Choose lens from drop down list

f-number

Additional circle of confusion

um

Landscape Mode Y or N

Depth of sharp focus

Menu "step"

8

Menu "image count"

This app is one of a series for calculating photo stacking

parameters for various lenses. Fouro camera types are used with

these lenses:

Nikon Z7: It is presumed but not tested that the Z7 app will work

on the Z6 and D850 too. The Nikon uses F-mount with adapter to Z-mount, or Z-Mount lenses. The Fujifilm x-T4. It is presumed that other APSC cameras of this series from Fujifilm will also work. Also from Fujifilm the GFX 100s. It is prresumed that the GFX 100 will also work.

Lumix (Panasonic) S1R and presumably the S1 and S1H too. The S1R uses L-mount lenses.

These cameras support acquiring photo stacks. This is called

“focus shifting” on the Nikon and “Bracketing” [focus] on the

Lumix and Fujifilm cameras. Both cameras have the same menu inputs: “focus step

width” and “number of shots” on the Nikon and “step” and

“image count” on the Lumix. Fujifilm uses "FRAMES" and "STEP."

The Panasonic S1R, Nikon Z7/D850, the Fujifrilm cameras and

variants of those cameras support automatic acquisition of stacks

for creating composite photos with great depth of field. Helicon

Focus and Zerene Stacker are apps that convert a stack to a

photo. The cameras have menu items that are set to control how

the stack is acquired:

The step width can be set from 1 to 10 on both cameras. The step

width determines how much loss of resolution can be tolerated

between adjacent photos in the stack. The higher the f-number

the greater the distance between photos can be, as each

individual photo has greater depth of field as f-number increases.

But changing the step width is not usually the right way to adjust

for different f-numbers, as the cameras do this, to some extent,

automatically.

Besides the step width multiplier from 1 to 10, the camera

modifies the basic step automatically, approximately proportional

to f-number. However, for some lenses this can be very

approximate, probably due to restrictions on the possible steps

that can be generated by the stepping motors on a particular lens.

If the automatic setup of step width were accurately proportional

to f-number, then It could be counted on that the step could be

dependably related to the sharpness of the stack. But this is true

only for some lenses.

Traditionally these menu inputs are set by trial and error

experimentation. There are great variations in the effect of these

menu parameters depending on the lens, camera and f-number.

This app aims to compute ideal values for these given user inputs

defining the desired stack. A different app (currently) is needed

for each lens.

The input to the app called “additional circle of confusion” is used

to compute the size of the menu step. This is based on the idea

that the resolution of a lens is described by the circle of confusion,

or the diameter of the image of an ideal point source of light, such

as a star. Lens aberrations’ and diffraction make the image of a

point source be larger. Typically, the circle of confusion has a

diameter from 5 um (millionth of a meter) to 20 um or more.

Diffraction introduces a circle of confusion equal to 1.3*f-number.

It is assumed that different sources of circle of confusion add

together. At the midpoint between two photos in a stack, the

camera is slightly out of focus. This introduces an additional circle

of confusion. Asking that the additional circle of confusion be

smaller increases the number of photos in the stack

proportionally. At f/8 the circle of confusion due to diffraction is

already 10um. Lens aberrations may add another 5um or more.

Usually a setting of 12um for the additional circle of confusion is

satisfactory. In order to get the sharpest possible stack a small f-

number, such as 1.4 to 2.8 should be used with a very high-quality

lens. In such a case the additional circle of confusion might be set

to 6 or even 3.

Landscape Mode

In Landscape Mode the user focuses the camera at the closest

distance where the stack will start and then activates stack

acquisition. The stack extends to infinity, i.e. distant objects. If

Landscape Mode is enabled the only inputs that control what

happens are the “f-number” and the “Additional circle of

confusion.” This is very convenient for landscape photography.

f-number

The f-number is the value to be used in acquiring the stack.

Notes:

On the Z7 the maximum number of steps allowed in the

menu is 300. Overcome this by acquiring another stack.

That will take over where the previous stack stopped.

The shutter button starts the stack on the S1R. On the

Nikon the start entry in the menu is used. On the S1R o take

a photo for documentation, set focus to manual to inhibit

stack start.

Distance is measured from the sensor, marked with a circle

with a vertical line on the camera body, not from the lens.

Focus shift on Z7 does not work if date and time are not set

or if focus is manual.

The focus must always be set manually to the stack starting

point. This can usually be done even if the lens is an

autofocus mode.

It is possible to acquire stacks handheld if the camera has

stabilization turned on and a sight can be used to keep the

camera closely pointing to the target. The Olympus Dot

Sight EE-1 plugs into the camera hot shoe and provides an

illuminated dot holding on the target. Stacking programs

align the images in the stack, compensating for small

offsets and rotations.