| Author | Message | ||
     Robert W. Coutant Member Username: Couman Post Number: 199 Registered: 01-2005 |
There are many ways to convert from color to black and white in PWP. Available transformations include tint, bit-depth conversion, monochrome, channel extraction, and desaturation, to name a few. Den(http://www.ncplus.net/~birchbay/tutorials/bw/bw01.htm)has addressed some of the issues involved in B&W conversion. The purpose here is to consider an alternative HSV-based method for preparing a specific type of color image for conversion. [In a private communication, Den has suggested an equivalent RGB-based approach for the same sample image used here.] Rationale --With color images, we visually distinguish different objects and areas of an image by differences in hue, saturation, tonal level (brightness), and sharpness. With B&W images, however, we have only tonal level and sharpness to guide our perception of an image. Except in special cases, we tend to refrain from changing sharpness during conversion from color to B&W, so definition, isolation, and emphasis of objects and areas must be based on localized adjustments to tonal levels. When an object has more or less the same tonal level as its surroundings, removal of its distinguishing hue and saturation makes for a flat image - the object tends to disappear into its surroundings. One approach (but not the only one) to this problem is to utilize the color correction transformation to selectively separate the tonal values of the color image. This is discussed along with an example here (http://www.greenapple.com/~rcoutant/tutorial/black%20and%20white.htm). Bob C. | ||
| Maciej Tomczak Member Username: Tomczak Post Number: 462 Registered: 08-2004 |
I'm not sure if I understand it, but the Color Picker in Monochrome and in Levels and Color transformations have no 'V' slider on the right (i.e. you can only move along the base of the HSV hexacone - one of RGB channels is always 100%). Even with filter bank, it always saturates one of the channels regardless of the filter actual RGB makeup. Is that how it should work? Cheers. Maciej Tomczak www.phototramp.com | ||
| Robert W. Coutant Member Username: Couman Post Number: 200 Registered: 01-2005 |
Maciej, My apologies if my discussion wasn’t clear to you. The suggested procedure involves three steps: 1.Prepare the color image by using the COLOR CORRECTION transformation to selectively adjust brightness – “separate the tonal values of selected colors” 2.Convert to B&W using any method you like. [Extraction of HSV-V channel works just fine.] 3.Use brightness curve to make final adjustments to the B&W histogram. Bob C. | ||
| Jonathan Sachs Member Username: Jsachs Post Number: 924 Registered: 08-2002 |
Color Correction is a good way to control how different colors are converted to different tones. Increasing/Decreasing the saturation of a color will increase/decrease local contrast of areas of that color when converted. Lightening or darkening a color will make that color lighter or darker in the result. The Monochrome transformation applied to the result of Color Correction affords additional tools for balancing the tonality of different colors. Finally Brightness Curve allows for final tuning of brightness and contrast. Jonathan Sachs Digital Light & Color | ||
| Maciej Tomczak Member Username: Tomczak Post Number: 463 Registered: 08-2004 |
Thanks Robert, I'm sorry I went on a tangent trying to compare different B&W techniques that you've mentioned, and noticed that the Color Picker in a filter in Monochrome (and Levels and Colors) can pick the Hue and Saturation, but didn't have the ability of adjusting Value (the RHS slider) as it does in other transformations. Is that intentional? Cheers! Maciej Tomczak www.phototramp.com | ||
| Jonathan Sachs Member Username: Jsachs Post Number: 926 Registered: 08-2002 |
Yes, it is intentional as this just darkens the entire image. Jonathan Sachs Digital Light & Color |
