This applies to all Fujifilm cameras and all Canon, Nikon, Sony…

A few days ago, I had a discussion with a photographer. She said that even when she provides images to her clients in low resolution, some clients have taken these “low resolution” files are have them printed at local labs into 16 inch by 20 inch. Even though she provided jpegs with a low resolution of 72.

The resolution is a flag written in the file. It’s associated with the flags:

Raw file

$ exiftool earl-tucker-20180321-4985.raf | grep -i resolution

X Resolution                    : 72
Y Resolution                    : 72
Resolution Unit                 : inches
...

The raw resolution is not of the image, but it’s the resolution of the embedded JPEG preview.

JPEG

$ exiftool earl-tucker-20180321-4985.jpg | grep -i resolution

X Resolution                    : 300
Y Resolution                    : 300
Resolution Unit                 : inches
...

These numbers, the X Resolution and the Y Resolution are only wishes! The printing or screen display application can change it on the fly to whatever number it wants.

for example, I’m going to change the resolution 33. This means 33 dots per inch for this jpeg.

$ exiftool -overwrite_original -P -xresolution=33 -yresolution=33 earl-tucker-20180321-4985.jpg 1 image files updated

$ exiftool earl-tucker-20180321-4985.jpg | grep -i resolution

X Resolution                    : 33
Y Resolution                    : 33
Resolution Unit                 : inches
...

or it can just as easily changed to 300, or 600 or 1200…

I didn’t reprocess or again export the image, I just changed the resolution flag.

File Resolution Purpose

The purpose of the resolution is to calculate the size of the image:

  • 1920 pixels at the resolution of 300 with a unit of inches will give a 6.4 inch wide image.
  • 1920 pixels at the resolution of 72 with a unit of inches will give a 26.6 inch wide image.

Both images can be sharp enough if viewed from far away enough.

The problem

People think that setting a resolution in Lightroom or in Photoshop or any other processing software will set the resolution in concrete.

Many programs can change the resolution and also enlarge the image while sharpening it at the same time.

Photoshop does a decent job, but there are many other program doing a much better job. The likes of:

  • A Sharper Scaling: which is free to download and use (Windows only)
  • Stoik Smart Resizer (Windows only)
  • ImageEnlarger.com: free online tool
  • Fotophire Maximizer
  • PhotoZoom
  • and many others.

exiftool and/or exiv2 will display all the detail information that you will need. Both are available for Linux and Mac. For Windows, the program is called: exiftoolgui

DPI v. PPI

  • DPI: Dots per Inch
  • PPI: Pixels per Inch

In general, DPI is for output like for screen/web or printing and PPI is for capture like the camera sensors or for scanners.