Coating on Canon EF lenses

[paulroth]

In the excellent blog 'The Online Photographer' Mike Johnston posted the following:

'Many legacy 35mm primes are not quite adequate for several reasonsﾗone of which is

that digital lenses need to be coated differently. Digital sensors are much more reflective

than film, so lenses for digital need to be coated against light impinging from the back as

well as from the front, not just from the front.'

I was wondering if the Canon prime lenses have a coating on the backmost element,

specifically the EF 1,8 28 mm which I was thinking of buying.

[yakim_peled1]

IIRC, Canon has never stated on special coatings. BTW, I have several lenses including the aforementioned 28/1.8 USM on my 1D. Never noticed any more problems than on my previous film bodies.

 

Happy shooting,

Yakim.

[PuppyDigs]

Sounds like internet BS. I've seen a hoe Canon lotta rear elements (!) and every single one was

coated. Having coatings on elements, interior flocking, glare blocking masks & hoods

improve image quality of all lenses, not just "digital."

 

My EF 50 2.5 CM is among the sharpest and contrasty optics I've ever used, and it's 15 years

old. Beats the living tar outta a "digital zoom" like the EF 18-55.

[lester_wareham]

My memory is Canon have stated (or reviewers claim) that newer lenses like the 17-40 have a rear coating, presumably that means older lenses do not. I am not sure how big an issue this really is, I have not noticed a problem with any of my kit most of which must be older lenses like the 100mm macro, 200/2.8.

[robin_sibson1]

Every lens I have used since I bought my Canon Pellix in 1965 has had coating on the rear face of the rear element. The point is that the more reflective surface of a digital sensor places extra demands on the control of unwanted light compared to film, and different coatings that would be over-specified for film may be desirable. What is probably much more important is to design the rear elements of the lens so that they do not have the effect of beaming stray light back at the sensor and creating a hot-spot; a few otherwise excellent film-era Canon lenses are thought to do this.

[steve_dunn2]

<p>Canon has indeed <a href="http://www.canon.com/camera-museum/tech/report/200308/report.html#t9" target="_blank">stated that some of their lenses have lens shapes and coatings optimized for digital photography</a>.</p>

[kevin conville]

From the Canon site:

 

"Optimized for digital SLRs: special coatings to minimize reflections and flare EF-S lens -

exclusively for EOS 20D, Digital Rebel XT and Digital rebel (as of March 2005)"

[PuppyDigs]

"My memory is Canon have stated (or reviewers claim) that newer lenses like the 17-40 have

a rear coating, presumably that means older lenses do not. "

 

Forget about reviewers. Sheesh, just look at Canon lens rear element for yourself and you can

see the anti-reflective coating.

[bobatkins]

All the surfaces on all the elements of all Canon EOS lenses are multicoated as far as I know. A possible exception might be internal fluorite elements. I'm not sure about coating technology for fluorite. Maybe they can multicoat it OK. I don't know.

 

You'd have to go back 20 or 30 years to find a lens that didn't have multicoating on all surfaces.

 

So called "digital" lenses may have improved coatings, but that's a different issue. Coatings technology improves all the time anyway.

 

Digital lenses DO NOT need to be coated differently. They just need to have efficient anti-reflection coatings on all surfaces, as should all lenses intended for use with film. Since digital is more susceptible to back reflections, some lenses do have had redesigned coatings to better supress reflections, but "film" lenses had AR coatings too.

 

How much of all this makes a real difference and how much is marketing strategy is anyone's guess. If you can do something and sell as lens a "digitally optimized", it's a marketing plus these days.

[desmond_kidman]

Lens manufacturers have a number of coatings at their disposal. Not all elements are equally coated, with differences on both the number and type of coatings. Various factors, including location of element and the overall color balance of the lens, which is adjusted by using different coatings, determine the decision for coating of each element. For some manufacturers cost is one of the important factors, for others much less so. This is one area where a little knowlege + speculation = many wrong conclusions. One thing I know is that I've never seen a modern high quality manufacturer of lenses that I've owned (Nikon, Canon, Zeiss, Mamiya, Schneider, Rodenstock)totally omit coating on the rear element.

[desmond_kidman]

There is so much marketing hype in this area of "digitally optimized lenses" along with some real information from some of the more straightforward manufacturers. In fact, some of the secondary manufacturers (Not Canon, Nikon, or any others I listed in the above post) have allowed their marketing departments to use some bogus explanations that actually stretch (polite term) the physics of lens design, and reviewers have parroted the words. (Have you noted a couple of Shutterbug reviewers who write as if they were extensions of the marketing departments of these lens suppliers?)

 

The fact is that reflection control and stray light supression is important in all lenses, but with the reflective sensors it is more important in some regards with digital. Further, the increased enlargement sizes possible with digital have pushed lenses further, and one element (no pun) if increased lens performance is reflection/stray light control. Although I'm not a Zeiss zealot, they seem to have been the ones to be most vocal about both coatings and stray light. Just look into a Hasselblad CFi lens (this series has improved light handling) and try to see the outer diameter of the elements or inside of the barrel. These areas are the closest to a "black hole" of any lens I've seen.

 

I'm hoping that the future will bring efforts from all of the manufacturers to supply higher quality lenses as sensors more and more push the envelope.