Monday, March 13, 2006
Colour to mono
Colour to mono There are several ways of converting your colour images to mono, and here we offer four of the simplest and most effective; each gives subtly different results, and you may want to try a couple of them out on a particular photo before you make a final choice. The methods we’ve outlined are for Photoshop – you’ll find similar options in most other image editing programs, although the exact commands may differ slightly. If you’re using Photoshop you can speed up this process by recording actions, and you can also save History snapshots of each conversion, so that you can compare them quickly. Three of these conversion processes are automatic, in that you have no control over the tonal relationships; the fourth, using the Channel Mixer, is the most complex, but also the most interesting.
Convert to greyscale Selecting Image > Mode > Grayscale is the simplest method for converting colour images to black and white, and it’s perhaps for this reason that it’s not generally well regarded by black and white aficionados. However, it actually does a pretty good job of separating colours tonally – more so than simply ‘desaturating’ the image; what’s more, it reduces the number of colour channels in the image from three (RGB) to one (greyscale), so your files become one-third their original size. The disadvantage of this method is that you’ll have to convert the image back to RGB mode (it’ll still appear mono, as the colour’s been removed) in order to apply many filters and image adjustments.
Desaturate the colours You can retain the three colour channels in your image by ‘desaturating’ it (Image > Adjustments > Desaturate); this saves you having to convert from greyscale back to RGB to apply adjustments that only work on RGB images. However, although desaturation sounds ideal in principle, because you’re removing the colours without altering the brightness values, it can leave images looking tonally very similar. Look at the red/yellow logo on our subject’s shirt – the greyscale conversion has distinguished the tones well, but the desaturate conversion produces identical brightness levels, and the red/yellow markings have become indistinguishable
Convert to Lab mode Many mono enthusiasts prefer this slightly more complex solution. If you switch to Lab mode (Image > Mode > Lab Color), Photoshop splits the image information in a very different way. Instead of red, green and blue channels, you’ll have a Lightness channel. el accompanied by two (‘a’ and ‘b’) colour channels. If you delete the ‘a’ and ‘b’ channels, then convert the image into greyscale mode, you have in theory ditched all the colour information and retained only the lightness values. You might think this would give the same results as desaturation, but it doesn’t; it separates colours just as well as the greyscale conversion, but also gives noticeably lighter, more ‘open’ tones.
Channel Mixer The Channel Mixer (Image > Adjustments > Channel Mixer) is the most complex conversion option, but it can also be the most effective. First, make sure the Monochrome box is checked; you can now adjust the proportion of the red, green and blue channels to mimic the effect of traditional black and white filters. In our example we’ve used only the red channel, and this has the same effect as using a red filter with monochrome film. Non-red colours (such as the blue sky) are darkened, while red colours (such as the subject’s face) are lightened. When the process is complete, you have an RGB image which is perfect for toning, or further editing.
Article from Digital Camera Magazine:
Published: 03/11/2005 12:28:00 GMT
© Digital Camera Magazine MMV
Convert to greyscale Selecting Image > Mode > Grayscale is the simplest method for converting colour images to black and white, and it’s perhaps for this reason that it’s not generally well regarded by black and white aficionados. However, it actually does a pretty good job of separating colours tonally – more so than simply ‘desaturating’ the image; what’s more, it reduces the number of colour channels in the image from three (RGB) to one (greyscale), so your files become one-third their original size. The disadvantage of this method is that you’ll have to convert the image back to RGB mode (it’ll still appear mono, as the colour’s been removed) in order to apply many filters and image adjustments.
Desaturate the colours You can retain the three colour channels in your image by ‘desaturating’ it (Image > Adjustments > Desaturate); this saves you having to convert from greyscale back to RGB to apply adjustments that only work on RGB images. However, although desaturation sounds ideal in principle, because you’re removing the colours without altering the brightness values, it can leave images looking tonally very similar. Look at the red/yellow logo on our subject’s shirt – the greyscale conversion has distinguished the tones well, but the desaturate conversion produces identical brightness levels, and the red/yellow markings have become indistinguishable
Convert to Lab mode Many mono enthusiasts prefer this slightly more complex solution. If you switch to Lab mode (Image > Mode > Lab Color), Photoshop splits the image information in a very different way. Instead of red, green and blue channels, you’ll have a Lightness channel. el accompanied by two (‘a’ and ‘b’) colour channels. If you delete the ‘a’ and ‘b’ channels, then convert the image into greyscale mode, you have in theory ditched all the colour information and retained only the lightness values. You might think this would give the same results as desaturation, but it doesn’t; it separates colours just as well as the greyscale conversion, but also gives noticeably lighter, more ‘open’ tones.
Channel Mixer The Channel Mixer (Image > Adjustments > Channel Mixer) is the most complex conversion option, but it can also be the most effective. First, make sure the Monochrome box is checked; you can now adjust the proportion of the red, green and blue channels to mimic the effect of traditional black and white filters. In our example we’ve used only the red channel, and this has the same effect as using a red filter with monochrome film. Non-red colours (such as the blue sky) are darkened, while red colours (such as the subject’s face) are lightened. When the process is complete, you have an RGB image which is perfect for toning, or further editing.
Article from Digital Camera Magazine:
Published: 03/11/2005 12:28:00 GMT
© Digital Camera Magazine MMV
# posted by Mick Hyde @ 11:25 am 
