker of the lights
do
weird things to exposure?

It may.

I just shot about 10 frames at 1/400 using a CF as illumination. All
the exposures were the same. I'm not sure what the mechanism is - it
could simply be that the "extinguish" decay is too slow.

Even the in-camera metering got it right (enough).

But with other lights (larger separate ballast lights) there may be a
difference. It pays to test before the talent arrives.

I'm thinking watch out when you say "shutter speed" on a focal plane shutter
camera. The specified "shutter speed" isn't necessarily the exposure
duration. At any speed faster than the flash sync speed (about 1/200th of a
second) the exposure is accomplished with a moving slit that traverses the
frame in more than the specified time period. I haven't thought about how
that might affect a fluorescent exposure, but that would be a great
experiment! Also not sure just how the fluorescent flickers.

What Dyer-Bennet said is what is important. Later fluorescents (and
CFL's definitely) switch at speeds well beyond the highest shutter speed
of the camera.

Older ballasts may switch at line freq or 2 times line freq - that's
where you would need to be careful. With digital it is so cheap to test.

--
"There were, unfortunately, no great principles on which parties
were divided – politics became a mere struggle for office."
-Sir John A. Macdonald