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02-10-2012, 11:59 AM   #136
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QuoteOriginally posted by UnknownVT Quote
Great input - I see our posts crossed -
you can read my meager input on correcting specifically for guitars with an example in that post.

Interesting that your version of the PDCU corrected JPG seems different from mine - can you remember where on the T-shirt you selected the Grey-point? Mine was on the shadow part of the shirt under the right breast area (same for my previous full-frame examples)

BTW - those lights in the back were not green spots but regular incandescent white -
the correction to magenta is what made them green (look at the original uncorrected JPG)
I think I was close to that area but I believe selected a whiter shade (of pale...). I'm going to make a test and try that area and see how it turns out, mostly just out of curiosity to see how color space and management between OSs may differ. Can you give me the co-ordinates from your selection point (if they have saved with the image)?

QuoteQuote:
The main problem with LED lighting is that they use separate RGB LED to generate their colors - so they can be "infinitely" variable - and each lighting person's "white" is likely to be different - last night for example the front lighting was set to white - but overall even though it did looks white to me - it was actually quite blue - especially when compared to the gel filtered incandescent lights in the back.

Because of the separate RGB LEDs the spectrum is also very spiky/peaky - not quite, but almost discontinuous - with spikes/peaks at each of the discreet RGB LED - I think this could make a difference, especially in color balance corrections.
I wonder if in theater they adhere to some form of standards to compensate for this variability, I imagine so (R= 4/B=2/G=5/Y=0 that sort of thing). I had considered the spectral nature of the light from them but hadn't seen any charts or read up on it in the least. I know that as a light source LEDs have a peculiar quality about them and I can see this in auto tail lights when I'm driving. My retinas respond differently to them and they have an odd persistence that other forms of lighting does not. i don't know how to explain it further and I've not really mentioned this 'quality' to anyone (thinking they might think me nutty...).

QuoteQuote:
In clubs of any size - most will probably have mixed lighting and use different colors on different parts of the stage -
so I think to try to balance things so that the faces are reasonable and giving guitar finishes the equivalent of studio lighting - is probably nigh on impossible with a single correction point -
True, but that's why I included the last 2 images. I wanted to show the range of lighting I had experienced thus far and that in those 2 examples I was able to get a very good balance. It seems to be the extreme (naturally) that causes the most issues. Kinda like politics or religion lol

QuoteQuote:
I would imagine having to do multiple isolated/selected corrections -
but I am impressed that we can even get what looks reasonable normal lighting out of these magenta lighting pics.
Same here and I thought about that but then my workflow would need to make a side trip down Photoshop way, which if I felt the image needed that degree of control and adjustment I'd certainly go there. I am impressed as well and I'm glad I found this thread and that you have put a good deal of effort into the issue to find solutions as well as create discussion of the matter (which is extremely helpful I feel). Thank you for those efforts!

I have some other images from past shoots I'm going to reevaluate and post.

02-10-2012, 01:24 PM - 1 Like   #137
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QuoteOriginally posted by d00d Quote
I think I was close to that area but I believe selected a whiter shade (of pale...). I'm going to make a test and try that area and see how it turns out, mostly just out of curiosity to see how color space and management between OSs may differ. Can you give me the co-ordinates from your selection point (if they have saved with the image)?
No I did not save the point - but just went back into PDCU and clicked on 2160,904 (on the JPG) and it seems about right - pretty inexact - I tend to do everything by eye.

QuoteOriginally posted by d00d Quote
I know that as a light source LEDs have a peculiar quality about them and I can see this in auto tail lights when I'm driving. My retinas respond differently to them and they have an odd persistence that other forms of lighting does not. i don't know how to explain it further and I've not really mentioned this 'quality' to anyone (thinking they might think me nutty...).
Color LED are close to mono-color - so have very pure color output and virtually nothing else in the spectrum - "white" from LEDs is almost, but not quite, three (RGB) spikes - whereas natural daylight white would be a flat horizontal line - so that is a real physical difference and probably detectable by the camera sensor.

Our eyes respond to different color lights differently
We are not that sensitive to Red as it is at an extreme end of our visible spectrum (despite being traditionally a attention getting color) - and with old-sight it becomes increasingly difficult to focus under red light.

Whereas the peak of our eyes' sensitivity is around Green, and at lower light levels it is closer to blue-green, like traffic lights - so they tend to dazzle our eyes which have become adapted to the dark conditions - so green traffic light will tend to persist.

Blue tends to be scattered by eyes' lens (just as advertized by Blu-Blocker sunglasses) - it is true, that's why we have difficulties in bright hazy conditions - not just because of haze - but the eye scattering of blue light......

FWIW - our yes see better definition in yellow light - this could be conditioning/evolution - humans used fire/candles and incandescent lights to see at night - that's why for years the AA in Britain (Automobile Association - not Alcoholics Anonymous!) used black lettering on yellow background, and street lighting used low pressure sodium (almost mono-color yellow)

QuoteOriginally posted by d00d Quote
I thought about that but then my workflow would need to make a side trip down Photoshop way, which if I felt the image needed that degree of control and adjustment I'd certainly go there.
....
I have some other images from past shoots I'm going to reevaluate and post.
Well, like I said, for any degree of control of white balance over different parts of a scene will need selective processing of those areas - since stages are very unlikely to be just one light source - but multiple colors......

Would really be interested to see more of your examples and how you evolve your processing.
02-11-2012, 03:14 PM   #138
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FWIW (slightly OT) -
a thread I started many years ago on CPF (CandlePowerForums.com - for flashaholics) -
I attempted to show how color LEDs affected our vision using photos of a map as a target/example:

LED Colors and Vision (pics)
(The formatting of the posts may be a little off as CPF had to recover some of their older posts)

There are several posts that try to explain our vision under different color lights -

But back on topic:
one of the most valuable for me was the discovery JPG compression is particularly hard with red illumination - losing details (see Post #36) - just like magenta (made up with only Red and Blue LEDs)

Then there was the realization that mono-color Yellow light is NOT the same as yellow made up from Red and Green LEDs - this may seem "obvious" written out like this - but our eyes see the combination of Red and Green as "Yellow" and it is hard for our eyes to see a difference - but our cameras do -
see Post #5
just as, perhaps "White" made up from discrete RGB LEDs - see the photo example in the OP #1

Last edited by UnknownVT; 02-11-2012 at 04:37 PM.
02-12-2012, 01:55 AM   #139
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Vincent, very instructive and I'll need some time to digest for sure. A quick G-search on LED spectrum yields mostly grow-light info for "herb" cultivation...

I attempted to replicate your results with the challenge image and forgot that you had performed the balancing act on the jpeg whereas I used the RAW image and found myself a little further from my first post work.

So as mentioned I'm posting some images of a band shot at a bar using LED stage lighting, and in addition the light there was for all intents crap. No spread, little diffusion just wrong for the purpose. Yet I was able to render something from my efforts. Initially I resorted to making the final output monotone or some variant thereof, but after playing with some recent shots and creating a workable preset in LR, I applied that for experiment. The results as follows:

Again (like Mark Sabatella), my first response to this lighting was to make the image either straight b/w, sepia or cyanotype. All are 25600iso, f/2.8 (and I forget the shutter speed):



Here's Amanda in modified color (her hair is pretty much that color):



Here's what can be done with nothing (or so it seemed):



(I didn't attempt to rework this one in color as I liked the final outcome in sepia)

Again, my first instinct was to make a monochromatic image:



But with a new light (Ha!), I can see in color now:




Though this one is interesting with the greenside light, I found the color background distracting so I went for a duotone effect (name drop here, Jim Croce's son AJ)



The full set of images as I first processed them is here, and actually I like them the way they are for several reasons: 1) I'm partial to black and white 2) Funky soul and jazz is best viewed under dim lights and the graphic reduction that b/w imparts and 3) sometimes it just comes together best in this manner (maybe I'm old and have too many William Claxton/Jim Marshall images swirling around my head when I shoot and process the results).

That said, I'm glad to find some effort on mitigation of what I find as deleterious effects of LED lighting for photography, because I'd like to have options in the editing stage and now I've found that I can. Cheers to Vincent!

02-12-2012, 11:29 AM   #140
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QuoteOriginally posted by d00d Quote
A quick G-search on LED spectrum yields mostly grow-light info for "herb" cultivation...
hmmm......
Just found this very interesting article:
What To Look For When Judging An LED Fixture's Colour Mixing Capabilities
figure from that page
showing the eyes' response (background faded curves) vs typical higher powered RGB LEDs

this shows even though our eyes "see" discrete RGB LEDs as "white" -
the actual spectrum is very peaky almost discontinuous.

Unsurprisingly Wikipedia has a very good write up under
Light Emitting-Diode > 3.2 White light >3.2.1 RGB systems

There's a website that has a lot of LED spectrum at
The LED Museum
@ about 3/4 down that page, or just do a search on "Spectra"
this is a good sample spectra page


QuoteOriginally posted by d00d Quote
That said, I'm glad to find some effort on mitigation of what I find as deleterious effects of LED lighting for photography, because I'd like to have options in the editing stage and now I've found that I can.
Thanks so much for continuing with your processing.

Like you, many times I actually like the magenta lighting, as it can be very attractive/flattering - but unfortunately our digital cameras just do not do well with just red and blue in the spectrum, and to compound this, JPG compression is terrible for Red and some degree Blue - so that's a double whammy. My continuing struggle is to try to present what I see - but without the losses from the difficult lighting (eg: things looking blurry and even out of focus!).

Stripping out the color using de-saturation is one way -
but it is hard to add back color that does not make the shot look artificial,
that's why I reduce saturation and add back in green (for the opposite of magenta) until it looks kind of right.

Using grey/white-point correction such as PDCU seems to give me a good compromise close to "neutral" shot -
so I can then add back in the magenta, red, or blue to get back to kind of what I saw - or at least what I would like to present....
but compromise is the operative word.

Last edited by UnknownVT; 02-12-2012 at 12:21 PM.
05-08-2012, 09:45 AM   #141
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Using the original problematic magenta photo from the opening Post #1:

Resized original:

the magenta has destroyed details due to JPG compression - and this is saved with low compression/High quality JPG (90% in PhotoImpact 8)

Using PDCU (Pentax Digital Camera Utility) v.4.34
(Free with Pentax dSLRs)
Gray Point selection on the laminate of female singer:
this is a jaw dropping result -

notice the detail - also there is quite a bit of strong green (opposite of magenta in what may have been white light areas)

Then to get the original feel - I re-added magenta and blue
not to match the original - but to get more or less the same sense of the original scene -

look at the difference in detail.

Both the latter 2 are saved with much higher compression/lower quality JPG (70% on PhotoImpact 8)

All photos have EXIF metadata attached.
05-19-2012, 12:50 PM   #142
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These were shot with LEDs too. I shoot RAW and either auto WB or day light, both work well. I use Lightroom to final editing.

This one was really difficult with all LED backlighting and no front lighting. The other had good front lighting.


Good front lighting

Last edited by john5100; 05-19-2012 at 02:09 PM.
05-19-2012, 01:17 PM   #143
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QuoteOriginally posted by john5100 Quote
These were shot with LEDs too. I shoot RAW and either auto WB or day light, both work well. I use Lightroom to final editing.
This one was really difficult with all LED backlighting and no front lighting. The other three had good front lighting.
Good front lighting
Many thanks for the input and photos -
did you have to deal with strong colored or mono-colored lighting in these shots?
eg: did any of the shots show strong color cast in their embedded jpgs?

Thanks,

05-19-2012, 01:41 PM   #144
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Sorry, but I'm not sure what you are referring too with embedded jpg. I used to shoot jpg but it drove me crazy with the in camera processing. The only time that I shot jpg recently was when I got called to shoot KISS and I only had my P&S with me. I didn't have my DSLR with me for this shoot. The Judas Priest photo does have a strong color cast that I just left because that's what my eye saw. since the lighting person went with it, so did I. Less headaches...



update - better example



LedZepAgain example had magenta lighting - (I put it back so that we can all learn)
(which can be troublesome - please see Post #141 above yours)

Last edited by john5100; 05-19-2012 at 02:12 PM.
05-19-2012, 01:48 PM   #145
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QuoteOriginally posted by john5100 Quote
Sorry, but I'm not sure what you are referring too with embedded jpg. I used to shoot jpg but it drove me crazy with the in camera processing. The only time that I shot jpg recently was when I got called to shoot KISS and I only had my P&S with me. I didn't have my DSLR with me for this shoot. The LedZepAgain photo does have a strong color cast that I just left because that's what my eye saw. since the lighting person went with it, so did I. Less headaches...
My understanding is that the RAW files have a "preview" low quality jpg embedded - so that viewers like FastStone, IrfanView can display the photo without first having to process the RAW file.

The LedZepAgain photo is what I meant when asking if any of the photos had strong color casts.

Thanks for your efforts, and posting photos.

Ah! I see our posts crossed -
the LedZepAgain example had magenta lighting -
(which can be troublesome - please see Post #141 above yours)

I see the new:
QuoteOriginally posted by john5100 Quote
update - better example
has a strong red/orange cast.

Last edited by UnknownVT; 05-19-2012 at 01:54 PM.
05-19-2012, 01:52 PM   #146
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Okay, I need to check that. You have me curious now. Oh I changed the color cast photo to a better photo but with more color. I might have messed up my example though. oops...

The biggest thing for me was to use daylight or auto wb because they preserve more of the light spectrum making it easier to edit in LR. If you look at iconic photos from the past they had all kinds of cast to them. They either shot BW or left them. I try doing the same because that's how the concert was.

I'm sorry but one more example which I turned BW to make it easier.

Last edited by john5100; 05-19-2012 at 02:04 PM.
05-19-2012, 02:37 PM   #147
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QuoteOriginally posted by john5100 Quote
The biggest thing for me was to use daylight or auto wb because they preserve more of the light spectrum making it easier to edit in LR.
Thanks, hadn't thought of that -
However with very strong colored lighting - there is no WB to speak of -
and I just leave it on AWB.

QuoteOriginally posted by john5100 Quote
If you look at iconic photos from the past they had all kinds of cast to them. They either shot BW or left them. I try doing the same because that's how the concert was.
I'm sorry but one more example which I turned BW to make it easier.
Earlier photos with strong color casts were "easier" because they are not LED - but regular incandescent lights with color gel filters -
this makes a huge difference because the lights are not restricted to spiky LED mono-colors -
the incandescent lights have more continuous and non-spiky spectrum.
(Please see Post #140 for the explanation) this was the point of this thread.

Black & white conversion is one way of not having to deal with color casts -
just like you, I try to present what I see as much as possible -
with strong colored LED lighting - the photos sometimes do not reflect what one actually sees
again, sorry to repeat, but the opening post #1, and post #141 shows why.

Thanks for the continuing discussion.
05-19-2012, 04:02 PM   #148
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Not sure about you but I find weddings harder because they are less forgiving. I have a hard time relaxing because the white dress has to be white. If anyone has any pointers, please help.



I threw in the towel here. :-)

Last edited by john5100; 05-19-2012 at 04:27 PM.
05-20-2012, 12:03 AM   #149
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QuoteOriginally posted by john5100 Quote
Not sure about you but I find weddings harder because they are less forgiving. I have a hard time relaxing because the white dress has to be white. If anyone has any pointers, please help.
I don't do wedding photography - so may not be much help...

If you have to have the white dress as white then one can quite easily achieve that by using the white or gray point selector which I am sure LR has, as most other photo editors.

In PhotoShop (which is probably similar to LR) it's under Adjustments > Levels, and the eye dropper tools (near bottom right) are for white, gray and black - clicking with the white dropper on the white of the dress ought to remove any color casts.
(FWIW - that's how I removed that really strong magenta cast using Pentax DCU in Post #141 -
I selected white point on the back of the female singer's laminate - which I knew ought to be white.)

BUT obviously the problems could be if the lighting is mixed -
what may render the dress white could mess up the flesh tones -
and what one may consider flattering flesh tone would make the dress non-white -
so the crude way would be to select the dress area and select white point,
then inverse the selection and adjust for the flesh tone?

Try these too?

Correcting Color Cast with Lightroom

Four Methods to Remove Colorcast in Photoshop

QuoteOriginally posted by john5100 Quote
I threw in the towel here. :-)
The sepia tone photo is rather nice, so it's not exactly throwing the towel......

Last edited by UnknownVT; 05-20-2012 at 12:41 AM.
05-20-2012, 10:05 AM   #150
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QuoteOriginally posted by john5100 Quote
Not sure about you but I find weddings harder because they are less forgiving. I have a hard time relaxing because the white dress has to be white. If anyone has any pointers, please help.
Here's a quick try of your wedding photo.

I think part of the difficulty is perhaps mixed lighting - a flash supplemented shot?
- which is bluer than the ambient light.

Used white point on the bright part near the seam of the wedding dress facing the camera (coordinates 144,480) - which made it a bit whiter -
that made the flesh tones too warm/orange - added a bit of teal (opposite of orange) in color balance
- still no where near perfect - but perhaps a little bit whiter in the dress?
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