Normally, aka by default, Lightroom does not save its work to the sidecars. You can create the sidecar by pressing Ctrl-S or Cmd-S. The problem is that the sidecar file does not include everything. DNG files do not have sidecars. All the sidecar information is embedded inside the DNG file.

What’s a sidecar you ask? It’s a text file that has the same name as your photo, except for the extension replaced with .XMP . It’s a format created by Adobe: the Extensible Metadata Platform.

It’s a “structured” text file in a language: XML.

I have a photo called: reifel-20110108-7153.cr2. The sidecar is called: reifel-20110108-7153.xmp and contains:

<x:xmpmeta xmlns:x="adobe:ns:meta/" x:xmptk="Adobe XMP Core 4.2-c020 1.124078, Tue Sep 11 2007 23:21:40">
 <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
  <rdf:Description rdf:about=""
    xmlns:tiff="http://ns.adobe.com/tiff/1.0/">
   <tiff:Make>Canon</tiff:Make>
   <tiff:Model>Canon EOS Tags: Lightroom</tiff:Model>
   <tiff:Orientation>1</tiff:Orientation>
   <tiff:ImageWidth>5184</tiff:ImageWidth>
   <tiff:ImageLength>3456</tiff:ImageLength>
  </rdf:Description>
  <rdf:Description rdf:about=""
    xmlns:exif="http://ns.adobe.com/exif/1.0/">
   <exif:ExifVersion>0221</exif:ExifVersion>
   <exif:ExposureTime>1/50</exif:ExposureTime>
   <exif:ShutterSpeedValue>5643856/1000000</exif:ShutterSpeedValue>
   <exif:FNumber>71/10</exif:FNumber>
   <exif:ApertureValue>5655638/1000000</exif:ApertureValue>
   <exif:ExposureProgram>3</exif:ExposureProgram>
   <exif:ISOSpeedRatings>
    <rdf:Seq>
     <rdf:li>400</rdf:li>
    </rdf:Seq>
   </exif:ISOSpeedRatings>
   <exif:DateTimeOriginal>2011-01-08T10:11:07.33-08:00</exif:DateTimeOriginal>
   <exif:DateTimeDigitized>2011-01-08T10:11:07.33-08:00</exif:DateTimeDigitized>
   <exif:ExposureBiasValue>0/1</exif:ExposureBiasValue>
   <exif:MaxApertureValue>5/1</exif:MaxApertureValue>
   <exif:SubjectDistance>738/100</exif:SubjectDistance>
   <exif:MeteringMode>5</exif:MeteringMode>
   <exif:Flash rdf:parseType="Resource">
    <exif:Fired>False</exif:Fired>
    <exif:Return>0</exif:Return>
    <exif:Mode>2</exif:Mode>
    <exif:Function>False</exif:Function>
    <exif:RedEyeMode>False</exif:RedEyeMode>
   </exif:Flash>
   <exif:FocalLength>400/1</exif:FocalLength>
   <exif:CustomRendered>0</exif:CustomRendered>
   <exif:ExposureMode>0</exif:ExposureMode>
   <exif:WhiteBalance>1</exif:WhiteBalance>
   <exif:SceneCaptureType>0</exif:SceneCaptureType>
   <exif:FocalPlaneXResolution>5184000/907</exif:FocalPlaneXResolution>
   <exif:FocalPlaneYResolution>3456000/595</exif:FocalPlaneYResolution>
   <exif:FocalPlaneResolutionUnit>2</exif:FocalPlaneResolutionUnit>
   <exif:PixelXDimension>5184</exif:PixelXDimension>
   <exif:PixelYDimension>3456</exif:PixelYDimension>
  </rdf:Description>
  <rdf:Description rdf:about=""
    xmlns:xap="http://ns.adobe.com/xap/1.0/">
   <xap:ModifyDate>2011-01-08T10:11:07.33-08:00</xap:ModifyDate>
   <xap:CreateDate>2011-01-08T10:11:07.33-08:00</xap:CreateDate>
   <xap:MetadataDate>2011-01-10T06:38:48.058+08:00</xap:MetadataDate>
  </rdf:Description>
  <rdf:Description rdf:about=""
    xmlns:dc="http://purl.org/dc/elements/1.1/">
   <dc:creator>
    <rdf:Seq>
     <rdf:li>Syv Ritch</rdf:li>
    </rdf:Seq>
   </dc:creator>
   <dc:rights>
    <rdf:Alt>
     <rdf:li xml:lang="x-default">Copyright © 2011 Syv Ritch</rdf:li>
    </rdf:Alt>
   </dc:rights>
   <dc:subject>
    <rdf:Bag>
     <rdf:li>Animals</rdf:li>
     <rdf:li>Birds</rdf:li>
     <rdf:li>Duck</rdf:li>
     <rdf:li>Wood Duck</rdf:li>
    </rdf:Bag>
   </dc:subject>
  </rdf:Description>
  <rdf:Description rdf:about=""
    xmlns:aux="http://ns.adobe.com/exif/1.0/aux/">
   <aux:SerialNumber>370302161</aux:SerialNumber>
   <aux:LensInfo>120/1 400/1 0/0 0/0</aux:LensInfo>
   <aux:Lens>120-400mm</aux:Lens>
   <aux:LensID>174</aux:LensID>
   <aux:ImageNumber>0</aux:ImageNumber>
   <aux:ApproximateFocusDistance>738/100</aux:ApproximateFocusDistance>
   <aux:FlashCompensation>0/1</aux:FlashCompensation>
   <aux:Firmware>1.2.3</aux:Firmware>
  </rdf:Description>
  <rdf:Description rdf:about=""
    xmlns:Iptc4xmpCore="http://iptc.org/std/Iptc4xmpCore/1.0/xmlns/">
   <Iptc4xmpCore:CreatorContactInfo rdf:parseType="Resource">
    <Iptc4xmpCore:CiAdrPcode>V5Z 4R3</Iptc4xmpCore:CiAdrPcode>
    <Iptc4xmpCore:CiEmailWork>syv@foto-biz.com</Iptc4xmpCore:CiEmailWork>
    <Iptc4xmpCore:CiAdrRegion>British Columbia</Iptc4xmpCore:CiAdrRegion>
    <Iptc4xmpCore:CiAdrCity>Vancouver</Iptc4xmpCore:CiAdrCity>
    <Iptc4xmpCore:CiAdrCtry>Canada</Iptc4xmpCore:CiAdrCtry>
    <Iptc4xmpCore:CiUrlWork>http://www.foto-biz.com</Iptc4xmpCore:CiUrlWork>
   </Iptc4xmpCore:CreatorContactInfo>
  </rdf:Description>
  <rdf:Description rdf:about=""
    xmlns:xapRights="http://ns.adobe.com/xap/1.0/rights/">
   <xapRights:Marked>True</xapRights:Marked>
   <xapRights:UsageTerms>
    <rdf:Alt>
     <rdf:li xml:lang="x-default">No reproduction of any type without prior written permission</rdf:li>
    </rdf:Alt>
   </xapRights:UsageTerms>
   <xapRights:WebStatement>http://www.foto-biz.com/usageterms</xapRights:WebStatement>
  </rdf:Description>
  <rdf:Description rdf:about=""
    xmlns:photoshop="http://ns.adobe.com/photoshop/1.0/">
   <photoshop:AuthorsPosition>Photographer</photoshop:AuthorsPosition>
   <photoshop:CaptionWriter>Syv Ritch</photoshop:CaptionWriter>
  </rdf:Description>
  <rdf:Description rdf:about=""
    xmlns:Iptc4xmpExt="http://iptc.org/std/Iptc4xmpExt/2008-02-29/">
   <Iptc4xmpExt:DigitalSourceType>nil</Iptc4xmpExt:DigitalSourceType>
  </rdf:Description>
  <rdf:Description rdf:about=""
    xmlns:lr="http://ns.adobe.com/lightroom/1.0/">
   <lr:hierarchicalSubject>
    <rdf:Bag>
     <rdf:li>Animals|Birds|Duck|Wood Duck</rdf:li>
    </rdf:Bag>
   </lr:hierarchicalSubject>
  </rdf:Description>
  <rdf:Description rdf:about=""
    xmlns:crs="http://ns.adobe.com/camera-raw-settings/1.0/">
   <crs:Version>6.3</crs:Version>
   <crs:ProcessVersion>5.7</crs:ProcessVersion>
   <crs:WhiteBalance>As Shot</crs:WhiteBalance>
   <crs:Temperature>6250</crs:Temperature>
   <crs:Tint>+11</crs:Tint>
   <crs:Exposure>+0.25</crs:Exposure>
   <crs:Shadows>4</crs:Shadows>
   <crs:Brightness>+42</crs:Brightness>
   <crs:Contrast>+50</crs:Contrast>
   <crs:Saturation>0</crs:Saturation>
   <crs:Sharpness>49</crs:Sharpness>
   <crs:LuminanceSmoothing>0</crs:LuminanceSmoothing>
   <crs:ColorNoiseReduction>25</crs:ColorNoiseReduction>
   <crs:ChromaticAberrationR>0</crs:ChromaticAberrationR>
   <crs:ChromaticAberrationB>0</crs:ChromaticAberrationB>
   <crs:VignetteAmount>0</crs:VignetteAmount>
   <crs:ShadowTint>0</crs:ShadowTint>
   <crs:RedHue>0</crs:RedHue>
   <crs:RedSaturation>0</crs:RedSaturation>
   <crs:GreenHue>0</crs:GreenHue>
   <crs:GreenSaturation>0</crs:GreenSaturation>
   <crs:BlueHue>0</crs:BlueHue>
   <crs:BlueSaturation>0</crs:BlueSaturation>
   <crs:FillLight>15</crs:FillLight>
   <crs:Vibrance>0</crs:Vibrance>
   <crs:HighlightRecovery>13</crs:HighlightRecovery>
   <crs:Clarity>0</crs:Clarity>
   <crs:Defringe>0</crs:Defringe>
   <crs:HueAdjustmentRed>0</crs:HueAdjustmentRed>
   <crs:HueAdjustmentOrange>0</crs:HueAdjustmentOrange>
   <crs:HueAdjustmentYellow>0</crs:HueAdjustmentYellow>
   <crs:HueAdjustmentGreen>0</crs:HueAdjustmentGreen>
   <crs:HueAdjustmentAqua>0</crs:HueAdjustmentAqua>
   <crs:HueAdjustmentBlue>0</crs:HueAdjustmentBlue>
   <crs:HueAdjustmentPurple>0</crs:HueAdjustmentPurple>
   <crs:HueAdjustmentMagenta>0</crs:HueAdjustmentMagenta>
   <crs:SaturationAdjustmentRed>0</crs:SaturationAdjustmentRed>
   <crs:SaturationAdjustmentOrange>0</crs:SaturationAdjustmentOrange>
   <crs:SaturationAdjustmentYellow>0</crs:SaturationAdjustmentYellow>
   <crs:SaturationAdjustmentGreen>0</crs:SaturationAdjustmentGreen>
   <crs:SaturationAdjustmentAqua>0</crs:SaturationAdjustmentAqua>
   <crs:SaturationAdjustmentBlue>0</crs:SaturationAdjustmentBlue>
   <crs:SaturationAdjustmentPurple>0</crs:SaturationAdjustmentPurple>
   <crs:SaturationAdjustmentMagenta>0</crs:SaturationAdjustmentMagenta>
   <crs:LuminanceAdjustmentRed>0</crs:LuminanceAdjustmentRed>
   <crs:LuminanceAdjustmentOrange>0</crs:LuminanceAdjustmentOrange>
   <crs:LuminanceAdjustmentYellow>0</crs:LuminanceAdjustmentYellow>
   <crs:LuminanceAdjustmentGreen>0</crs:LuminanceAdjustmentGreen>
   <crs:LuminanceAdjustmentAqua>0</crs:LuminanceAdjustmentAqua>
   <crs:LuminanceAdjustmentBlue>0</crs:LuminanceAdjustmentBlue>
   <crs:LuminanceAdjustmentPurple>0</crs:LuminanceAdjustmentPurple>
   <crs:LuminanceAdjustmentMagenta>0</crs:LuminanceAdjustmentMagenta>
   <crs:SplitToningShadowHue>0</crs:SplitToningShadowHue>
   <crs:SplitToningShadowSaturation>0</crs:SplitToningShadowSaturation>
   <crs:SplitToningHighlightHue>0</crs:SplitToningHighlightHue>
   <crs:SplitToningHighlightSaturation>0</crs:SplitToningHighlightSaturation>
   <crs:SplitToningBalance>0</crs:SplitToningBalance>
   <crs:ParametricShadows>0</crs:ParametricShadows>
   <crs:ParametricDarks>0</crs:ParametricDarks>
   <crs:ParametricLights>0</crs:ParametricLights>
   <crs:ParametricHighlights>0</crs:ParametricHighlights>
   <crs:ParametricShadowSplit>25</crs:ParametricShadowSplit>
   <crs:ParametricMidtoneSplit>50</crs:ParametricMidtoneSplit>
   <crs:ParametricHighlightSplit>75</crs:ParametricHighlightSplit>
   <crs:SharpenRadius>+1.9</crs:SharpenRadius>
   <crs:SharpenDetail>42</crs:SharpenDetail>
   <crs:SharpenEdgeMasking>21</crs:SharpenEdgeMasking>
   <crs:PostCropVignetteAmount>0</crs:PostCropVignetteAmount>
   <crs:GrainAmount>0</crs:GrainAmount>
   <crs:ColorNoiseReductionDetail>50</crs:ColorNoiseReductionDetail>
   <crs:LensProfileEnable>1</crs:LensProfileEnable>
   <crs:LensManualDistortionAmount>0</crs:LensManualDistortionAmount>
   <crs:PerspectiveVertical>0</crs:PerspectiveVertical>
   <crs:PerspectiveHorizontal>0</crs:PerspectiveHorizontal>
   <crs:PerspectiveRotate>0.0</crs:PerspectiveRotate>
   <crs:PerspectiveScale>100</crs:PerspectiveScale>
   <crs:ConvertToGrayscale>False</crs:ConvertToGrayscale>
   <crs:ToneCurveName>Medium Contrast</crs:ToneCurveName>
   <crs:ToneCurve>
    <rdf:Seq>
     <rdf:li>0, 0</rdf:li>
     <rdf:li>32, 22</rdf:li>
     <rdf:li>64, 56</rdf:li>
     <rdf:li>128, 128</rdf:li>
     <rdf:li>192, 196</rdf:li>
     <rdf:li>255, 255</rdf:li>
    </rdf:Seq>
   </crs:ToneCurve>
   <crs:CameraProfile>Camera Neutral</crs:CameraProfile>
   <crs:CameraProfileDigest>31DE765188B0CE5CFB739E8744B937C9</crs:CameraProfileDigest>
   <crs:LensProfileSetup>LensDefaults</crs:LensProfileSetup>
   <crs:LensProfileName>Adobe (SIGMA APO 120-400mm F4.5-5.6 DG OS HSM, Canon)</crs:LensProfileName>
   <crs:LensProfileFilename>Canon (Sigma_120-400mm_F4.5-5.6_APO_DG_OS_HSM ) - RAW.lcp</crs:LensProfileFilename>
   <crs:LensProfileDigest>9C1DF871C09BED9D66BF72861167C5FB</crs:LensProfileDigest>
   <crs:LensProfileDistortionScale>100</crs:LensProfileDistortionScale>
   <crs:LensProfileChromaticAberrationScale>100</crs:LensProfileChromaticAberrationScale>
   <crs:LensProfileVignettingScale>100</crs:LensProfileVignettingScale>
   <crs:HasSettings>True</crs:HasSettings>
   <crs:CropTop>0.049794</crs:CropTop>
   <crs:CropLeft>0.105118</crs:CropLeft>
   <crs:CropBottom>0.944676</crs:CropBottom>
   <crs:CropRight>1</crs:CropRight>
   <crs:CropAngle>0</crs:CropAngle>
   <crs:CropConstrainToWarp>0</crs:CropConstrainToWarp>
   <crs:HasCrop>True</crs:HasCrop>
   <crs:AlreadyApplied>False</crs:AlreadyApplied>
   <crs:RawFileName>reifel-20110108-7153.cr2</crs:RawFileName>
  </rdf:Description>
 </rdf:RDF>
</x:xmpmeta>

The file created by Lightroom has several section:

  1. TIFF: Yes, all raw files use the TIFF format. What makes it proprietary to Canon, Nikon… are the makers notes (extra data that every camera manufacturer thinks is important and should be tracked) and how they are interpreted.
  2. EXIF: All the EXIF data
  3. ABOUT: That’s the date/time, IPTC
  4. CRS: The Lightroom Develop module changes. Only the results of all the changes. So if you took multiple crops, only the result of all the crops will be saved in XMP sidecar.

BTW, the sidecar created by Lightroom will be different from the sidecar for the same photo created by Aperture or Bibble or… Even if you get an exact match of the colors, crops… The IPTC and the descriptions will be identical but the CRS section will be completely different and will be ignored by the other processing software.

On of the big problem is that not everything done in Lightroom is written to the XMP file:

  1. Virtual Copies
  2. Flags like Pick and Reject, but ratings are included in the XMP sidecar.
  3. Stacks
  4. Collections
  5. Develop changes history.
  • If you lose the Lightroom catalog and you do not have a backup, you can re-import the photos into Lightroom. Lightroom will automatically apply the changes from the sidecar.
  • The most important thing that you will lose is the collections. They will have to be recreated either by hand or through Smart Collections.