[simons-photography]

Well I thought I'd take the 2.5 £ gamble on a car boot sale and picked up a 2X teleconverter, its an older one so one of the lens information contacts is not there and theres no autofocus drive available so it makes thing manual focus for that I'd prefer the old split screen but thats another matter.

the results I get with it are from terrible to "oh well not that bad for a bit of just off the car boot sale"

its a SFE AUTO TELECONVERTER 2X (PKA) JAPAN if that explains anything to anyone who hopefully in turn can explain to me just how futile my efforts are at using it. if anything it makes my camera into a small telescope (with a 300 mm lens giving a total equivalent forval length of 900 mm) just for looking through and making a reasonable record shot that I could probably get from the same image upscaled taken without it. of course it does mean I have the lens bayonet which I can turn over to a very mechanically minded friend who could use it as the basis of a telescope adapter which would be much cheaper than the 70 £ I'm being asked for the same item

Why not post a couple of shots and describe the conditions. You may just have been trying the wrong type of shot.

[Eaglerapids]

Well, I have the Pentax A 2X-S and it's pretty good except I have to be very careful using it with my DA* 300/4. The only way I can get a decent pic is if I use a tripod AND use mirror lockup.....and there still is a bit of IQ loss. We're talking some serious magnifications here and because of the two stop loss, slower shutter speeds. I believe I need to upgrade my tripod and head to more effectively use it, also.
I just got the Tamron AF 1.4X and took it out today and it's awesome. Much easier to work with and great IQ. But I'm still using it on the tripod.
But, you know, I couldn't imagine shooting a 600-900mm lens without a tripod anyway!

[simons-photography]

I think the main issue is that I have to manually focus and thats not too easy on a 900 mm and of course depth of feild is minimal and I have to have as large an aperture as i dare. I tried mirror lockup and it was no help, infact the only decent shots are of the moon, I think maybe this is best served for making a telescope adapter that would otherwise cost 75 £ and perhaps look for a better teleconverter, or just get better and longer lenses. I see pentax teleconverters that cost as much as a very good quality lens, might as well just get the longer lens...

[mtngal]

I had an old Pentax 2X TC (K-Mount) that had been purchased by my father. I tried it on a couple of lenses, and managed only one shot that I kept - all others were lousy. After a little "surgery" with a hammer and screwdriver, it made a fine extension tube.

[simons-photography]

hm thats an idea what exactly does an extension tube do ? do I remember correctly that it alows one to focust closer than would otherwise be possible ? I would do with that for a bit before i make it into a telescope adapter

[mtngal]

Yes - an extension tube does change the minimum focusing distance. I've used mine with a couple of my manual lenses, and on occasion with the 77 ltd, turning it into a manual lens (but a really sharp one!) for macro photography. I've been recently experimenting with using it on my Viv 105mm macro lens to get larger than 1:1 (that's fun but frustrating since it's hard to hand-hold and I still don't understand how to operate my flash very well).

[simons-photography]

well i need to get closer without reducing depth of feild like i would by zooming in more, I am taking pictures of shells and fossils for my dad