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03-04-2011, 11:21 AM   #1
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WB woes: light bulbs very yellow in interiors

I've been trying out a Pentax K-r to shoot home interiors for virtual tours. I'm having a devil of a time sorting out the white balance for this job. These are mixed lighting situations. I use a flash to clean up the color and boost light levels, but I also keep the ambient exposure strong enough that my flash doesn't overwhelm and wash out the natural light from windows and the glow of light fixtures. Done correctly, this approach looks very natural.

The K-r seems to be very sensitive to yellow light from light bulbs. First, I correct the color of the room I'm standing in to a good neutral shade. But often there's a next room visible through a doorway, lit primarily by incandescent light bulbs. Those rooms are taking on a very strong yellow color cast. I've shot similar rooms with Sony Alphas and a Nikon D40, and while the secondary rooms do take on a warm color cast from the bulbs, it's nothing like as strong as the Pentax's yellow tendencies. I rarely ever had to think about color balance with those cameras.

After studying the current lower-priced DSLRs, I think Pentax rules in ergonomics and features. I love the way the K-x is laid out and put together. But if it can't give me consistent JPG colors without RAW or PP, it's worthless to me.

I'm sorry there isn't a Kelvin WB setting, that's what i prefer. And I know there's a custom function setting to "AWB in tungsten light/ string correction." I don't use AWB, however, because I need consistency in white and pastel walls from shot to shot, though the walls often are decorated with strong colored artwork that might trick AWB into unnecessary corrections.

Any advice before I send this K-r back?

03-04-2011, 12:11 PM   #2
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I don't have a K-r but in this lighting you have to set a custom WB, period.

If you have a grey card, white card, or other custom WB device, you quickly do a custom WB that you should find satisfactory. I've do this routinely on my K-100/ k-10 /k-20. I also believe that this would be required on other brand DSLRs as well. This problem is not unique under this lighting.
03-04-2011, 12:22 PM   #3
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The way you describe the problem and the difference between the K-r and Sony or Nikon, it makes me think you've selected CTE (Color Temperature Enhance) for white balance, or some other setting for JPEGs. There shouldn't be that big a difference to start with, but different JPEG settings could do it.

On the K-7, there's a Kelvin WB setting, but I don't see how that would help; the color temperatures of each light source will still be different. It's the same as if you shot RAW; you have the freedom to choose one number, but the problem is the difference, not which number you choose.

Consider black and white: solves everything.
03-04-2011, 01:23 PM   #4
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Thanks for the replies. Custom white balance takes extra time, and defeats my goal of having consistent WB in every room, day after day.

I did wander into CTE at some point, but it wasn't part of my experiments today. I was using the Bright custom image setting, that may have exaggerated the errors. But you hit it, Dave-- it's the difference between bulbs and flash/daylight that's the big problem. The other cameras seemed to minimize that problem, while the Pentax maximizes it.

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03-04-2011, 01:24 PM   #5
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If you shoot in mixed light, you will get mixed results.

Try replacing the bulbs with a higher color-temp bulb, or cover the windows (and flash) with the film made for the purpose. They do it all the time on movie locations.
03-04-2011, 10:20 PM - 1 Like   #6
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No camera can white balance different colored light sources. Its simply not possible. Perhaps the other cameras didn't expose well (had shorter shutter time) and didn't capture that tungsten ambient

The best and cheapest solution would be to simply slap a $0.50 CTO gel on the flash and set your white balance to tungsten.
03-05-2011, 12:29 AM   #7
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Maybe I just got too slow with my shutter speeds today, letting the yellow tungsten light emerge. There's a sweet spot, probably about two stops faster, where you can still see the glow of light sources without having their color take over the whole wall.

Tonight I tested my K-r and A700 in the same lighting, at the same settings, and got almost identical results. The wild card between them may be that the A700, with its Kelvin WB setting, allows you to fix the color response firmly. From my reading, the K-r's presets allow the camera to make color adjustments as it sees fit. The K-r was set for highlight and shadow+3, and I cheated in its favor by cranking the flash up to +3 (the Sony flash got no adjustment).

If color isn't the difference between them, DR control is. Here's the A700 and the K-r in a harshly lit scene, boosted with bounce flash, no PP. With DRO at the max, the Sony easily caught the blue of the sky and rendered the shadows about one stop brighter. I'd hoped the Pentax DR feature was the equal of Sony's, but I'm afraid it's not.
03-05-2011, 12:53 AM   #8
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QuoteOriginally posted by Wheatridger Quote
Thanks for the replies. Custom white balance takes extra time, and defeats my goal of having consistent WB in every room, day after day.
I'm trying to follow your meaning here (blue). Custom White Balance takes about 10-30 seconds at the most. It will take less the more you practice it.

But the part that baffles me is "defeats consistent WB".... no, i don't think so.

Setting CWB tells the camera what WHITE is in that particular lighting. So, you will always be exposing for WHITE WHITES regardless of the lighting for the room. In fact, setting CWB will give you more consistent color across rooms/lighting, because whites will actually remain white in different lighting.

In the two photos you posted in #4 above, the left photo appears to have the foreground lighted by daylight flash. The room in the background has strong actual daylight streaming in the window. Even though the incandescent ceiling bulb is on in the rear room, the daylight is stronger and the two rooms remain relatively in balance.

In the one on the right, it looks like you're again using a daylight flash but an incandescent bulb in the room through the door. And with yellowish toned walls in the first place. So, naturally they contrast due to the wide differences in color of the strongest lighting for each room.

What enoeske said is true: "No camera can white balance different colored light sources. Its simply not possible."

You can use a yellow/golden gel or film on your flash as he suggests to balance the color of the lights, then use Tungsten to get "white".

An alternative solution would be to use a larger aperture prime - you can readily find manual lenses for the purpose - and take existing light photos for which you use a CWB to get white in every shot consistently.

Or, it could be that I have failed to comprehend what it is you are trying to do. In that case, sorry I wasn't able to help.


Last edited by yucatanPentax; 03-05-2011 at 02:01 AM.
07-05-2012, 08:21 AM   #9
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Hello!

I am a newbie to this forum and to panoramas shooting.

I have a Pentax k-r with Samyang fisheye 8mm f/3.5 lens and a pano head.

What camera setting should I use for shooting interior pictures for Virtual Tours please?

Thank you for all your help!
07-05-2012, 08:32 AM   #10
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QuoteOriginally posted by meteorstorm Quote
Hello!

I am a newbie to this forum and to panoramas shooting.

I have a Pentax k-r with Samyang fisheye 8mm f/3.5 lens and a pano head.

What camera setting should I use for shooting interior pictures for Virtual Tours please?

Thank you for all your help!
If you are shooting pano, definitely do NOT use AWB. Much easier to select one of the presets or a custom one. Otherwise you'll have a lot of fun trying to match white balance between each shot.
07-05-2012, 08:37 AM   #11
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Thank you!

And what about other settings please? Can I use auto-settings or rather manual Av priority?
07-06-2012, 12:23 PM   #12
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Here are the results of very detailed review of K-r on optyczne.pl (unfortunately only in polish, they have so far english version of lenses reviews only at lenstip.com) The table below shows the color error (dC) and saturation measured with GretagMacbet color table.

The dC parameter means how far you are from true color and saturation is in % showing how over- or under-saturated is the picture. Perfect camera gives dc = 0 and s = 100% but for practical purpose saturation within +/-10% and dC below 10 is good.

Essentially Auto WB setting is quite good for everything except for bulbs when you definitely should use dedicated setting. Probably you would need to set temperature parameter adjusted to your bulbs type (eg. traditional bulbs are very different the energy saving bulb). In the test they have used bulbs with calibrated spectral temperature. Another interesting observation is that, apart from Bulbs, Auto WB is usually better then dedicated WB settings!

Light type | WB setting | dC | Saturation[%]
------------------------------------------------------------------
Bright day | Auto | 6.13 | 103.7
Bright day | Bright day | 9.52 | 105.2
6400 K | Auto | 5.56 | 108.2
Flash | Auto | 4.79 | 86.86
Flash | Flash | 3.14 | 83.99
3000 K | Auto | 19.3 | 127.3
Bulb | 3000 K | 6.58 | 98.92

And here's a link to source: Test Pentax K-r - Balans bieli - Test aparatu - Optyczne.pl (table is at the bottom)
07-07-2012, 01:30 AM   #13
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A no to idealnie, bo Polskim posluguje sie najlepiej

Czy zechce Pan pomoc mi w kilku kwestiach? Np. - robiac zdjecia dworu z wnetrza chcialbym, zeby niebo bylo widocznie jako niebieskie z chmurkami a nie jako jedna wielka biala plama - na co powinienem zwrocic uwage?
07-07-2012, 04:46 AM   #14
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Sorry guys for this few sentences in Polish below! Chmury w oknie to trudna sprawa, bo to kwestia zakresu dynamicznego aparatu, który jest największym problemem cyforwych aparatów. Rozwiązania są 3: 1) Filtr polaryzacyjny (niezastąpiony przy wszystkich krajobrazach robionych z chmurami) 2) Doświetlić pierwszy plan fleszem 3) Tryb HDR, prawdopodobnie potrzebny będzie statyw.
07-07-2012, 04:53 AM   #15
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Do you mean you are using flash and have an issue with multiple light sources? You might want to try putting a colored gel over your flash to match the color of the other light source. Then you can set your white balance for that other light source or do it in post if you are shooting RAW.
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