The basic method in photoshop to convert a scan of a negative to a positive is: (1) Sample the orange mask of the negative (i.e., use the eye dropper to grab the color of the mask from the very edge of the film where it did not get exposed), (2) Make a new layer with the color of the orange mask (i.e., after you make a new layer, select all and use the paint can with the sampled color of the mask) (3) Invert the color of this new layer and then subtract this layer from the layer with the negative; (4) Split and equalize each of the color channels separately, (4) Merge channels and then invert the negative to a positive. Really only takes a short time after you do it once. You need to get the mask color for each type of film, but once you do one image of a given type of film you can store the steps as an action that takes only a few seconds.