新規プロジェクト

//FPSを固定する
Application.targetFrameRate = 30;

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

[ExecuteAlways]
public class AspectManager : MonoBehaviour
{
    [SerializeField] private Camera targetCamera;
    [SerializeField] private Vector2 aspectVec;


    void Update()
    {
        var screenAspect = Screen.width / (float)Screen.height; //画面のアスペクト比
        var targetAspect = aspectVec.x / aspectVec.y; //目的のアスペクト比
 
        var magRate = targetAspect / screenAspect; //目的アスペクト比にするための倍率
 
        var viewportRect = new Rect(0, 0, 1, 1); //Viewport初期値でRectを作成
 
        if (magRate < 1)
        {
            viewportRect.width = magRate; //使用する横幅を変更
            viewportRect.x = 0.5f - viewportRect.width * 0.5f;//中央寄せ
        }
        else
        {
            viewportRect.height = 1 / magRate; //使用する縦幅を変更
            viewportRect.y = 0.5f - viewportRect.height * 0.5f;//中央余生
        }
 
        targetCamera.rect = viewportRect; //カメラのViewportに適用
    }
}

using System;
using System.IO;
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEditor;

public class ScreenshotTools
{
    [MenuItem("Tools/Screenshot %F3", false)]
    public static void CaptureScreenshot()
    {
        string productName = Application.productName;
        if (string.IsNullOrEmpty(productName))
        {
            productName = "Unity";
        }
        string directory = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.DesktopDirectory), productName);
        DateTime now = DateTime.Now;
        string fileName = string.Format("{0}_{1}x{2}_{3}{4:D2}{5:D2}{6:D2}{7:D2}{8:D2}.png", productName, Screen.width, Screen.height, now.Year, now.Month, now.Day, now.Hour, now.Minute, now.Second);
        string path = Path.Combine(directory, fileName);

        if (!Directory.Exists(directory))
        {
            Directory.CreateDirectory(directory);
        }
        ScreenCapture.CaptureScreenshot(path);
        Debug.LogFormat("Screenshot Save : {0}", path);
    }
}