The first step of any photogrammetry project is taking pictures of the object or environment that you want to model. You can use any camera to gather photos, even the camera on your smartphone. It is best if you have a camera that can take pictures in RAW file format, such as a Nikon or Canon DSLR or mirrorless camera. A RAW file is a photograph as seen by your camera’s digital sensor. When you take a picture and save it as a different file format (e.g. JPEG), your camera applies a number of pre-determined settings to the image before saving it to an SD card. Saving the image as a RAW file allows you to make many types of changes to images after-the-fact, such as changes to lighting. RAW files are fairly large, and they must be converted to a more concise image format before being loaded into Agisoft Metashape or other photogrammetry program. You can use a program such as Adobe Photoshop to convert RAW files to a processable file format, such as TIFF or JPEG. Agisoft recommends using TIFF files due to the fact that less noise (i.e. graininess) appears in TIFF files than in JPEG files. Adobe products can now be accessed and downloaded for free by UNC students through the Software Acquisition office. If you do not want to worry about converting files, it is perfectly fine to take photos in whatever format the camera is already set (often JPEG).
As far as camera settings, you need to have consistency between photos. The focal-length, focus, ISO, and aperture should remain consistent for best results. To attain consistency, zoom in to the desired setting, focus the camera by depressing the shutter button half-way, and then switch the cameras focus setting from “A” (automatic) to “M” (manual). This setting is located on the upper-left side of the lens on our Nikon D3200. You should also shoot in “Aperture priority mode,” which you can switch to by twisting the dial located on the top-left of the camera to the “A” setting. Once set to aperture priority mode, you can twist the dial located on the upper-back of the camera to alter the aperture. The lowest aperture setting you should use is f/5.6 If possible, shoot at a higher aperture, but keep in mind that the higher the aperture, the slower the shutter speed. If the shutter speed becomes to slow, we recommend setting the camera on a tripod.
The camera focus should not be changed after the initial photo and the ISO setting should be as low as possible to reduce graininess. If you need help altering these settings on the camera, please view Nikon’s guide here.
You need to take multiple series of photos around an object from a number of angles. For example, if I am making a model of a statue, I need to take several photos from a high angle (above the object), a straight-on angle, and a low angle. We suggest taking a minimum of eight photos from each angle. It is always good practice to take more photos than you need. While you are shooting, make sure the photos overlap with one another by 30 percent so the program can build the model.