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03-11-2010, 05:31 PM   #1
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Odd color rendition (random) on new K-x

Took a bunch of scenics today (32 deg. F, blowing wind - so cold). Bright out, though cloudy. Camera on Aperture Priority @ f11. Most exposures were around 1/500th sec. Using the 18-50mm DA-L kit lens. Freshly charged batteries. Because I knew it was cold, I turned the camera off between shots, knowing my shooting might be limited. I ALWAYS wait for the red light on the back (beside the LV button) to go out before switching off. Shooting in DNG+Jpeg mode.


Has anyone else run into this? If so, what caused it, and what can I do to ensure I don't lose critical images to this problem. Yes, I can salvage them in post processing, but quality degrades in the process.

I can post full size if needed. BTW, the problem is in both the JPEG and the DNG files.

Thanks in advance for any assistance.

Tim

Her's a screen shot of some of the images. Note that at random, some look as if they were shot through a blue filter.

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03-11-2010, 05:57 PM   #2
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post exif on the blue-est one. AWB?
03-11-2010, 06:19 PM   #3
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QuoteOriginally posted by MJB DIGITAL Quote
post exif on the blue-est one. AWB?
+1, wb looks off but inconsistent.
03-11-2010, 07:33 PM   #4
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Here's the most severely blue image. The board won't let me post a link to it, so remove the spaces in the link below to access the file. No program I have available shows me how white balance was set when I look at the exif data. I always keep WB on auto when shooting outdoors.

Since I shot 62 images, and the "bad" ones are not consecutive, I think it's unlikely I managed to change the WB randomly by accidentally pressing buttons while shooting.


http:// www. postimage. org /image.php ?v=PquYWNA


Tim

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Last edited by Tim_R; 03-11-2010 at 07:58 PM.
03-11-2010, 08:06 PM   #5
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Why don't you set your WB to the situation you are using? I've always thought that the one place Pentax really falls short is the AWB. Moreso indoors but not limited to indoors.

03-11-2010, 08:24 PM   #6
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That image you posted had no EXIF in it.

I'm thinking the cold may have been a factor in some of this. What temperature was your camera body when those photos were shot? That data, along with colour info etc, is in the EXIF too.

exiftool by phil harvey is a comprehensive command line tool that I believe can run on linux and it can get bucket loads of info out of your exif.
03-11-2010, 09:00 PM   #7
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This is AWB. The scene is fooling the camera's AWB algorithm. Set WB to Daylight outdoors for consistency.

Tip: shoot RAW, so white balance can be adjusted if necessary.
03-11-2010, 10:36 PM   #8
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QuoteOriginally posted by rawr Quote
That image you posted had no EXIF in it.

I'm thinking the cold may have been a factor in some of this. What temperature was your camera body when those photos were shot? That data, along with colour info etc, is in the EXIF too.

exiftool by phil harvey is a comprehensive command line tool that I believe can run on linux and it can get bucket loads of info out of your exif.
Thank you for the link to exiftool. Here is the complete output from exiftool on the pic I posted:

Code:
File Name                       : imgp0279.jpg
Directory : .
File Size : 5.8 MB
File Modification Date/Time : 2010:03:11 12:59:16-07:00
File Permissions : rwxr-xr-x
File Type : JPEG
MIME Type : image/jpeg
Exif Byte Order : Big-endian (Motorola, MM)
Make : PENTAX
Camera Model Name : PENTAX K-x
Orientation : Horizontal (normal)
X Resolution : 72
Y Resolution : 72
Resolution Unit : inches
Software : K-x Ver 1.01
Modify Date : 2010:03:11 12:59:11
Artist : ROBINSON,TIM
Y Cb Cr Positioning : Co-sited
Copyright : ROBINSON,TIM
Exposure Time : 1/1000
F Number : 11.0
Exposure Program : Aperture-priority AE
Exif Version : 0221
Date/Time Original : 2010:03:11 12:59:11
Create Date : 2010:03:11 12:59:11
Components Configuration : Y, Cb, Cr, -
Flash : Off, Did not fire
Focal Length : 26.2 mm
Pentax Version : 5.1.0.0
Pentax Model Type : 0
Preview Image Size : 640x480
Preview Image Length : 18055
Preview Image Start : 12744
Pentax Model ID : K-x
Date : 2010:03:11
Time : 12:59:11
Quality : Best
Flash Mode : Off, Did not fire; Internal
Focus Mode : AF-A
AF Point Selected : Center
ISO : 400
Exposure Compensation : 0
Metering Mode : Center-weighted average
Auto Bracketing : 0 EV, No Extended Bracket
White Balance : Tungsten
DSP Firmware Version : 1.01.00.07
CPU Firmware Version : 1.01.00.07
Effective LV : 15.0
Image Processing : Unprocessed
Picture Mode : Aperture Priority; 1/3 EV steps
Drive Mode : Single-frame; No Timer; Shutter Button; Single Exposure
Preview Image Borders : 28 28 0 0
Lens Type : smc PENTAX-DA 18-55mm F3.5-5.6 AL II
Sensitivity Adjust : 0
Image Processing Count : 0
Camera Temperature : 12 C
AE Lock : Off
Noise Reduction : Off
Flash Exposure Comp : 0
Image Tone : Bright
SR Result : Not stabilized
Shake Reduction : On (7)
SR Half Press Time : 0.47 s
SR Focal Length : 26 mm
Shutter Count : 364
Dynamic Range Expansion : On
High ISO Noise Reduction : Unknown (4 0 56)
AF Adjustment : 0
Black Point : 47 50 50 47
White Point : 9216 8288 8288 21408
Picture Mode 2 : Aperture Priority
Program Line : Normal
EV Steps : 1/3 EV steps
E-Dial In Program : P Shift
Aperture Ring Use : Prohibited
Flash Options : Normal
Metering Mode 2 : Center-weighted average
AF Point Mode : Select
Focus Mode 2 : AF-A
AF Point Selected 2 : Center
ISO Floor : 400
Drive Mode 2 : Single-frame
Exposure Bracket Step Size : 0.5
Bracket Shot Number : n/a
White Balance Set : Auto
Multiple Exposure Set : Off
AE Exposure Time : 1/965
AE Aperture : 11.3
AE ISO : 400
AE Xv : 0
AEB Xv : 0
AE Min Exposure Time : 1/5461
AE Program Mode : Av, B or X
AE Max Aperture : 0.2
AE Max Aperture 2 : 4.0
AE Min Aperture : 4
AE Metering Mode : Center-weighted average, [7]
Flash Exposure Comp Set : +8.0
Auto Aperture : On
Min Aperture : 32
Lens F Stops : 6
Nominal Max Aperture : 4.0
Nominal Min Aperture : 27
Max Aperture : 3.8
Flash Status : Off
Internal Flash Mode : Off, Normal
External Flash Mode : Off
Internal Flash Strength : 0
TTL DA A Up : 150
TTL DA A Down : 28
TTL DA B Up : 174
TTL DA B Down : 0
AE Metering Segments : 14.2 14.1 14.9 15.1 14.9 14.8 14.1 14.6 13.4 15.0 12.2 12.5 12.2 13.1 15.1 13.1
Flash Metering Segments : 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Slave Flash Metering Segments : 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Manufacture Date : 2010:01:25
Production Code : 2.1
Internal Serial Number : 8134438
Power Source : Unknown (0x22)
Battery States : 3 0
Battery AD Body No Load : 2
Battery AD Body Load : 78
Battery AD Grip No Load : 2
Battery AD Grip Load : 33
AF Predictor : 2
AF Defocus : 4
AF Integration Time : 0 ms
AF Points In Focus : Center (horizontal)
WB Shift AB : 0
WB Shift MG : 0
Serial Number : 3581354
Flashpix Version : 0100
Color Space : sRGB
Exif Image Width : 4288
Exif Image Height : 2848
Interoperability Index : R98 - DCF basic file (sRGB)
Interoperability Version : 0100
Sensing Method : One-chip color area
File Source : Digital Camera
Scene Type : Directly photographed
Custom Rendered : Normal
Exposure Mode : Auto
Focal Length In 35mm Format : 39 mm
Scene Capture Type : Standard
Contrast : High
Saturation : Normal
Sharpness : Hard
Subject Distance Range : Distant
Compression : JPEG (old-style)
Thumbnail Offset : 54592
Thumbnail Length : 7723
Image Width : 4288
Image Height : 2848
Encoding Process : Baseline DCT, Huffman coding
Bits Per Sample : 8
Color Components : 3
Y Cb Cr Sub Sampling : YCbCr4:2:2 (2 1)
Aperture : 11.0
Image Size : 4288x2848
Lens ID : smc PENTAX-DA 18-55mm F3.5-5.6 AL II
Preview Image : (Binary data 18055 bytes, use -b option to extract)
Scale Factor To 35 mm Equivalent: 1.5
Shutter Speed : 1/1000
Thumbnail Image : (Binary data 7723 bytes, use -b option to extract)
Circle Of Confusion : 0.020 mm
Field Of View : 49.6 deg
Focal Length : 26.2 mm (35 mm equivalent: 39.0 mm)
Hyperfocal Distance : 3.10 m
Light Value : 14.9
You'll note that WB for this pic is set by the camera for tungsten, even though I had Auto selected. That fact explains the color being off, of course. What is NOT obvious to me is how WB could have been changed from Auto to Tungsten (AND BACK) 11 times during 62 shots, by the camera. If the affected images were consecutive, I could blame myself, but it takes 6 separate button presses to make that change. Not something I might accidentally do when shooting.

Guess I simply can't trust the internal software for WB. Makes me wonder just what else might not be trustworthy.

Tim

03-11-2010, 10:50 PM   #9
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It seems that the cameras AWB was fooled into thinking it needed Tungsten for those shots.
03-11-2010, 11:15 PM   #10
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I've generally found the K-x AWB to be surprisingly reliable, even under very difficult conditions (ie stage lighting of various sorts, in my case). I'd be surprised if it was indeed barfing over some pretty static landscape scenes. I haven't shot too much landscape, but where I have it has never gone weird like this.

I still suspect the fact that the camera body was just 12 degrees C may have had an impact on the operation of the camera somehow. Also the battery power seems to be indicating quite low.

I may as well also raise my favorite bug-bear: were you using any filters on that lens (eg UV or protector)? They can often account for all sorts of weirdness in images and camera metering.
03-11-2010, 11:23 PM   #11
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I've just recently started setting my white balance on my K200D for the conditions I'm shooting in. I've noticed an improvement in the color rendition of my pictures. Now I just have to remember to change it when the conditions change.
03-12-2010, 12:02 AM   #12
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No idea how the Wb got set to tungsten, but since you said you shot DNG + JPEG, those should be *completely* recoverable with no quality loss whatsoever, since WB doesn't affect the RAW data. Setting the Wb back to sunny - or auto - in your PP software shoudl work just fine,
03-12-2010, 07:33 AM   #13
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QuoteOriginally posted by rawr Quote
I've generally found the K-x AWB to be surprisingly reliable, even under very difficult conditions (ie stage lighting of various sorts, in my case). I'd be surprised if it was indeed barfing over some pretty static landscape scenes. I haven't shot too much landscape, but where I have it has never gone weird like this.

I still suspect the fact that the camera body was just 12 degrees C may have had an impact on the operation of the camera somehow. Also the battery power seems to be indicating quite low.

I may as well also raise my favorite bug-bear: were you using any filters on that lens (eg UV or protector)? They can often account for all sorts of weirdness in images and camera metering.
Rather disappointing, if the temperature was the problem. 12C is about 50F. If I'm unable to shoot @ that temp, then I lose more than half the days each year! As for nattery power, yes, I knew because of the temperature that I might run out. But the "3" value is only one step below full, so that shouldn't have been the problem. The battery display on the LCD showed green the entire day. I kept checking it BECAUSE of the low temp. If it had showed even a little bit low, I had a spare set in my coat pocket, nice and warm, ready to go.

And no, I rarely use ANY filter, as I believe adding anything in front of the lens has to result in at least some degradation.

BTW, no one asked, but I'm running v1.01 firmware. I understand there was some problem with the battery circuitry on v1.0

I'm heading out again today (almost identical conditions) and will report back if there are further problems. Thanks, all, for the help.

Tim
03-12-2010, 07:52 AM   #14
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QuoteOriginally posted by Tim_R Quote
Guess I simply can't trust the internal software for WB. Makes me wonder just what else might not be trustworthy.

Tim
I wouldn't trust anything the camera does by itself. the best processor has to be behind the camera
03-12-2010, 08:52 AM   #15
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QuoteOriginally posted by Tim_R Quote
Guess I simply can't trust the internal software for WB. Makes me wonder just what else might not be trustworthy.
Auto Exposure
Auto Focus
Auto ISO

basically any Auto setting is untrustworthy in some situations.
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