Sonar Floating Element

[Rollin]

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The upcoming UK made Omnar Bertele FLB 50mm f/2 Sonnar addresses focus shift with a new Floating Lens Block (FLB) Technology that moves a lens block when you change the aperature. Chris Andreyo, Managing Director & Head Engineer at Skyllaney Opto-Mechanics in Scotland, has published a technical white paper, peer reviewed by "Sonnar Brian" Sweeney, on the unique FLB technology:
 https://skyllaney.com/floating-lens-block-technology/

Omnar lenses: https://omnarlenses.com/ 

Edited June 5 by Rollin

[jaapv]

23 hours ago, Rollin said:

The upcoming UK made Omnar Bertele FLB 50mm f/2 Sonnar addresses focus shift with a new Floating Lens Block (FLB) Technology that moves a lens block when you change the aperature. Chris Andreyo, Managing Director & Head Engineer at Skyllaney Opto-Mechanics in Scotland, has published a technical white paper, peer reviewed by "Sonnar Brian" Sweeney, on the unique FLB technology:
 https://skyllaney.com/floating-lens-block-technology/

Omnar lenses: https://omnarlenses.com/ 

Yes. Floating element technology to correct focus shift is a well-established technology that has been around for many years. Not that unique. Example: Summilux 35 M and Summilux 35 M FLE. Summilux 50 asph has it without advertising, etc. 

[Rollin]

2 hours ago, jaapv said:

Yes. Floating element technology to correct focus shift is a well-established technology that has been around for many years. Not that unique. Example: Summilux 35 M and Summilux 35 M FLE. Summilux 50 asph has it without advertising, etc. 

Screenshot from the linked technical write up:

 

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https://skyllaney.com/floating-lens-block-technology/ 

[jaapv]

While I accept the difference in specific application, the FLE technology in for instance the Summilux 35 was introduced to counteract focus shift by aperture changes.

[LocalHero1953]

9 minutes ago, jaapv said:

While I accept the difference in specific application, the FLE technology in for instance the Summilux 35 was introduced to counteract focus shift by aperture changes.

Not sure what you mean. The 35mm FLE doesn't move an element when you turn the aperture ring AFAIK.

[jaapv]

The Summilux 35 FLE  lens has a floating element to compensate for the aperture focus shift that the predecessor suffered from. That is in fact the only real difference between the two. I have no idea how it is activated. My only remark was that the use of a floating element for this purpose is not new. 

[LocalHero1953]

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3 hours ago, jaapv said:

The Summilux 35 FLE  lens has a floating element to compensate for the aperture focus shift that the predecessor suffered from. That is in fact the only real difference between the two. I have no idea how it is activated. My only remark was that the use of a floating element for this purpose is not new. 

No, a floating element is not new, and no one claimed that this was, but please keep digging😉!

Edited June 6 by LocalHero1953

[Michael Geschlecht]

Hello Everybody,

Hello Rollin,

Welcome to the Forum.

The 24mm f2.8 Elmarit-R was released by Leitz in 1974. At that time it was advertised as having a floating element.

I think the lenses were manufactured by Minolta in Japan & the mount was manufactued by Leitz Wetzlar. & the lenses & their mount were assembled by Leitz in Wetzlar. This was during the time period when Leitz & Minolta were co-operating in a number of areas.

Sometimes floating element lenses can produce a sharper image at the plane of focus than some conventional lens designs can.

In return for this, in certain circumstances, the depth of field of the lens with the floating element might fall off more rapidly on either side of the plane of sharpest focus, than might be the case with a lens of an equivalent focal length & aperture without a floating element.

Which means, when both are focusing on the same image plane, sometimes a lens with a floating element can have a narrower depth of field than a lens of the same focal length & aperture without a floating element.

Best Regards,

Michael.

 

Edited June 7 by Michael Geschlecht

[AZD]

I’m not an expert by any means, but it seems like the difference, whether new and innovative or not, is this:

- Floating elements have long been used to correct for focus and sharpness inaccuracies as the lens moves from infinity to close focus. The floating movement is actuated via the focus helicoids and the relative geometry between groups varies with focus setting. 

- The Omnar’s entire lens block moves forward or back without changes in geometry between individual elements or groups. This is actuated by the aperture ring rather than the focus helicoids, and is therefore independent of focus distance. By doing so it corrects for characteristic sonnar back focus when stopping down, presumably by moving the entire block forward slightly as the aperture is made smaller. The goal is to do away with the need to shim a Sonnar to perform optimally at either wide open or stopped down, but not both. Think of FLB as a variable shim. 

In any case, it’s an interesting passion project for a very specific customer base. The lens looks very nice. I can see how it will appeal to those who enjoy close focus and circular aperture blades. Also, like other Sonnars, it is quite small. 

[PCPix]

I don't know of any lens historically that has a floating element block that moves with the aperture ring -  so a really intesesting concept. It would be good to find out how accurately it corrects focus shift.

 

Edited June 8 by PCPix

[AZD]

My guess - and only a guess - is that it makes a fairly accurate focus correction. I have tinkered with shimming Industar lenses to focus correctly up close. The difference is on the order of thousands of an inch. Say, a layer of masking tape or aluminum foil tape. Such minor variations could be easily achieved with fine cut helicoids moving through a partial rotation. Some empirical or mathematical determination of the movement needed for accurate focus changes would then be translated into the particular thread pitch required, and there you’d have it.

In theory it is a very simple concept. In execution it is several layers of additional mechanical complication intended to solve a problem - achieving accurate focus without viewing through the lens - mostly inherent to rangefinder cameras. That’s probably why it’s not been done before. I would love to see one in person. 

[LocalHero1953]

It's not just on rangefinders that one would see the benefit. I will use it on film Ms, but perhaps also on the SL2-S; it would make focusing wide-open before stopping down to shoot a more reliable practice. Beyond a certain amount of stopping down the benefit may be negligible because the DoF would greatly increase.

[farnz]

3 hours ago, AZD said:

Some empirical or mathematical determination of the movement needed for accurate focus changes would then be translated into the particular thread pitch required, and there you’d have it.

Since we're talking thousandths of an inch and presuming that the helicoid would be brass with its coefficient of thermal expansion (19 x 10^-6 per °C) how do you see the thermal expansion and contraction coping with ambient temperature changes and still provide the appropriate degree of correction to control the 'focus delta'?

Pete.

[BernardC]

22 hours ago, PCPix said:

I don't know of any lens historically that has a floating element block that moves with the aperture ring -  so a really intesesting concept. It would be good to find out how accurately it corrects focus shift.

I remember reading that some Panasonic broadcast zooms were fully-floating, meaning that every lens group has its own actuator and moves independently. Typical zooms use cams, so the relationship between lens elements is fixed for a given position of the zoom and focus rings. I don't know these Panasonic lenses take aperture into account, but they certainly could.

[LocalHero1953]

19 hours ago, farnz said:

Since we're talking thousandths of an inch and presuming that the helicoid would be brass with its coefficient of thermal expansion (19 x 10^-6 per °C) how do you see the thermal expansion and contraction coping with ambient temperature changes and still provide the appropriate degree of correction to control the 'focus delta'?

Pete.

My recollection from the Zeiss ZM Sonnar 50mm f/1.5 is that for portrait shots I was swaying backwards and forwards by at least 50cm when opening up to f/1.5 from f/2 (at which mine was calibrated). That is consistent with what this review found (given that I didn't measure my 'sway').

I would expect modern lenses to be able to focus to much better than 50mm precision at close distances, so in principle this new correction mechanism shouldn't stretch technology too far.

[farnz]

51 minutes ago, LocalHero1953 said:

My recollection from the Zeiss ZM Sonnar 50mm f/1.5 is that for portrait shots I was swaying backwards and forwards by at least 50cm when opening up to f/1.5 from f/2 (at which mine was calibrated). That is consistent with what this review found (given that I didn't measure my 'sway').

I would expect modern lenses to be able to focus to much better than 50mm precision at close distances, so in principle this new correction mechanism shouldn't stretch technology too far.

Thanks, Paul, and I understand what you're saying. 

However, in this instance it is correcting for focus shift relating to change in aperture which is corrected by a block of elements that are incrementally(?) moved by the aperture ring so the tolerances must be tiny, hence my question. 

I have to wonder whether it might turn out to be one of those wonderful creations that works perfectly and reliably in the lab but has problems in the outside (real) world where it is subjected to changes in temperature, humidity, impact, etc; I sincerely hope they've been accounted for because I'd like to see it succeed rather than be assigned to the 'dustbin of false dawns'.

Pete.

[LocalHero1953]

Yes, I take your point, but would the tolerances be tighter than are currently needed for normal focusing at close range with a wide lens?
Well, we'll see! They've been talking about this lens for 5 years so I hope they've worked through the same questions.

[pgk]

FWIW I am told that 'floating element' designs in many lenses are often used to compensate for changes in astigmatism at closer focus and as a result the adjustment of the position of the floating element is linked to the focus ring. But Skyllaney are now using a shift in a part of the optics to correct for spherical aberration due to change of aperture, and as such the adjustment is linked to the aperture ring. I suppose both could be described as 'floating element' designs but this would be confusing as they are activated in different ways. So Skyllaney have opted for a differing description which makes good sense.

Tolerances sound tight but I don't know enough about machining to know whether they are exceptional or not. As ever though, precision will cost both time (especially in terms of QC checking) and thus money; consequently will increase cost. I also don't know whether there are electronically controlled systems which already exist and which use positioning control which is sensor determined. This wouldn't surprise me though for very high end applications.

As to temperature criticality and wear well time will tell. Sounds a very interesting project but of limited use for consumer camera equipment given that it seems to be fundamentally linked to mechanical (and thus mostly) rangefinder lenses. The quest for 'perfection' goes on.

[Keith (M)]

Aside from moving the aperture blades, turning the aperture ring will also simultaneously adjust the internal helicoid so as to reposition the 'lens block'.  I wonder at the effect on 'feel' (resistance to movement) of the aperture ring.

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[Rollin]

On 6/11/2025 at 9:43 AM, Keith (M) said:

Aside from moving the aperture blades, turning the aperture ring will also simultaneously adjust the internal helicoid so as to reposition the 'lens block'.  I wonder at the effect on 'feel' (resistance to movement) of the aperture ring.

I asked someone who has the version of the lens that is to be released and he said "smooth is the answer."