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Yes, useless. You asked for it, you got it. "Photo Physics". Beats me whyever you even asked for it ... but you did :-)

As also mentioned, the usual pragmatic "infinity focus" (for typical apertures) is just a few hundred FLs away. That much is actually useful.

WDCash Loc: Milford, Delaware, USA

Wow.

WDCash Loc: Milford, Delaware, USA

That is usefull, thanks. It adds weight to the x200 idea suggestion

dpullum Loc: Tampa Florida

WDCash asked a physics question, what constitutes infinity? Mathematician would say 1/0, Priest would have an angelic answer, Astrophysicist would say James Web Telescope will show us. Photographer would look at an old lens and it would be marked. WD's question and the talk about "Tap- in console" confused me... the photo technical world streaks by me at "infinite" speed, leaving me as Einstein would say ... in the dark because of its faster than light speed.

I am a for fun photographer, tho sophisticated in acquiring knowledge because of education and my years of science in industry. I shoot using manual adjustments as opposed to every thing automated... same applies to my preference for real women vs Japanese "fully functional female robots!!"

When I saw the topic "A question for the Photo Physicists" it peaked my interest. Then "Tap to Focus" What the heck is that??? Mr Google gave me info and it was explained regarding Cellphones:
https://www.dpreview.com/articles/0095681477/photo-tip-tap-focus

Panasonic has a touch screen to focus:
https://www.panasonic.com/uk/consumer/cameras-camcorders/lumix-expert-advice-learn/lumix-expert-advice/using-your-lumix-camera-touch-features-part-1.html

Also Post Focus which takes 30 frames/second so you can select and combine!
https://www.photoreview.com.au/stories/general/how-the-panasonic-post-focus-function-works/

I wondered if automation become complicated vs old fashion focus using the rule of thumb 1/3 2/3. Cambridge discusses this: "The one thirds/two thirds is just a general rule of thumb for estimating. If you use a Depth of field calculator you will see that the ratios actually change quite dramatically." Humph there goes my thumb.
https://www.cambridgeincolour.com/forums/thread38034.htm

Tragic, point focus setting, wedding photo, Bride and Groom dancing, shot them and found infinity was trees across the lake several miles away in clear focus and the couple out of focus. The camera focused between them not on them!!! Old manual focus would have done better with a number of 20' as a setting. That defined infinity for that 200mm lens in a tragic way.

Thank you WD for getting me to have an early morning education adventure.

DirtFarmer Loc: Escaped from the NYC area, back to MA

For a lens, infinity is an approximation. It is the distance beyond which you don't have to change the focus to get a sharp image.

It is an approximation because for an object far away the focal spot is never just a point, it is a small area (lenses are never perfect). When the area becomes small relative to the sensor elements, it is deemed to be "in focus". There is not a single lens setting that will achieve that focus, but there will be a range of settings.

So 'infinity' will depend not only on the lens, but on the sensor.

DebAnn Loc: Toronto

Cripes - I'd have to send mine in to Topaz and have them do it!

Strodav Loc: Houston, Tx

Yes, I set the camera to manual focus and set the focus ring so the center of the infinity symbol lines up with the little white line on the 150-600mm f/5-6.3 G2. In Live View mode you can zoom in on the LCD screen to see what is in focus. That's the spot in the trees that I declared as infinity. It took a bit of playing around to find a good spot where AF would lock. Concentrating on those branches, I took some shots in manual focus Live View and AF Live View, then AF-S, single point AF through the viewfinder, all wide open aperture, went back to the computer and compared them. When the LV shot is the same as the viewfinder AF shot, it's calibrated and it's the best the lens can do.

I read some articles that said the infinity symbol is pretty precise and lenses are designed to focus past infinity for calibration purposes. In other words, the focus ring doesn't stop at infinity, but can be turned a little further. In any case, it works. I have calibrated several Tamron lenses using this technique, although the point in the tree line gets closer for shorter focal lengths. That's a fov and camera sensor resolution thing.

walkurie Loc: East Stroudsburg, PA

Sent mine to Tamron along with my 70-200 G2 and the D500 for calibration. Should be back next week.

WDCash Loc: Milford, Delaware, USA

Larry.
The reply from me you responded to was not a reply to you.

WDCash Loc: Milford, Delaware, USA

Thank you. This is usefull. Which seems uncommon. Anyway when th r light improves a bit qIll give it a shot. I have selected some "targets" at 600' and 1200' both of which have it r ms nearby that should be usefull it determining if I need to add or subtract.

Strodav Loc: Houston, Tx

See my earlier FWIW reply to this post on sending camera and lens to Tamron for calibration. Let us know if you have any better luck than I did.

larryepage Loc: North Texas area

Thank you for the clarification. Sorry to over react.

There are a couple of important points to be made based on those physical principles. And they interact with each other, sometimes in conflict.

The first is that while one can verify where infinity focus falls on a focusing ring at any of several distances, in general greater distances provide better onformation than shorter distances.

The second is that many (probably most) modern lenses have a really tight "pitch" in the area of infinity...a tiny movement of the ficus ring corresponds to a huge difference in focus distance. Most of my lenses jump from 10 feet to infinity in an extremely short distance. This makes it extremely difficult to focus precisely at distances greater than 15 feet or so. A couple of my lenses also have noticeable slack between the focus ring and the focus position of the lens.

None of this really matters when using Auto Focus but all of it makes life difficult when trying to focus manually or when trying to read object distance from the numbers on the focus ring.

It's not that it's a bad design for an AF lens...just inconvenient when we try to do some of these more specialized things.

imagemeister Loc: mid east Florida

Will you be auto-focusing a subject @ "infinity" ??

I just did a simple calibration - 500mm @ about 40 feet - that is the focal length and distance I want to be "perfect" and dialed in the number compensation on my body to make it so (Sony A99)
.

SuperflyTNT Loc: Manassas VA

I’m looking forward to trying that out on my OM-1. The E-M1X doesn’t have it. Gotta love those Olympus features nobody else has. Although right now I’m pretty peeved at them. They cut the E-M1X price to $1300. That’s what I was gonna ask for mine.

SuperflyTNT Loc: Manassas VA

I don’t think Topaz will do that, but they’ll try to sharpen your out of focus photos after the fact. 😜🤪