Onion Ring Bokeh ball 50mm Lux ASPH?

[georg]

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In the pressing method different areas of the lens element cool at different rates causing the glass to block the light rays at different rates causing the rings.

Controlling the temperature gradient is a big issue with this process but usually causes problems with image performance/adjustment from my experience.

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[pgk]

Controlling the temperature gradient is a big issue with this process but usually causes problems with image performance/adjustment from my experience.

 

So is there significant variability in samples made using this process.? Is QC a big issue?

[georg]

Of course, making (pressed or ground) aspherical lens elements and implementing/adjusting them into an optical system is more complex then just using simple ground spherical lens elements. Various things could go wrong and finding out whats actually is wrong with an aspherical lens element is much more tricky. Do I know of huge sample variation between pressed aspherics? Yes I do - but it doesn't directly relate to surface defects causing "onion rings debated here, but it's not unlikely, IMHO.

[mmradman]

Onion rings are well known anomaly and it was discused here in the past.

I may have posted this link when OR were discussed on Summilux 50mm SL lens, Panasonic is apparently working on the solution and thanks to partnership with Leica benefits may be already implemented in lenses designed post 2014.

 

http://www.imaging-resource.com/news/2014/05/02/the-end-of-onion-ring-bokeh-panasonic-beats-the-curse-of-aspheric-lenses

[georg]

Very nice article to understand some basics. But keep in mind that this a marketing article authorized by Panasonic. Handpolishing precision turned tools is nothing new and pressing aspherics is not the only way to go. But it might be possible that the SL lenses contain Panasonic lens elements.

[pgk]

Had a chat with a lens designing friend today who confirms much of what has been said here. In spite of all this technology he suggests that lens element costs (even aspherics of expensive glass types) are probably only a relatively small part of the cost of the lens as individual elements made by the pressed aspheric method are usually made in significant quantity in order to be economic, and so will not be terribly expensive individually. QC/wear may be an issue though.

[adan]

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"...significant quantity in order to be economic..." - and "Leica" - are mutually exclusive concepts.

 

Leica probably makes and sells on the order of 4500 50 Summilux ASPHs a year, whereas Canon likely makes 50000 24-70 f/2.8 ASPHs a year (and Apple may make or order 1000000 or more ASPHs for the iPhone lens, per year).

 

Unless Leica wants to be up to their eyebrows in stored ASPH elements (a 10-year supply), they make theirs in insignificant quantities. But - it is still cheaper than hand-grinding, where I think Leica produced about 1500 35mm "Asphericals" over a couple of years.

 

That's not some fanboy "Ooo, ain't Leica unique and bespoke!" thinking - it's just a tough reality for a niche company for whom "economies of scale" are something that happens to other people.

[pgk]

I would guess that several thousand elements is probably a reasonable number to produce by such a method. As has been pointed out here that pressing elements wears the die so perhaps such 'low' numbers are better economically as QC is less of an issue - but I'm guessing. You do have to realise that some lens elements are produced in vast numbers for numerous applications (just search online) but then again I am told that some are produced in very low numbers indeed (ground as almost 'one offs' and even so, not always mega bucks). So for a bespoke, specific glass design, several thousand may well in the 'economically viable' area and still not be a huge amount per element (in fact it can't be can it or the Summilux would be vastly more expensive than its eye watering cost now)>

[mmradman]

Number and complexity of optical elements in the camera lens may not be a big factor in the price we pay.

 

For example Macro Elmar M is only four spherical elements yet it retails for similar money to Summilux 50mm ASPH (8 elements in 5 groups) - £2470 vs £2870 (prices Red Dot Camera).

[georg]

Productions costs vary greatly, a simple spherical element with a regular diameter may cost 10€, a similiar looking lens element with a different glass material or tighter tolerances can cost several hundred € to manufacture - despite looking just the same! It's the same with aspherical lens elements.

Economy of scale of course also works for lens element production, but it has it's limits. Ordering 100 pressed aspherics is very expensive (the tool alone costs about as much as a decent car), ordering 10000 is cheap and 100000 might be a little bit cheaper but not that much.

Pressed aspherics are reasonable for Leica M-lenses, when the geometry, precision requirements and glass type make this "cheapish" production method feasible at all.