Wednesday, October 12, 2016

Macro image stacking


Introduction

I make use of this technique for many of my macro images, and have been asked by my Photographic Society to do a short talk on the subject. These are my notes for the talk. Any suggestions for improvements, or comments on any corrections that need to be made will be most appreciated.

Please click on the images for a large view.

This is an essential technique for macro images where one needs more depth of field than a single normal macro image can deliver. It is also a technique that can be used in landscape photography, where the use of the hyperfocal distance method does not give an acceptable result.

There are also different methods and software that can be utilised, but these notes are based on the following equipment and software, namely:

  • Photoshop CS6 as the software
  • Canon 6D as the camera
  • Canon EF 100mm f/2.8L IS USM as the macro lens
  • Manual focus
  • Shoot in RAW
  • In Adobe Camera RAW, I use the following settings:

o   Colour space:          sRGB
o   Depth:                     16 Bits/Channel
o   Resize to fit:            Default
o   Resolution:              300 ppi
o   Sharpen for:             Screen
o   Amount:                   Standard
  • If the initial image needs RAW adjustments, those settings can be saved as a Preset, and the same Preset applied to all images that will be stacked. The workflow illustrated below differs slightly from this, but is quicker and achieves the same result. After applying the Preset to all images, I just click on the Done button, i.e. I do not open the image into Photoshop at this stage.

Setup essentials (in addition to camera and lens)
  • Tripod
  • Remote shutter release or cable release
  • If lens has stabiliser, turn it OFF
  • Select aperture priority, ISO at 100 or smallest number camera will accept, shutter speed will then be automatic
  • No air movement, i.e. studio setup desirable


Method

Generally speaking, one can use trial and error to determine the number of images that need to be taken for the stacking process. Technically, it’s reasonably (in my case – very) complicated! There is an excellent article on macro photography, explaining these intricacies, and it can be found here:  http://www.cambridgeincolour.com/tutorials/macro-lenses.htm. Good luck! Note: The magnification factor calculator provided there should be ignored as it doesn't cover all situations. Instead, to calculate the magnification factor, simply take the height (or length if you are doing a portrait shot) of your sensor (in the case of a full-frame camera the sensor size is 36mm x 24mm), and divide that by the height (or length if you are doing a portrait shot) of the subject.

Here is an extract from the website, showing a calculation for the effective depth of field for a full-frame camera with a sensor size of 36mm x 24mm, using an aperture of f/8, and for an object which is 48mm high (twice the height of the sensor, giving a magnification factor of 24mm divided by 48mm = 0.5). You will see that the DOF is minimal at just over 3mm!!! So if an image had a depth of 30mm, and you wanted to capture all the detail, you would need at least 10 images for the stack.



Stacking Procedure

Prepare for shooting and set up subject, lighting, tripod and camera. It’s important at this stage to test the setup to ensure that when focusing both at the front and back of the subject, that the full subject is in the frame and that no edges are cut off. Move the camera further away from the subject until this has been achieved.

The images below illustrate the procedure for photographing a watch, with an actual required depth of field of 48mm, an aperture of f/11, and a magnification factor of 0.3 (24mm divided by 80mm). The DOF as per the http://cambridgeincolour.com calculator is approximately 10mm, so at least 5 images will have to be shot.








Take the required number of photographs, making sure that all sections of the object have been captured in focus. There are different ways of taking the photos to be stacked. One way is to use a rack – they can be extremely sophisticated (and expensive), or very simple (and cheap), like this one:





For my personal tastes, though, I just prefer to focus on selected areas along the subject. I make use of the LiveView option on the camera, use the magnification option to zoom in to the particular area, focus and shoot.






Load the images into Bridge and select the images for the stack.






Double-clicking on one of the images opens them up in Camera Raw (if they are Jpeg images, then hold down the Ctrl button on Windows (cmd button on Mac) and press “r” to open in Camera Raw. Click on the Select all button as indicated, make adjustments as required, and then press the Done button.











Back to Bridge and from the menu, select Tools, Photoshop, Load Files into Photoshop Layers.










Photoshop will open and stack the images one on top of the other in different layers. Select all layers.






From the Photoshop menu, select Edit, Auto-Align Layers, and click Auto. After the processing has been completed, from the Photoshop menu, select Edit, Auto-Blend Layers, and click Stack Images and Seamless Tones and Colours.

Photoshop after Auto-Align and Auto-Blend:




Check stacked image and crop as required, merge layers (Layer, Flatten Image), and then do any final adjustments.  Final image:



2 comments:

Daniel Rossouw said...

Very informative, detailed and well presented. I have made a hard copy of this and now it forms part of my Photoshop Instruction library. Thanks very much for posting this

dobbino said...

Only a pleasure! Thanks Daniel.