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iPhone ProRAW photos that are too big to send from a Mac

· 6 min read

A ProRAW photo from an iPhone is a DNG file, a raw format that keeps far more data than an ordinary photo, so a single shot can be too large for an email or an upload form. To send one, make a JPEG or HEIC copy: export it from Photos, convert it in Preview or Finder, or run a batch through Manatee. Keep the DNG as your master. If the person at the other end actually needs the raw file, send the DNG by link instead of converting it.

Why ProRAW files are so large

An ordinary iPhone photo is a finished picture. The phone decides on color, contrast and sharpening, compresses the result efficiently as HEIC or JPEG, and discards the rest.

ProRAW is the opposite idea. It stores far more tonal information per pixel, with very little thrown away, so that you can change exposure, white balance and shadows later. That headroom is what you are paying for in megabytes: each ProRAW photo is many times the size of the same scene shot normally.

On a Mac, a ProRAW photo shows up as a file ending in .dng. Select it in Finder and press Command-I to see its size. In Photos, the Info window (Command-I) labels it as RAW.

How the big file got onto your Mac

Sharing a photo straight from the Photos app usually sends a converted copy, which is why this problem tends to appear only on certain routes:

  • You chose File, Export, Export Unmodified Original in Photos, which hands you the DNG exactly as the camera wrote it.
  • You copied the photos off the phone with a cable, or with a transfer option that sends the original files.
  • Someone sent you the DNG files directly.

Decide what the recipient needs

  • They want to look at the photo. Send a JPEG. It opens everywhere.
  • They use Apple devices and you want smaller files. HEIC gives a similar looking picture in less space; HEIC explained covers who can open it.
  • They are going to print it or edit it further in finished form. TIFF is lossless, though large; see how to convert a DNG to TIFF.
  • They are an editor or retoucher who asked for the raw file. Do not convert. Skip to the section on sending the DNG itself.

Export a sendable copy from Photos

If the photo lives in your Photos library, this is the most faithful route, because Photos renders ProRAW the way the iPhone intended and includes any edits you made.

  1. Select the photos.
  2. Choose File, Export, Export Photos. The menu item shows how many are selected.
  3. Set Photo Kind to JPEG and JPEG Quality to High.
  4. Set Size to Large for sharing, or Full Size if the picture will be printed or cropped.
  5. Uncheck Location Information if the photo is going anywhere public.
  6. Click Export and pick a folder.

Maximum quality at Full Size produces much larger files for a difference that is hard to see on a screen; why photos get bigger when you export them goes through each of those settings.

Convert loose DNG files

When the DNG files are sitting in a folder, you do not need to import them into Photos first.

Finder, for a quick batch. Select the files, right-click, and choose Quick Actions, Convert Image. Pick JPEG or HEIF and an image size, and the converted copies appear in the same folder.

Preview, for one photo with control. Open the DNG, choose File, Export, pick JPEG or HEIC, and move the Quality slider. Preview shows the resulting file size as you adjust it.

Terminal, for a folder. This makes JPEGs at quality 85 in a new folder and leaves the DNG files alone:

mkdir ~/Desktop/Send
sips -s format jpeg -s formatOptions 85 ~/Desktop/ProRAW/*.dng --out ~/Desktop/Send

Manatee, for a batch without Terminal, or when macOS will not open the file. Open it, choose Convert, drop in the DNG files or the whole folder, and pick JPEG, HEIC or TIFF. Manatee uses its own bundled decoder, so it does not depend on which raw formats your version of macOS understands, which helps on an older Mac faced with files from a newer phone. Each copy is written next to its original, the original is never modified, and nothing is uploaded. It is free for 24 hours with every feature, then $9 once.

One honest caveat applies to every route outside Photos. A raw file has to be interpreted to become a picture, and different converters interpret it differently. A JPEG made by Preview or Manatee can look a little different in brightness or contrast from the same photo in the Photos app. Convert one photo and compare before you do a hundred. If the look matters, export from Photos.

When they really do need the DNG

For someone who will edit the raw file, a JPEG is no use. Send the original a different way.

  • Mail Drop. In Mail, attach the file as usual. If it is too large for the mail server and your iCloud account has Mail Drop available, Mail offers to send it as a download link instead.
  • A shared link. Put the file in iCloud Drive or another file sharing service you already use, and send the link.
  • AirDrop. For someone in the same room with an Apple device, drag the file onto their name in an AirDrop window.

Zipping the files first will not help much. Why zipping photos barely makes them smaller explains the reason. For what each mail service accepts, see email attachment size limits by provider.

Stop it happening by accident

Many oversized photos were never meant to be ProRAW; the setting was simply left on.

In the Camera app, a RAW button appears at the top of the viewfinder when ProRAW is enabled. If it is not crossed out, every shot is a raw file. Tap it to turn raw capture off for everyday pictures and back on when you plan to edit.

To manage it properly, open Settings on the iPhone, go to Camera, then Formats. There you can switch ProRAW off entirely, or keep it available and choose a lower resolution for it, which makes each file considerably smaller. The exact options vary by iPhone model.

Questions

Does the JPEG copy lose quality? It loses the editing headroom, not the look. A High quality JPEG of a well exposed photo is visually very close to the raw rendering. What you give up is the ability to rescue shadows and highlights later, which is why the DNG is worth keeping.

Will the location still be in the converted photo? Often, yes. Converted copies generally carry the camera details and GPS position from the original. Uncheck Location Information when exporting from Photos, or run the copies through Manatee’s Clean mode, which strips GPS and camera data; see how to remove GPS location from photos.

Preview shows a blank window or refuses the DNG. Is it corrupted? Probably not. Newer iPhones can save ProRAW with compression that an older version of macOS does not read. Update macOS if you can, or convert the file with Manatee, which brings its own decoder.