HOW TO USE PHOTOSHOP’S MEDIAN FILTER
Not sure why, but last week I started playing around with the Median Filter and found out it is a pretty nifty Photoshop Filter. It is found by going to Filter -> Noise -> Medium. It works great with other filter or plugin effects and seems to be one of those overlooked older filters that Photoshop packs with its software. Using this filter basically creates an image made of softer shapes with less detail.
The funny little Great Orange Tip Butterfly photo taken at the Rainforest Exhibit at the University of Florida’s Museum used this filter. I did use Topaz Gigapixel (as the image was cropped really tight – see my How to Use Gigapixel AI as a Plug In to Photoshop blog) and Topaz Denoise AI since the crop really showed up any noise in the image. (Topaz website can be found in the sidebar at my Tidbits Blog.) Then I tried out the Medium filter – it actually provided a really interesting beginning background for this image. When set to Multiply blend mode, it gave a really rich feel to the background and made lots of the lines fade into the background. (The other filters used in this image were Corel Painter’s Particle Shop using the Heat Trail filter which gave the pretty string effect and Photoshop’s Spherize filter which really rounded up my butterfly – I will blog on this one soon as it is actually a lot of fun to use also.)
How does this filter work? Heads Up – technical info here – skip if you do not care
The filter is controlled by adjusting the size of the Radius slider which goes from 0 to 600. The following info is from Adobe Photoshop Special Effects Focus Guide from 2003. Amazing this filter is still around and useful. If you set a Radius of 25, the Median filter will select the image using groups of 25 pixels. It blends these pixels together according to the closeness of their color and brightness – any pixels that are too different from the average color in a group of pixels will be discarded.
Adobe says the Median Filter “reduces noise in an image by blending the brightness of pixels within a selection. The filter searches the radius of a pixel selection for pixels of similar brightness, discarding pixels that differ too much from adjacent pixels, and replaces the center pixel with the median brightness value of the searched pixels. This filter is useful for eliminating or reducing the effect of motion on an image.” Yawn!
When would you use this filter?
The filter can be used as an alternative to the Gaussian Blur filter to blur parts of an image to change the depth of field. The result can be more natural-looking similar to a real photograph effect.
At a very low level (like 1 or 2), it has a smoothing effect which can help reduce moire patterns and noise in an image. With scanned images, try setting it to a minimum amount to fill in small white scanning speckles. See my Scanning with a Black Box Blog for more on this.
The filter averages out colors that are too different from those found in the set Radius value. Here is an example of a Radius set very low at 19 and it gives a nice soft depth of field with just the guitar strings sharpened by removing the effect with a layer mask using a brush set to black. This image is one of my favorite images for practicing new techniques from ISO Republic called Guitar Man.
At higher levels, it produces soft, abstract images that still contain fairly distinct edges in contrast areas. This could be used for some very interesting effects.
The Median filters seems to work really well to just soften up any distracting things in the background but does a better job than the Gaussian Blur filter. I will try using this more and decide if it really is better. I tried to soften a waterfall with this filter and use a layer mask so only the water was affected. PS says it works well with motion blur, but I actually found the Motion Blur filter works better for this. (See my Smoothing Those Waterfalls Blog on how to do this.) It would probably be an easy experiment so give it a try. I plan on being a little more sporadic with my blogging for awhile but I will continue blogging. Just not on a very regular schedule. In the meantime, continue working in Photoshop and trying out all the cool things it has…..Digital Lady Syd