Monday, July 25, 2016

Getting Ready for a Trip

I'm off to the US next week for a business trip and want to travel light: so I've decided to make use of my EOSM, which, of course, comes with Magic Lantern :-)

The current weakness of the EOSM is that the lens focus features in Lua don't work. So my landscape focus bracketing script is a no go. But, I have other options for achieving great depths of field: namely my Rokinon 12mm Full Frame Fisheye, which fits the EOSM via the Canon Adapter.

The great thing about the 12mm, on the EOSM cropped sensor, is the huge depth of field. For instance at the hyperfocal distance of about 5ft at F/8, everything from about 2.5 ft to infinity is at acceptable sharpness. 

But is the HFD the right approach? Are there other focusing strategies? There is one that all photographers should try and remember and it follows from the work of Harold M. Merklinger of Halifax, Nova Scotia, Canada. Merklinger stated that by focusing your lens at infinity, the smallest object resolved in your image will effectively have the same width as the focal length divided by the aperture of your lens.

So for my 12mm lens at f/8, this size is 12mm divided by 8, or 1.5mm.

Yes, I can carry on using the HFD, but this will mean the distant details will not be optimally sharp, just acceptably sharp according to the Circle of Confusion criterion I have selected.

Using the Merklinger strategy, I simply focus for the farthest object, ie towards/at 'infinity' and that's it. Details greater than 1.5mm are resolved from near to far.

To test things out, and show the power of the defishing software, here is one bracket from a six bracket Auto Exposure Bracketing capture, taken with Magic Lantern.

You can clearly see the fisheye distortion.

Post processing followed these lines:
  • Ingest all six images into Lightroom;
  • Use LR's Merge to HDR to create a 32bit DNG;
  • Correct the basic exposure for this 32bit DNG, before exporting a 16bit TIFF to Photoshop;
  • Once in PS-CC, use the Fisheye-Hemi Plug-in to correct the fisheye distortion;
  • Return to LR and finish off, finally arriving at this test image, with no fisheye distortion and everything looking 'crisp' from near to far.
I've got the rest of the week to 'muck about' with the EOSM, deciding what other gear to take with me. But one thing is clear: the Rokinon 12mm Fisheye is the one thing I will not be leaving at home!

No comments:

Post a Comment