How often do you calculate the depth of field?

It is only very basic cameras that do not have a distance metering facility in the camera. Every single-lens reflex camera, every twin-lens reflex, every rangefinder camera has the ability to determine the focus distance when using a manual focus lens with a distance scale.

With SLRs and TLRs, you simply focus on your subject in the viewfinder and read the distance from the scale on the lens. With rangefinder cameras such as most Leicas, you focus on your subject in the rangefinder and read the distance from the scale on the lens.

Yes. Calculating the DOF would involve reading the near and far DOF distances as well. Most of times that is not done, at least I do not.

Yes. Calculating the DOF would involve reading the near and far DOF distances as well. Most of times that is not done, at least I do not.

You think either of these were accurate?? Did you test them for accuracy?

DoF depends on print size, as well as other factors unrelated to the lens, and is somewhat subjective. Also, the scales on manual lenses are crude.

It's not that the cameras are unable (lack the capability or lack necessary information). It's that manufacturers choose not to implement it.

Yes, I often checked the infinity position for accuracy and in most of my lenses it was accurate to my ability to test the accuracy, which is all that really matters for a lens distance scale.

I only occasionally checked the close focus distances for accuracy and they were usually reasonably accurate as well.

Why do you think they would not be accurate?

The problem is precision, as well as accuracy.

I have a 135mm f/2 fully manual lens.

At 3m (10') at f/2, the depth-of-field is a few cm (an inch or two). Even if I lined up the focus on the lens to the 3m mark, and used a tape measure or laser rangefinder to make sure that the subject is 3.00m from the image plane, I'm not going to guarantee focus. If I stopped down to f/8, I'd probably be OK.

To assure focus, I need tools in the camera to help me, whether they are digital contrast enhancement, or an old skool split-prism focussing screen.

The Astro folk are a bit obsessive about accurate infinity focus.

These days its so easy to bracket and pick your favorite.

If you're real picky about focus, at short to moderate distances, then putting the camera on a macro rail, and racking the macro rail with the lens focus fixed, is the way to go.

Aperture or focus point bracketing?

Advanced cameras even offer in-camera focus stacking.

In-camera focus stacking (assembly) can produce pleasing results but is not for serious application. The number of images that can be stacked is small, and the result is JPEG only. Also, artifacts cannot be handled as they can be in the post (e.g., using the Helicon brush).

In-camera focus bracketing is more advanced thing. You can work with those raw shots in post.

I was thinking aperture

I got interested in that long ago when I was fixing wristwatches for sale. Back then, there was some controversy as to which was "better" - by focus or by rail?

Is there a consensus these days?

Depends on the magnification.

Terse and, no doubt, to the point - which I didn't get.

Moving the camera and lens as a unit works well at high magnifications. At lower magnifications, the high road is leaving the lens still and moving the sensor. But that requires special equipment. Moving the lens and leaving the sensor still is a decent compromise.

I can say what was going through my head.

The scenario I described is a bit of a test of the camera's autofocus / available focus aids / the user's skill.

To repeat, that scenario was photographing a static object 3m away at 135mm f/2 on an FF camera. Depending on your personal idea of depth-of-field, this scenario might imply a depth-of-field of something like 3-5cm. The field-of view in the plane of focus will be about 0.8m x 0.5m, so magnification is about 1/20.

If we'real picky about focus in this scenario, we can mount the camera in the middle of the travel of a macro rail and then focus.
We can probably confirm we're close to the focus we want by taking a picture, and checking the magnified captured image.
If we now lock the focus (assuming that's possible with a modern fly-by-wire lens) we can maybe divide our depth of field estimate by - say - 10, and use that distance as a step between half-a-dozen macro rail positions either side of our initial position on the rail. Then either focus stack, or choose whichever looks best.

I think Jim Kasson wrote some stuff about the effect of defocus on MTF.