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06-29-2010, 02:06 PM   #76
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Those are nice results, Vincent. I've found the K-x has exceeded my expectations indoors.

06-29-2010, 02:25 PM   #77
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QuoteOriginally posted by GeneV Quote
I've found the K-x has exceeded my expectations indoors.

Yes, that's what I have found too
both indoors and outdoors -
with a very few exceptions -
which are normally what I'd consider extreme lighting conditions -
so the "difficulties" are kind of expected.

This whole thread shows how well the K-x does -
sometimes even in those extreme lighting conditions.

It used to be -
- muttering under breath d*mn camera!
Now it's d*mn
photographer......
06-29-2010, 02:58 PM   #78
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Wow, the lighting is awesome. Have you played around with the white balance?
06-29-2010, 03:37 PM   #79
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QuoteOriginally posted by plillehoj Quote
Have you played around with the white balance?
Many thanks!

Which photos please?

If you mean the most recently posted ones in the church in #75 (link) -
then those are all are AWB on the K-x with the Subtle/default Tungsten correction.
(link to first pic of 23)

Actually almost all my shots are on AWB the only change I make to the camera's WB is to choose between the Subtle and Strong Tungsten correction in the C(ustom) menu.

eg: at the dark jazz club - for the stage I shoot with Subtle AWB -
but for the off-stage situations I have to shoot Strong AWB.

06-29-2010, 05:52 PM   #80
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QuoteOriginally posted by Deni Quote
Generally you take pictures of a subject to "capture the moment". So under artificial lighting, should we try to replicate the original lighting, rather than try to show natural (under day light) skin color?
My usual approach is the split the difference and try to convey something of both.
06-29-2010, 06:34 PM   #81
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QuoteOriginally posted by Marc Sabatella Quote
My usual approach is the split the difference and try to convey something of both.
I don't think I would know how to do that -
(other than AWB might be doing a kind of "averaging")
would yo please explain how?

Thanks,
06-29-2010, 06:45 PM   #82
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Nothing tricky really. Just look at where the WB sliders are for the two extremes (eg, the "flash" to show the color of the light, the "tungsten" preset to show the local color if shot under that light), and set the sliders somewhere between.

For instance, setting "tungsten" WB in ACDSee results in a temperature of 2850, and that renders objects under tungsten light with their local colors. Setting "flash" results in 5500 and renders everything orange. Setting temperature someone in the mid-3000's does what I want - makes local color recognizable, but leaves enough orange so you can still tell what kind of light it was shot under.
06-29-2010, 07:04 PM   #83
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QuoteOriginally posted by Marc Sabatella Quote
Nothing tricky really. Just look at where the WB sliders are for the two extremes (eg, the "flash" to show the color of the light, the "tungsten" preset to show the local color if shot under that light), and set the sliders somewhere between.

For instance, setting "tungsten" WB in ACDSee results in a temperature of 2850, and that renders objects under tungsten light with their local colors. Setting "flash" results in 5500 and renders everything orange. Setting temperature someone in the mid-3000's does what I want - makes local color recognizable, but leaves enough orange so you can still tell what kind of light it was shot under.
Ohhhh.... DoH!
you're talking about doing it PP -
I'm so entrenched using JPGs
that I was wondering how to do that in-camera!

I guess I could use the same effect using Open As.. in PhotoShop Elements to open the JPG in ACR and adjusting the color temperature slider that way -
EDIT to ADD - actually I only just realized/found out that one can open K-x (Pentax dSLRs? - works for K100D too) JPGs in Pentax DCU Photo Laboratory - and apply any of the RAW manipulations to K-x/K100D JPGs there too - that's quite a discovery for me (well, OK better very late, than never ) -
thanks for the hint.

Although I hasten to point out that if one has extreme colored lighting such as mono-color or like magenta - white balancing is not going to help - so I have to either bite the bullet and present it as-is (which often is just what I want to do) or use select white or gray point and allow the editor to balance out the extreme colors......


Last edited by UnknownVT; 06-30-2010 at 08:24 AM.
06-30-2010, 09:57 AM   #84
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I was kind of wondering why you were surprised by my statement...

With "normal" lighting, you probably could pull it off in-camera with sufficiently clever manual WB (like setting it off a carefully chosen non-neutral surface, or using the in-camera controls to push one of the presets - some cameras probably allow you to WB temperature/tint directly). But the really "artificial" light like magenta LED's are going to be tough no matter what. I got some really crazy colors at the outdoor evening Chick Corea concert I posted images from recently. Attempting to remove the magenta color cast on the skin tones rendered the sky yellow-green.
06-30-2010, 10:26 AM   #85
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QuoteOriginally posted by Marc Sabatella Quote
I was kind of wondering why you were surprised by my statement...
That's because I can be so slow and dense at times
having a too focused/blinkered view...

QuoteOriginally posted by Marc Sabatella Quote
But the really "artificial" light like magenta LED's are going to be tough no matter what. I got some really crazy colors at the outdoor evening Chick Corea concert I posted images from recently. Attempting to remove the magenta color cast on the skin tones rendered the sky yellow-green.
Yes, I had that as well where obviously normal background turns to something quite psychedelic when one corrects for the main subject.

That's where one has to use masking or in my simple-minded case, select limited area to apply one's correction, leaving the rest of the photo as-is....

I have discovered that using the select white point (or gray point) can be very helpful, instead of trying to guess a color temperature, or figure out how to remove color cast by using color balance.

Of course if the main subject has radically different lighting, then that would render the rest of the scene to some really strange colors - hence select limited area or masking has to be done -

This is one of the reasons why I seem to harp on about selecting limited ares so much as one of my "excuses" for the (lack of) feature in RAW's non-destructive editing. As I use select area a lot (and would love to be able to preserve that non-destructively), when any photo is "difficult" - there may well be other workarounds - but the most intuitive way for me - is the way I look at any photo eg: that area needs manipulation, and the rest doesn't - hence select limited area.....

Great discussion.

But wait til I pose the next difficulty for digital photography -
rendering violet........
06-30-2010, 03:11 PM   #86
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QuoteOriginally posted by UnknownVT Quote
next difficulty for digital photography -
rendering violet........
These shots had strong violet/purple rim lighting - as I saw them -
you have to take my word that's what I saw -
but they came out -

(left: Pentax K-x, right: Canon G10)
EXIF data should be attached (caveat - PhotoBucket can mysteriously drop metadata) if one checks the EXIF metadata the times are within minutes of each other on two different cameras - that's because I knew that violet lighting would not come out properly with my digicams, and why I took the same/similar scene with both my K-x and the Canon G10 compact to compare.

There is a slight hint that these weren't just blue shots that I mis-remembered.
Look at the K-x shot just above the right hand - one can see the violet -
so why didn't the other parts of the lighting come out that way?

A wider view:

(left: Pentax K-x, right: Canon G10)
the K-x shot shows more yellow in the front lighting, whereas the Canon seems to have balanced those better -
but the point is neither are showing the strong violet rim/back-lighting.
They have both rendered them as blue!

My problems is that the K-x is capable of showing violet/purple - here are some shots from the same gig that do -




So why the difference?

I even went as far as to take a pic of a Macbeth chart to show that purple was not a problem -


So what is going on?
Why does the K-x and Canon G10 both render a strong violet/purple lighting as blue instead?
07-01-2010, 03:50 AM   #87
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QuoteOriginally posted by UnknownVT Quote
So what is going on?
Why does the K-x and Canon G10 both render a strong violet/purple lighting as blue instead?
I guess these were shot in jpeg, right?
I had similar issue with a series of flower macro shots before, violet/purple flowers became blue in camera jpeg and with default raw conversion (in LR, Bibble and RT). The cause of it turned out to be a combination of slight hue shift of "bright" image mode (used by cam jpg and PPL using camera settings), not wide enough working color space (default sRGB instead of ProPhoto in Bibble and RT), curves applied by cam jpg and raw developer apps and slight oversaturation. Using "Neutral" in PPL, setting ProPhoto as working space and a preset with the most neutral/conservative curve in other raw apps resulted in much better colors. I guess all the "wrong" settings combined together somehow shifted the original colors.
07-01-2010, 08:18 AM   #88
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QuoteOriginally posted by simico Quote
I guess these were shot in jpeg, right?
I had similar issue with a series of flower macro shots before, violet/purple flowers became blue in camera jpeg and with default raw conversion (in LR, Bibble and RT). The cause of it turned out to be a combination of slight hue shift of "bright" image mode (used by cam jpg and PPL using camera settings), not wide enough working color space (default sRGB instead of ProPhoto in Bibble and RT), curves applied by cam jpg and raw developer apps and slight oversaturation. Using "Neutral" in PPL, setting ProPhoto as working space and a preset with the most neutral/conservative curve in other raw apps resulted in much better colors. I guess all the "wrong" settings combined together somehow shifted the original colors.

That sounds about right - however there is another wrinkle as I found out - I had posted the same question over at CPF - where there are some people who are very experienced on lights and lighting -
and I got this reply in post #26 (link):

QuoteOriginally posted by blasterman:
Shooting in sRGB -vs- Adobe doesn't help for one thing.

Also, the blue cutoff for most dSLRs is around 455nm, which is deep blue, but not violet.

If these are high end stage lights using HID with filters, then the filter used might be a bit less than 455nm. I looked this data up and was shocked at how much energy deep blue / violet theater filters have below 450nm. This is why it looks deep violet to your eyes, but looks blue on camera.

There's a difference between purple, which is just standard blue+red and violet, which is < 450nm.
The problem of course is that for any photo that is displayable on the web has to be sRGB - so photos kind of becomes self-limiting -
Of course one might have 42- or even 48-bit RAW and process only with Adobe RBG or other superior color space -
BUT when one has to display the thing on the web it has to be one of the common graphics files like JPG, and has to be sRGB......
so what becomes of one's 48-bit color wide gamut?

I think the explanation that there is a cut off on dSLRs (any Bayer matrix digicam) of 455nm makes the most sense in this case.

RAW and any wider gamut processing is not going to help if that part of the spectrum is not captured in the first place.

Let me also clarify my colloquial mistake - violet and purple are not the same (as pointed out) - the problem is in trying to be clear I described violet as "purple" which is kind of the dictionary description of violet "purple-blue" -
but violet is a wavelength 380-450nm - whereas purple is a mix of red and blue -
even the Wikipedia uses that colloquialism :

" Violet (color), which is primarily used to describe a color also called purple "

In that link for purple there is a section 2 Purple versus violet :

" Violet is a spectral color (approximately 380-420 nm), of a shorter wavelength than blue, while purple is a combination of red and blue or violet light.[9] The purples are colors that are not spectral colors – purples are extra-spectral colors. In fact, purple was not present on Newton's color wheel (which went directly from violet to red), though it is on modern ones, between red and violet. There is no such thing as the "wavelength of purple light"; it only exists as a combination.[4]

On the CIE xy chromaticity diagram, violet is on the curved edge in the lower left, while purples are the straight line connecting the extreme colors red and violet; this line is known as the line of purples, or the purple line.[10][11]
One interesting psychophysical feature of the two colors that can be used to separate them is their appearance with increase of light intensity. Violet, as light intensity increases, appears to take on a far more blue hue as a result of what is known as the Bezold-Brücke shift. The same increase in blueness is not noted in purples.
Pure violet cannot be reproduced by a Red-Green-Blue (RGB) color system, but it can be approximated by mixing blue and red. The resulting color has the same hue but a lower saturation than pure violet."

It seems that the Wikipedia is suggesting that RGB Bayer matrix sensors do not capture violet wavelengths but approximate it with red and blue - which is really "purple"?

So I think the reason why the true violet light photos are shifted toward deep blue is simply because my digicams have a cut off around 455nm and violet is below that, and the RGB Bayer matrix is unable to capture true violet - instead approximates with a combination of red and blue to give a hue of "purple" -
but because of the cutoff the colors are rendered the shortest wavelength (adjacent) to violet - which is deep blue.

My other photos showing "purple" were not violet - but real purple - which was probably made up of mixing red and blue.

Thanks for the discussion I have learnt a lot here.

Last edited by UnknownVT; 07-01-2010 at 08:50 AM.
07-01-2010, 10:17 AM   #89
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QuoteOriginally posted by UnknownVT Quote
That sounds about right - however there is another wrinkle as I found out - I had posted the same question over at CPF - where there are some people who are very experienced on lights and lighting -
and I got this reply in post #26 (link):
Wow, that makes total sense, but is something I wouldn't have considered. FWIW, my K200D renders what I assume is that same light as purple/violet, even leaning toward red (definitely not blue). I posted an example in my review of the M135/3.5 in the lens review section of this site, but didn't realize until now what was going on:



QuoteQuote:
Let me also clarify my colloquial mistake - violet and purple are not the same
That's debatable. The distinction being made here is not really universally agreed upon. Well, at least the *terminology* isn't agreed upon - I mean, sure, no one who knows physics would disagree that there really is a different between a color that consists of equalish parts of red and blue wavelengths versus a color that consists of a narrower band of purple/violet wavelengths. But the words "purple" and "violet" both predate knowledge of that phenomenon, so any attempt to co-opt the two terms to describe that difference is really kind of arbitrary. And the eye basically cannot tell the difference - it is essentially a RGB array just like a camera sensor (see below). So I'd say Wikipedia is justified in their "colloquialism", as are you or I.

QuoteQuote:
It seems that the Wikipedia is suggesting that RGB Bayer matrix sensors do not capture violet wavelengths but approximate it with red and blue - which is really "purple"?
Well, think about it - a Bayer sensor never captures anything but red, green, or blue (the primary additive colors of light). All other colors are formed as a result of demosaicing those three component colors. Eg, yellow is equal parts red and green, gray is equal parts of all three colors, etc. An object that actually puts out only a single wavelength of light that isn't squarely red, green, or blue is going to be captured kind of funny. You have to hope the colored filters on the sensor aren't *too* picky about the wavelengths they let through. Presumably, both the red and blue filters would admit some of the "violet" wavelengths. Might seem odd, since they are opposite ends of the spectrum, but for whatever reason, it seems many if not most real life pigments do work that way in terms of what they reflect.

Last edited by Marc Sabatella; 07-01-2010 at 10:30 AM.
07-01-2010, 10:56 AM   #90
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QuoteOriginally posted by Marc Sabatella Quote
Wow, that makes total sense, but is something I wouldn't have considered. FWIW, my K200D renders what I assume is that same light as purple/violet, even leaning toward red (definitely not blue). I posted an example in my review of the M135/3.5 in the lens review section of this site, but didn't realize until now what was going on:
Many thanks for your input - valuable as usual.

However without seeming pedantic - I think your photo may well be like my last three that seem to show the K-x can capture "purple" - so without being there - the light may not have been the deep violet (as defined by the short wavelengths of 380-420nm).

I think in both my shifted to blue and the "purple" shots may well have been gel over some incandescent light - might have been the HID lights alluded to - but I can't be sure - but they were very powerful and did give a really nice deep violet lighting -
that's why I was so disappointed that my K-x showed on the instant review only deep blue - and the reason I used my Canon G10 compact when I saw that deep violet again to see if it'd do any better .....

QuoteOriginally posted by Marc Sabatella Quote
That's debatable. The distinction being made here is not really universally agreed upon. Well, at least the *terminology* isn't agreed upon - I mean, sure, no one who knows physics would disagree that there really is a different between a color that consists of equalish parts of red and blue wavelengths versus a color that consists of a narrower band of purple/violet wavelengths. But the words "purple" and "violet" both predate knowledge of that phenomenon, so any attempt to co-opt the two terms to describe that difference is really kind of arbitrary. And the eye basically cannot tell the difference - it is essentially a RGB array just like a camera sensor (see below). So I'd say Wikipedia is justified in their "colloquialism", as are you or I.
Thank you for being kind and cutting me some slack -
however that quote/link from the Wikipedia I feel is pretty accurate -
violet is a well known wavelength (range) of light in the spectrum -
purple is an extra-spectral color...... so not part of the true spectrum.

Our eyes may not see much difference - hence the colloquialism -
unfortunately measuring instruments and cameras can differentiate them.

QuoteOriginally posted by Marc Sabatella Quote
Well, think about it - a Bayer sensor never captures anything but red, green, or blue (the primary additive colors of light). All other colors are formed as a result of demosaicing those three component colors. Eg, yellow is equal parts red and green, gray is equal parts of all three colors, etc. An object that actually puts out only a single wavelength of light that isn't squarely red, green, or blue is going to be captured kind of funny. You have to hope the colored filters on the sensor aren't *too* picky about the wavelengths they let through. Presumably, both the red and blue filters would admit some of the "violet" wavelengths. Might seem odd, since they are opposite ends of the spectrum, but for whatever reason, it seems many if not most real life pigments do work that way in terms of what they reflect.
I did -
that's why I have a headache!

That's precisely as you yourself just said - violet is a wavelength of light that is hard for the RGB Bayer matrix to capture/render - added to the the possibility as suggested by the poster over at CPF dSLRs/digicams have a cut off at 455nm - then violet light as defined above - cannot be captured - just like InfraRed and UltraViolet are out of range - so apparently seems that is also for true deep violet (ie: 380-420nm) - so the sensor only captures the components above 455nm - hence the deep blue (instead of violet)
(edit to add) and even if it were in the range of capture - think about this: only the "blue" receptor would be active since the wavelength band /peak is between 380-420nm - so the red receptor would/should not even come into play......
as opposed to colloquial Purple which may have been made up of red and blue - which are separately detectable by the RBG Bayer matrix - I hope that made sense, and doesn't cause headaches

Wonderful discussion - thank you so much.

Last edited by UnknownVT; 07-01-2010 at 12:55 PM.
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