My dream lens has finally come. I have been waiting for Canon to make a 400mm f/4 lens for years, and now it's coming. Not only does it have IS technology but it will also be the first to offer Canon's revolutionary breakthrough lens element called multi-layer difractive optical element. Check out the link below for more information and feel free to post your thoughts. I think this lens will fill the gap in many nature photographer's lineup. While the 300 f/2.8 is nice, you have to use a 2x tc to get out to 600. With a 400 f/4 you use a 1.4x tc to get to 560 and still maintain an f/5.6 aperture and image quality; with a 2x tc you get out to 800mm and f/8 (AF w/ EOS 3 and 1v)and lose some image quality but with the help of IS it should still be pretty good. I'm looking forward to this lens!

http://www.canon.com/do-info/index.html

-- Bill Meyer (meyerwj@louisville.stortek.com), September 06, 2000

Answers

The concept is not quite a revolutionary breakthrough. It has been in general use on lighthousees and marine lanterns since 19th century. Typical reading magnifiers also employ the same principle, as do a number of camcorders and inductrial-optical devices. But there were probably impressive technical hurdles that Canon overcame to make it good enough for camera lenses.

Now how long will it be before someone starts to use concentric hyperboloid elements for cameras? That kind of element, which uses minute grazing reflections, would in theory allows lenses absolutely without chromatic abberation to be made using only a single element.

-- Chuck Fan (chaohui@msn.com), September 06, 2000.

Progress is good. We'll have to wait and see if the final product meets the marketing hype.

Wonder why they chose to make it an 400 f4 lens? Is it to fill a gap in the lineup, or aren't DO elements "good enough" for a 400 f2.8? I also have to wonder if a TC may work differently with a DO lens.

That said, this could be the biggest thing since IF and multicoating.

-- Geoffrey S. Kane (grendel@pgh.nauticom.net), September 07, 2000.

Chuck - it's not a Fresnel (lighthouse) lens. It's a diffractive optic. They are significantly different!

-- Bob Atkins (bobatkins@hotmail.com), September 07, 2000.

The pictures on the Canon web page certainly made it LOOK like a fancy Fresnel lens. I was under the impression that truly diffractive optics were only useful for working with light at a single wavelength, and not for full color work. Can you possibly point us to some resources that explain more fully what diffractive lenses are, and how they can be useful with color?

-- John Morris (jtmorris@slb.com), September 09, 2000.

I think the Canon diagrams are oversimplifications. Diffractive optics do have significant chromatic "abberations", but maybe that's the point. The other, convential, optics have aberrations too and the two cancel out?

I don't know any good references, but a web search on diffractive optics should dig something out.

-- Bob Atkins (bobatkins@hotmail.com), September 09, 2000.

Not being a "techhie", I,m curious, after reading the ifo on this lens, as to how it might perform against Canon,s L glass, or is this DO element designed as a replacement for the L glass? The 300, 400, and the 100-400 L lenses are hard to beat in terms of sharpness even with the 1.4x in front.

-- Jeff Hallett (franjeff@alltel.net), September 10, 2000.

Geoffrey, you bring up a very good point. Will the DO lens be usable with the teleconverters? It would seem that they ought to be usable with this lens as according to the Canon website, the refractive optical element cancels out the reverse wavelength of the defractive element, so the light shouldn't have any problems passing through a tc as well, but I'm not an expert in optical elements.

I enjoy learning how optics work and understanding their design, but my expertise is in using the optics to take pictures, which is why we're all here for the most part - we all want to take good pictures.

-- Bill Meyer (meyerwj@louisville.stortek.com), September 11, 2000.

Sorry, Bob. I stand corrected. The light houses and marine laterns uses a simple fresnel lens, not diffraction grading. I should have known from the wide pitch between the rings that it wasn't diffraction based.

-- Chuck Fan (chaohui@msn.com), September 13, 2000.

I've been trying to find out how much this lens will cost (roughly)? Canon won't give me any information, they claim it's still in development(BS). My guess is they were trying to fill a gap in their line-up with a faster lens because 2.8 is to expensive and 5.6 is too slow. This should be a great selling lens.

-- Rob Olling (mamie@meld.com), September 19, 2000.

I expected that Canon would release a 400 f/4 mainly because with their latest cameras, f/4 is the smallest aperture that would still allow the full use of 2X teleconverter. So it makes sense for them to release one of that aperture.

I don't think it's BS that lens still in development. Canon wants to announce something new and exciting for Pros during Photokina. All of its other releases are plain vanilla lenses mainly inteneded for the budget crowd. So it's perfectly reasonable for it to push up the announcement date of this lens, which has a great deal of hype potential, to coincide with Photokina, before the lens is ready to ship. Nikon choose to announced its own hype-worthy VR zoom to coincide with PMA show, 9 month (and counting) before it is ready to ship.

-- Chuck Fan (chaohui@msn.com), September 20, 2000.

It seems so long ago that I last posted something here.

Do a search on holographically corrected optical elements (telescopes to confocal microscopes) on the web. It seems to be a rapidly growing field in optics with great promise especially when coupled with dynamic correction. I'm quite impressed that Canon is already so close to releasing a lens based on diffractive optics. One of my last postings here, that was deleted, linked up to a proposed idea for the next space telescope that will be based on a gas inflated reflecting surface that will be holographically corrected in space. Unfortunately, I can't seem to find that link right now.

-- Carlos Co (co@che.udel.edu), January 10, 2001.

Has anybody heard anything about a price yet??

If it is going to sell, one assumes it will be cheaper than the 300mm f/2.8. It seems pointless if it is the same price as the 300mm f/2.8 (and 1.4x multiplier), the only advantage would be its size and a major disadvantage would be a lack of flexibility compared to the 300 f/2.8 and 1.4x.

Andy

-- Andy Thompson (prsast@bath.ac.uk), April 10, 2001.

Hi, I read the incredible! price of 15.000 german marks - there is nothing more to say!

-- Dr. Tassilo Seeger (webmaster@drtseeger.de), April 24, 2001.

Follow-up question.....Has anyone heard anything about when this lens technology will be available in a commercial product? Will it be 400mm or a zoom??

thanks

-- Bill Fleming (safaribill@yahoo.com), May 12, 2001.

The diffractive element causes the spectrum to appear the OTHER WAY AROUND to a normal refractive element. Thus, when combined with refractive elements, the spectrum is not just minimised, but with careful design, it is ELIMINATED.

The DO is NOT L series, but should be TC compatible.

There is a rumoured 200-600 F4 DO zoom, in addition to this lens.

A 400 F4 seems sensible to me. Since the DO element means expensive materials like fluorite and UD are not required, the lens won't be much more expensive than the 400 F5.6, but with the obvious one stop advantage. As you can see from the page given above, it is small and light compared to a normal lens equivalent.

-- Isaac Sibson (Isibson@hotmail.com), August 08, 2001.

Another design goal of DO lenses is shorter & lighter, as well as less expensive. All this by reducing the amount of glass necessary to get a sharp picture. Has anyone heard about susceptiblity to flare, etc.?

-- Hung James Wasson (HJWasson@aol.com), August 14, 2001.

I have heard that there is a significant flare problem with the lens when pointed toward bright lights. With light behind you, the lens is incredibly sharp. The flare correction may take quite a while yet, which is why Canon has not put out more information about this lens.

Warren Jacobi E:mail wjacobi@dcmdi.dcma.mil

Warren, Thank you for your e-mail. I also clipped & pasted it to the 400mm f/4 DO IS thread, so that it could be shared with everybody. What you said makes perfect sense to me, with all of those added planes & angles to factor in. I would love to see test photos taken with a DO lens in various lighting conditions.

-- Hung James Wasson (HJWasson@aol.com), August 17, 2001.