Thanks David I need that support! It seems to me that points being made by Alan (for example) are not really supporting the need for longer focal lengths on FF, but rather the need for more focussing aids such as a higher viewfinder magnification. If 300mm is long enough for the subject but on FF you can't see it clearly enough then then you're really looking for, perhaps , a viewfinder magnifying function (say 1.5x), or use the live view already available. Its not therefore necessary to go and buy a 500mm lens just to help you focus more easily.

The higher number of mp is only one aspect of the IQ equation. Your FF owing friend can content himself that he doesn't need that massive 500mm monster after all!

I think the 'problem' arises from a human factor, not technological. We have a human need to 'fill the frame', that's been ingrained as a human best practice. In fact the only requirement is to select the right focal length to get the magnification needed .. This depends solely on how far away we are from the subject. This plus lens focal length is the same for both formats. What our FF photographer will not get is his human need for frame filling as much as the aps-c photographer. But he doesn't need a longer telephoto to fullfill that need, he just needs to crop his image.

Equally, if he can't see the subject clear enough or his focus points are too small, he doesn't need a longer lens, he needs more viewfinder magnification or to use live view and zoon in on the LCD.

I don't see it as being sensor related, rather its solely about lens focal length and the resulting perspective effects of different lengths ... These two factors are exactly the same on both formats. Andrew and his friend standing together shooting the same thing each with a 300mm lens will record the subject at exactly the same magnification and with the exact same effects of perspective ... The only thing his FF-using friend needs to do to make his image identical to Andrew's is to crop off a lot of the edges.

I don't really recognise the points made by Alan about focus points as relevant. We don't see the senor or the image projected onto it at all ... We see the scene through a viewfinder which is magnified to fill the amount of space the camera maker has allocated for it. It makes no difference how big the sensor is, we just see the full image circle because the viewfinder magnification is set to show us that, on both cameras (assuming a spec of 100%).

hey thanks, that's very nice of you, but would there not be a noticeable technical quality boost that would make my shots better just for having been taken on the larger format? Or would any extra complexities or higher demands caused by the technology just in fact be more challenging for me and introduce new problems?

Dynamic range, yes, that would be improved I guess. I've always been interested in analysing different system features with a view to determining key suitability for different categories of photographer, or differing genres and conditions.

So the aim might be to construct some kind of table that would tell me personally what I would gain for my images by moving to a 645, or say, a possible future FF dslr. This would allow better planning and organisation (such as choosing lenses) to make an eventual transition less difficult.

So what would my photography gain if I switched to a 645z system tomorrow?

Beautiful colours, a fine example and a bright effective exposure. Perhaps a tighter crop would have even more impact?

Well I can't imagine you'll find a better lens for the price! Its a starting point and a reference you can use if you decide you need something else, good for comparisons.

Oh dear, you're looking for super bargains...does this mean
you've spent all your budget on a new CAMERA??

I need to get processing images fast, hopefully during this coming week I'll get shots up. I am delighted with the performance of this lens, and you certainly have got an amazing bargain there

Maybe the tilt is more a secondary effect of some distortion ... Is there an option in ice to adjust for this, it gives the impression of having pincushion distortion? But what do others think? Is it distortion or is it tilted rightwards?

If you could have sat the camera down steadily then I think the rocket image would be a great candidate for in-camera HDR.