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Post by Darren on Sept 8, 2008 11:25:18 GMT 10
Margaret Ehrlich from Glen Burnie Md, who is active on the forum, submitted this photograph via the website. The story Behind the photograph : "My daughter, her friend, and myself went to Annapolis and I was taking a picture of them on the dock with my Kodak digital 34mm 8.1 mega pixels camera. When I got home and downloaded them to my computer I saw something to the left of the picture and enhanced it on my computer so I could get a better look. The picture shows a sailor in the background that wasn't there when I took the picture and you can see through him. It was a dry night."Looking closer at the pic it seems to be a couple rather than a lone sailor .... what do you think of this pic? |
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Post by Darren on Sept 15, 2008 23:58:40 GMT 10
Further to the above, the full EXIF data is below:
JFIF_APP1 : Exif
JFIF_APP3 : META
JFIF_APP2 : FXPR (offset:20931 size:108bytes)
JFIF_APP2 : FXPR (offset:21050 size:418bytes)
JFIF_APP2 : FXPR (offset:21479 size:27714bytes)
Main Information
Make : EASTMAN KODAK COMPANY
Model : KODAK EASYSHARE M893 IS DIGITAL CAMERA
Orientation : left-hand side
XResolution : 1296039936/2097152
YResolution : 1296039936/2097152
ResolutionUnit : Inch
DateTime : 2008:08:31 23:42:29
YCbCrPositioning : centered
ExifInfoOffset : 220
Sub Information
ExposureTime : 1/2Sec
FNumber : F2.9
ExposureProgram : Portrait Mode
ISOSpeedRatings : 125
ExifVersion : 0221
DateTimeOriginal : 2008:08:31 10:22:08
DateTimeDigitized : 2008:08:31 10:22:08
ComponentConfiguration : YCbCr
ShutterSpeedValue : 1/2Sec
ApertureValue : F2.9
ExposureBiasValue : EV0.0
MaxApertureValue : F2.9
MeteringMode : Division
LightSource : Unidentified
Flash : Fired(Auto/red-eye)
FocalLength : 5.70(mm)
MakerNote : Unknown Format : 11112Bytes (Offset:790)
FlashPixVersion : 0100
ColorSpace : sRGB
ExifImageWidth : 3296
ExifImageHeight : 2472
ExifInteroperabilityOffset : 11906
ExposureIndex : 2097152000/16777216
SensingMethod : OneChipColorArea sensor
FileSource : DSC
SceneType : A directly photographed image
CustomRendered : Custom process
ExposureMode : Auto
WhiteBalance : Auto
DigitalZoomRatio : 0/1
FocalLength(35mm) : 34(mm)
SceneCaptureType : Portrait
GainControl : Low gain up
Contrast : Normal
Saturation : Normal
Sharpness : Normal
SubjectDistanceRange : Unknown
ExifR : R98
Version : 0100
Compression : OLDJPEG
Orientation : left-hand side
XResolution : 1207959552/16777216
YResolution : 1207959552/16777216
ResolutionUnit : Inch
JPEGInterchangeFormat : 12042
JPEGInterchangeFormatLength : 8807
FlashPixExtention
/Extension List
/Screen Nail_bd0100609719a180
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Post by Darren on Sept 20, 2008 12:49:32 GMT 10
From the EXIF data it can be determined that the image provided is not the raw version from the camera. This is evident in the multiple APP data entries, but mainly the inconsistent times given in the DateTime/DateTimeOriginal and DateTimeDigitized fields. In talking with Margaret the original was adjusted to bring out detail. There is always a stronger case if it can be said the original was not changed in any way, but this does explain inconsistent information in the EXIF data. We can also determine the following from the EXIF data: - The the camera's clock was not set accurately
- There was low light available for the camera to take a clearer picture. Such less than ideal conditions promote the formation of anomalies.
- The camera was set to portrait mode rather than night scene which may have assisted in image quality.
- The automatic settings of the camera gave an exposure of 1/2 second at F2.9 at ISO125 flash was fired.
When faced with less than ideal conditions automatic digital cameras attempt to adjust settings to give an acceptable image. This is a balancing act and can lead to various anomalies, especially in low light environments. In this case it seems the camera has extended the exposure (1/2sec) and fired the flash to attempt to get foreground and background detail. This has effectively resulted in settings similar to a technique known as "flash ghosting" or "dragging the shutter". The flash has fired at a given intensity to brighten the foreground subject with reference to the ambient light. The flash time is typically 1/1000th of a second. This has successfully lit the subject and only partly impacted on the background. The shutter however has remained opened for the balance of the 1/2 second exposure - so the shutter has continued exposing using the ambient light for about .499 seconds. This has allowed the background which was less impacted by the flash to expose over a longer time period. Any motion encountered during this is effectively blurred or "ghosted" hence the term "flash ghosting". In looking at the image the fastest moving object would have been the "sailor and friend" who were walking in the background. The .001 second flash exposure has provided some partial illumination of them and frozen them. The white uniform definitely helped with this. The proceeding/subsequent .499 second exposure of ambient light provided a slight blur but more importantly allowed background detail to show through.  Here's an exaggerated example of flash ghosting created to show the effect at short range in a single exposure using the technique. There are other possibilities for the image but flash ghosting seems to be the most likely, which application of Occam's razor would deem to be the true cause. Regardless, this is certainly a great photo and great example of what anomalies can happen in digital photographs. |
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Post by Darren on Sept 22, 2008 18:42:44 GMT 10
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