Thursday, September 3, 2020

DOFIS: Auto Bracketing Mode

Up until now, focus bracketing in DOFIS has been manually achieved, with DOFIS alerting you to the perfect position to be at, relative to your last captured image.

In the latest version (download from the right) I've added an auto focus bracketing feature, designed for one use case: auto focus bracketing from a focus position less than the hyperfocal to an image captured just beyond the hyperfocal, at which point, using the DOFIS blur feedback, you can manually add an additional infinity shot.

This use case is targeted at those seeking deep focus, eg landscape photographers.

The DOFIS menu now looks like this:

Here we see the new Auto Bracketing feature has been set ON. Note, auto focus bracketing only works for registered, AF on, lenses, ie using a spilt lens model. 

Before using auto bracketing you need to make two changes to the script, as auto bracketing needs to know what trigger key/button you wish to use, and how the lens moves, as it is not guaranteed that all lenses move in the same way.

-- Lens #1
mylens[1] = {}
mylens[1][1] = "12-24mm" -- lens name
mylens[1][2] = 0.156 -- Mag
mylens[1][3] = 280 -- FD
mylens[1][4] = 24 -- FL at Mag (use longest FL on a zoom)
mylens[1][5] = -1 -- move direction

In the above we see the lens registration now includes a 5th entry, that tells DOFIS how the lens moves towards infinity. In the case of the 12-24 Sigma, we need to use -1. If this entry is 0, auto focus bracketing will not be accessible with this lens, for example:

--Lens #3
mylens[3] = {}
mylens[3][1] = "EF100mm f/2.8L Macro IS USM" -- lens name
mylens[3][2] = 1.0 -- Mag
mylens[3][3] = 300 -- FD
mylens[3][4] = 100 -- FL at Mag (use longest FL on a zoom)
mylens[3][5] = 0 -- move direction

I have switched auto focus bracketing off on my 100mm macro lens, as the DOFIS auto focusing algorithm is not designed for macro use.

The only other script change you will need to make, is to tell DOFIS what button you are using to trigger auto focus bracketing, eg:

button = KEY.RATE --(change to suit your camera)*

As you can see, on my 5D3, I use the RATE button. If auto focus bracketing is switched on, then the RATE button will trigger auto focus bracketing. If auto focus bracketing is switched off, then the RATE button will work normally.

The speed the lens moves is totally dependent on the camera and lens. On my 5D3, things move reasonably quickly. Auto focus bracketing should be quicker than doing it manually, and it will guarantee positive focus overlap.

To illustrate how useful the new auto focus feature is, I set up one of my usual desk top test scenes, using my Sigma at a focal length of 16mm, with an aperture of f/8. I set the ML CoC to 30 microns and set diffraction aware on in DOFIS. I also switched on Dual ISO in ML. Note DOFIS disables advanced bracketing.

I set the lens to minimum focus, ie 280mm from the sensor plane, ETTRed with ML, and pressed the RATE button. 

Auto focus bracketing has an inbuilt 2 sec delay, after which DOFIS automatically captured five images, finishing at around twice the hyperfocal.

BTW the focus bracketing algorithm used in DOFIS first moves towards infinity with medium steps, then back towards the macro end in small steps, until there is a positive focus overlap.

Once finished I was able to confirm the infinity blurs were acceptable, by looking at the DOFIS LV feedback, and thus I stopped the capture session at this point, ie not bothering with an additional/refocused infinity shot.

The five images were ingested into Lightroom, Dual-ISO processed, sent on a round trip to Helicon Focus, with the final image toned back in Lightroom:

 As usual, I welcome feedback on this post and DOFIS.




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