To use Photo Mode, you will need to hit the start button or what the key is for your system. You can find out what key this is by visiting controls via the options tab in the main menu. For PC, the button will be ESC, and for consoles, you will need to press L3 and R3. Once clicked, pushed, and punched, you will then need to select photo mode by clicking on it when the option shows up.
After this, you'll be able to use photo mode to zoom in and out, and you will be able to take zoom in and out and use a list of options to get the perfect screenshot. These options include changing the depth of field and changing the angle of the screenshot. You can also hide the UI, but beyond that, there's not much else you can do with it really.
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There are no filter options or anything extra such as stickers or an option to change brightness, and contrast. However, you will still be able to use photomode to take excellent screenshots, and once you are done, hit either enter, A, and X to take the screenshot. When you take your screenshot, it will save it to your gallery on consoles, and on PC it will save in the game's screenshot folder.