From http://answers.unity3d.com/questions/119918/transitions-between-changing-scenes.html change to only fade, add hook function, you need to add image in gameObject.

FadeInOut.cs

using UnityEngine;
using UnityEngine.UI;
using UnityEngine.EventSystems;
using System.Collections;
using System.Reflection;
using System;

public class FadeInOut : MonoBehaviour {

	[Serializable]
	public class EventTrigger : UnityEngine.Events.UnityEvent {}
	public Entry onStart = new Entry();
	public Entry onZeroAlpha = new Entry();
	public Entry onFinish = new Entry();

	public float fadeIn = 1.0f;
	public float fadeOut = 1.0f;
	public float fadeStay = 0.5f;
	public Color fadeColor = Color.black;

	[System.Serializable]
	public class ToggleMobileController {
		public bool hideOnStart = true;
		public bool showOnFinish = true;
	}

	public ToggleMobileController mobileController;

	[Serializable]
	public class Entry {
		public EventTrigger callback = new EventTrigger();
	}
	
	private Image image;

	void Awake() {

		image = GetComponent<Image>();

	}
	
	private void ChanageAlpha(Color aColor,float aAlpha) {

		aColor.a = aAlpha;
		image.color = aColor;
	
	}
	
	private IEnumerator Fade(float aFadeOutTime, float aFadeInTime, float aFadeStayTime, Color aColor) {

		if (onStart.callback.GetPersistentEventCount () > 0) {
			onStart.callback.Invoke();
		}

		float t = 0.0f;
		while (t < 1.0f)
		{
			yield return new WaitForEndOfFrame();
			t = Mathf.Clamp01(t + Time.deltaTime / aFadeOutTime);
			ChanageAlpha(aColor,t);
		}

		yield return new WaitForSeconds(aFadeStayTime / 2.0f);

		if (onZeroAlpha.callback.GetPersistentEventCount() > 0) {
			onZeroAlpha.callback.Invoke();
		}

		yield return new WaitForSeconds(aFadeStayTime / 2.0f);

		while (t > 0.0f)
		{
			yield return new WaitForEndOfFrame();
			t = Mathf.Clamp01(t - Time.deltaTime / aFadeInTime);
			ChanageAlpha(aColor,t);
		}

		if (onFinish.callback.GetPersistentEventCount() > 0) {
			onFinish.callback.Invoke();
		}
		
	}
	
	private void StartFade(float aFadeOutTime, float aFadeInTime, float aFadeStayTime, Color aColor) {
		StartCoroutine(Fade(aFadeOutTime, aFadeInTime, aFadeStayTime, aColor));
	}

	public void FadeNow() {
		StartFade(fadeOut, fadeIn, fadeStay, fadeColor);
	}

}