Monday, September 20, 2021

Landscape Bracketing Script (M3): now with a simulated ND filter option

Just a quick post to say I've brought the M3 version of my CHDK Landscape Bracketing Script, into line with the non-M3 version.

The M3 version, downloaded from the right as usual, now has a menu item called "ND Filter?", with values of 0 to 5.

If 0 is selected then no ND brackets will be taken. If the value of this menu item is between 1 and 5, then a simulated ND bracket set will be taken, as part of the focus and exposure bracket set.

An ND2, will take 2 images that you can post process, whereas an ND5 will take 32 images. Each ND bracket set can be processed in Photoshop, for example, to create a Long Exposure image for blending with the others in the bracket set, eg the focus images and the sky ETTR capture.

The ND images are taken at the foreground exposure value, ie the one used for focus bracketing.

As with the sky exposure bracket, the ND filter bracket set is taken at the infinity focus point that you set, eg three times the hyperfocal, say.

Once captured, the bracket set is easily identifiable in Lightroom, as the script makes use of dark frame bookends at appropriate places, eg:


In the above we see that the entire bracket set has bookends at the start and end of the bracket set, and the ND set is also delineated, eg the 4 images towards the end, in the above example. Also seen are (4) focus brackets, at the start: two before the hyperfocal, one at the hyperfocal and one at, in this case, 3 times the hyperfocal, for a defocus infinity blur of about a third of the overlap CoC, which was set at 15 microns in this test capture.

The script automatically took the focus brackets, as, in this case, I had selected the X2Inf option. Thus all I needed to do was to focus on the foreground point of interest, note the number of focus brackets and accept or adjust the aperture, focus or focal length.

Then, with a single button press, the M3 captured a perfect focus bracket set, plus capturing a simulated ND bracket set for 'statistical processing in Photoshop, and an ETTR sky image at infinity. 

Once the focus and ND bracket sets are pre-processed, these two images can be blended with the sky ETTR image, eg using masks.

As usual I welcome any comments on this post or any of my posts.

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