This guideline document describes important photo and video encoding parameters that affect file size, quality, data accuracy, and thus the scientific potential of acquired image data. It aims to enable scientists to encode the best image data for their use cases. The purpose of this guideline is to describe essential parameter choices when compressing marine images (photos and videos) for scientific use. The goal of this document is to raise awareness of various encoding parameters, their impact on quality and file size, and to assist in selecting appropriate parameters when creating or converting images. The scope of this guideline applies to the encoding of digital marine images captured by cameras and recording systems for scientific purposes. Adhering to the guideline will result in pristine images where the encoding parameters are tailored to the research purpose of the recording, without any unintended data loss or impact on the visual quality.