Today’s Question: How do I shoot to guarantee I am getting a 300 ppi resolution? I have a Sony a7R III.
Tim’s Quick Answer: You don’t actually establish an output resolution in the camera, since at that stage of your workflow the output resolution doesn’t matter. All you really care about is making sure that in general you are capturing the maximum resolution so you have the most flexibility in terms of final output.
More Detail: I’ve been teaching about photography and digital imaging in various ways for about two decades now, and the subject of resolution continues to be one that many photographers are confused by. That is absolutely understandable, considering that resolution is a factor in a variety of contexts.
First off, we have the capture resolution, which basically means how many pixels the image sensor is capturing information for. This is generally described as the number of megapixels for the sensor, or the millions of pixels being captured.
Another type of resolution is essentially the density of information. In other words, how much information do you need in order to be able to produce output of a particular size with good quality. A monitor display requires far fewer pixels than a high-quality print, for example.
With digital displays, you can generally simply refer to the number of pixels, rather than a pixel per inch (ppi) resolution value. So the only time the pixel per inch (ppi) value really comes into play is when you are printing.
You can change the output resolution to any value based on how the image is being printed. Ultimately, all that really matters is that you are providing enough pixels to produce output at the intended print size. That either means having a camera with an adequate resolution, or using software to enlarge the image by adding pixels through a process referred to as “interpolation”.
The appropriate output resolution (ppi) will be based on the specific printer being used to produce the print. In most cases an output resolution of 300 ppi will produce excellent results, though a higher ppi resolution may be helpful in some cases. But the bottom line is that you aren’t really able to alter the final output resolution at the time of capture.
When you’re capturing a photo, the sensor resolution determines how much information is being captured, which in turn determines how large a print you’re able to produce. In other words, the only thing you can really do to ensure the best capture in terms of final output size is to buy a camera with a relatively high resolution, and to make sure you’re using the full-resolution setting for the camera when capturing photos.