[ElJamoquio]

From what I heard, this lens doesn't telescope at a, it's just big.

What's the thumbscrew nearest the front element do?

[JinDesu]

ohgodiwantone.

I'd definitely bring this on a safari or something. Time to go work out!

[DeadJohn]

I marked the 2 spots that caused speculation about it being collapsible. The circled knob could theoretically be loosened to allow the front of the body to slide back. When in the collapsed position, the knob would be retightened. The circled smudge on the body *might* be a mark from the knob (or it could just be rough handling shipping to the show, or a flawed paint job on an early prototype).

It's an interesting concept but difficult to manufacture with tight tolerances needed in order to maintain optical alignment.

[tjk911]

Now to find a job as a reporter that will pay me enough for me to afford a beast like this. And then insures it for me. Instead of making me shoot with a P&S.

[oneeyedhawk]

Being of astronomical design maybe it has an 8.4 fl objective, a focusing lens group near the camera end, and a 2/3 focal reducer combined with a field flattener lens set before the camera mount. The field flattener will match the objective to the sensor and with the focal reducer you will have a faster 5.6 fl setup. This focal reducer flatener combination is used in astro scopes to get shorter length scopes and a flat field to the edge. Of course no auto-focusing lens groups are used in astro scopes, instead a quality focusers are used before the eyepiece.
Hank

[ElJamoquio]

I marked the 2 spots that caused speculation about it being collapsible. The circled knob could theoretically be loosened to allow the front of the body to slide back. When in the collapsed position, the knob would be retightened. The circled smudge on the body *might* be a mark from the knob (or it could just be rough handling shipping to the show, or a flawed paint job on an early prototype).

It's an interesting concept but difficult to manufacture with tight tolerances needed in order to maintain optical alignment.

It wouldn't need any tighter tolerances than the actual mount of the lens to the camera. Since the diameter is at least twice as much, you could probably get away with a much looser fit.

[Ex Finn.]

It would be really cool if it was a dual fl lens, 560-5.6 and 400-4.0.

[Giklab]

I think that's the hood. If you look at the above pic you can see the front ring (around the front element). If you look in line with the reflections on the left of the lens there is a white dot (3rd from the left). That dot is on the filter ring. The distance from the opening to that dot seems similar to that between the circled items.

[Adam]

Why the 2nd?

Limiter

[Paul Ewins]

Like Mistral75 suggests, it is really looking like this is a long focus design, not a telephoto. I guess that makes sense if it is based on a telescope. While that means it is physically long it might mean fewer elements and perhaps a lower weight and especially cost than if it was a telephoto design.

[Ex Finn.]

Long focus design = minimal aberrations without having to spend a boat load of money.

[goubejp]

Long focus design = minimal aberrations without having to spend a boat load of money.

I estimate the length around 45 cm (assuming that the front element is 100 mm). This is consistent with the design of a A*600, the lens seems longer because of the smaller front element. Anyway the use of ED glass for the front element will maintain the price point rather high

[Ex Finn.]

My 900mm f 7.5 telescope (120mm objective) with FPL-53 glass is a "long" design and fairly cheap, coming in at sub $2k. So there is hope for this Pentax to be somewhat affordable.

[aguest]

If the pictures in the lens database (SMC Pentax-DA 560mm F5.6 Reviews - DA Prime Lenses - Pentax Lens Reviews & Lens Database) are not a mockup I think it's safe to say that the DA 560 will be able to telescope.

In the first picture we see the DA 560 with retracted lens hood and extended front section. In the second picture we see it with retracted lens hood and collapsed front section. In both pictures the lens hood is never extended unlike in the pictures posted before in this thread. You can clearly see that the second picture shows a more compacted DA 560 compared to those where just the lens hood is retracted. Also it's easy to spot that the thumb screw which secures the front section is pulled back to the lens colar.

[Asahiflex]

Please be advised that those are photoshopped photos; made by one of our fellow members on this forum. IMHO, the final word is not out yet wrt it to be retractable/telescoping (although it does seem like that way).