Will deleting JPEGs from SD card on MacBook Pro preserve DNGs?

This was the perfect and correct answer to my quest.

I just looked at my SD card on the Macbook and followed your "Move to trash" idea for all jpegs on the SD card. I also deleted two inadvertently taken videos. And all disappeared from the card.

I put it into LrC thereafter and tried to "import' from the card and only DNG files were present.

I went from 715 entries to just 85 DNGs on the card and I checked through them on LrC and then on my Leica Q3: there were exactly 85 taken shots from the last few days. And the Leica Q3 users guide does not even mention this feature. They should include it in a subsentence ...

Finally I looked at my Box files in LrC and they were all developed as I had done recently.

And thus you deserve a victory round of applause. Clap - clap

I had not thought of that approach and everyone on LrC, Apple and the Leica forum had missed the point.

One does not need to take low res jpegs in order to view shots on camera from their DNG version.

How simple!

Thanks, FrankU

It is certainly possible to delete .JPG files from a SD card without deleting .DNG files – assuming that we are actually talking about separate files, and not about your camera having embedded a preview image within a Raw file such as a .DNG file.

Note that memory cards may not be the most reliable archival media compared to hard drives or SSDs. I would not consider them to be

• A place where you should store the master copies of your .DNG files, or
• A substitute for making proper backups on more reliable drives such as hard drives and SSDs

If you do archive files on memory cards, I would suggest

• Never storing your only copy, or only backup copy, of a file on a single memory card
• Periodically inserting all of the memory cards into card readers. Data can theoretically evaporate from flash memory (memory cards, USB flash drives, SSDs) left unpowered for several years.

If you are planning to wipe and reuse the memory cards, you could just skip the "pick off the .JPGs" step entirely – and simply reformat the cards

• In the camera where you will be using them, or
• Using the SD Memory Card Formatter for Windows/Mac . (The SD Association says "It is strongly recommended to use the SD Memory Card Formatter to format SD/SDHC/SDXC/SDUC Cards rather than using formatting tools provided with individual operating systems.")

Dear Servant of Cats

You wrote:

It is certainly possible to delete JPG files from a SD card without deleting DNG files – assuming that we are actually talking about separate files, and not about your camera having embedded a preview image within a Raw file such as a DNG file.

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I have just checked with my Leica Q3 28mm camera and there was or is no way to delete any files from the SD card there. There was also no way to separate the jpegs from the DNG files. Or I did not find a way for this task.

So the only option is to try and do it on the computer: maybe via Lightroom itself or via the Macbook Pictures folder in some way; if I only knew how....

So maybe I should just leave this mess alone and find a better way to spend my time and in a few weeks when the current card is full, just store it and start with a new SD card.

Thanks, FrankU

The Q3 numbers images sequentially, with the file suffix being the differentiator between JPG & DNG. (See p. 70 in the Q3 manual).

I do not see why it would be necessary to examine the JPGs for "composition, extraneous items, sharpness issues" ... because you can just as well examine the DNGs instead without needing the JPGs. And if you have set up in-camera adjustments to the JPGs those adjustments aren't carried over the the DNGs anyway. You yourself said you have no desire to retain the JPGs.

Regarding deleting the JPG files from the SD card with your Mac, do a test case first. Experience has shown you have to be cautious about formatting or modifying a camera SD card outside the camera. With an empty SD card, shoot a few images. Then delete the JPGs from that card. Insert it back into your Q3 and see if the card still works. If all is well, great. But if not then you have your answer about not deleting the JPGs.

I also do not recommend using your SD cards as any form of "archival" storage. That's not what they were designed for and history has shown that SD cards can and do degrade under longterm storage.

I was referring to deleting the files on the card using the computer. If you have the right options checked off in Finder > Settings, a formatted memory card will show up as a disk on the Desktop and in the sidebar of Finder windows. You can then go into that disk and delete files much as you would with any other volume.