[WorksAsIntended]

I understand it to be more the interface rather than the technology inside. The KAF4 lenses, which have electronic control of aperture inside the lens {instead of the old mechanical system begun with the KA mount nearly forty years ago} will not work with older cameras, although there is a firmware update for cameras as old as the K-50.

I complelty agree. For the owner of a camera however it does not matter if it is a missing interface or firmware, as long as he does not proceed to write his own firmware.

[reh321]

I complelty agree. For the owner of a camera however it does not matter if it is a missing interface or firmware, as long as he does not proceed to write his own firmware.

It also matters in purchasing decisions. A member has hacked the K-50 firmware update to include the K-30. I have chosen not to install that on my K-30, with the result that I cannot use KAF4 lenses on my old camera body, but that doesn't matter to me since I have some even older FA lenses to use with it.

[Kunzite]

The SDM require physical power contacts (Pentax reused the old power zoom contacts, but until the K10D the DSLRs didn't had them (neither did many film SLRs).
KAF4 doesn't need any additional contact; that doesn't necessarily mean any camera would work after a firmware change.

[totsmuyco]

I still wish the KAF4 lenses can be used on the K-5 series. It's such a great series. I love the images I get from my K-5 II.

[reh321]

The SDM require physical power contacts (Pentax reused the old power zoom contacts, but until the K10D the DSLRs didn't had them (neither did many film SLRs).
KAF4 doesn't need any additional contact; that doesn't necessarily mean any camera would work after a firmware change.

I don't see the relevance of this comment since we don't know of anyone who has tried to push KASF4 updates before the K-30, which most definitely does have the contacts.

[Digitalis]

About usage of fresnel lenses: Using fresnel lenses allows for less mass and volume but you get diffraction issues at the lenses costing you optical resolution.

You are speaking of Diffractive optics? Canon and Nikon have such lenses in their lens line-ups and while you do have savings in terms of weight and mass, the losses in optical quality can be made up by simply sharpening your images more than you ordinarily would. However Diffractive optics have a disruptive effect on Bokeh


OOF Highlight Bokeh from the Canon 400mm f/4 DO IS Lens [From the digital picture.com]

Nikon have their own variant of the optical technology referred to as Phase Fresnel, which has similar effects on bokeh rendering.




OOF Highlight detail from the Nikkor AF-S 300mm f/4 PF ED VR Bokeh [Image from PhotogapyLife]


The upshot of using diffractive optics is that it eliminates chromatic aberration which is inherently problematic with long lenses and makes the optical design need fewer corrective elements than what would ordinarily be needed and therefore reduces the weight of the lens. The drawbacks are images from these lenses are softer than classic refractive lenses and the potential for bokeh artifacts to show up in highlights.

[WorksAsIntended]

Sharpening in postprocessing is no answer to building lesser sharp lenses, in this matter i can use a smartphone instead.

Those bokeh pattern you show however are caused by non plain waveforms at the aperture area, not directly by the fresnel lenses themselves. This is more often to be seen in compactly build lenses of course and funnily enough is approximated best by using fresnel diffraction equation.

Diffraction lenses suffer a different kind of chromatic abberation causing micro "rainbow pattern".

In the end you loose weight and size, change the abberation issue and loose sharpness.

[Digitalis]

Sharpening in postprocessing is no answer to building lesser sharp lenses

I agree, however when one is working with with lenses such as those with diffractive optics which reduce edge accutance compared to classic refractive optics, increased sharpening is all we can do to restore the image to what it would look like if a standard refractive lens were used.

Those bokeh pattern you show however are caused by non plain waveforms at the aperture area, not directly by the fresnel lenses themselves.

The interference wouldn't exist if the diffractive optics weren't in the optical path in the first place, so I'd say visual evidence is strongly leaning in favor of them being thought of as a causative factor.

[WorksAsIntended]

Well, you can also build a lens causing this without having diffractive optics (in fact I should have some simulation results showing this pattern on my computer, maybe I can find it when I am at home) and one having diffractive optics not suffering from this.
It is a design decission to loose length of the lens and this is achieved by using the diffractive optics.

I agree however that when looking at lenses on the market chances are both will be found in the same lenses together.

[totsmuyco]

I hope the rumors for the DFA 70-300 is true. I'm interested in this one. Well, I'm still lusting for a 55-300 PLM for travel if it can run on the k-5II. Sorry, just my wishful thinking.

[Des]

About usage of fresnel lenses: Using fresnel lenses allows for less mass and volume but you get diffraction issues at the lenses costing you optical resolution. I am not completly up to date with industrial progress against this and maybe the diffraction limits are rather low with current products, but it stays tradeoff for more comact design against a sharper image for sure.

According to the Optical Limits review (Nikkor AF-S 300mm f/4E PF VR (FX) - Review / Test Report), the Nikon 300 f4 PF has excellent centre resolution from wide open to f8, which is all most users would care about. Edges and corners are very good. CA is a bit high but not too bad. The weakness identified by OL - attributed to the fresnel element - was with flare and halos. Let's hope that lens designers can work out how to deal with this issue, because high-quality lighter weight telephoto lens would be very welcome.

[larryaustin3]

Instead of buying the Sigma 16mm f/1.4 for my Sony, I'd rather buy the equivalent Pentax lens for my K-01. I want to support my favorite brand.

[PJ1]

Instead of buying the Sigma 16mm f/1.4 for my Sony, I'd rather buy the equivalent Pentax lens for my K-01

If you mean that lens adapted for K mount - or even that or a similar optical formula licensed for a DSLR lens - that's not going to happen - ever. The Sony E mount and EOS M mount, which it is offered for, have a registration distance of 18mm. That's a long way short of the K mount 45.46mm. In theory, if there was enough distance between the rear element and the sensor it might be possible to build the lens to suit another mount. But I don't think a wide angle lens would ever be a candidate because, in my (admittedly limited) experience, wide angle lenses tend to focus fairly close to the rear element. L mount, which I think has the potential to become the industry standard for mirrorless, has a registration distance of 20mm. I don't think that any lens developed for mirrorless is ever going to be usable on K mount (except maybe reversed).

[Rondec]

Sharpening in postprocessing is no answer to building lesser sharp lenses, in this matter i can use a smartphone instead.

Those bokeh pattern you show however are caused by non plain waveforms at the aperture area, not directly by the fresnel lenses themselves. This is more often to be seen in compactly build lenses of course and funnily enough is approximated best by using fresnel diffraction equation.

Diffraction lenses suffer a different kind of chromatic abberation causing micro "rainbow pattern".

In the end you loose weight and size, change the abberation issue and loose sharpness.

I agree, however when one is working with with lenses such as those with diffractive optics which reduce edge accutance compared to classic refractive optics, increased sharpening is all we can do to restore the image to what it would look like if a standard refractive lens were used.





The interference wouldn't exist if the diffractive optics weren't in the optical path in the first place, so I'd say visual evidence is strongly leaning in favor of them being thought of as a causative factor.

Well, I just like lenses that are a little smaller in size, but if it has major drawbacks then I suppose that's that.

[monochrome]

Pentax - Wikipedia

"The company was renamed Pentax Corporation in 2002."

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