K10D or.......

unless I was dreaming, Samsung have already announced re-branded versions of the DA* lenses. It would be a bit pointless the GX-10 having SDM capability otherwise. Admittedly I cannot currently find any reference to this announcement on Google, so perhaps I've been daydreaming again.

Wasn't implying that they didn't have any coatings, just that it would appear to be unlikely that it's SMC. But that doesn't mean it's not...

Dan

It could be that, possibly due to copyright or contractual restrictions, the Samsung/Schneider branded lenses are indeed SMC coated, but they are not allowed to say so. I agree that their lenses must have some kind of coating, and if it is their own, why not say so . . . somewhere . . . anywhere?

Edit:

If we had somone that knows how lenses are made, and when the coating is applied, that may give us a clue. Is the coating applied to the blanks before they are cut/ground to size, or is it the last process applied to the glass/plastic before the lens is assembled?

That's true... Hadn't thought of it that way.

Dan

Techno geeks, try this site . . . . it's way beyond my comprehension.

I don't know the exact ins and outs of lens manufacture, but my physics degree covered the theory of coatings. As far as I can see they have to be the last thing you do to the lens element before it's assembled, since the thickness of the film is absolutely crucial to its effectiveness. If you applied the coating to a blank and then polished, the coating would end up thinner in some places than others.

Unfortunately I still don't think this answers the question, it seems to me that it will depend on

1. whether or not the Samsung/Pentax lenses actually roll of their own separate production lines

2. if it's the same line, how hard is it to switch coatings. It may actually be more expensive for Pentax to insist that Samsung use their own coatings than to simply do as Manesty suggested and prevent them from shouting about having SMC.

Can you substantiate this in any (non-technical) way?

To me, a coating is simply an additional layer, multi-coating being more than one additional layer, that would actually attenuate the lens's ability to pass light, not improve it. Hence flare control ! ! !

Most lenses having a minimal coating actually block (as much as they can) light in the infra-red and UV bands. That's not improving light transmittance.

I think what we need is someone who has both versions of the same lens to perform a visual comparison and real life tests. Matt, get your credit card out

When any material meets another, we have a surface that can reflect light. So a glass/air interface will mean that a certain percentage of light will get reflected from the surface. The amount of light reflected depends on the materials.

The coatings will have different characteristics with regard to the amount of light reflected off their surface, and again at their boundary with the glass. Careful choice of materials means that very little light is reflected.

I think that's it!

Dan

What about Chris at SRS? What better way to encourage us to buy proper Pentax glass, if he shows us that the Samsung stuff is inferior.

Dan

Not entirely sure that Chris sells Samsung - perhaps we should send him down the street to Currys???

it does seem counter intuitive when you first hear it doesn't it?

It's somewhat hard to explain without going into physics mode, but I'll do my best.

As you know, every time light hits a glass-air surface, a certain amount of it is reflected back. Uncoated glass in air will reflect approximately 4% (at this point I may have got my maths wrong earlier, I'm not totally sure if it's 4% per surface or 4% per element (2 surfaces), I assumed 4% per element). Total light transmission is therefore 96% to the power of the number of elements in the lens, 0.96^10 = 0.66, 66%

Coated glass takes advantage of the wave nature of light to reduce this. The amount of light reflected at a surface is controlled by the difference in refractive index between the two media (glass and air or coating). By picking your coating material carefully, and having a coating exactly 1/4 wavelength thick, you can arrange for the light reflected from the second surface to be exactly out of phase with the light reflected from the first surface. These two reflections then cancel out. Since energy is always conserved, and nothing is now being reflected, all the light has to be transmitted through the system.

In practice there are various reasons why it can't be done with just one coating, there isn't usually a material of exactly the right refractive index, and the coating would need to be a different thickness to be effective for different colours. By stacking several coatings, Pentax SMC is able to get the transmission rate up to 99.8% (again not sure if thats per surface or per element, I have assumed the latter) which gives the same 10 element lens coated with Pentax SMC a total transmission ratio of 98%.

Incidentally multi-coating is the main reason we are able to use simple F stops with a high degree of accuracy rather than having to compensate for the number of elements in a lens. Modern zooms would be impossible, or at least impractical, without it.

yup, Dan has it right, and without my physics mumbo jumbo

Peter, I don't mind you getting your credit card out and sending the Samsung lens to me to check out
Matt

Mongoose & Dan,

from what you have both said, in varying degrees of techno-speak which, surprisingly, I do understand (kind of), I deduce that there is no way that Samsung/Schneider lenses lack any form of coating. So why don't they say so? I think this perhaps lends weight to my argument that their lenses are SMC coated, but they are not allowed to say.