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Dealing with large digital files for events and other applications where large file size is not necessary.

Dealing with large digital files for events and other applications where large file size is not necessary.

Ok, admit it. It’s a first world problem. Your yacht, house, digital file is too big. But if you are photographing events with say, a Sony A7rII, this really is an issue. You reasonably won’t want to shoot JPGs, which can be dumbed down in camera settings. But you should shoot raw files that can’t be reduced in camera to a reasonable pixel count, they’re always 42mp on this camera. 

So here’s a strategy to consider. Use the Adobe DNG Converter app to both compress (or further compress) and at the same time reduce the pixel dimensions of your raw files. 

Give this a try (see screen shots):

  • Download Adobe DNG Converter (free)
  • Select folder for files to convert, and destination (maybe try testing this on your memory card with your latest images first)
  • Rename if you like

In the bottom dialog box change preferences to the most recent compatibility, jpg preview to full size (speeds editing), embed fast load data (speeds editing), use lossy compression (reduces file size with compression), limit pixel count to 20mp, don’t embed original (that would make the resulting file much larger than the original)

A quick test with a random Sony A7rII raw file starting life at 42mp using this method to go down to 20mp resulted in a ~8mb DNG file on my HD vs 37mb for the full size (in camera lossy compression) 42mp ARW.

20mp is still plenty of resolution. Here are some sizes at given resolutions to ponder:

  • @400ppi 8.5x13” (high resolution art print)
  • @300ppi 11.5x17” (good quality print)
  • @200ppi 17x26" (decent quality print)
  • @100ppi 35x52" (low quality print, good projection resolution)
  • (all sizes approximate)

For some other lossy DNG observations, check out these other entries: Lossy DNG file size by ISO, The Magic of Lossy DNGs.


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