1. A method of increasing the luminance dynamic range of an original image from a first luminance dynamic range to a second luminance dynamic range, the original image comprising a plurality of pixels each having a luminance value within the first luminance dynamic range, the method comprising: determining filtered image having a filtered luminance value corresponding to each pixel of the plurality of pixels, wherein each filtered luminance value is determined according to luminance values of the pixels in a predetermined area surrounding the corresponding pixel; determining a minimum, a median and a maximum of the filtered luminance values, providing a plurality of conversion factors having a minimum conversion factor less than a predetermined value and a maximum conversion factor greater than the predetermined value, wherein a range of conversion factors is determined based on a difference between the first and second luminance dynamic ranges; selecting a conversion factor for each pixel of the original image from the plurality of conversion factors, wherein the selecting is based on the luminance values of the pixels in the filtered image and a constraint that maps the minimum conversion factor to the pixel with the minimum filtered luminance value, maps the maximum conversion factor to the pixel with the maximum filtered luminance value, and maps a conversion factor having the predetermined value to the pixel with the medium filtered luminance value, and converting the original image from the first luminance dynamic range to the second luminance dynamic range by multiplying the luminance value of each pixel of the original image by the corresponding conversion factor; wherein the minimum conversion factor is calculated as 2 to the power of the minus square root of the result from second luminance dynamic range divided by the first luminance dynamic range, and the maximum conversion factor is calculated as 2 to the power of the square root of the result from second luminance dynamic range divided by the first luminance dynamic range.