When entering an observation, you can add one or more photos by using the photo icon on the toolbar. You can either add photos from your camera or from the photo library. Each photo will be presented by a thumbnail. You can click on the thumbnail to see the full photo, and click again to return to the observation entry screen.
iObs will store a local copy of the photo, with the long side automatically scaled down to a maximum of 800 pixels. When you take a photo using the camera from within iObs, a full resolution copy will be saved on the camera roll as well.
Note that when you add a photo for the first time, you will be asked to grant iObs permission to access the camera or photo library. Click "Agree" to give this permission. If you fail to do that, you will not be asked again. You can check and change the permission in the Settings app.
You can reorder photos by drag and drop the thumbnails. The order is preserved in the upload.
You can remove a photo by clicking on it, and while the image is shown in preview mode, swipe the image off screen.
When an observation is already uploaded, you cannot change the observation anymore, and also not remove any photo. When you want to save space, you can remove all photos from uploaded observations by going to Menu/Observations and click on the delete icon . See Manage observations for the delete-options.
iObs doesn't offer facilities for editing photos. If you want to do that, for instance to crop an image or align the horizon, take a photo with the camera app and then use a dedicated app like Snapseed to edit the photo and save the edited version to the camera roll. You can use iObs to add the edited photo from the camera roll.