Can EXIF data reveal the original pixel dimensions of a resized JPEG?
Asked 12/4/2019
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2 answers
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I have a resized JPEG that still contains some original EXIF/XMP metadata. I want to know whether the camera’s original image size in pixels can be determined from that metadata.
The file shows tags such as:
- Camera model: Nikon D850
- XResolution / YResolution: 240
- ResolutionUnit: inches
- FocalPlaneXResolution / FocalPlaneYResolution
- FocalLength / FocalLengthIn35mmFormat
- XMP crop values
Can the original pixel dimensions be derived from this data, and if so, which metadata tags should I check?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
6y ago
2 Answers
1
The XResolution and YResolution tags are supposed to contain the image resolution. Unfortunately they're meaningless for a camera image, because the camera doesn't have a fixed resolution - it varies based on the distance to the subject. They will be filled in with a constant, typically 72 DPI. Those fields were put in the EXIF specification for things like scanners that have a useful resolution to fill in.
Originally by user775. Source · Licensed CC BY-SA 4.0
user775
6y ago
0
Generated from our catalog & community — verify before relying on it.
Usually, yes—but not from the DPI-style fields you listed.
XResolution and YResolution are typically print/display resolution values, not the camera’s capture size in pixels. For photos, they’re often arbitrary defaults (for example 72 or 240 DPI) and do not tell you the original image dimensions.
The EXIF tags that matter are:
PixelXDimension(A002)PixelYDimension(A003)
If those tags are present and were preserved when the JPEG was resized, they can indicate the original pixel dimensions.
The other fields you listed—such as focal-plane resolution, focal length, and crop values—do not reliably let you calculate the original image size. They describe sensor scaling, lens metadata, or edits, not the camera’s saved pixel dimensions.
So the practical answer is:
- Check for
PixelXDimensionandPixelYDimensionin the EXIF. - If they are missing or were overwritten during resizing/export, you generally cannot recover the original resolution from the remaining metadata alone.
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