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Old Apr 28, 2007, 11:13 AM   #1
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Why do pentax DSLRs have a yellow cast when capturing tungsten-lit scenes on AWB mode?

The manual explains it!

AWB range starts at 4000 K
The Tungsten WB setting is ~2850 K

So you will NEVER get proper white balance on auto indoors.

Either shoot raw, set Tungsten WB manually, or measure your own WB....

And I hope these reviewers stop bitching. this behavior is by design.
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Old Apr 28, 2007, 2:08 PM   #2
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I have the K100D and like it quite a bit, but I still consider the AWB problem to be a considerable one. The fact that it's by design somehow doesn't make it seem like less of a problem. The Nikon D40 doesn't have an AF focus motor, a top LCD, or the ability to auto-bracket, but I still consider it fair game to criticize the lack of functionality despite it being by design.

The fact that my Panasonic FZ30 does significantly better using AWB indoors is truly a nuisance to me. It seems to me if all that is holding back the AWB on the K100D is a built-in firmware limitation, they should either fix it immediately with an update or give a legitimate reason why they designed it fail, other than, "So we can enable it on future cameras we want you to buy".
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Old Apr 28, 2007, 4:15 PM   #3
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Corpsy wrote:
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I have the K100D and like it quite a bit, but I still consider the AWB problem to be a considerable one. The fact that it's by design somehow doesn't make it seem like less of a problem. The Nikon D40 doesn't have an AF focus motor, a top LCD, or the ability to auto-bracket, but I still consider it fair game to criticize the lack of functionality despite it being by design.

The fact that my Panasonic FZ30 does significantly better using AWB indoors is truly a nuisance to me. It seems to me if all that is holding back the AWB on the K100D is a built-in firmware limitation, they should either fix it immediately with an update or give a legitimate reason why they designed it fail, other than, "So we can enable it on future cameras we want you to buy".
You can either look at it as 1) That's how film handles it. Without a blue filter or "tungsten balanced film" that's how your indoor shots would be normally. or 2) It leaves the decision and creative freedom to you. Sorry that you find it a burden to throw the camera on "tungsten" when your indoors...besides if you use flash then AWB is just fine.
I'd be just as annoyed if I took a shot indoors, candle light and it came out "correct" and ruined the mood...


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Old Apr 28, 2007, 7:39 PM   #4
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oreo57 wrote:
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You can either look at it as 1) That's how film handles it. Without a blue filter or "tungsten balanced film" that's how your indoor shots would be normally. or 2) It leaves the decision and creative freedom to you. Sorry that you find it a burden to throw the camera on "tungsten" when your indoors...besides if you use flash then AWB is just fine.
I'd be just as annoyed if I took a shot indoors, candle light and it came out "correct" and ruined the mood...

Why would I be concerned how an image may have come out had it been taken with film? How do I lose creative freedom if auto white balance is more accurate? If AWB was accurate, why wouldn't you be able to get a warm shot by candle light?

The point of using AWB is that you don't want to or can't set the WB manually for each shot. Many indoor situations encompass a broad mixture of different color temperatures. Perhaps you prefer to set a custom WB before every photo, but I can imagine that some would appreciate an auto setting that can adjust to every circumstance.

When you boil it all down, AWB is really only necessary in indoor settings. Manually white balancing for an outdoor shoot is far simpler than for an indoor one. Perhaps your argument should be that the camera doesn't need to have an AWB setting at all.
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Old Apr 29, 2007, 2:54 AM   #5
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Corpsy wrote:
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The fact that my Panasonic FZ30 does significantly better using AWB indoors is truly a nuisance to me.
I also had the FZ30, and yes the AWB of the FZ30 was better indoors. But when I was shooting indoors with the FZ30 I allmost allways was using the flash, because of the bad high iso noise.

With my K100D I can choose how to take a picture, use the flash or change the AWB and shoot without the flash and use higher iso.

So at least I have more to choose and that means more freedom.

Still it would be great if a fimware update would fix the AWB when shooting tungsten lit subjects.......

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Old Apr 29, 2007, 3:39 AM   #6
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Gazander wrote:
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Why do pentax DSLRs have a yellow cast when capturing tungsten-lit scenes on AWB mode?
Well the cooL thing about the K10D is that not only do you have 3 CUSTOM WB's but ANY preset WB can also be tweaked to taste

PRESONALLY my Tungsten (usually manufacturer set to studio/stage lighting vs dim home like conditions) is now set much bluer, and conversely my FLASH preset (too blue default) Is set much yellower.... making BOTH much more acceptable.

Ans a third.....one of the customs is a WB originally created for shooting under pink streetlights.... BUT also works quite WELL neutralizing standard PINK flood CLUB/BAR STAGE LIGHTING.
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Old Apr 29, 2007, 10:29 AM   #7
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To Corpsy, This Nikon article explains it better:

BTW: Theirs cuts out at 4200K

But what about Auto, shouldn't that setting with it's variable range work better, make our life and photographs better? I'm here to tell you, Auto WB is the last option you should use! When I hear digital shooters tell me they have their cameras set to Auto WB, I know they haven't done their homework and are causing themselves ultimately more work (I'm amazed how many NEF shooters shoot on Auto WB and then wonder what's wrong with the color of their previews. All of that info and the wrong WB)! I've yet to shoot with any digital SLR, Kodak, Canon or Nikon that had a Auto White Balance that delivered what I desired let alone close to what the subject required. Why? In a nutshell, keep in mind that our CCD's captures B&W with color being added on the image's path to the CompactFlash card. To really over simplify the problem, in that path, something gets lost in the translation.

http://www.nikondigital.org/articles/white_balance.htm

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Old Apr 29, 2007, 3:00 PM   #8
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oreo57 wrote:
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In a nutshell, keep in mind that our CCD's captures B&W with color being added on the image's path to the CompactFlash card. To really over simplify the problem, in that path, something gets lost in the translation.
Actually, a CCD is covered in photosites that each capture light from the 3 primary colors of the visible spectrum. Half the photosites collect green light, a quarter collect red, and another quarter collects blue. The light values measured on each cluster of four photosites are averaged together to produce a color value for an individual pixel.

So far, nobody has explained why accurate auto white balance would not be a benefit, but some of you seem to be arguing that AWB shouldn't even be an available feature. Personally, I shoot AWB all the time since I shoot RAW anyway and can fix anything that doesn't come out right later on. Even when I set white balance to an appropriate setting, like tungsten or daylight or cloudy, it's frequently visibly inaccurate to the actual temperature of the light conditions, so why not have an AWB that can cover the whole range for me when I don't feel like resetting the white balance every time I step into a different room or go into the shade or a cloud moves over the sun?
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Old Apr 29, 2007, 3:15 PM   #9
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Corpsy wrote:
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oreo57 wrote:
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In a nutshell, keep in mind that our CCD's captures B&W with color being added on the image's path to the CompactFlash card. To really over simplify the problem, in that path, something gets lost in the translation.
Actually, a CCD is covered in photosites that each capture light from the 3 primary colors of the visible spectrum. Half the photosites collect green light, a quarter collect red, and another quarter collects blue. The light values measured on each cluster of four photosites are averaged together to produce a color value for an individual pixel.

So far, nobody has explained why accurate auto white balance would not be a benefit, but some of you seem to be arguing that AWB shouldn't even be an available feature. Personally, I shoot AWB all the time since I shoot RAW anyway and can fix anything that doesn't come out right later on. Even when I set white balance to an appropriate setting, like tungsten or daylight or cloudy, it's frequently visibly inaccurate to the actual temperature of the light conditions, so why not have an AWB that can cover the whole range for me when I don't feel like resetting the white balance every time I step into a different room or go into the shade or a cloud moves over the sun?
Accurate AWB would be fine. Just doen't look to be as easy as you believe. To make a long story short, how do you distiguish between a late morning sunrise and indoor tungsten? these would need 2 different sets of coefficients to make the conversion accurate to the intent. Not that it couldn't be done but it just gets a bit more complicated. Since apparently many DSLR's do not have accurate WB in indoor ambient light, what does that suggest to you? This is not a Pentax issue per say.
(EDITED OUT
If you buy a K10 and set the WB at 5000K (shooting RAW of course), you get a better representation of the actual range on the histogram re: blowouts

http://forums.dpreview.com/forums/re...ssage=22957362

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Old Apr 29, 2007, 4:04 PM   #10
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oreo57 wrote:
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Accurate AWB would be fine. Just doen't look to be as easy as you believe. To make a long story short, how do you distiguish between a late morning sunrise and indoor tungsten? these would need 2 different sets of coefficients to make the conversion accurate to the intent. Not that it couldn't be done but it just gets a bit more complicated. Since apparently many DSLR's do not have accurate WB in indoor ambient light, what does that suggest to you? This is not a Pentax issue per say.
As to any implied superiority over DSLR's and P&S, most P&S's meter off the taking sensor, giving them an extreme advantage in area and resolution. DSLR's have much smaller metering chips w/ low resolution (low pixel count relative to the sensor).
Unfortunately using the sensor has it's drawbacks in speed and shutter lag, which of course gets improved on as we speak
If you buy a K10 and set the WB at 5000K (shooting RAW of course), you get a better representation of the actual range on the histogram re: blowouts

http://forums.dpreview.com/forums/re...ssage=22957362
AWB and light metering have nothing to do with each other. Light metering determines what the camera estimates to be a proper exposure, and white balance is applied to the RAW data after the image is capture. No matter what white balance setting you use, the exact same RAW data is collected.

I don't know how the AWB works exactly in different circumstances, only that as long as it is within it's set temperature range it tends to do a decent job. I imagine it's very close to how I manually white balance a photo in Photoshop, by balancing the 3 color channels throughout the luminosity range.
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