DNG conversion question

Jiggo0109 wrote in post #17319815
That's quite a load of work for backing up files.

Lots of earthquakes in New Zealand. Tim's house might disappear into a big hole.

Something that was alluded to earlier, but maybe not entirely clear to the OP: There are two kinds of DNGs, non-lossy and lossy. Both kinds are compressed, but the lossy is compressed much more. The amount of loss is comparable to the highest quality jpg, i.e. not visible to the human eye. But unlike jpgs, the data remains raw - 14 bit, linear and Bayer mosaiced. The non-lossy kind uses a compression algorithm that is different from the compression used by Canon for CR2s, usually the DNG is slightly smaller than the CR2, but not always.

I like DNGs for a couple reasons. You can opt to have "Quick Loading Data" included in the DNG metadata, which means that LR does not have to draw data from the CR Cache directory when loading the image in Develop. Moreover, the xmp data is internal in DNGs but if you elect to save your edits to xmp with a CR2, it has to be external, a sidecar file. By having my edits in xmp as well as in the LR catalog, I can open the DNG in PSE12/ACR and although that ACR lacks the interface to do the advanced edits in LR and full ACR, it can read and apply all the edit data in the xmp.

If you choose to convert to DNG during the importation into LR and also choose to have a second copy made at the same time, the second copy will be CR2. So I have DNGs on an external usb3 SSD for editing and CR2s as backup on an external HHD. Periodical the backup drive gets mirrored to another external that resides in a steel box in the security room (not many earthquakes here, but sometimes rockets from Lebanon).

Jiggo0109 wrote in post #17319902
It's about camera's settings in shooting raw (Picture styles' sharpness and contrast). If it affects PP if I set sharpness to 6 or 7?

Picture Styles do not affect Raw data. They are primarily parameters used by the Raw converter in the camera when it makes a jpg, but since they are also recorded in the metadata they are also automatically read and used by Canon's DPP converter. LR is blissfully blind to that part of the metadata, both P.S. and sharpening setting, although you can manually select camera profiles that emulate the profiles used in the P.S.s, but without the added contrast and sharpening.

tzalman wrote in post #17319912
But unlike jpgs, the data remains raw - 14 bit, linear and Bayer mosaiced.

Not necessarily. There's also "linear DNG", which has been demosaiced but remains in 14-bit linear (non-gamma) space.

Especially with the lossy DNG, which as far as I can see was intended to let you take a "preview" view with you on the road, DNG has now become a container format rather than a specific format. It carries the risk that you might misconfigure software or mix files up, and months down the track find yourself with some lossy version of your data.

This is exactly why I don't like DNG. The timestamp gets updated every time you do an edit, which means you would be backing up the image data over and over again. With XMP+CR2, I can edit for hours and have a very quick backup to finish. (I believe you can set Lightroom to save XMP sidecars even with DNG.)

It's not as if a raw processor from one vendor can read the processing instructions from another vendor's. If they were standardised, with exact meanings of "exposure" etc., it would be right to put this stuff in the DNG file. But, as it is processor-specific stuff, it belongs in the raw processor's database, whether as a database file or sidecars. To have included it in the DNG specification is outright incorrect design, unless you regard DNG as Adobe proprietary files.

Space savings for DNG mainly apply to some other camera brands, which don't/didn't have losslessly compressed raws. Canon does.

My DNG files from my 18MP Monochrom as DNGs are 36mbs. My raws from my 21mp 5DIIs are 26mbs. There is no loss of data. It is what Leica M uses instead of raw.