[dakight]

Only 3? I'm up to 22...in 5 different lens mounts...

I suspect that you've been at it far longer than I and on top of that I only have 1 system; the Pentax in K-mount. I a past life I had a couple of bodies with the M42 screw mount system but when I switched to K-mount I gifted the entire system to my sister in law. For many years I only had a single zoom lens on a film body. The system languished in the top of a closet until my interest was rekindled last fall. However, having said all that, I doubt that I will see the need for another 50 unless it is part of a package with other components I do need. I have no interest in pursuing another mount system and being semi-retired and on a limited budget I am forced to be somewhat judicious in my acquisitions.

[boriscleto]

I suspect that you've been at it far longer than I and on top of that I only have 1 system; the Pentax in K-mount. I a past life I had a couple of bodies with the M42 screw mount system but when I switched to K-mount I gifted the entire system to my sister in law. For many years I only had a single zoom lens on a film body. The system languished in the top of a closet until my interest was rekindled last fall. However, having said all that, I doubt that I will see the need for another 50 unless it is part of a package with other components I do need. I have no interest in pursuing another mount system and being semi-retired and on a limited budget I am forced to be somewhat judicious in my acquisitions.

No one has a more limited budget than me When you are buying old film bodies on ShopGoodwill.com for a lens that is included, you tend to end up with a 50 as well...

[stevebrot]

...We (PentaxForums) are currently writing an in-depth comparison article between the DA50/1.8 and the M50/1.7 and two other 50mm lenses...

Well then, you beat me to it! I have been planning on a formal test of my DA 50/1.8 vs. the M 50/1.7 including some with film, but have been too lazy.


Steve

[dakight]

No one has a more limited budget than me When you are buying old film bodies on ShopGoodwill.com for a lens that is included, you tend to end up with a 50 as well...

Shopgoodwill.com.. I wish you hadn't told me about that... my wife wishes you hadn't told me about that. *sigh*

[ChristianRock]

It's been said many times that the DA 50 1.8 has the same design as the 50 1.7 lenses but if you look closely it's not exactly true. The two cemented elements are different. I have been reading up on how the shape of the joint can mean a sharp lens with harsher bokeh when the joint is perfectly straight, to butter smooth bokeh when the joint is curved. The DA 50 is slightly curved so it is a bit more expensive to make than the straight joint design. So the difference in bokeh is not only down to the rounded blades. That is also why it's slightly less sharp wide open.

[clackers]

I"ve got the DA50, an old SMC f1.4 and the FA50 f2.8 Macro.

Only the FoV are the same!

[fuent104]

Do you shoot film, or may you in the future? The F series lens will have more compatibility with film cameras, due to the aperture ring. That is why I chose it over the DA 50.

[mgvh]

From other reports on this forum, the DA 50 works fine as a full frame lens. It just won't work so well on older film bodies since it has no aperture ring, so you have to shoot wide open.

[skierd]

Yup, the DA50 worked great on my ZX-7 yesterday. I used both the F and the DA on my K-30 and on the ZX-7 this weekend, once I get the film back I'll decide and sell one or the other.


Side note, the ZX-7 and a DA40 limited makes a great lightweight almost pocket-sized SLR!

[stevebrot]

Both lens use the same optical formula (6 elements in 5 groups). So results should be pretty much the same.

It's been said many times that the DA 50 1.8 has the same design as the 50 1.7 lenses but if you look closely it's not exactly true.

Yes, both (like almost all Japanese fast 50s) have a planar heritage and the lens diagrams are similar, but not identical.

Pentax-M 50/1.7 (From B. Dimitrov's site)



Pentax-DA 50/1.8 (From Pentax Forums)



The relative diameter, thickness and curvature of the various elements differ significantly. I would say at least as much as between Pentax and Nikon


Steve

[ChristianRock]

Yup, that front element is quite different as well.

So it's a new 50mm design. Not the same as the 50 1.7 lenses that came before. I think we can put that myth to rest

[Na Horuk]

I wouldn't put much trust in those diagrams. I don't think they are accurate technical drawings, but just marketing brochure pictures.
Of course, it is possible the design evolved over the decades. That is fine. But its still the same lineage

[ChristianRock]

I would put trust in the shapes and the joints, otherwise why would they create an optical design picture of the lens?

[skierd]

Marketing would be my guess. Drawings without dimensions are just pretty pictures

[stevebrot]

I wouldn't put much trust in those diagrams. I don't think they are accurate technical drawings, but just marketing brochure pictures.
Of course, it is possible the design evolved over the decades. That is fine. But its still the same lineage

Marketing would be my guess. Drawings without dimensions are just pretty pictures

It is hard to say except that publication of the lens diagrams used to be the rule and it was easy to see how the product offerings differed. The diagrams were also provided in the press kits with intent to assist the technically-inclined members of the photo press with thebasis to do valid in-depth reviews of the product. Yes, back in the old days the level of technical expertise of reviewers was usually quite high.

The diagram at top was, IIRC, originally published in the Pentax-M technical brochure in the late 1970s. I don't know the source of the one for the DA 50 except that there are other identical copies on the Web, all of which assign it to the DA 50/1.8. Based on visual inspection of at least the front element of my M 50/1.7 vs my DA 50/1.8, I believe at least that aspect is accurate.

As for "shared lineage"...I would suggest again that the DA 50/1.8 is a cousin once or twice removed from the M, A, F, FA lenses rather than direct-line descendent. Ditto for the K 55/1.8. What they share is a specific adaptation to the SLR of the Zeiss planar design from the late 1800's. Almost all of the f/2 and faster normal lenses out of Japan in the last 50 years have been close variations on the theme.

Diagrams for the last 50 years or so courtesy of the Wikipedia...





To be blunt, they all look the same. Does that mean that there is shared lineage between the DA 50/1.8 and the AF Nikkor 50/1.8D. Absolutely. The relationship goes way back and the glue that binds is the behavior of light and the performance expectations of the class.

AF Nikkor 50/1.8D (courtesy Nikon, USA)




Look familiar? Probably a Pentax copy, eh?


Steve