Nowadays, we are spoilt by technology and there is a tendency to think in terms of a camera controlling the output of flash guns via its DTTL exposure system. Even better, it can do this without the use of cables via a WiFi set up. However, the arrival of digital cameras has made the use of older manual flash guns easy, even though you are denied the camera’s DTTL system.
Once upon a time, a flash gun was simply triggered by a camera hotshoe or, off-camera, via its flash synchronisation (synch) socket. Other ‘slave’ flash guns for fill-in or back lighting could be triggered via simple photoelectric triggers that fit the flash hotshoe and reacts to the main flash pulse with a very slight delay.
To get correct exposure demanded a flash meter – an exposure meter that can respond in a very short time (milliseconds). Readings were transferred from meter to camera and flash gun positions adjusted accordingly. Many professionals in studios used a polaroid film back to get a rapid assessment: with close-up work experiments had to be done with flash gun position noted and frames taken over a range of apertures to find the optimum. Nowadays you can use your camera’s LCD screen to make a visual assessment of exposure.
Shortly after I put my experiences with the Pansonic GH4 4K post focus mode on the Learn Macro site I had a very helpful email from Catherine at Helicon Focus. The more recent versions of Helicon Focus cope directly with MP4 video snippets which you can send directly from Lightroom thanks to a plug in. Last year I had a hard drive in my iMac fail and re-installed most of what I had lost but omitted to upgrade the version of Helicon Focus… I can also speed things up by ‘trimming’ clips in QuickTime™
The program cleverly extracts the individual frames and they appear in the right hand panel in Helicon Focus. There will often be far more of them than you need – at both the beginning and end there might be extraneous frames:
It is also better to remove these because you tend to get artefacts in the image which take time to clean up in Photoshop and I also like the soft Bokeh achieved by working at f/4 – 5.6 in the original frames and do not need the sharp background images.
NB I find this happens to a much greater extent when using a cable release than when using ‘touch focus’ from the LCD of the Panasonic GH4 or via the App for my iPad Air. In the latter case the camera focuses first on the closest detail and then the sequence begins: with the cable release there is a tendency to start recording whilst focus is being found. Read More
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