What, exactly, does it mean when Canon "patents" a lens?

[NiceShotSteve]

For instance, CR reported that Canon has patented a 35/2 IS lens. Does this mean that other manufacturers cannot produce a 35/2 IS (or VC or VR or ...)? Or does it mean there's a thingamajig inside the lens that has been patented? Or does it mean the optical formula has been patented? Or ... ? As an aside, I seem to recall that many years ago Konica/Minolta had a patent on a 24-105 lens, and that Canon couldn't produce theirs until it received "permission". Any thoughts from someone who knows these things?

[neuroanatomist]

It can mean any or all of them, depending on the claims of the patent.  Often, it's an optical formula; but it could be a new coating applied to an existing optical formula, etc.  What it means is that other manufacturers can infringe upon those claims, so yes, in some cases it means they can't make a lens like that, or to do so would be more difficult (more design work to get around the patent, etc.).

[Mt Spokane Photography]

Usually, patents of a lens are for the optical design or formula.  There are a almost unlimited number of optical formulas, but only a relative few that are practical to build and give high quality.  Before computers, designers would lay out a lens design drawn to scale and trace the rays of light as they passed thru each element.  As you can imagine, it was very difficult, and expensive to search for a better design.

Now computers do the ray tracing, and even so, its difficult, and expensive.  So, when a practical formula is found, its patented.  This prevents someone else from using the formula that you spent so much money finding.

Patents can, and are sold or licensed, so even if a company doesn't use the patent, it had value.

Take that nikon 14-24mm zoom.  That optical formula is patented, so anyone caught copying it would be quickly shut down by Nikon's attorneys.  It could very well take years of searching optical formulas to find something equal or better, its not something a engineer just sits down and sketches overnight.  There are undoubtedly ones that cost a fortune to manufacture, but something practical and good is rarely found.

[phemark]

...
Take that nikon 14-24mm zoom.  That optical formula is patented, so anyone caught copying it would be quickly shut down by Nikon's attorneys...

What if someone would create 14-25mm, is it infringing? What about 14-24.5mm? 14-24.1mm? Where is the limit? (well i guess even smallest shift in the mm would probably require different optical formula...)


Also, a bit different question: is there a rule of some sorts that is required for lens manufacturing that requires certain lenght? (for instance there are a few lenses that start at 15,17,18,24mm, but not at 16 or 21mm, why is that?

[nightbreath]

Also, a bit different question: is there a rule of some sorts that is required for lens manufacturing that requires certain lenght? (for instance there are a few lenses that start at 15,17,18,24mm, but not at 16 or 21mm, why is that?

You've forgotten about 16-35 I don't think engineers are bound to specific focal lengths, they are just looking at how current task from research team can be resolved. After new formula appears I think it may be even aimed on 15.42mm to 35.74mm range, but it gets a nice looking length of 16-35mm in description to be better selling.

[Mt Spokane Photography]

...
Take that nikon 14-24mm zoom.  That optical formula is patented, so anyone caught copying it would be quickly shut down by Nikon's attorneys...

What if someone would create 14-25mm, is it infringing? What about 14-24.5mm? 14-24.1mm? Where is the limit? (well i guess even smallest shift in the mm would probably require different optical formula...)


Also, a bit different question: is there a rule of some sorts that is required for lens manufacturing that requires certain lenght? (for instance there are a few lenses that start at 15,17,18,24mm, but not at 16 or 21mm, why is that?

Patents usually give several examples of focal lengths and cover the optical formula, which is independent of the focal length.  They are carefully worded to indicate that they cover not only camera lenses, but projection lenses, etc as well.  However, many of the formulas only work well for a limited range of focal lengths.

Many of the older Canon  EF prime lenses are said to share the same optical formula, even with the FD lenses.