Focus Stacking in the field has become a practical reality for me thanks to what Panasonic calls 4K post focus, avaiilable in the GH4 and several other models…..
The very first time I saw the remarkable images that a scanning electron microscope could generate I was completely hooked. The Sunday Times colour supplement, a journal of quality in those pre-Murdoch days published a series of images by the remarkable Lennart Nilsson. Every detail was revealed in sharp focus by taking layers within the target and building up an image created via reflected electron beams from these. I dreamed of one day being able to do something similar with natural light and with living material, not the dead specimens coated with a thin layer of gold deposited in a vacuum chamber…now I can.
The Revolution: 4K post focus in the Panasonic GH4 (and various other Panasonic cameras that boast a 4K video capability)
For the past few weeks I have been like a kid in the proverbial candy store using a feature of the Panasonic GH4 called 4K Post Focus. The result has been some superb stacked image results.What this camera does differently is to use its high resolution video capability (something for which many pros have bought it) rather than a burst involving the shutter. The 4K video mode employed allows super detailed video for the 4K refers to the approximate value of the long edge of each frame captured.
a. The frame rate is 30 fps and the exposure of individual frames is set beforehand. I use f/4-f/5.6 as the marked lens aperture for this tends to cover the proverbial ‘sweet spot’ where the lens has its optimal performance.
b. You also get the Bokeh associated with the wide aperture and this gives soft backgrounds that accentuate the detail of the final stacked image
c. I then adjust the ISO between 200 and 400 (say) to get a shutter speed that will freeze movement. The stacking software can cope with tiny movements between frames when it aligns images but the more you can cut down movement of subject and camera the better. To this end I always use a tripod and a flexible arm when possible to steady plant stems during the scanning of the subject and focus shift by the camera. Read More
I particularly like working with rectangular fisheye lenses for my wide-angle macro work because they exhibit better good close-focusing capability than normal ultra-wide lenses. I have extolled the virtues of the Sigma 15 mm f/2.8 rectangular fisheye on many occasions when I was using it on APS-C format (with Nikon bodies and with a Sony NEX 7). Using a lens like this, designed for full frame, with formats smaller than that, permits the utilisation of the centre part of the image circle. The images then show remarkably little distortion – just a bit of curvature towards the edges: sharpness is excellent as is contrast and the close focusing capability is remarkable. In fact, this was the main lens that both Clay Bolt and I used when gathering images for our e-book: Wide-Angle Macro | The Essential Guide.
Of course, I can use also this lens with the micro 4/3 (MFT) format and a suitable adapter (Nikon to micro 4/3) but then it behaves as a 30 mm wide-angle compared with 22.5 mm forAPS-C, that is, unless you use the Metabones SpeedBooster. Then with the model I use it behaves as a 19.2mm lens with a maximum aperture 1 1/3 times wider than f/2.8…around f/1.8 – but more about that in the next post.
With a change of format to MFT, I wanted to go that bit wider…
Samyang 7.5 mm f/3 .5 rectangular fisheye