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Sally Jane Photographic Art

Adobe Photoshop Tutorial


Photoshop Layers Pallet - Adjustment Layers - Channel Mixer (BW conversions)

black and white conversions

There are many ways of creating a black and white image in photoshop (with a new one added in cs3 that I'll discuss in another chapter) ranging from the extremely basic to creatively advanced. The two most obvious are to either go to the menu bar and select Image - Mode - Grayscale or Image - Adjustments - Desaturate. Both are likely to produce a rather flat bw image which may be OK if the original image was sufficiently punchy but will often simply disappoint. In the days of black and white film, creative photographers improved their black and white images by using coloured filters either over their lens of during processing. This strengthened certain parts of the spectrum and weakened others to give more contrast and drama. In photoshop you can do this digitally using the channel mixer which is one of the adjustment layers you can select from the bottom of the layers pallet.


OK, so lets go through this set-by-step. Open the image you want to convert. For this tutorial I am going to use a simple image of a tree and sky. Convert it to 18 bit by going to Image on the menu bar and select Mode - 16 bit. Now, in the Layers pallet click on the add an Adjustment Layer icon. From the pop up list select Channel Mixer.

black and white conversions

You will get a dialogue box with a series of sliders one each for the Red, Green, and Blue channel. The fourth channel, Constant, lightens or darkens the overall image. You will notice in this image, below the Blue slider is the word Total and +100%. This is a cs3 addition and will not be present in earlier versions. The idea is that when you alter any of the sliders you aim to keep the total to 100%, certainly not over, to prevent blown out areas. It is only a rough guide because as you will see you can get blown out areas even with it staying at 100%. In previous versions you just had to work this out in your head but now they have saved you a little mental arithmetic.

At the bottom of the box is a check box saying Monochrome. Click on this and your image will be converted. Before, you get too excited though, this is just the beginning!

black and white conversions

Another difference here from earlier versions of Photoshop is that before the conversion was always set to 100% Red and 0% for Blue and Green. Now the default is 40,40,20. It's all academic as we will be changing these values anyway but I mention it just so as you know. If you now uncheck the Monochrome box nothing much will happen. The image will still be monochrome but moving the sliders will induce a colour cast. Leave the box checked, we don't want to see any colour, I'm just telling you so you don't panic because you expected all the colour to return when you unchecked the box.

black and white conversions

Generally, when there is sky present I like to darken it and I do that by decreasing the Blue and increasing the Red. That tends to give a kind of infra red effect. Notice my values are still totaling 100% but you will also see that I am beginning to lose some of the detail in the highlights on the bark of the tree which was originally reddish. If I were to show this image full size you would see it clearer. Still, I like the contrast better, the darker sky and lighter tree produces more punch. We need to find a compromise.

black and white conversions

Now I've reduced some of the red and replaced it with more green. The result is subtle but believe me, it is far better than it was when viewed full size. You get the idea anyway. Just keep playing around with the sliders until you find something that suits your image. It will vary depending on what colours you originally started with. If there were leaves on this tree, by sliding the Green slider up, you can really make them stand out for example.

I'm still not totally happy with the sky but to make it darker using the channel mixer without losing the effect on the tree we would have to go outside our 100% total. There is a better way to do this. Click on OK to close the channel mixer dialogue window. Click on the add New Layer icon in the bottom of the Layers Pallet and set the blending mode to Overlay. Now select the gradient fill tool with black as the main colour and fading to transparent. Drag on your image from the top to near the bottom of your sky.

black and white conversions

Initially it may look far too dark but you can change this by reducing the opacity of the layer in the Layers Pallet. I've taken mine down to around 30% but this will vary for you and your personal taste.

black and white conversions

Some times, darkening the sky can create a lot of unwanted noise with will be even more apparent once you add an overlay layer as we have here. In this particular image it is not too bad but if you look carefully as a full size section of this image you will see the sky looks a bit blotchy. We can fix this.

black and white conversions

black and white conversionsReselect the background layer in the Layers Pallet. Using the magic wand tool with the continuous and sample all layers boxes unchecked and a tolerance of about 10, click on the sky to select it. You may need to shift + click on further areas of sky if you don't get it all in one. This is a zoomed in image but you will want to see the whole sky when selecting initially so you don't miss any.

Make sure you get all the sky nice and evenly but don't worry too much if you don't go right up tight to the edges as a few pixels out won't really notice.

Once you are happy you have all the sky hold Ctrl + J on the keyboard to copy this selection to a new layer.

black and white conversions




Now go to the top menu bar and select Filter - Noise - Reduce Noise. You will get a new dialogue window appear. Put the strength slider up to 10 (fully right) We are not worried about preserving details unless you have clouds, if you do have this slider at about 60% otherwise it can be 0. Colour noise isn't the problem here so this can be low and we don't need any sharpening. Just above all the sliders there are two radio buttons. Once for basic and one for advanced. check the Advanced button. This allows you to make specific noise reduction adjustment to each of the three colour channels. Remembering which was the strongest channel when we used the channel mixer (In my case it was Red at 80%) select the Red channel from the drop down list and shift the slider all the way over to the right. Now click OK for the changes to take effect.


black and white conversions



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The images above are the before and after of our noise reduction process. Remember you can reduce the effect by simply changing the opacity slider in the Layers Pallet if you think it is too strong. If it hasn't taken enough of the noise out you can re-apply the effect by holding ctrl + F on the keyboard. This shortcut always reapplies the last filter settings used. If you still need more noise reduction you can add a small amount of gaussian blur but be careful as this will spread over into twigs and other neighbouring details.

Now all you need to do is to flatten the layers and convert the image back to 8 bit mode. Make sure you convert after flattening the image or you will lose tonal range. Before saving the file ypou can now convert it to grayscale to reduce the file size.

Below I am showing the same image I have worked on but the left one is as a result of following the procedure above while the right one I have converted to monochrome by simply changing it to Grayscale as first mentioned. I'll leave it to you to decide which you prefer as Photoshop is about being able to make choices and develop your own creativity.


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