Image Stacking with the Panasonic GH4 revisited…speeding things up

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™

2016-09-05 20-07-48 (extended)(B,Radius3,Smoothing5)frame_0001

The depth of detail in this image of an Oleander hawk caterpillar (Daphnis nerii) is something I cannot achieve in any other way… it employs macro lenses used at optimal apertures, diffraction minimised by not closing down to small apertures and a soft background blur associated with a wide aperture.

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:

  1. where recording begins before the first frame of the stacking sequence
  2. at the end where it extends focus to the background.

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.

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Trimming the video clip generated by the 4K post focus process considerably lessens the stack size: eg, in the image shown above there were 112 images in the trimmed stack from a total of 247 taken in the clip – those 135 discarded were of no use as the focus went all the way to the background.

Getting rid of these frames speeds things up but, at the moment, there is no batch delete feature in the Mac version of Helicon Focus (they will fix this) and you have to delete each extraneous image separately.

However, I have found a way around this  by trimming the clip in QuickTime™ – incorporating a step between Lightroom and the Helicon Focus rendering stage.

QT trim

I play the clip in QuickTime™ first to get a general idea and then move the bars at either end..with a little practice you get to see where the sequence you want starts via the screen image… where detail closest to the lens comes into focus and where the furthest detail you wish to incorporate drops off: hairs on insects or plants are good guides for this. Never dispense with the full clip until you have the final rendered image you want.

a.   Open each video sequence in turn in QuickTime™ where they can be played and trimmed as needed …usually just a few frames at the start and more at the end. NB. You see a distinct ‘jump’ in focus where the sequence starts properly and another where the subject is recorded and focus goes to background.

b.  For convenience when working I export each Trimmed clip to a working file on the desktop and then eventually add them to my Lightroom catalogue with a fully rendered image from each stack (saved as Tiff or PSD) and create a back-up on a hard drive.

c.  When I am ready to process I open each trimmed clip in Helicon Focus…just by the ‘drag n’ drop’ facility. The frames are extracted to create the stack and before rendering I set two parameters Radius (3-4) and Smoothing (5) and use Method B (depth map) which works well for me.

d.  Finally, I get rid of the full video sequences (and and clips on the desk top) to save space and only store the reduced versions as keepers….these stacks pile up into gigabytes very speedily.

Density map

The program works quickly through each image, builds up a density map of each layer and then combines them…the first time you do this and see the detail on screen is a revelation. You record things no other method allows you with both detail and textures.

The program works quickly through each image builds up a map of each layer and then combines them…the first time you do this and see the detail on screen is a revelation. You see things no other method allows you to.

Written down it seems like a complicated thing to do but in practice it is pretty speedy and worth it for the results.

©  Paul Harcourt Davies – neither images(s) nor text may be used in whole (or in part) without the express permission of the author.

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