Fab short film Bill, very informative / interesting. Your thoughts on some aspects of photography mirror mine, although I think you are light years ahead of me in terms of your skill and creativity.

You have made me want to travel up to Northumberland, I have a couple of weeks off work in late Feb, so I might just take a few days out to go there.

Regards
David

I fully take JAK's point and I agree with him regarding the difficulty in applying fine focus settings, however, I have a slightly different point to make about Sigma lenses vs. Pentax lenses. I've owned (and still own) a fair few Sigmas, 50-500, 150-500, 50mm Macro, 105mm Macro, 70-300, 17-70 f2.8-4 HSM DC Macro and my son has the latest 17-70 f2.8-4. All of these lenses have been superbly accurate at focusing, apart from the 50-500, from which I couldn't get a sharp image with any camera body, so I suspect the lens had some sort of issue. By contrast, I've had poor focus issues with some Pentax lenses, notably the 17-70 f4, the 55-300 (focus hunting) and the 100mm macro. My experience with the Sigma lenses is that they are generally excellent and don't require much adjustment, but there are always exceptions to the rule.

Also, my experience with the K-5 body and AF focus accuracy has been poor. I used to own 2 of these bodies and both were variable at best in the focus department. I've had no such issues with the K-5iis or the K-3, both of which continue to be excellent.

Regards
David

Cool, having not gone down that route, I had assumed the glassless zoom would be on the camera, leaving the 70mm reversed on it, without any means of changing aperture.[/quote]Hi Derek

You are correct, but you don't need to change the aperture on the reversed lens, typically that lens is wide open with the aperture controlled by the butchered zoom. That's one reason why you need quality glass in the reversed lens.

Cheers
David

These are beautifully presented images Dave, the second one is sublime.

Regards
David

Hi Derek, not restrictive for a butchered zoom as you would have the aperture contacts on the glass-less zoom. Probably not a great setup though, a butchered zoom is more useful with a reversed 50mm lens or a reversed enlarger lens.

Regards
David

I'm not suggesting you should be any particular distance away from the subject, but what I am suggesting is this will make a big difference. For example, depth of field errors become less the further you are from the subject. Also, the camera / lens combination could be accurate at one distance and not at another. The only thing you can do is to adjust the fine focus for real world usage, which for a medium length zoom would be somewhere from middle distance to infinity?

It's a compromise whatever you do and if there is a fault with either the camera or lens you may never get it right. IT's been suggested above to try the lens on a different body, I think this would be a good idea as it may rule out one or the other as being the culprit.

Regards
David

Just one further thought / question on this:

When you took the images of the test chart with both lenses, were you exactly the same distance away from the central point of the test chart as you were from the edge of the door in the outside shots? If not, it is not a fair / good comparison. Your tests need to be done at exactly the same distance away from your subject. For example, it could be that the lens or camera is focusing correctly from a distance of let's say 6 feet away, but not from a distance of 12 feet away?

Regards
David

I think your issue may be that a zoom cannot be fine-focus adjusted for all focal lengths, you can only adjust it at an 'average' setting and it may well be out for other focal lengths. Also, as others have mentioned, the AF on Pentax cameras is not infallible and you can get different results on the same settings each time you focus! I found that in particular my K-5 suffered from this trait, which my K-5iis and K-3 don't seem to. It's much easier to fine-focus adjust a prime lens than a zoom.

Regards
David

I know it's not the topic of this thread, but I think your quote is not quite correct John if you include the DA*16-50 and DA*50-135. The continued failure of SDM motors in these lenses is not just a reputation on the internet it's absolute fact and they continue to fail even on the most recently manufactured or repaired lenses.

My second DA*50-135, bought from a forum member only a couple of months ago has started to display the failure symptoms now, although it was fine when I got it. My original one has already failed and will be converted to screw drive soon. There are too many reports of this for it to be an internet reputation, I think your head is stuck in the sand on this topic.

Regards
David

These are really superb and they have got me thinking that it would be good to do some frost images with my butchered zoom and reversed Nikkor enlarger lens.

5 and 6 are the ones that really hit me in the eye.

Regards
David