[Frogfish]

Sure I jumped in the middle, I've only been lurking through the both threads looking for nice little tidbits on the new 560. The plain fact is that black objects absorbs heat better than white objects. I suggest you look up the concept of albedo. As for that US Government study that you pointed out, please provide a link so we can take a look at it. .

It's in the thread .. as I said a little legwork (use the search function) will find it. As others are also referring to it then it's here somewhere

As for do black objects absorb heat more than white ? Well obviously they do, I really thought it wasn't worth discussing that since it's so obvious, however the question is whether this has a detrimental affect on the optical properties of lenses. It seems it does not otherwise all long lenses would be white/silver.

As for Nikon and Sigma's black lenses, have you ever considered that perhaps they use a different method of combating the heat? White makes a great way of reflecting heat. SIlver more so. Space probes and satellites take advantage of this..

That most certainly is a possibility of course, that there is a simple, and cost-effective, way to combat heat absorption in lenses and that Canon / Pentax use white/silver as another means of achieving the same goal.

As it turns out, black is better for re-radiating that absorbed heat too (the concept is called emissivity). What does this prove? That the issue of white vs. black and heat is more complicated than most people think..

White lenses may not heat up as fast, but black lenses probably lose that heat faster (once there's some shade or a good breeze).

I agree. It seems obvious, from everyday experience, but in fact is far more complicated.

Frogfish, I am only asking for proof. You have provided none as far as lenses are concerned. Proof would be a technical paper from Nikon or Canon explaining this, or some scientifically minded person performing well thought out experiments with actual lenses (and not cars). Something along those lines, not an an analogy (black vs. white cars) that may not apply because it's cars vs. lenses. It also depends on the testing methodology used and the exact circumstances.

Well we can only use what we have and certainly the black vs white car tests (even though as Falk pointed out the window glass was a greater influencing factor in the US Govt tests) seems to be the only evidence available (hardly likely that Nikon/Sigma would publish their production secrets to their competitors), bar the fact that Nikon/Sigma continue to use black lenses throughout their ranges (though may have an alternative method of heat dispersion - or have found it is not an optically disruptive factor).

EDIT: You know what, enough of this prattling on the merits of black vs. white, let's get back to how much this dang lens will cost, and when it'll be available for purchase...

We are all awaiting that announcement with bated breath but in the meantime .......

To those who don't find this interesting (I'm learning a lot from this debate, it's obviously not of interest to all) .... well you can always skip past these posts !

[Greyser]

There is a simple not scientific truth. I live in Los Angeles. I often hike at 90-100F (+35oC and higher) ambient temperature and under direct harsh sunlight. So, I assume that my camera+lens system is equally heated up to the same extent. However, when I touch my black DA*60-250/4 extended to the full 250mm plus hood attached it is noticeably, sometimes burning hot. At the same time my silver (hate this color!) FA*300/4.5 appears much cooler under the same conditions.
Second of all. I remember a few complains here or in DPR/Pentax forum about loosing AF micro-adjustment accuracy after lens exposure to substantial heat (left in a hot car, all day exposure to the sunlight, etc.).
So, I think color matters; especially for the large lenses. The bigger longer lens is prone to more thermal elongation, which may not be reversible due to some warpage and deformations in the system. Remember, there are many different materials, e.g., glass, lubes, metals, plastics with very different properties and different coefficients of thermal expansions are tighten together, creating a whole system.
Personally aesthetically I prefer black lenses. I like the look of DA*60-250 or Sigma 100-300. But, I would go with no doubts for the white 560/5.6, if the white color helps to create more stable and optically consistent system.
Just my two non-scientific cents.

[zapp]

What would you expect from this lens?
AF, size, ED glass, close up focus, performance

How does the lens fit in the Pentax porfolio?
There is currently no 2.8/300 in the Pentax portfolio, but a 5.6/560 would compete against a more versatile combo like the Sigma 2.8/300 + 2x TC or a Sigma 4.5/500.
Carrying a 4/300 and a 5.6/560 or a Sigma with TC - what would you prefer?

The 300 mm Sigma combo with TC costs approximately $3500. Add a 1.4x TC as well to make it $3750. The weight is 2.4 kg for the lens only.

The Pentax lens should be superior in quality to the Sigma with dedicated 2x converter. DA* ED glass could help. SDM autofocus would be a feature not available from Sigma (for Pentax).
The weight should not exceed the weight of the Sigma combo. Less than 2.5 kg - the 4.5/500 mm from Sigma weighs 3 kg.
Pricewise $3000-4000 would be fair. The Sigma 500 is $5000, but offers f/4.5. Anything more expensive would not fit in the portfolio as the second most expensive lens would be to far away feature and price wise.

I think price and size are key factors here. A 2.8/300 from Penatx would costs $5000+ (check out Canon/Nikon pricing). There is no significant market among Pentax customer base for such an investment - used lenses, 3rd party options are too appealing. Make an appealing long lens and keep the price low at around $3000. Give the lens a nice form factor to separate it enough from 3rd party glass. That's your lens. Think about it, it's a smart move by Pentax.

...and make sure to provide a real good 1.4x TC. The performance of the Sigma with 2x and 1.4x TC should be beaten by a 560 mm plus a 1.4 TC from Pentax.

IQ wise long lenses (not tele designs) like the Leica series (400/560/800) will provide really good image quality in the center with a visible drop towards the edges. An image format smaler than full 35 mm would be of advantage here - APS-C is good.
The Pentax A 5.6/600 is listed at cambridge.com for $5500 - not sure if they really have one - the new design should cut cost to a much lower price tag.


Pentax 5.6/600 A was 3.3 kg while the 2.8/300 A was 3 kg -> the 600 is a 300 with 2x converter build in.
The FA 2.8/300 was just 2.5 kg, so a derived 5.6/600 (actually almnost 10% less focal length) could weigh in at less than 3 kg! The new lens design could make this a lens with less than 2kg weight (compare Leica/Novoflex designs). And the Leica had a huge focusing mechanisms build in that can be replaced with a more lightweight AF engine. Don't make the lens too light, but anything less than 3 kg is great for walking around. The 4/600 FA was close to 7kg!

[nicolas1970i]

Good summary Zapp, additionnally as I mentioned above the huge advantage a DA(*)560/5.6 would have over the Sigma 300/2.8 + 2x TC combo is that SR would be effective (the body will recognize the focal lenght as 560mm, instead of 300mm) - I've had to turn it off when using the Sigma with TC as it seemed the results were poorer with SR on. That would make the DA(*) up to 3 stops "faster".

That said I'm a little uncomfortable with the idea of carrying a physically very long lens - for a start it'd have to fit into my bag with a body attached, and I'm not really sure how it'd handle compared to the Sigma + TC, which is fairly short in the end.

PS: are you sure the A*600/5.6 is a 300/2.8 + 2 TC? What would be the point of that? Looking at the lens' desings on B.Dimitrov's website this is not the impression I'm getting...

[falconeye]

Pentax 5.6/600 A was 3.3 kg while the 2.8/300 A was 3 kg -> the 600 is a 300 with 2x converter build in. The FA 2.8/300 was just 2.5 kg, so a derived ...

Please, take notice of a simple fact:

A tele lens weight (and cost) is basically determined by it's physical front lens diameter, which simply is Focallength/Fstop. With 560mm/5.6 it is 100mm.

Beyond this absolutely trivial fact, there is nothing you can deduce in the way you did.

E.g., a 300/2.8 and 600/5.6 have nothing in common, except that F/N is 107mm for both.

[Frogfish]

Pricewise $3000-4000 would be fair. The Sigma 500 is $5000, but offers f/4.5. Anything more expensive would not fit in the portfolio as the second most expensive lens would be to far away feature and price wise.

Falk's estimate's put it in the US$2,000 - 2,500 range, and I think that is the right price bracket. Above that is not the right pricing for the mass market and would put it in the same bracket as more exotic and expensive lenses - i.e. for only the lucky few.

Give the lens a nice form factor to separate it enough from 3rd party glass.

This may be a problem (as Nicolas says above), because a long telescope style prime is not going to be easily transported and used in the field.

Pentax 5.6/600 A was 3.3 kg while the 2.8/300 A was 3 kg -> the 600 is a 300 with 2x converter build in.
The FA 2.8/300 was just 2.5 kg, so a derived 5.6/600 (actually almost 10% less focal length) could weigh in at less than 3 kg

I certainly hope so !

[Pål Jensen]

A tele lens weight (and cost) is basically determined by it's physical front lens diameter, which simply is Focallength/Fstop. With 560mm/5.6 it is 100mm.

...and the physical lenght of the lens. The lens barrels weight something too and they are almost always metal in such a lens...

[Pål Jensen]

Falk's estimate's put it in the US$2,000 - 2,500 range, and I think that is the right price bracket. Above that is not the right pricing for the mass market and would put it in the same bracket as more exotic and expensive lenses - i.e. for only the lucky few.

I'll be very surprised (but pleasantly so) if it is sold that cheaply. A conventional 560/5.6 lens from Pentax would probably have costed between $6000-$7000......

[Frogfish]

I'll be very surprised (but pleasantly so) if it is sold that cheaply. A conventional 560/5.6 lens from Pentax would probably have costed between $6000-$7000......

The 400/5.6 from Canon is US$1,500 and Sigma's 500/4.5 around US$4,500 - there is no way a 560/5.6 conventional lens, which is far smaller and easier to produce than a f4/f4.5, would cost anywhere near $6,000-$7,000 thank goodness !

[Col]

The 400/5.6 from Canon is US$1,500 and Sigma's 500/4.5 around US$4,500 - there is no way a 560/5.6 conventional lens, which is far smaller and easier to produce than a f4/f4.5, would cost anywhere near $6,000-$7,000 thank goodness !

Has anyone told Sony?

[Frogfish]

Has anyone told Sony?

Sony's 500mm is a max f4 not f5.6 .... that's a huge difference in price and weight. And of course there's then Sony's insane pricing. Better refer for Canon/Nikon for accurate pricing !

[Luin Gor]

If I may interrupt this conversation, the only question that matters to me is :

Do you know when the specs will be announced ?

[zapp]

Just two more thougts. The long telescopic lens from Leica, the telyt 560 mm is 530 mm long - basically as long as the focal length. Such a lens is hard to place on your carry on luggage. Typical 600 mm lenses are somewhere in the 450 mm length range and 300 mm lenses in the 250 mm length range. A 2.8/300 plus a 2x TC will be easier to carry - the Sigma 4.5/500 mm is 350 mm long, still fine for carry on.

[nicolas1970i]

That's right. I just searched the size restrictions for carry-on luggage (this is always the way I take my photo gear with me when I travel - can't afford the risk of it getting lost or damaged, given the "compensation" offered) and the maximum measurement I see is 24", or 60cm, which would not be enough for a 500mm+ long lens attached to a body and fitted into a bag. That would be a problem for me.

[jpzk]

If I may interrupt this conversation, the only question that matters to me is :

Do you know when the specs will be announced ?

Agreed !

"Do you know when the specs will be announced ?" as you mention!

Until then: pure speculation.

JP