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fluorescent lights

 
 
RichD
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      09-19-2012
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.


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RIch
 
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Martin Brown
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      09-19-2012
On 19/09/2012 20:30, 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.


Depends what you are photographing but you can get standard filters that
roughly correct fluorescent light to approximately daylight.

Mostly the problem comes from too much green so digitally a tweak of the
green channel and auto white balance will get you something like.

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Mort
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      09-19-2012
Eric Stevens wrote:
> On Wed, 19 Sep 2012 12:30:51 -0700 (PDT), RichD
> <(E-Mail Removed)> 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.

>
> The problem is that no specific light spectra are associated with all
> fluorescent lamps. They vary from make to make: many manufacurers
> offer several different types and they all can suffer from changes as
> they age. See http://en.wikipedia.org/wiki/Fluorescent_lamp
>
> "Color rendering index (CRI) is a measure of how well colors can be
> perceived using light from a source, relative to light from a
> reference source such as daylight or a blackbody of the same color
> temperature. By definition, an incandescent lamp has a CRI of 100.
> Real-life fluorescent tubes achieve CRIs of anywhere from 50 to 99.
> Fluorescent lamps with low CRI have phosphors that emit too little
> red light. Skin appears less pink, and hence "unhealthy" compared
> with incandescent lighting. Colored objects appear muted. For
> example, a low CRI 6800 K halophosphate tube (an extreme example)
> will make reds appear dull red or even brown. Since the eye is
> relatively less efficient at detecting red light, an improvement in
> color rendering index, with increased energy in the red part of the
> spectrum, may reduce the overall luminous efficacy.[19]
>
> Lighting arrangements use fluorescent tubes in an assortment of
> tints of white. Sometimes[weasel words] this is because of the lack
> of appreciation for the difference or importance of differing tube
> types.[citation needed] Mixing tube types within fittings can
> improve the color reproduction of lower quality tubes.
>
> Depending on your camera, you may get fairly close to a good
> adjustment. Otherwise you have to deal with it in post processing.
>
> It can't be too difficult. You are not the first person to be faced
> with this problem.
>

Hi,

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.

Mort Linder
 
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David Dyer-Bennet
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      09-19-2012
RichD <(E-Mail Removed)> writes:

> 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 modern cameras have seven different "fluorescent" white-balance
presets. But if color is important, then I *strongly* suggest you just
set a custom white-balance. That will take care of the cases where the
lights in use don't exactly match any of your presets, and will do about
the best possible with the case where the lights don't actually all give
out the same color (different brands of bulbs and such).

Also, shoot raw, so you can sort it out later if you absolutely have
to. But doing a white balance in the camera is going to help in that
situation, so do that even if you're shooting raw.
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Wolfgang Weisselberg
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      09-20-2012
Savageduck <savageduck1@{REMOVESPAM}me.com> wrote:
> On 2012-09-19 14:25:23 -0700, Mort <(E-Mail Removed)> 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.

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.

"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.

-Wolfgang
 
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Paul Ciszek
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      09-20-2012

In article <(E-Mail Removed)>,
RichD <(E-Mail Removed)> 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?

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Chris Malcolm
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      09-21-2012
Paul Ciszek <(E-Mail Removed)> wrote:

> In article <(E-Mail Removed)>,
> RichD <(E-Mail Removed)> 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 might do. It might also do odd things to the white balance. Best to
experiment on site.

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Chris Malcolm
 
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David Dyer-Bennet
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      09-22-2012
http://www.velocityreviews.com/forums/(E-Mail Removed) (Paul Ciszek) writes:

> In article <(E-Mail Removed)>,
> RichD <(E-Mail Removed)> 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?


Modern fluourescents have electronic ballasts, which drive the lights at
something like 40,000 Hz, so the flicker won't show photographically.
This includes all compact fluourescent bulbs, and modern long-tube
fixtures.

The old, simple ballasts (the only kind around in the 1960s; not sure
when or how fast the changeover happened, but you can still buy the
bulbs for that type) simply used the power-line frequency so in the USA
the bulbs flickered at 120 Hz, which some people could see and which you
COULD catch at a bad level in a photograph.

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Wolfgang Weisselberg
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      09-22-2012
Alan Browne <(E-Mail Removed)> wrote:
> On 2012.09.20 15:12 , Paul Ciszek wrote:
>> RichD <(E-Mail Removed)> 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.


Nope. You've simply got fluorescent lights that simply flicker
way faster (a 20k, 30k, 40k Hz) than with the 50 or 60 Hz net
frequency.
https://en.wikipedia.org/wiki/Electr...tal_ballast.29

> 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.


Yep, some lights may be bad there; especially with net frequency
and short exposure times you may well get bad colour shifts as
the phospors fade with different speeds.

-Wolfgang
 
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Wolfgang Weisselberg
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      09-22-2012
Savageduck <savageduck1@{REMOVESPAM}me.com> wrote:
> On 2012-09-20 09:12:40 -0700, Wolfgang Weisselberg
>> Savageduck <savageduck1@{REMOVESPAM}me.com> wrote:


>>> 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.


In other peoples' Worlds, shooting RAW is best, then!


>> 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?


Does the card have colour fields? No? Then I don't need to
look at the videos to know it can ONLY do white balance.


> What do you mean, "your white balance card will show OK"?


"seem white/gray, e.g. under the colour picker, even though
some colours are very weak or overly strong in the light."


> 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.


It's as good as calibrating a monitor simply on a single gray patch.


>> "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.


Not only perhaps.


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


> 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.


You could use
http://www.qpcard.com/

Or use the info from
http://staffwww.itn.liu.se/~karlu/di...201_argyll.php
to do that with any colour card, most RAW converters and
argylcms.

> 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.


99%? No way. With basically black body emitters with some green
or magenta filter it works. The more the light source diverges
from that (fluorescent lights come to mind), the more some colours
will be off. Of course, if you only shoot in daylight or
with RA 98 or better lights ...

-Wolfgang
 
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