We know that the JPEG produced by in-camera RAW conversion is very close to that produced by using the RAW converter provided by the camera manufacturer, but how close is it in detail?
I'm interested in this as a general question, but for a specific data point I looked at my Canon 550D (firmware 1.0.9) and Digital Photo Professional (version 126.96.36.199). What I did:
- Take a photo in RAW + JPEG; I used standard picture style, auto white balance, no automatic lighting optimizer, no highlight tone protection.
- Load the RAW file into DPP and convert it to JPEG at quality 7 - quality 7 chosen as that makes GIMP's view of the JPEG quality parameter match the in-camera JPEG at 97.
- Compare the two JPEGs. While they're pretty close to each other, they're not identical. As well as some trivial differences in the metadata, it looks like the in-camera JPEG possibly has slightly more sharpening than the DPP converted one. This is particularly obvious around the white flecks towards the bottom centre of the photo.
If you want to see the files here, I've put them all on Dropbox, including a PNG of the difference between the two JPEGs.
This is potentially two very related questions:
- Is it possible to get DPP to produce identical output to the in-camera JPEG engine?
- Is it possible for other camera manufacturers / own brand RAW converters?
For avoidance of doubt, this is almost entirely a theoretical point; I'm well aware the differences are small enough they're not going to make a difference in practice.