Excerpt blogs

I'm looking for some help when it comes to blogs and excerpt. Why can't I use excerpt with image blogs? If I write a long blog and use the standard format I get the "Continue Read ->" like in this screenshot: screenshot 1 But if I have a long blogtext + image and use the format "Image" it don't excerpt if there any way to fix that? Screenshot 2: screenshot 2 Best regards. Micke S