This is a walkthrough of how I edited this image in LAB color space.

The image I started with:

Step 1:

Convert to LAB color mode.

Step 2:

Make a curves adjustment layer. Adjust the A and B channel curves like below.

The colors will become very saturated in a way that looks much nicer than using hue/saturation in RGB mode.

Step 3:

Duplicate the background layer and apply Shadow/Highlight to the Lightness channel.

Select only the Lightness channel but keep all channels visible by clicking the eye icon next to the Lab channel.

Then apply the Shadow/Highlights adjustment by going to Image:Adjustments>Shadow/Highlight. My values are not cut in stone, you need to experiment a bit here. The image can look a bit flat but we will fix that in the next step.

You can adjust the opacity of the Shadow/Hightlights if you want to bring back some more shadows.

Step 4:

Edit the Curves layer with an S-curve on the Lightness channel to bring back contrast and depth.

Step 5:

Sharpen the image (preferably in the Lightness channel) and your done.

Digital camera sensors do not capture b&w images, they capture color images with three channels, each describing the lumniosity of each of the colors red, green and blue. Consequently, there is always a conversion taking place when you make a b&w photo. The three channels must be made into one grayscale channel. If you let the camera do that for you, you give up all control of how it is done, and how much of each channel is used in the mix.

If you do it in post processing on the other hand, you have full control. One way is using the channel mixer. It can be applied as an adjustment layer.

Check the Monochrome checkbox and you will get a grayscale image. The sliders control how much of each channel is used. The total percentage should be around 100%, but can vary pretty much from image to image.

To demonstrate the difference I’m going to convert this image of a bright yellow leaf you saw at the beginning of the post.

If we choose the three color channels separately it looks like this.

Red: Green: Blue:

As you can see there is quite a bit of difference. In the red one the leaf is very bright, in the green the leaf has a nice texture but blends in too much with the background. In the blue channel the leaf is very dark and the background very bright.

If we convert this image using Image>Mode>Grayscale we get an image that looks like this:

This is about what you could expect to get from an in-camera b&w image. As you can see there is not much contrast between the leaf and the background. The image becomes hard to read and it looks really bad.

How would we use the information in the r,g,b channels to improve this image? We would like to have the texture from the green and the contrast from the red. The blue channel is useful in this case, because we can use it to darken the distracting background by adding a negative amount of it in the mix, without affecting the leaf much.

So above is my version using the channel mixer. Click here to see the settings I used: Channel mixer settings. Adding a simple curvers layer to get some more contrast I get this:

That’s a whole lot better than the first conversion if you ask me, although there is a finer gray scale in the previous version. It depends on what effect you want to archieve.

Changing the settings you can get very different results. Here is another version where I subtracted a bit more of the blue channel to almost remove the background completely:

You might notice this last image is pretty noisy in the background. As a rule of thumb, the blue channel is the noisiest one while the green is the least noisy and most detailed and the red is the most contrasty.

There are many other ways to convert to b&w than just the channel mixer, the “black & white” option in Photoshop cs3 is one.

Thanks for reading!

This image has lots of perspective and is also a bit rotated. By making a crop selection and clicking and draging outside the selection, it can be rotated and cropped in one action.

Press Enter or click the commit button to crop the image. You should get something like below.

The image is now rotated, but if you want you can also correct the perspective at the same time, with the Crop Tool. In this image the perspective looks nice, so normally we wouldn’t correct it, but just for the sake of demonstration we will. To correct the perspective you make the vertical lines, which are now converging upwards, parallell.

First make a crop selection in your image, then check the Perspective checkbox in the top toolbar. You can now move around the corners of the selection individually. You want to make the left and right edges of the selection line up with the lines in the image like below. By holding Shift when moving the handles you can make sure the horizontal edges stay horizontal.

Then use the middle handles of the selection to enlarge it.

Then make the crop and we are done. The image now has parallell vertical lines, something that a tilt-shift lens would accomplish.

The image is degraded more the less parallell the lines are, so it gives the best results if you try to keep the vertical lines as parallell as possible when shooting. A wide angle lens typically gives lines that converge more, so if possible use the longest lense you have when you know you will be correcting the perspective.

Daniel

Tilted horizons can often ruin the impression of a photo. Here is a useful tip when you need to quickly straighten the horizon in a photo using photoshop.

Select the Ruler Tool , and make a line following the horizon in your photo.

Now if you go to Image > Rotate Canvas > Arbitrary… the proper amount of rotation is already filled in.
Click OK.

Now all you have to do is crop the image and you have a photo with a perfectly straight horizon:

You can also use the Crop Tool and do both the rotating and cropping at the same time as below, but I find this method more precise on the rotation. See this post for info on the crop tool.

Daniel