I disagree a little, but I know what you mean.

The only reason I mention, blades, is that you can (and do sometimes) see the defined blade outline on the bokeh. for example the hexagon. Where as having more curved blades lessen the impact on the harsh straight lines that lesser blades can give. It is not a myth. However, the impact only affects shorter lenses (up to 50mm in reality) as longer lenses counter the blade structure more and more. For instance once you get beyond 200mm, and wide F stop then the effect is non-existant, nice smooth bokeh.

As for the links, leave it with me. I might have to do them again.

I suppose Bokeh preference is to the viewer.
Personally I love the Bokeh that Leica lenses produce (just go on flickr to see). But with their curved 15 blades, what do you expect? Very creamy no harshness at all, and of course sharp as anything.....
Of course Pentax primes are not far behind, as are 3rd party lenses.
Personally the best bokeh that mine produce ar as follows:-

Sigma 105mm Macro
link
Tamron 90mm F2.5 SP Macro with 2x
link
SMC-Pentax FA 50mm F1.4
link

The Pentax 50mm produce a little harder bokeh, but still it is very nice.

So, unless you can afford £4K for a Leica M9 and a further £7K for a 50mm Noctilux F0.95, then the Pentax option does not seem so bad.....

I know what you mean, I have the Sigma 105mm Macro, which is a stunner. The only things I would want from the new lens is the WR and curved blades, with the blade structure being more important. Still, at least it is Full frame (like my Sigma) and has additional coatings.
Wish though it was like the new C***n 100mm Macro and its new 2 way image stabiliation. link

If I had the money, I would consider it, but I think the 105mm will suffice for the time being.

I love the spec - Weather resistance, curved blades, full frame compliant, but in all honesty it is pig ugly to look at. It looks like a stretched 35mm or 77mm limited (and they are beauties). I know the important thing is IQ, but they could have made it more Aesthetically pleasing. However, at least it is not as bad as the FA series with the rubber MF ring (the old FA100mm macro a case in point)
Personally I would have preferred the distance indicator further down the body, and a larger MF ring to balance the look.
Would I have one though? Well yes, WR and curved blades, who would'nt?

Thank god I am not so bad (I hope.....)

In order

Praktica MTL-5B
Pentax MZ-5n
Pentax MZ-50


However if you include digital as well

Pentax *istDS
Pentax K10D
Pentax K20D

Not too bad.



Hang on, I was given these working cameras too......

Zenit SLR
Rolleiflex F3.5
Bronica ETRS

Looks like I have the same problem too.
(I have not included the various 35mm compacts, APS, Digital compact/bridge cameras either....)

Thanks Greytop. I wonder where the 1.4x converter Pentax promised us over 12 months ago is? That might be the solution.

Thanks all, awful lot to think about.
Nice to hear that the 60-250 does have an excellent IQ, and the examples from Richard prove it. Far better than my 170-500.

In reply to Anvh, mainly Motorsport, where 500 can be too long, but if you couple with nature, 500 is a good range. Ultimately I would have two lenses, one up to 300mm for motorsport and longer for nature, where I need extra length and speed (this is where a 2x converter would not suffice).

Shame about your mates experiance of the 120-400 Mike, but I am wondering if this more to do with the 7D than the lens.....

So, time to have a good think, but I like the idea of the 60-250 with 1.4x converter (where is it Pentax!), but also the Sigma 120-400 or 100-300, again with a 1.4x converter.
It is a shame I live so far from SRS in Watford, as I could have tried them myself, not many Pentax dealers in Manchester, and certainly not with the lenses I mentioned!

Once again thanks all, this is very useful.

I am looking to replace my Sigma 170-500 with something better, but which one? Obviously a little saving up will be needed, but I am prepared to do this.

Now the shortlist is thus:-

Sigma 150-500mm
Sigma 120-400mm
Sigma 50-500mm
Pentax 60-250mm
Sigma 100-300mm

Now I can put the adv and disadv to each, so here goes

150
adv - good IQ, has SDM, slightly wider than the 170, quite cheap, good reviews.
disadv - is it better than the 170? still slow at long end, slightly soft at 500?

120
adv - good IQ, has SDM, wider than the 170, smaller, cheapest here, great reviews
disadv - not constant speed, a bit shorter at long end, not an EX

50 (Bigma)
adv - EX optics, huge zoom range, has a cult following.
disadv - not SDM, heavy, not constant F stop, expensive, soft after 450mm, expensive

60
adv - Pentax!, SDM, constant F4, weather sealing.
disadv - Expensive, short at long end, no 1.4x converter yet, heard IQ is so so.

100
adv - EX optics, constant F4, quality IQ, optimum 3xzoom.
disadv - No SDM, heavy, expensive, a bit short?

So which one? Any have their advantages and disadvantages.

Which would you choose?
In case you are interested, it needs to be both Sports and Nature, hence needs wide and long focal lengths (170 is too long and 250 too short if you know what I mean).
Ideal would be 100-400 at F4 at under a grand, but that ain't gonna happen! LOL

there are two Takumars. There is the ones that were M42 mount (the SMC Super-Takumar 135mm F2.5) which were the best Pentax or Asahi-Pentax lenses then (like the DA*/Limiteds now)
Then there is the Takumars of the mid to late eighties which were a budget range. Only manual control and coated, but not SMC coated.

However, don't let the single coating put you off. I have one of these Takumar 135mm F2.5 from the late eighties, bought for a mere £40 from a classic dealer, and it is FAB! Only manual, but nice and sharp! It is also light too (can you say that with other fast 135mm lenses?) Makes you slow down, but hey, that is part of the fun
Some people say that the CA and flare are a problem, but I have not really had a problem at all (no flare at all, and CA can be corrected in PS, but not really had it.)
Might not be in the 85FA* or Limited in quality, but for £40, how can you complain? I can't.

Makes me wonder about this. If experience at a couple of camera shops in Manchester are concerned, the K-7 is flying off the shelves. Every time they get them in, they go out of the shop. Even CaNikon users are changing systems (EOS 50D is a primary body being exchanged - wonder why? :lol
I know this is only what is happening in my neck of the woods, but even on photo shoots, you do see more Pentax bodies around the necks of people, in the past I was the only Pentaxian.
With third party companies now bringing their better optics with a K-mount, makes me think that Pentax are on the up with togs.
So, with this in mind, Pentax could re-introduce the FA* range, should they find the capacity, as interest in the system is on the increase. Plus, if Pentax did have more high grade optics, then even more togs would serious consider changing, or indeed change, to Pentax, as they know that they can get high quality glass to suit their needs, rather than looking at the others and think, "well they have more glass that I need/aspire to, so I will go with them", even if their bodies are not as good as the Pentax! (50D and 7D spring to mind........)