whothafunk said:
Don Haines said:
Remember, Canon is working on DO technology to save ... cost...
HAHAHAHA. Nice troll, much fan. I would give you a proper reply, but neuro already beat me to it. Get your facts straight.
It's not a troll. outside of Canon, everywhere you see fresnel lenses used, it is to provide a cheap, easy to manufacture, low cost lens. Canon has figured out how to make them of relatively high quality. Like many new manufacturing techniques/products it is introduced at a premium price and as the ability to produce comes up to speed, one can expect price drops.
For a traditional lens, double the size and you bump up the cost by a lot more than that.... the lens blank becomes twice as wide and that means 4 times the area... That means a lot more material, and in the case of fluorite elements, a lot more time to grow the crystals... That lens of twice the diameter is also a lot thicker, and that means even more material is needed for that larger element. The grinding of the element now requires much more material removal and that takes even more time. We are probably looking at a cubic function for cost/size.
A DO element cost scales as a square function. Double the diameter and you get 4 times the material and 4 times the etching time.
Even more important are time and production. Exotic glass elements take a lot of time and you are limited in production quantities. This is obviously a factor in DO elements as it has the ability to speed up the production lines and as they say, time is money.....
With small elements, DO buys you little if not none for space savings and costs more. As you progress to larger elements you eventually hit the point where they make sense. The large element of a 600F5.6 would make sense. The unanswered question is "what is the state of the DO manufacturing process" and does it make economic sense yet? None of us know the answer.