These terms are often used interchangeably, but professional photographers will tell you they’re very different.
When you take photos on a digital camera or smartphone, you might end up with “noise.” Image noise looks similar to grain, and it usually crops up on images shot in dark conditions or with a high ISO. That’s because digital sensors convert light into pixels, and those factors and settings can interfere with that process.
On the other hand, film cameras embed light-sensitive crystals into the film emulsion, and grain is the result. It happens organically, and on purpose. The higher the ISO, the more crystals there are and the grainer your photo will be.
The key difference between these two terms is that film grain is a desirable look, whereas noise isn’t. Luckily, advanced DLSRs and mirrorless cameras are capable of drastically reducing noise. If you typically shoot in low-light, it’s worth investing in a full-frame camera to save yourself time during editing.
Otherwise, you can edit noise in post-production for cleaner images. If you shot in RAW (which we always encourage you to do), software like Lightroom or Camera Raw has noise reduction options. Photoshop has a few filters that can fix noise, as well as a number of plugins you can add to the program.