Shutter Speed Vs. Shutter Speed Reported in Exif

[RichardSwearinger]

Looking at the metadata of a photo from my D810 in Shutter Priority mode the Camera Data Panel reports the shutter speed as 1/1800 but the Raw Data panel reports it as 9643856/1000000.

Does this mean there's a difference between what I set and what the camera actually used? Or am I reading this wrong?

Here's the rest of the raw data

xif:ExifVersion>0220</exif:ExifVersion> <exif:ColorSpace>65535</exif:ColorSpace> <exifixelXDimension>1500</exifixelXDimension> <exifixelYDixif:ExifVersion>0220</exif:ExifVersion> <exif:ColorSpace>65535</exif:ColorSpace> <exifixelXDimension>1500</exifixelXDimension> <exifixelYDimension>1645</exifixelYDimension> <exifateTimeOriginal>2018-06-05T09:58:48</exifateTimeOriginal> <exif:ExposureTime>1/800</exif:ExposureTime> <exif:FNumber>63/10</exif:FNumber> <exif:ExposureProgram>4</exif:ExposureProgram> <exif:ISOSpeedRatings> <rdf:Seq> <rdf:li>125</rdf:li> </rdf:Seq> </exif:ISOSpeedRatings> <exif:ShutterSpeedValue>9643856/1000000</exif:ShutterSpeedValue> <exif:ApertureValue>5310704/1000000</exif:ApertureValue> <exif:ExposureBiasValue>0/6</exif:ExposureBiasValue> <exif:MaxApertureValue>20/10</exif:MaxApertureValue> <exif:MeteringMode>5</exif:MeteringMode> <exif:LightSource>0</exif:LightSource> <exif:Flash rdfarseType="Resource"> <exif:Fired>True</exif:Fired> <exif:Return>3</exif:Return> <exif:Mode>1</exif:Mode> <exif:Function>False</exif:Function> <exif:RedEyeMode>False</exif:RedEyeMode> </exif:Flash> <exif:FocalLength>1350/10</exif:FocalLength> <exif:FocalPlaneXResolution>67122044/32768</exif:FocalPlaneXResolution> <exif:FocalPlaneYResolution>67122044/32768</exif:FocalPlaneYResolution> <exif:FocalPlaneResolutionUnit>3</exif:FocalPlaneResolutionUnit> <exif:SensingMethod>2</exif:SensingMethod> <exif:FileSource>3</exif:FileSource> <exif:SceneType>1</exif:SceneType> <exif:ExposureMode>0</exif:ExposureMode> <exif:WhiteBalance>0</exif:WhiteBalance> <exifigitalZoomRatio>1/1</exifigitalZoomRatio> <exif:FocalLengthIn35mmFilm>135</exif:FocalLengthIn35mmFilm> <exif:SceneCaptureType>0</exif:SceneCaptureType> <exif:GainControl>0</exif:GainControl> <exif:Contrast>0</exif:Contrast> <exif:Saturation>0</exif:Saturation> <exif:Sharpness>0</exif:Sharpness> <exif:SubjectDistanceRange>0</exif:SubjectDistanceRange> <exif:SubSecTime>89</exif:SubSecTime> <exif:SubSecTimeOriginal>89</exif:SubSecTimeOriginal> <exif:SubSecTimeDigitized>89</exif:SubSecTimeDigitized> </rdfescription> </rdf:RDF> </x:xmpmeta>mension>1645</exifixelYDimension> <exifateTimeOriginal>2018-06-05T09:58:48</exifateTimeOriginal> <exif:ExposureTime>1/800</exif:ExposureTime> <exif:FNumber>63/10</exif:FNumber> <exif:ExposureProgram>4</exif:ExposureProgram> <exif:ISOSpeedRatings> <rdf:Seq> <rdf:li>125</rdf:li> </rdf:Seq> </exif:ISOSpeedRatings> <exif:ShutterSpeedValue>9643856/1000000</exif:ShutterSpeedValue> <exif:ApertureValue>5310704/1000000</exif:ApertureValue> <exif:ExposureBiasValue>0/6</exif:ExposureBiasValue> <exif:MaxApertureValue>20/10</exif:MaxApertureValue> <exif:MeteringMode>5</exif:MeteringMode> <exif:LightSource>0</exif:LightSource> <exif:Flash rdfarseType="Resource"> <exif:Fired>True</exif:Fired> <exif:Return>3</exif:Return> <exif:Mode>1</exif:Mode> <exif:Function>False</exif:Function> <exif:RedEyeMode>False</exif:RedEyeMode> </exif:Flash> <exif:FocalLength>1350/10</exif:FocalLength> <exif:FocalPlaneXResolution>67122044/32768</exif:FocalPlaneXResolution> <exif:FocalPlaneYResolution>67122044/32768</exif:FocalPlaneYResolution> <exif:FocalPlaneResolutionUnit>3</exif:FocalPlaneResolutionUnit> <exif:SensingMethod>2</exif:SensingMethod> <exif:FileSource>3</exif:FileSource> <exif:SceneType>1</exif:SceneType> <exif:ExposureMode>0</exif:ExposureMode> <exif:WhiteBalance>0</exif:WhiteBalance> <exifigitalZoomRatio>1/1</exifigitalZoomRatio> <exif:FocalLengthIn35mmFilm>135</exif:FocalLengthIn35mmFilm> <exif:SceneCaptureType>0</exif:SceneCaptureType> <exif:GainControl>0</exif:GainControl> <exif:Contrast>0</exif:Contrast> <exif:Saturation>0</exif:Saturation> <exif:Sharpness>0</exif:Sharpness> <exif:SubjectDistanceRange>0</exif:SubjectDistanceRange> <exif:SubSecTime>89</exif:SubSecTime> <exif:SubSecTimeOriginal>89</exif:SubSecTimeOriginal> <exif:SubSecTimeDigitized>89</exif:SubSecTimeDigitized> </rdfescription> </rdf:RDF> </x:xmpmeta>

 

[ggbutcher]

The vagaries of metadata pique my curiosity, so I had to go digging...

The exif:shutterspeedvalue is a different way of expressing the time of exposure as specified in a thing called the APEX system. Wikipedia has a rather obtuse treatise:

https://en.wikipedia.org/wiki/APEX_system

I found this stackexchange exchange that more precisely deals with your question:

https://photo.stackexchange.com/questions/108817/shutter-speed-from-the-exif-shutterspeedvalue

Learn something new every day, I does....

Edit: BTW, your image's shutter speed is 1/800sec, not 1/1800sec...

 

[RichardSwearinger]

Metadata, there's never a dull moment.

Fascinating answer. Thanks for finding that and for bringing attention to the typo. I composed the question on an iPhone screen which is in retrospect is the wrong place to try to proofread fractions.

The vagaries of metadata pique my curiosity, so I had to go digging...

The exif:shutterspeedvalue is a different way of expressing the time of exposure as specified in a thing called the APEX system. Wikipedia has a rather obtuse treatise:

https://en.wikipedia.org/wiki/APEX_system

I found this stackexchange exchange that more precisely deals with your question:

https://photo.stackexchange.com/questions/108817/shutter-speed-from-the-exif-shutterspeedvalue

Learn something new every day, I does....

Edit: BTW, your image's shutter speed is 1/800sec, not 1/1800sec...

 

[bclaff]

Definitely the APEX (or APES) value for 1/800s

Among the places you can read up see Additive Photographic Exposure System (APES) at my site PhotonsToPhotos.

Note that 2^( -9643856 / 1000000) = 0.00125 = 1 / 800.000

 

[ProfHankD]

Looking at the metadata of a photo from my D810 in Shutter Priority mode the Camera Data Panel reports the shutter speed as 1/1800 but the Raw Data panel reports it as 9643856/1000000.

Does this mean there's a difference between what I set and what the camera actually used? Or am I reading this wrong?

Actually, the standard shutter speeds are not really the ideal values anyway. For example, 1/60s and 1/25s should really be 1/64s and 1/128s.... The internal use of APEX values is also a potential source of roundoff.

For example, CHDK reveals that Canons internally use integer APEX*96 values, which means the internal shutter value should be -96*log2(seconds). However, it also reveals that there are "real" and "market" values. The market values are what the camera GUI reports and allows you to set; the real values are what actually get used. For shutter speeds, the difference between market and real is usually small -- mostly roundoff error.

However, things are screwier than that. In cameras that have been hacked, such as Canon PowerShots under CHDK , it becomes clear that camera manufacturers play various games with the shutter speed and other parameters.

For ISOs, the market vs. real difference can be quite dramatic, with market values spreading both lower and higher than the real values -- e.g., a camera might report ISO 9600 while really using 4000, and ISO 50 while really using 110. Truth is, ISO for digital cameras isn't defined very tightly, so this isn't something CIPA testing will fault them for. Incidentally, DxO does report what they measure the ISOs to be, but DxO doesn't actually measure the shutter speed, etc., -- they trust market values reported by the camera, so even their computed ISO values are probably a bit inconsistent.

So, how come nobody gets upset about this? Because nearly everything we see in a photo is really log scaled -- so it takes an exponentially-large error for us to notice.

 

[RichardSwearinger]

Thank you.

Definitely the APEX (or APES) value for 1/800s

Among the places you can read up see Additive Photographic Exposure System (APES) at my site PhotonsToPhotos.

Note that 2^( -9643856 / 1000000) = 0.00125 = 1 / 800.000