Sunday, August 30, 2020

DOFIS: Update

As I wish to get DOFIS 'fighting fit' for all photographers as well as videographers, I've been rapidly field testing and updating the code. In this post I'll recap the status of DOFIS and talk about a few of its features.

DOFIS is, IMHO, the only focus tool you will need when running Magic Lantern. In fact DOFIS switches off the ML DoF info as this is limited by being based on a thin lens model. The only ML information that DOFIS uses is the ML CoC setting and the ML-Canon focus position, which is from the sensor plane.

The DOFIS menu is positioned under the ML Focus menu and now looks like this:

Here we see:

  • DOFIS display is set to on;
  • The display option is set to always show the infinity blurs, ie defocus, diffraction and the total;
  • Bracketing feedback is switched off;
  • Diffraction aware is switched on, thus DOFIS will use the ML CoC as the total blur, and calculate the DoF defocus blur using diffraction. You can clearly see if diffraction is on or not in the DOFIS LV display, ie - means diffraction aware is off, while + means it is on;
  • The lens model is in auto mode and has successfully found a lens model. DOFIS comes preloaded with a few of my lenses, but you can easily register your own in the script. DOFIS tells you what model is in use by displaying an S, for a split lens model, and T for a thin lens. Remember the thin lens in DOFIS may be different to the thin lens feedback in ML, as the ML DoF and hyperfocal feedback ignores lens extension, where as the DOFIS thin lens model uses the thin lens equation to estimate magnification and hence lens extension;
  • The additional info is showing the hyperfocal distance from the sensor. At the bottom we can also see DOFIS can show other info by toggling through the options.

The DOFIS display options cover three scenarios, designed to support photographers and videographers:

  • In Blurs mode DOFIS will always/only show the three infinity blurs, ie defocus, diffraction and the total blur at infinity. This mode will be useful for photographers who mainly infinity focus and don't worry too much about the near field, ie they know that their subjects of interest are beyond the hyperfocal;
  • In A-DoFs mode DOFIS will display the absolute near and far DOFs, relative to the sensor, as long as focus is less than the hyperfocal. Once focus goes beyond the hyperfocal, DOFIS will switch to showing the near absolute DoF and the infinity blurs. This mode should appeal to landscape photographers and is my preferred mode;
  • In R-DoFs mode DOFIS will display the relative (to the point of focus) near and far DoFs, once again, as long as focus is less than the hyperfocal. Once focus goes beyond the hyperfocal, DOFIS will switch to showing the near relative DoF and the infinity blurs. This mode should appeal to portrait photographers and videogaphers.
As an example of the R-DoFs mode, here are a few screen captures showing the DOFIS LV information. The ML CoC was set to 30 microns.

Here we see DOFIS has found a lens to use (in ths case a 12-24mm Sigma), as it is displaying an S, rather than a T. A negative is next being shown, which means diffraction awareness is switched off. DOFIS is next showing that, from the current focus (51cm), you will need to take two focus brackets (#2) to get to the hyperfocal distance. If you see =H then you are beyond H but the infinity blur is within 10% of the defocus CoC value, whereas >H means you are focusing beyond H. Remember that the defocus blur tells you your position relative to H, eg if the defocus CoC is 30 microns and the infinity blur is 15 microns, then you are at about twice H.
As an R, rather than an A, is being shown next, we are in relative DOF mode and that DOFIS is estimating the near DoF, relative to the focus position, at 15cm, and the far DoF at 70cm.

If we now move focus to beyond the hyperfocal, ie >H being shown, we will see the following:

The DOFIS display has now changed so that you can correctly infinity focus, as well as still see the near DoF (relative or absolute according to how set). In this case I have decided to focus for a total blur of 16 microns, ie a high quality infinity focus, that gives a (near field) DoF of 97cm. Remember that if we focused at infinity the near DoF would be H.

Note: when infinity focusing, DOFIS will always show the defocus, diffraction and total blurs, irrespective of whether diffraction aware is set. Diffraction aware only impacts the DoF calculations.

In a future post I'll show how to use DOFIS for focus bracketing. 

As usual I welcome feedback of any kind.

1 comment:

  1. Cool, thanks for sharing! I'm waiting for the next part!