A method of forming microlenses for an image sensor having at least one large-area pixel and at least one small-area pixel is disclosed. The method includes forming a uniform layer of microlens material on a light incident side of the image sensor over the large-area pixel and over the small-area pixel. The method also includes forming the layer of microlens material into a first block disposed over the large-area pixel and into a second block disposed over the small-area pixel. A void is also formed in the second block to reduce a volume of microlens material included in the second block. The first and second blocks are then reflowed to form a respective first microlens and second microlens. The first microlens has substantially the same effective focal length as the second microlens.