Varifocal photographic lenses - Benefits for the user?

[ic-racer]

A slightly related question—it seems like a varifocal lens couldn’t have a focus scale without some way to move the scale when focusing, or am I wrong there? Has anyone made a varifocal lens with a focus scale?

You see on the Hexanon in post #7 has three focus scales. Each color-coded to the color of the focal length on the zoom ring.

However meanwhile I got a 1981 sample and I learned of another one. Both made by Kino Precision at about the same time.

Didn't your example have a focus scale similar to the Hexanon?

 

[AgX]

I got the Kiron 28-80 and it is a weirdo lens, scalewise. As between 28 and 50mm FL by focusing to nearby the universal operating ring moves outwards the same time as in zooming. The distance curves in that range are that scarce that at first sight at the scale one gets the impression that focusing implies zooming too... Looking through the finder though shows that it operates normally...

 

[ic-racer]

This one? The dot on the focus ring will need to follow the curve line to stay in focus as you zoom (except infinity, of course).

 

[AgX]

Yes, but you better say than do so...
The curved focusing track makes sense with theses curves, however when you start at 28mm and infinity there are no curves visible yet, and what comes is scarce and the 26cm limit is wrong/lacking.
In any case I was irritated, what never happened before on this subject.


(By the way, the front lens peak is just behind the filter thread. The lens needs a stub shade (have to make one) or an added pane or a cap.)

 

[peoplemerge]

So a few years ago when I was getting on a kick with other Canon 5d2 cinematographers, I did a deep dive into the subject of trying to collect parfocal zooms. As has been mentioned, cinematographers want to be able to zoom while shooting, maintaining the focal point constant, so a varifocal zoom is effectively useless. The cheapskates among us wanted to use still camera lenses for this purpose, which introduced a whole new set of headaches I won't get into.

What may interest you in what I've gathered is that in the early days prior to autofocus, parfocal designs seem to have been fairly common among the incumbent camera and lens manufacturers. This predates me as a photographer by some decades so please keep me honest here, but I understand that what photographers wanted to do when they had to critically focus was to zoom all the way in, nail the focus, then zoom back out to compose as they saw fit. I think camera manufacturers designed their zooms with this workflow in mind. Leica Vario-Elmar-R lenses are one specific example, which has had a lot of attention as Leica R is one of the mounts that easily adapted to Canon EOS used by this 5D crew. I once had a Tokina close focusing 35-105/3.5 manual lens in M42 tested as parfocal enough for 1080p video. So the data fits the theory. You can google for parfocal lenses for your system if you must have one, like this one for Pentax https://www.pentaxforums.com/forums...cussion/201887-list-parfocal-zoom-lenses.html . I gathered many if not all of the Canon FL/FD pro zooms were parfocal as well (my FD 35-105/3.5 copy is), with the FD 50-300/4.5L being parfocal and particularly sought after, with street prices around $1000.

Most Vivitar series 1 zoom lenses were a well publicized counterexample: they made public claims on how much sharper (possibly lighter?) their varifocal lens designs were, leading to some early confusion when they were introduced from new users on their first few rolls to discover they had made mistakes on critical focusing.

Much later when autofocus came about, there was no longer any need for the parfocal optical design since photographers generally relied on autofocus, so the tradeoffs mentioned by others on this thread no longer made sense. There still were some holdout zooms for reasons I can only speculate. I can confirm in my tests that the non-IS Canon 70-200/2.8L I bought in the late 90s seems to be sufficiently parfocal for my needs when mounted on the various Canon digital cameras. Perhaps with this lens, it was a desirable feature for sports photographers who wanted to be able to work quickly, or was it a continuation of an FD design?
Lensrentals wrote about the subject in 2011, as they deal with only new lenses. https://www.lensrentals.com/blog/2011/02/photo-lenses-for-video/4 and later sort of contradict themselves later by saying there are no parfocal zooms any more https://www.lensrentals.com/blog/2016/03/mythbusting-parfocal-photo-zooms/

Again, perhaps someone who was avidly in the 35mm stills scene in the manual focus era can speak up if this rings true.

 

[Oren Grad]

What may interest you in what I've gathered is that in the early days prior to autofocus, parfocal designs seem to have been fairly common among the incumbent camera and lens manufacturers. This predates me as a photographer by some decades so please keep me honest here, but I understand that what photographers wanted to do when they had to critically focus was to zoom all the way in, nail the focus, then zoom back out to compose as they saw fit.

Yes, back in the '70s and '80s this was widely promoted as best practice for using zooms. This also relates to the debate about two-ring vs one-ring zooms, as it was easier to do this and not mess up your carefully-achieved focus when the zoom ring was separate from the focus ring.

In those days, before 35-70mm and later 28-to-something zooms displaced 50mm primes as the standard kit lenses, the most popular zoom type was the 80-200mm - or, a bit later, also 70-210mm - telephoto zoom. But these telezooms usually combined focus and zoom in a single control ring, making zoom-out-to-focus harder to do.

 

[wiltw]

My impression is that in the years since autofocus became the norm for mass-market cameras, a substantial proportion of lenses sold as "zooms" have in fact been, strictly speaking, varifocals. So far from going away, this category has if anything grown substantially. But hardly anybody pays much attention to the distinction any more, because it no longer has much practical significance. It's assumed that most users under most circumstances will use AF linked to the shutter release, so that focus will be automatically adjusted just before exposure after the lens has been zoomed to the desired focal length, making the distinction moot.

^^^ It used to be (back in the days of film and less care about cost to manufacture) that more zoom lenses were constant focus...focus would not change if you zoomed in/out. And in terms of best method of focus accuracy,zoom all the way in, nail the focus, then zoom and zoom back out to frame and compose as desired. Now, with AF making refocus so convenient and with more attention to cost of manufacture, a higher percentage of zoom lenses omit the cost-increasing constant focus design. The only 'benefit' to the user of varifocal design is merely to the pocketbook.

 

[AgX]

Most Vivitar series 1 zoom lenses were a well publicized counterexample: they made public claims on how much sharper (possibly lighter?) their varifocal lens designs were, leading to some early confusion when they were introduced from new users on their first few rolls to discover they had made mistakes on critical focusing.

I got a listing of all Vivitar Series 1 lenses and only 2 models are varifocal: 28-90, 35-85mm
The plain series 28-85 is so too.

 

[Sirius Glass]

The hard to get Hasselblad Varifocal Extension Tube is a great match for the 135mm lens. The two being more useful that fixed length extension tubes.