John
Junior Forum Member
Posts: 232 
Open to constructive criticism of photos: Yes
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Post by John on Jun 10, 2015 1:03:25 GMT
When I shoot in JPEG and import to Lightroom the size of the JPEG file is 3 meg. I take the same 3 meg file and export it as DNG and I have a new DNG file size of 7 meg. Have I created a RAW like file from the JPEG? Where did the extra pixels come from?
Crap like this gives me a headache.
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Post by Tpgettys on Jun 10, 2015 4:21:07 GMT
AH, I just saw you said LR, which I don't use. However, that does make sense anyway. The point of JPEG is that it provides a compressed version of an image, whereas a DNG is not compressed; all pixels will be present in the DNG (as opposed to reconstituted when a JPEG is interpreted). The file size ratio 7/3 gives you a sense of the size saving offered by using JPEG.
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preeb
Established Forum Member
Posts: 376
Open to constructive criticism of photos: Yes
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Post by preeb on Jun 10, 2015 18:37:16 GMT
Also, I can export a raw to jpeg, using the same parameters and image 3 times and get 3 slightly different file sizes. Jpeg conversion is not exact. It can change depending on how the compression is executed each time the raw file is read, and then how the expansion is made when converting back to dng. Different converters can get noticeably different file sizes when converting raw to jpeg.
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