[thepedant]

It would be very useful to be able to nudge the focus backwards and forwards in small increments between each shot using the USB or wireless remote software.

[Adam]

I second this. The USB SDK almost supports this, and likely would make this possible through just some simple improvements and fixes.

[photoptimist]

The trick is coming up with the required lens movement increment that shifts the plane of focus by just the right amount.

For simple lenses, it's a function of the size of the circle-of-confusion, the lens focal length, lens aperture, lens motor step-size, gearing, and helicoid pitch.

The bigger issue is whether the USB SDK supports low-level lens motor movement such as a command to move +13 ticks.

[rawr]

In cameras that already support AF Fine Adjustment, focus bracketing could simply be achieved by just cycling through the -10 to +10 AF adjustment range and taking a [specified] sequence of shots along the way.

I'm not sure if the SDK supports AF Fine Adjust, but it would make sense for it to, since I imagine AF Fine Adjust is a very common service request.

[Wheatfield]

In cameras that already support AF Fine Adjustment, focus bracketing could simply be achieved by just cycling through the -10 to +10 AF adjustment range and taking a [specified] sequence of shots along the way.

I'm not sure if the SDK supports AF Fine Adjust, but it would make sense for it to, since I imagine AF Fine Adjust is a very common service request.

I do a lot of focus stacks and I can say with confidence that the AF fine adjust wouldn’t provide enough focus deflection to be useful, not to mention how much of a PITA it would be to use the focus adjust in that manner.
The most useful method would be to set near and far focus by manual adjustment of the focus ring, tell the camera how many images to shoot and let it work out how far to move the focus between exposures to accomplish the exercise.

[rawr]

the AF fine adjust wouldn’t provide enough focus deflection to be useful

But with macro, for example, shooting a range of even small AF adjusted shots could still give you enough focus spread to do a useful stack.

The in-camera AF adjustment range available 'out of the box' of -/+ 10 may be conservative. The camera may really be able to do, for example, -/+ 100 AF adjust. Which could translate into a focal depth range that's useful for many stacking purposes.

All speculation on my behalf, of course.

[Wheatfield]

But with macro, for example, shooting a range of even small AF adjusted shots could still give you enough focus spread to do a useful stack.

Probably not. The range of focus movement in macro is much greater than in general photography. If you have a macro lens, look at how much distance on the focus ring is taken up by close focus compared to distance.
In macro, one is better served by moving the entire camera in increments on a focus rail. This gives less shift of reproduction ratio.

The in-camera AF adjustment range available 'out of the box' of -/+ 10 may be conservative. The camera may really be able to do, for example, -/+ 100 AF adjust. Which could translate into a focal depth range that's useful for many stacking purposes.

All speculation on my behalf, of course.

In other words, rewrite the AF adjust routine, expand it’s range, put it in another spot in the menu and give it a new name. Pretty much what I said in the first place.

[stevebrot]

I do a lot of focus stacks and I can say with confidence that the AF fine adjust wouldn’t provide enough focus deflection to be useful, not to mention how much of a PITA it would be to use the focus adjust in that manner.

My understanding of how the focus shift feature in Nikon and other cameras works is that the feature simply sends step increments to the AF drive motor from an arbitrary initial start point rather than attempting to acquire focus anew at each step. With the Nikon D850 the flow works something like this:

1. Focus to set the initial plane of focus
2. Set the camera up for "focus shift" choosing # of shots (300 max), step width (1-10), and time interval between shots
3. Start the shifted exposure set from within the focus shift shooting menu dialog (not the shutter release)
4. The camera will step through the set number of shots, moving the plane of focus one "step width" more distant for each step.

In addition:

• Focus Shift only works with AF-S and AF-P lenses. AF series (no focus motor) are not supported.
• "Step width" is not defined, but based on the tables on the linked page below, the steps appear to grow deeper with distance
• The NPS advisors suggest trial and error to attain the correct settings for number and width
• Setting interval to "00" results in about 3 fps in either of the "quiet" modes and about 5 fps otherwise

More information on the D850 implementation:

NPS : D850 Tips | Focus Shift

Also D850 manual : Nikon | Download center | D850

Steve

[rechmbrs]

I'd like to suggest that you guys write the document that explains what you want. We all know that Pentax will probably not put this is the firmware so it would only get produced by the user community. To me we should bug Pentax to add options that we can't implement in a cross-platform set of tools. With the SDKs, we should be able to a great many things. This one seems pretty easy. Taking the load off of Pentax might make them free up more ways to work with the firmware across wifi, USB, ...

If you can get a agreement among you (ROFLOL) on what parameters are needed and how they are used but do not recommend how to code it. A coder should be able to fit it into their app in a much faster time without your help. You should document by using real data which can be processed in PhotoShop, etc. With this group's experience, don't oversimplify as you know what is needed. Think of the future needs also and document but mark as in the future.

RONC

[photoptimist]

I'd like to suggest that you guys write the document that explains what you want. We all know that Pentax will probably not put this is the firmware so it would only get produced by the user community. To me we should bug Pentax to add options that we can't implement in a cross-platform set of tools. With the SDKs, we should be able to a great many things. This one seems pretty easy. Taking the load off of Pentax might make them free up more ways to work with the firmware across wifi, USB, ...

If you can get a agreement among you (ROFLOL) on what parameters are needed and how they are used but do not recommend how to code it. A coder should be able to fit it into their app in a much faster time without your help. You should document by using real data which can be processed in PhotoShop, etc. With this group's experience, don't oversimplify as you know what is needed. Think of the future needs also and document but mark as in the future.

RONC

From an SDK point of view, the minimum functionality is just one new command that moves the lens motor some number of ticks. That command can be used in conjunction with existing commands for taking the shot, pausing, and looping back to take more shots.

A more advanced new command would first tell the camera to focus on the most distant object among all the focus points as a prelude to lens-movement stacking.

Of course, the other alternative is for Pentax to implement an in-camera focus-stack interval mode analogous to the Nikon one.

[stevebrot]

We all know that Pentax will probably not put this is the firmware so it would only get produced by the user community.

Unless the published API as documented in the SDK is expanded, this is not something that is accessible even through tethered operation, much less a firmware hack.

Correction: The SDK does support something like Nikon's flow detailed in my comment above, but only for USB tethered operation. If I had a supported camera to test it with, I would write the code. Sadly, my K-3 is not supported, so I would be coding blind.


Steve

[stevebrot]

From an SDK point of view, the minimum functionality is just one new command that moves the lens motor some number of ticks. That command can be used in conjunction with existing commands for taking the shot, pausing, and looping back to take more shots.

Yep...That is exactly what Nikon does, in-camera, with the D850.


Steve

[kernos]

Focus stacking on macro would really help me. If Pentax made a flagship camera that did it I would undoubtedly buy it.

[sculptor666]

this would only work at 1:1, there's no oem extension tube that has af or aperture contacts... for macro, i'd rather have something like an automated macro rail as a grip accessory. of course i realize a company that hasn't updated their extension tubes since the 70's isn't going to all of a sudden decide to cater to me even if their macro lenses are wonderful and deserve more flexibility.

[Wheatfield]

Focus stacking on macro would really help me. If Pentax made a flagship camera that did it I would undoubtedly buy it.

As I mentioned previously, macro is about the last place focus stacking with the focus ring is useful because of how much the reproduction ration changes with focus ring adjustments in close focus.
You would be far better to look into something like a StackShot which moves the entire camera in very small increments.
StackShot - Automated Focus Stacking Macro Rail