Make macro shots sharp throughout

James Pater son reveals how to expand an images depth of field by focus stacking in Photoshop CS

What youll need

Photoshop CS4 or CS5

What youll learn

How to load images into layers, use Photoshops auto - align and auto - blend features, and use Layer Masks to tweak the effect

It only takes

20 minutes

Depth of field is determined by three things: focal length, distance to subject and aperture. With close - up photography, depth of field is naturally limited, firstly because macro lenses usually have long focal lengths, but also because you have to get so close to your subject. This leaves you with a very shallow plane of focus, which in many cases is what the photographer wants. But what if you want sharpness throughout your subject?

Make macro shots sharp throughout

The answer is to shoot several images, each with a tiny focus adjustment, then use Photoshop to bring all the sharp parts together into one seamless, pin - sharp image. You need a sturdy tripod and a subject that wont move between exposures. Focus manually on the closest part of the scene you want sharp, then capture a series of shots, each with a slight adjustment to the focus ring, until you have a set of images with overlapping planes of focus that cover your whole subject from front to back.

If this sounds too difficult, dont worry. Photoshop can do much of the hard work for you, first by loading all of your images into one layered file, then by automatically aligning and blending the layers to reveal the sharp parts. Its a great time - saver, but as with most automated functions you cant rely on it completely. The hundreds of spikes on our subject all weave in and out of different planes of focus, so Photoshops auto - blend feature can only take us so far.

Here, well show you how to fine - time the look by painting on Layer Masks.

Open in Adobe Camera Raw

Open Adobe Bridge, then navigate to your files - weve provided seven source files on this issues Video Disc. Click on the first file, then hold Shift and click on the last file to select them all. Right - click and choose Open in Adobe Camera Raw. You can do this with both raw and JPEG files.

Adjust the tones

Click Select All at the top left of the window, then use the sliders in the Basics panel to tweak the tones. For our images, we set Exposure to +15, Recovery to 30, Fill Light to 12, Blacks to 4, Contrast to +5 and Clarity to +15. When youre happy with the result, hit Done.

Load into layers

Head back to Bridge and go to ToolsPhotoshop Load Files into Photoshop Layers. Now wait a few seconds while this handy function automatically opens all of your images into Photoshop and copies them into a single layered document.

Align the layers

Hold Shift and click on the bottom layer in the Layers palette to select all the layers, then go to EditAuto - Align Layers. In the Auto - Align Layers box, choose Auto then hit OK. Photoshop will nudge and transform the layers so that the image elements align.

Blend the layers

Go to EditAuto - Blend Layers. In the Auto - Blend box, choose Stack Images and make sure Seamless tones and colours is checked. Hit OK, then wait while Photoshop does the hard work for you by adding layer masks to each layer that isolate the sharpest parts of the image.

Crop the edges

The Auto - Align and Auto - Blend functions often leave a blurred edge, so grab the Crop tool from the Tools palette. Next, click on Clear in the top options bar to clear any previous settings, then drag over the image to make a new crop that excludes the blurred edges.

Learn the lingo

Focus stacking

Focus stacking is a technique used to increase depth of field beyond the capabilities of a lens. Its a clever digital solution to optical limitations, and if s becoming increasingly popular with macro photographers because of the level of control it gives over the plane of focus. Whaf s more, with the right tools and a little help from Photoshop, its also a fairly simple technique to master.

Merge a copy

Click on the top layer in the Layers palette, then click the Create New Layer icon to add a new empty layer. Press Cmd/Ctrl+Shift+Alt+E to merge a copy of all the layers below to the new layer. Doubleclick the layer name and call it Merged.

Delete the masks

The Auto - Blend function has missed a few areas of sharpness. You can paint a new mask on the Merged layer to find those overlooked sharp parts. First you need to delete the existing masks, so right - click each thumbnail and choose Delete Mask.

Make a shortcut

You need to be able to quickly and repeatedly compare the merged layers with those below. To make a shortcut that toggles layer visibility on/off, go to EditKeyboard Shortcuts. In the Layer drop - down, choose Hide Layers and assign a suitable key.

Add a mask

Highlight the Merged layer, then click the Add Layer Mask icon at the bottom of the Layers palette. Select the Brush tool; hit D then X to set black as your colour. Choose a soft - edged circular brush from the Brush Preset Picker in the options bar.

Reveal the sharpness

Toggle the Merged Layer visibility on and off so you can compare the sharpness with the layer below. If part of the underlying layer is sharper, use the Brush tool to paint on the Merged layers mask with black to reveal the sharper detail below.

Merge layers

Once youve found all the sharpness in the layer below your Merged layer, type Cmd/Ctrl+E to combine the layers into one. Add a mask and repeat from step 10 by comparing your merged layer with the layer below and masking the softer parts.

Learn the lingo

Sharpening

To ensure the best quality prints, sharpen your images at the end of the editing process. As is often the case with Photoshop, there are several methods you can use. You could apply the Unsharp Mask or Smart Sharpen filters, or even use the Sharpen tool. Or you could apply the High Pass filter on a merged layer set to the Overlay Blending Mode, as weve done here.

Work through layers

Continue until youre happy you have all the sharp areas of the plant on your Merged layer. Concentrate on the spiky edges of the plant; dont worry too much about the layers where the stem is sharp because the focus is more uniform there.

Adjust the tones

Click the Create Adjustment Layer icon at the bottom of the Layers palette. Choose Curves. Plot two points on your curve line and drag one down in the shadows and the other up in the highlights to make an s - shaped curve that boosts contrast.

Create a Dodge/Burn layer

Hold Alt and click the Create New Layer icon in the Layers palette to access the New Layer options. Name the layer, then choose Overlay from the Mode drop - down. Check the box next to Fill with Overlay - neutral colour, then hit OK.

Paint light and dark

Grab the Bum tool from the Tools palette and in the options bar set Range to Midtones. Paint on the grey layer to selectively darken the corners of the image, then switch to the Dodge tool, set Range to Highlights and paint over the plant to lighten tones.

Make a Smart Object

Create a new layer at the top of the stack. Press Cmd/Ctrl+Shift+Alt+E to merge all of the layers onto this new layer. Right - click on the top layer. Choose Convert to Smart Object, then go to FilterOther High Pass. Set an Amount of 5 pixels and then hit OK.

High Pass sharpening

In the Layers palette, change the Blending Mode of the new layer to Overlay. This produces a great sharpening effect in the edge details. Lower the Opacity to around 70%. Select the top plant layer and use the Clone tool to tidy up any rough edges.

Learn the lingo

Smart Objects

Smart Objects allow you to make non - destructive changes to image layers, such as adding filters. Each edit appears in the Layers palette under the layer. Simply double - click this part of the layer to re - enter the settings you applied earlier and tweak them at any time. For example, you can adjust the strength of the High Pass sharpening effect in step 17 whenever you want.

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