Do you want to achieve critical sharpness and maximum depth of field in your images?
I will now think twice when I need to dial the aperture down to f/16 or f/22 to get more depth of field. Don’t let anyone tell you to shoot at f/16 or smaller to get sharper images. This is a total misconception and is misleading. Depth of field and image sharpness are two entirely different things. When you stop the lens down, there is a huge sacrifice in sharpness through what is known as ‘diffraction’. Just have a look at the comparison examples here. In the sample image on the left shot at f/16 there is a noticeable overall softness to the fine detail. Whereas, in the focus stacked image shot at f/8, you can see the veins in the leaves with absolute critical sharpness throughout all of the sunflowers.
This procedure is so easy, but needs a little attention when making the exposures in the field. It’s best if nothing is moving, but any slight movement can be retouched later in Photoshop.
Using the optimal aperture of f/8, make as many exposures as necessary focusing closest to the camera right to infinity making sure you cover every point of focus throughout the scene. I prefer to do this using manual focus and looking through the viewfinder. I can quickly make a series of exposures before anything moves, especially clouds. You can use Live View using auto focus to precisely set each focus point, but this takes more time.
Tip: Make an exposure of your finger or hand before and after the series so you can distinguish the series of images from others in post processing.
Focus Stack in Photoshop
1. You can open the series of images as layers in Photoshop or you can select them in Lightroom then go to Photo>Edit In>Open as Layers in Photoshop.
2. In the layers palette, select all of the layers by holding down the shift key.
3. Edit>Auto-Blend Layers. Click OK on the stack images window.
4. Go to Layer>Flatten Image
Check for any out of focus points especially around the edge of the frame. This is caused from the differential in subject size between the focus points. Just crop this out.