I've been using the CC40M Lee filter, and I took a couple of photos to compare the histograms and photo quality with and without the filter. Both were taken in full sunlight, and these are after they were white-balanced using a white balance gray card. I also adjusted the shutter 2/3 ev to compensate for the photo without the filter. Here is the first one without the filter: Now with the filter: The one without the filter is a little brighter, but the one with the filter is more detail rich, (look at the bubbles on the Pepsi label). Also the color of the apple around the blown highlight looks more correct to me. Here's the histogram of the one without the filter. Notice the excessive clipping. There's much less clipping in the one with the filter: My understand is that the CC40M magenta filter is good for sunlight and flash pictures, and helps with cloudy day pictures, too.