Lens quality control

Started Sep 24, 2013 | Discussions thread
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Re: Lens quality control
In reply to OpticsEngineer, Sep 26, 2013

OpticsEngineer wrote:

"Is lens design really so difficult these days? Don't you just need to pump a few reflective/refractive indexes into a MathCad model and out pops your answer? Optics is a very well established field and there are no 'mysteries' there and so I would imagine (I have never done it myself) optical design is just a case of chosing between compromises of cost/quality"

It is easy to analyze a design once you have it.   To come up with a new design is considerably more difficult.   Millions of combinations of variables.

But even then, it is somewhat easy to come up with a lens design that performs fantastic when everything is perfect.   What is difficult is to design a lens that still performs well with variations in curvatures, tilts, decenters, thicknesses and variations in index of refraction.   That process is known as tolerancing and it actually is 90% of the work in making a good lens design.  You have to know many details of your process capability, sometimes making guesses that improvements are going to there when you need them.   That is where I see Sony's move into short registration distance and small and light as being technical challenge.   And when you tolerance, you need to know costs associate with increased tolerance levels.

I don't think anyone has been complaining that E-mount lenses are bad when they are perfectly made.   There are great copies out there.  It is the consistency.

Designing something versus making a few hundred thousand is a completely different thing.  Completely different teams of people.

By the way, Mathcad would not be used by lens designer making lenses for a DSLR.  Low end software is like Zemax.  That is what I use, so real lens designers consider me an amateur.  It cost $4000 and works forever.   CODE V last time I checked was $25000 and expires yearly - requires $5000 a year to license.  It has much better optimization routines than Zemax.  Companies like Zeiss have their own lens design software that they continually are improving and in my conversations with them, I believe the Zeiss software is a step up in capability.  They have Phd mathematicians working on it all the time.  I assume companies like Nikon and Canon also use internally developed softwares but I do not actually know what they use.

It is not a mystery how to design good optics for small registration distances. Leica, Zeiss, and Kodak, Yashica, Voigtlander, Canon, Nikon, and others have all created many lenses like this since the 1930s. The challange for Sony is cost: how to make a good enough and small enough lens in China for as little money as possible. This is not the pure engineering problem you are making it out to be.

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Sony Cyber-shot DSC-RX100 III Canon EOS 70D
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