pico Posted August 2, 2016 Share #1 Posted August 2, 2016 Advertisement (gone after registration) I bet this has been answered and my search skills are poor. Leica M9, When I open a DNG in Photoshop (5.1 2) and even if I do nothing, the original DNG shrinks. Before opening it is 18.3MB. After that it is 9.1MB. Even if I made no changes. (the exact sizes depend upon the size of storage media due to cluster-size, but it does not account for this huge difference.) What's happening, please? Quote Link to post Share on other sites More sharing options...
Advertisement Posted August 2, 2016 Posted August 2, 2016 Hi pico, Take a look here Why do my DNG files shrink.... I'm sure you'll find what you were looking for!
Exodies Posted August 3, 2016 Share #2 Posted August 3, 2016 What options are set when you import? Quote Link to post Share on other sites More sharing options...
MarkP Posted August 3, 2016 Share #3 Posted August 3, 2016 because the water's too cold.... 1 Quote Link to post Share on other sites More sharing options...
adan Posted August 3, 2016 Share #4 Posted August 3, 2016 (edited) Adobe products (well, at least Camera Raw) compress DNGs on saving them. PhotoShop does not open DNGs directly, always by using the Camera Raw plugin module (that window that opens the picture first, with tabs for exposure/lens corrections/calibration/etc.). Once you get the image into Camera Raw, then doing either of the following will result in an overwrite "save" of the DNG original, and thus a compressed file: - Proceeding to Photoshop by clicking the "Open Image" button, whether you make a change in ACR or not - Making a change in ACR, and clicking "Done." The only way to avoid the compression of the DNG is to either click "Cancel" to get out of the ACR module (not terribly useful) - or make absolutely no changes in ACR, and click "Done" (also not terribly useful). The compression only happens once per image. Interestingly, with my Monochrom (which does not allow in-camera DNG compression, and thus produces 35 Mb files from 18 Mpixels) - the compression reduces those files to 19 Mpixels - but on reopening multiple times, that never gets any lower after the first time. Edited August 3, 2016 by adan Quote Link to post Share on other sites More sharing options...
pico Posted August 3, 2016 Author Share #5 Posted August 3, 2016 Andy, that makes sense. Thank you. Quote Link to post Share on other sites More sharing options...
ramarren Posted August 3, 2016 Share #6 Posted August 3, 2016 The DNG compression that Photoshop applies does not cost you any pixels ... It is not, for instance, converting the file from '35 Mpixel' to '18 Mpixel'. It's reducing file size by applying the DNG lossless compression to the data, saving you nearly 50% on disk space. The DNG lossless compression algorithm, listed in the DNG Specification since v1.0, is very clean and does a great deal of space savings. It is somewhat compute intensive, however, and for this reason it was recommended practice (by Adobe) that implementors of DNG in low-powered devices should store DNG files without compression. The algorithm has until recently only been implemented on high-power devices (desktop and laptop computers) to do the compression after the fact. The DNG lossy compression that has been implemented more recently to save space on storage cards in camera is not the same thing at all. It is an algorithm that, while still pretty good on quality, does show measurable data loss in operation. The other potential way that DNG files can get smaller is that the contained JPEG preview is being reprocessed by a more efficient algorithm or to a higher compression. So don't worry at all about the fact that your DNG file size is being reduced: it's just saving you storage space. 1 Quote Link to post Share on other sites More sharing options...
pico Posted August 4, 2016 Author Share #7 Posted August 4, 2016 Advertisement (gone after registration) Thanks for that, Godfrey. FWIW I do not use in-camera compression. Quote Link to post Share on other sites More sharing options...
adan Posted August 4, 2016 Share #8 Posted August 4, 2016 (edited) DOooh - sorry about that typo - should have read ACR compresses Monochrom's 35 Mbytes to 19 Mbytes - pixels stay the same, as Ramarren says. Edited August 4, 2016 by adan Quote Link to post Share on other sites More sharing options...
terrycym Posted August 23, 2016 Share #9 Posted August 23, 2016 The M9 / ME allows the user to use lossy compression The M240 allows the user to use loss-less compression I switched compression off when I had an ME I have now switched on with my M240 Quote Link to post Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.