I believe that I have a duff 16-50 as well and am currently arranging to return it.

I have two problems with mine:

1) the SDM focusing motor is sticky. Initially when half pushing the shutter release button the focus motor refuses to move and the camera seems to go through a continuous reset cycle where the in-viewer display goes blank, followed by a click and restarts. With a little help it can be unstuck. I do this by leaving the lens cap on and half pushing the shutter release button to try and make the focus swing to minimum and back to infinity. Doing this a few times slowly un-sticks the SDM focus motor and it speeds up. Manual swinging of the focus ring makes no improvement. The focusing then seems to work fine. However if the lens is not used for a while, say 12-24 hours, it becomes very sticky again and can't be relied on. From my direction it seems as if the motor has been over "greased" and it takes a while for the grease to warm up and when not used congeals again.

2) Even when the focus motor is working the auto focus system seems to be very unreliable. It does not focus in lower lighting conditions, even outside at midday on cloudy days, and often at the long end of the zoom gives up straight away even in good lighting conditions. In this respect it is far worse than my, much cheaper, Sigma 18-50mm f2.8.


When it does choose to focus it does take very good pictures but it just can't be trusted and as, by far, the most expensive lens that I own I expect it to be much better.

Glyn

Alton Bus Rally, in this instance 2007.
K10D with Sigma 10-20, 1/180 @ F8, ISO 200 @ 19mm

I remembered that I had some instructions for an Adaptall2 lens.

It is not conclusive but it does suggest that you can't use an old Adaptall lens with an Adaptall 2 mount on most cameras. Unfortunately this part of the table does not reference Pentax cameras although the upper part, describing the availability of Adaptall and Adaptall2 mounts does.

I have scanned the page with details of the mounts so that you can see it:




I also have the instructions for an Adaptall2 mount which states:

"NOTE: Adaptall 2 mounts are designed for use only with Tamron SP and Adaptall 2 lenses. Use with any other lens will result in incorrect meter couping."

So I think my original conclusion that you can't use an old Adaptall lens on an Adaptall2 mount probably still stands.

I hope this is useful,

Glyn

All the Adaptall 2 lenses that I own have "Adaptall 2" written on them. I don't have any pre "2" lenses but have always assumed that the older Adaptall lenses were not compatible with the Adaptall 2 mounts which come in two types for Pentax, KM & KA. Pentax KA mounts go for stupid prices on Ebay.

I have found the following a very good resource when considering the purchase of an Adaptall lens:

http://www.adaptall-2.com/index.html

Glyn

This is the sort of buzzing flying thing we get around here. (Which does not say much about the neighbourhood). 600mm mirror lens, f8, 1/90s, hand-held.

This just looks really hot and fiery. It is a crocosmia in my garden shot in bright, but low, sunlight just after a rain storm earlier this evening. K10D with an old FA 28-200 @ 200mm, 1/60s, F5.6. Cropped to remove a couple of other flower heads.

I have to agree with all your comments. Taking pictures of the moon is about the only thing I have felt happy with it and even then getting a good focus takes a lot of careful adjustment.

I've had it for less than a week. I have only walked it around the garden. Hand-held it is very difficult to get a good result even with the SR on the K10. I have tried using it for macro stuff. It has a very shallow depth of focus and although some of the results were good I can get better results with a higher return of acceptable results using a traditional lens.

There have been some fantastic bird pictures in this forum using a similar lens but so far I've not managed to get any of my local birds to keep still or fly along slowly at a constant distance, long enough to focus the lens. Hopefully I might get a bit better at it. I suspect that the trick is to have something to a lure the birds to a particular spot, focus on that spot and wait for a bird to arrive. I must go and buy some bird seed.

The Sigma gives an extra 100mm over the equivalent Tamron and I assume that this will provide an advantage for moon shots but might make it slightly harder to use for other purposes. I am waiting for a fuller moon and more clear skies to give it another go.

I agree with your comments about its size and weight. It is certainly easier to lug around than my 135-400 which is my next longest lens. Its my new toy and I'll be carrying it around until the novelty wears off.

From my direction its just one of those things that I had to try. I don't think I payed too much for it and it is in excellent condition. I certainly intend to hang onto it but then I'm a hoarder, particularly where lenses are concerned.

Glyn

I think it is also worth pointing out that camera shake is a problem at these distances. I try to get round this by using the 2 second delay which does a mirror-up at the start of the sequence.

I have also been told that hanging a large weight underneath helps to dampen the tripod but I have not tried this. I think having a stonking great lens probably has a similar benefit.

As mentioned by others the camera settings have to found by experiment. I found that the display on the camera looks very bright in the dark and this caused me to under expose. I had to take the camera inside, down-load the pictures, look at them on the PC, then go back outside, make some adjustments and try again to get the best result.

Glyn

I had a go at some moon shots last night as well.

I was desperate to try out a newly acquired Sigma 600mm mirror lens.

The lens was too long to get both the moon and Venus into one shot but after a lot of tweaking with the exposure this was about the best I could do with the moon:

http://i172.photobucket.com/albums/w20/GlynM/Moon%20shots/IMGP1610-c1.jpg

The lens is fixed f8 and the camera was set to an ISO of 200 and an exposure of 1/20.

I think I'm going to have to wait till the end of the month for a near to full moon to achieve something better.

I found that the moon shifts in the sky quite fast and I was having to constantly adjust the tripod head to keep it in shot.

Glyn

I have also noticed that the KA adaptall 2 adaptors are going for stupid prices on ebay. I think I saw the same one as you going for over £60 last week. Since then I have seen one go for £26, which I missed, and another for around £45. There is one coming up in the next day which is currently running at £26.90 and will undoubtedly go higher. I therefore think if you can get one for £28 then you are onto a winner and should go for it.

Sometimes these things go cheaper when they are sold attached to a lens but you need to think if you want the lens or what you might be able to sell the lens on for without the adaptor.

Glyn