Telephoto Lens Range Limiter - why only a close range limiter?

[garymak]

This question is open to anyone with a good, logical opinion or better, knowledge of the inner workings of Canon's corporate mind (such that it might be...)

Question: Telephoto Lens Range Limiter - why is there only a close distance limiter and not a long distance limiter???

On most of the zoom lenses I have (and EF or RF doesn't matter) there is a "range limiter" switch on the lens to speed up the autofocus mechanism for acquisition of targets far away.  The switch allows the AF to "skip past" objects within a close range (- for example, 3m in the case of the RD 100-500mm L, or 12m in the case of the 600mm ƒ11 -) supposedly to make for faster focusing and acquisition of the target and not be "distracted" by objects in the foreground.  Reasonable concept.

However, in my experience using these (and other) lenses, the acquisition of the target is often WITHIN these ranges and the inability to limit the AF from trying to find something between here and infinity and back when the subject is in close range inhibits the ability for faster focusing and acquisition of the target.  Often, for moving targets and/or small targets, the opportunity is lost because the AF can't, to use a phrase, find the end of its nose on its own face with both hands... AF, regardless of settings for "animals" regardless of the various "tracking sensitivity" modes, tends to grab the biggest things it can find first.  Those are usually large background objects, not smaller foreground objects.  It's also not very good at fast-moving targets, again, regardless of any of the "tracking sensitivity" settings.

Therefore, a paired limiter, say, of LESS THAN OR EQUAL TO whatever the long distance limiter is would seem to be a logical - and necessary - pairing and extremely practical .  Add the usual "off" switch to give you the full AF range, and you've got quite a useful set of tools.

As it is, the thinking seems to be that "the only thing that you'd ever want to shoot is far away anyway."

In shooting birds, for example, the inability to limit the AF range to the foreground to acquire the target that you know is going to appear quickly in the foreground results in lots of blurred shots of the subject with fine images of the neighbors' houses, and trees and telephone poles...

So, unless I'm missing something, I'd be curious if anyone has an explanation as to why there isn't a long-distance limiter on these lenses...

[Peter]

My EF 300/2.8L IS USM has 2.5-6.4 m as a choice.

[garymak]

Interesting.  I've never used (was aware of) a lens with a long-range limiter.  Then it begs the question "What is Canon's logic behind which lenses have one and which don't."  Seems arbitrary and inconsistent (which, IMHO, is Canon's logic often...🤷‍♂️🙄)

[Peter]

And EF800 has 6-20 m.

[Tronhard]

I would hazard that since most people shoot a long lens for the reach, they decided to make it less complicated to build and operate - in that respect I have come across several instances of people who have inadvertently, or intentionally and forgotten to take off the short range limiter.   I use only zooms and I have only come across long range limiters on fixed focal length lenses so far.

[Waddizzle]

It depends on the lens.  I believe my old Sigma 150-600mm C had three fhree ranges:  Full, 3-10m, and 10m to Infinity.  These workout to be full range, short range, and long range.

[ebiggs1]

" I believe my old Sigma 150-600mm C had three fhree ranges: "

And I think you can customize the focus limiter distance using the dock.

[garymak]

"customize the focus limiter distance using the dock."

??

What "dock"??🤷‍♂️

[kvbarkley]

Some Sigma lenses have a dock that lets you set things on the lens directly:

[p4pictures]

Most lenses have have more steps for the focus system at closer distances than for longer ones. This is logical if you think that the difference between 30 feet and 32 feet is not a lot, but the difference between 12 inches and 13 inches is significant and would have more focus increments. 

If you assume that each focus increment takes the same time to process, then avoiding the lots of steps at the closer distances makes the lens respond faster over a longer working range. Some lenses are commonly used for specific sports, and in this case the necessary working range is known in advance, and this accounts for lenses with mid-range focal limits.