I have an AF240 (not directly helpful I know but bear with me)

I thought since it has no PTTL and no A setting, it would be close to useless on a K10D, but after trying it the other day I am very pleasantly surprised. M mode is a lot easier to handle than I expected.

thanks for the comprehensive description of your pp, that's given me some ideas to work with

looking forward to seeing more of your pics in future.

wow that's sweet!

gorgeous colour in the nebula, really well done! I'm looking forward to having another go at Orion now that I have my equitorial mount all sorted out. Recently I've been shooting for the pleiades, but not quite got what I'm looking for yet.

Can you explain a little more about your pp workflow for Astro shots? I use Hugin to line the shots up, then registax to do final alignment and stacking but after that I get a little lost. Any tips you can offer would be very useful indeed.

I studied digital image processing as part of my degree, the maths involved in switching between colour spaces is shockingly complicated, and a certain amount of rounding errors will always turn up.

Treat it like saving to JPG, once is absolutely fine, a few times you can get away with if the quality is high, but it should be kept to a minimum where possible.

really? awesome! if they pass through all 7 data contacts plus the two power contacts, then SDM should work.

no TC I am aware of passes through the power contacts for the SDM/PZ motors, so yes you'd loose SDM completely. Should still be able to focus using the screw drive (given an AF teleconverter of course), though obviously it wont be as fast or as quiet.

Other than that the DA*'s should be ideal for TCs, very high quality, very fast lenses.

My 2p regarding teleconverters:

With one or two exceptions (the Pentax SMC-F 70-210 being one), consumer F4.5-5.6 zooms should not be used with them.

This is because the combination is too slow to be reasonably used hand held even wide open, and most authorities agree that a teleconverted lens should be stopped down at least a stop or two in order to get decent quality. You end up with a working aperture of at least F16 and camera shake ensues.


With decent fast primes (and presumably F2.8 zooms, I've never owned one) a teleconverter becomes very useful indeed. My Tamron 90SP makes a lovely 180mm F5 when combined with my Tamron 2x SP Flat Field converter.

As a general rule, if you can keep wide open aperture wider than F5.6 then things will probably be ok. Combinations having a max aperture narrower than F5.6 are at best hard to use.

Thank you all very much for your advice. Suffice to say, the next time I have £300 I shall be getting myself a Sigma 10-20.
Not today however.

While perusing the SRS website, I came upon a Tamron 300mm F2.8 for £350. At that price I could not resist and it is at this very moment mounted on my K10D and pointing out the window at a bird feeder.

I've taken a couple of test shots so far and all I can say is lenses this sharp should have a warning on them, I think I cut myself. At F2.8 it is slightly better than my 80-320 at F5.6. By F5.6 it is, to quote Red Dwarf, "sharper than a page of Oscar Wilde witticisms which have been rolled up into a point, dipped in lemon juice and jabbed into someones eye".

Now, if only I can aquire a 112mm lens cap......

That's more or less what I was thinking, in my case most of the other lenses are likely to be "jack of all trades, master of none". Ultimately I probably will replace the 18-55 with a 16-45 or Sig 18-50 F2.8, but for the moment the 18-55 does what I ask it to so long as I keep it in moderate apertures and mid range focal lengths.

I'm leaning quite heavily towards the 10-20 at the moment. I'd love to follow the "Riley Rule" and get the DA 12-24, but it's just more money than I am likely to have available for several years (£300 is a stretch). The DA10-17 would undoubtably be fun on occasions, but I can't see me getting £300 of use out of a fisheye.

Help! I think I'm about to spend rather a lot of money.

Through a sequence of happy events I have on the order of £300 burning a hole in my back pocket.

Although up to now most of my photography has been in the telephoto or macro ranges, I have recently developed an interest in wide angle. The 18-55 is as wide as my kit goes at the moment, and it doesn't quite cut the mustard, being neither particularly wide nor particularly good at 18mm. My wide angle fun and games have centered around using the perspective to make a close subject seem larger than life, rather than panoramic landscapes which I tend to prefer to do with stitched shots at longer focal lengths.

I am considering a number of options:

The Sigma 10-20:

Not a direct replacement for my 18-55, but would take over the roll of wide angle lens and support the kit zoom where it is weakest (I have a 50mm prime to deal with the other end if needed!)

Sigma 18-50 F2.8 DC Macro

No wider than the 18-55, but faster and I would hope better quality. Would come in handy at fencing matches where I am currently limited to my 35, 50, 90 and 135mm fast primes.


Sigma 17-70 F2.8-4

A nice walk around focal length, faster than the 18-55 and longer/wider too. Is it better though?


Pentax 16-45 F4

Wider than the 18-55, better optics and a stop faster at the long end. Given the better quality, probably effectively more like 2 stops faster than the 18-55 since using it wide open is not a total fantasy. Not as wide as the 10-20 though.



Also nagging at the back of my mind as ever is the fact that I'm not totally happy with my 80-320's long end performance, but I have my doubts that the Sigma or Tamron 70-300 4.5-5.6 lenses would actually be better and there's just no way I'm going to get £750 together for a Sig 100-300 F4 any time soon, so I think I'm going to concentrate on the end of the range I can actually afford to improve for now.