You should know that DNG files are generally larger than raw files, often much larger.
As far as doing blocks of conversions, look into the free DNG converter Adobe offers. It's a standalone application that works on whole folders at a time.
You need to be careful DNG files are not supported as well as RAW file are many camera makers sofrware do not support DNG so you will not be able to use programs like Canon software to see what auto focus area should be in focus. You would need to use the DGN conversion option to embed the original RAW file in the DGN file so you can extract it if you need to use it. When you use that converter option DGN file become much larger then RAW file and require a lot more external disk space. DGN file are not a standards file file format they are just an other RAW format the many image processing prograns do not support.
I have been working with two Scott Kelby instructional books CS4 and now CS5 to self educate myself in PS. In CS4 Chapter Four Kelby writes, "There are three advantages to converting your RAW files to Adobe DNG: (1) DNG files are generally about 20% smaller. (2) DNG files don't need an XMP sidecar file to store Camera Raw edits, metadata, and keywords-the info's embedded into the DNG file, so you only have to have one file to keep track of. And, (3) DNG is an open format, so you'll be able to open them in the future."
I'm now totally confused, again, as how to organize my work flow when processing my RAW files. It seems there's a plethora of ideas in this genre.
As with most thing there is no simple answer. Apparently some RAW file are not compressed (olympus) and others like cannon are not. Conversion of a uncompressed file will result in a larger file.
Also there is apparently a setting (at least in LR) to imbed RAW and jpeg into the DNG which would make them 2x the size.
Here is the link for the above statements http://photography-on-the.net/forum/showthread.php?t=792275
Sorry, I didn't mean to throw out incomplete info... I kind of misspoke based on my own experience. You *can* make a DNG slightly smaller than a raw file with certain settings, but I'm not sure I'd recommend them. My experience has been with converting to DNG where I always embed the original raw file inside the DNG (JJ mentioned that above). I have never been comfortable with the idea of eliminating my original raw files entirely, so I have always selected the option to embed the raw file.
You can reduce the data size from the out-of-camera raw file if you optimize everything for smallest size - i.e.,
- Don't embed the original raw file in the DNG.
- Don't embed a JPEG preview or Fast Load data.
- Use Lossy Compression (note; this causes degradation of the image).
- Don't choose a Custom conversion where the image is uncompressed.
I have heard that there is also a possibility under some conditions that a camera file could be de-Bayered, which can cause an increase in size, though I don't recall what those conditions are at the moment.
Here's an example with the settings above set to minimize size (except Lossy Compression - I cannot recommend that):
I'm very sorry I gave a too-simple answer earlier.
As I'm totally wet behind the ears in this mine field I have decided to purchase another external harddrive where I'll park all my original RAW files and play with copies elsewhere. At present I'm trying, with some success, to manage seven different harddrives and three computers.