Thursday, 12 March 2015

Focus Stacking - Test

I have the need to revise my macro techniques for a future project. I have a 60mm and a 105mm macro lens, together with 3 extension tubes. Even at F45 the depth of field is very narrow, especially when at minimum focusing distance. A view camera or maybe a short tele tilt and shift on the DSLR would improve this but the cost would outweigh the benefits. One other item (given to me by a good friend) is a focusing rail. It is a rack and pinion device that allows movement of the camera to change the focus rather than the normal lens focusing. A few years ago I tried focus stacking, a technique whereby you take a number of images, starting from the front of the subject to the back, each in focus. Software, using layers stacks these, applies masks and produces a composite image of all the in focus bits. The result is a photograph with a very wide depth of field. In the image below I used a single Bowens strobe so there are too many reflections, but that will be rectified as my light tent has now arrived and a diffused light is now available.
The image is from 12 frames. Each movement on the focusing rail no more than 2mm. The images are then processed in CS5 using photomerge and align. An i7 with 32gb, 36MP frames and the processing took no more than 45 seconds so I am happy to make further stacks of up to 20 layers.
While just testing I have reverted to .jpg files rather than raw to speed this up a bit. This work continues.

Another experiment with the light tent and acrylic sheet lit from above and below. The paper weight is from assignment 2. Being glass it is difficult to not get reflections but here I think I have a reasonable effort.

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