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Hi Paul 
I downloaded these and had a good look. I agree the difference is very subtle... although the most obvious (as you'd expect) is between the f3.5 and f22 versions.
According to your EXIF data, you have the 18-200 set to a wide 22mm for this test. There are a number of factors playing hardball against a blurred background here.
First is focal length. Wide-angle shots are unlikely to give you a blurred background unless you're focused really close, like in the region of half a metre. If you tried the lens set to 80mm, or better 200mm you'd see the difference straight away and it would work at reasonable subject distance. The closer the better, though, for maximum effect. It's a fairly complex explanation, best understood by trying it out!
Second is the size of the sub-APS format sensor, which by its nature gives you more depth of field than a full-frame chip. Third is the lens itself; the optics in a super-zoom like the 18-200 are very complex and geared towards combatting distortion, rather than engineered to give pleasing bokeh.
Hope that's of some use.
Cheers
Mick
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Hi Paul
I downloaded these and had a good look. I agree the difference is very subtle... although the most obvious (as you'd expect) is between the f3.5 and f22 versions.
According to your EXIF data, you have the 18-200 set to a wide 22mm for this test. There are a number of factors playing hardball against a blurred background here.
First is focal length. Wide-angle shots are unlikely to give you a blurred background unless you're focused really close, like in the region of half a metre. If you tried the lens set to 80mm, or better 200mm you'd see the difference straight away and it would work at reasonable subject distance. The closer the better, though, for maximum effect. It's a fairly complex explanation, best understood by trying it out!
Second is the size of the sub-APS format sensor, which by its nature gives you more depth of field than a full-frame chip. Third is the lens itself; the optics in a super-zoom like the 18-200 are very complex and geared towards combatting distortion, rather than engineered to give pleasing bokeh.
Hope that's of some use.
Cheers
Mick
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Hi Paul
I don't work on the technical support side as such, but Sony do pick up on comments made here, if that's what you mean. Always worth posting this kind of feedback on a separate post, ideally on one of the 'suggestions' threads, if you want to be sure of getting noticed 
The issue you're struggling with isn't to do with focussing – you need to focus on the subject, regardless of the focussing method – nor are scene settings really relevant. Some scene settings will automatically select a larger aperture, which is the only thing they can do to affect the amount of blurring you get, but it seems you are happy to select that manually. So far so good.
Aside from keeping wide apertures (low f settings) you need to concentrate on two things:
First, don't use wide-angle (lens zoomed all the way out) as you will get too much depth of field, and even at f3.5 your backgrounds could stay quite well-defined... zoom in, the more the merrier, and as you do so your background will become progressively more blurred.
Second, get as close as you can to your subject, and choose a background as distant as possible beyond your subject. The closer you are, and the more distant the background, the greater the background blurring.
These two things are by far the biggest variables in achieveing a blurred background. After that, all you can change of any significance is the lens, and I'm afraid it can be quite a big change. Wide open and zoomed to 200mm your 18-200 is at f6.3, compared to more expensive zooms, the best of which are a constant f2.8. That's a big difference and it shows in the shots.
But do remember those two main tips: they should make a big difference on their own.
Cheers
Mick
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Hello again Paul
Re: your original tests 3 and 4: even at 2m distance, with the lens zoomed out to 22mm you have very little background blur, because at such a wide angle setting, a lens will provide too much depth of field at that distance. I'd recommend reading up on this term, as it's fundamental to understanding why there is little or no background blur at this setting, and conversley why there is maximum background blur at 200mm.
This page explains everything you need to know (especially halfway down the page) with some good examples you might find instructive: http://www.mir.com.my/rb/photography/fototech/htmls/depth.html
Looking at your new examples, you demonstrate a similar result to previous ones with the flower (Zoom 18 at F4.JPG) although you are closer (1m) to the subject, so there is now a small but noticeable amount of background blur compared to your statue photos.
However the background blur is more noticeable as you zoom in to 35mm (Zoom 35 at F4.5.JPG) and very noticeable in the final frame at 100mm (Zoom 100 at at 5.6.JPG) which is as I would expect, and – I thought! – exactly how I described it in my last post. Sorry if that wasn't very well explained, but you have now demonstrated very well how this technique is supposed to work: if you had zoomed in to 200mm, you would have got a totally smooth, defocussed background at that subject distance.
You do have to take care with camera shake at 200mm, but in Aperture Priority (A) mode, with your lens wide open (f5.6) the camera will select a very fast shutter speed, especially if you have good light, so it shouldn't be a problem.
I can only refer you back to my two main points and assure you they are correct. The key with any photographic technique is to practice and experiment with it, but also to remember that no single technique is ideal for all photographs. Wide apertures are a great way to approach a lot of photography, but background blur is not always the result. It is the natural product of zoomed-in photos of very close subjects, and it gets harder to achieve the more you zoom out and the further away you place your subject.
Let me know how you get on. I'll be happy to explain further if you like
Cheers
Mick
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Hello Mike
Appreciate your time.
This is a last attempt. I understand the usage of the F or A settings to get background blur. Sony Support told me the same thing.
2 new phots attached. I see very little difference the depth of field between the shots.
Both pictures taken from 2 metres of the bottle.
1st picture - zoom 35 and F4.5
2nd picture - zoom 35 and F25.
What I expect is that the background from Pic 1 is much more blurred than pic 2. Is this right?
Maybe I am just expecting too much from the camera.
Pre-digital, when I used 3.5 for a portrait then all the background was blurred. Now it doesn't seem to make a lot of difference. F22 gave me everything in clear focus.
Unless you have somethog to add to this, then I will live with what I have, thank you for your help and probably go back to Nikon the the future. 
Paul
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Hi Paul
There's a big difference there, if you look at the rooftops in the background. At f4.5 they're nicely defocussed; at f25 they're almost as sharp as the bottle. Also look at the foliage to the left and right of the frame in each example. The difference you see between those two frames is a perfect demonstration of shallow and deep depth of field, respectively.
With the first shot, the overall blurring effect is exactly what I'd expect with an f4.5 consumer zoom lens at 35mm on any APS-chipped camera body... I'll come back to that point later.
Let me just reiterate: you won't see a fully defocussed background with the lens set at 35mm unless the subject is much closer than 2m; it needs to be something like a metre or less. Or you use a longer zoom, say 70mm or more. To prove it, set it up again and try these two things:
Longer zoom = more defocussed background: set the bottle up at 2m distant again, but this time zoom in until the bottle fills the frame. Now zoom in to just the label on the bottle. Look at the background in each case; it will become more blurred as you zoom in.
Closer subject = more defocussed background: set it up again, but this time keep the lens at 35mm and instead move the camera closer to the bottle, around a metre away, so that the bottle fills the frame. Then move the camera closer still, so you see only the label, and refocus.
You'll get a subtly different blur to the first exercise, but the point to note is that the closer you focus the subject, the more blurred the background gets... crucially, the less you are zoomed in to your subject, the closer you have to be to it, in order to blur the background.
The only other point I would make is to make sure your background is sufficiently distant. You can see that in your first shot, where the distant rooftops are much more blurred than the foliage in your garden. Where there is detail right through the whole shot, from foreground to background (as there is with your example) the blur will become more pronounced with distance. Here's another example, from the link I posted last time, showing the same thing: http://www.mir.com.my/rb/photography/hardwares/classics/nikonfmseries/fm2/morris.htm
So I'd say you've done extremely well in demonstrating exactly what I was hoping to prove!
I did say I'd come back to your camera and lens. Lens first: an 18-200 zoom is not the best tool for this technique. You'll get much cleaner, more controllable and softer-looking background blur with a quality telephoto prime lens, like an f2.8 200mm, because that's what they were designed to do. You may well have used one on an old SLR and be struggling to reproduce that finesse with your more general-purpose zoom, and this might explain your frustration..?
And yes, the camera is a factor too. Like the vast majority of 'prosumer' DSLRs, the big full frame of the film-based SLR has been replaced with a much smaller, DX or APS-sized sensor chip. This has a direct impact on depth of field, working against the sort of effect you're looking for. The only way to combat this on most DSLRs is to engineer special lenses that counteract the 'small chip' problem. They're very expensive - I have a Nikon one that works very well indeed, but it cost £1500...
And I suppose this is where I'm bound to mention that it's not your A33 that's at fault, nor will a Nikon be any improvement... Nikon have used nothing but the exact same Sony sensor chips in their DSLRs for years however, with a bit of knowledge and practice, you can still 'do' the blurred background very convicingly on your DSLR.
Here endeth another long lecture 
hope it was of some help!
Mick
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Hi Mick
Thanks again for the "tome".
Close to the end.....
Looking at the original photos of the fountain and Test 3 and 4. (First posting)
They both look the same and so as a last question, "How can I get the background to blur with my existing lens?" as these 2 shots with 3,5 doesn't show any noticible blurring?
I have read all your comments and looked at the "Moments which is what I want from my lens/camera.
Is this possible, and if so what do I have to do to get this? A different lens?
Or, is this possible with my existing set-up?
The photo doesn't look the photographer was using a 18-200 Tamron!
Bye for now
Paul
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There's no mystery there: with your fountain shot you were too far from your subject, using too wide a zoom, to get any background blur. With those two things 'wrong', it barely matters if your lens is at f3.5 or f22, as you discovered.
Do you mean the photo that I linked to in my last post? That was a 300mm lens on a Nikon FM2 film camera, so no, it wasn't your 18-200mm zoom but yes, you should be able to get a similar result with your existing kit. You simply need to practice, persevere with it and you'll get there.
Ok, a better lens would certainly help – one that will let you get f2.8 (or even f3.5) at 200mm, instead of the maximum f6.3 that the Tamron has – but you really must be nearer the 200mm end of the zoom and you have to get the subject distance right.
Apart from that, all you really need is a pretty girl, a nice evening and an overgrown field in the country
Have fun!
Mick
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