How to Create Photoshop Filters
By David Weedmark
Photoshop's Filter Gallery includes dozens of filters you can use to quickly change the appearance of any image. Using the Custom Filter feature, you can also create your own filters and save them for future projects. Like most other aspects of Photoshop, experimentation is key to creating useful custom filters. Take a few minutes to understand how this feature works, then you can freely play with the different values to create a wide variety of filters beyond basic black or sheer white.
Understanding Custom Filter Values
Open any image in Photoshop. For best results, use a relatively high resolution JPG. It doesn't have to be larger than 1MB in size, but a 10K file won't give you very good results.
Click the "Filter" menu. Select "Other," then click "Custom." The Custom Filter panel appears, with a grid of 20 text fields, each representing a pixel. When you type a value in any text field, it provides a weight for that pixel relative to the others. If you type "1" in the center text field with no other values, the center pixel has a weight of "1" while the remaining pixels have a weight of "0." The resulting filter basically doesn't change the image noticeably at all.
Type "-1" in the center pixel field. Delete all of the other pixel fields if there are numbers entered in them already. Type "1" in the Scale field. Type "255" in the Offset field. If you check the "Preview" check box, the resulting filter creates a photographic negative of the original image.
Change the "-1" in the center pixel field to "-999" and the image becomes extremely dark. This is because you are multiplying the brightness of the pixel by a very large negative number. Pixel values can be any number between -999 and 999. If you changed the center pixel field to "999," the image becomes white.
Change the Scale to "999." Notice that the image becomes a photographic negative again. This is because the Scale is divided into the equation determining the brightness of the pixels. For best results, the Scale should be the sum of all the values entered into the pixel fields. If the sum of all pixel weights is negative or positive, use a positive number in the Scale field. If the sum is "0," use "1" in the Scale field. The Scale field can be any number between 1 and 9999.
Change the Offset field from "255" to "0" and the image becomes black. This is because the Offset is added to the equation used to determine the appearance of the pixels. It can be any number between 0 and 255. The Offset can be any value between -9999 and 9999.
Experimenting With Custom Filters
Open a high quality image in Photoshop. An image file of around 750K in size with a resolution of 600 by 400 pixels, or an image close to this size and resolution works well. Anything significantly higher or lower in quality may not get the same results. Launch the Custom Filter panel. Delete all of the numbers in the Custom Filter text fields.
Create a Sharpening Filter by typing "5" in the center grid text field. Type "-1" in the text fields directly above and below and to the left and right of the center field. Type "1" in the Scale field and "0" in the Offset field. Click the "Preview" check box to see how the filter changes the image compared to the original.
Create a Gaussian blur filter by typing "3" in the center field, "2" in the nine fields surrounding it, then "1" in the outer 16 fields. Set the Scale as "35" and the Offset as "0."
Create an emboss filter by clearing all of the text fields and typing "1" in the center field and "-1" in one of the other fields. Type "1" in the scale field and "128" in the Offset field.
Click the "Save" button to save a custom filter. To use that filter again on another image, click the "Load" button in the Custom Filter panel.
- Photoshop uses your specified Scale value to scale back any pixel ratios that fall outside of the 0 to 255 range. Consequently, if parts of your image are too dark, increase the Scale value. If parts of the image are too bright, decrease the Scale value.
- Photoshop uses the Offset value to control the overall brightness or darkness of an image. Increasing the Offset value makes the entire image brighter, while decreasing it makes it darker.
- Information in this article applies to Photoshop CC. It may vary slightly or significantly with other versions or products.
A published author and professional speaker, David Weedmark has advised businesses and governments on technology, media and marketing for more than 20 years. He has taught computer science at Algonquin College, has started three successful businesses, and has written hundreds of articles for newspapers and magazines throughout Canada and the United States.