Hi there,

I currently use a number of Minolta film SLRs - generally a Dynax 800Si and 700Si. I am currently thinking of moving to Digital, and am reasonably keen to move to Sony to retain use of my lenses - which although not wonderfully expensive would cost quite a lot to replace. For day to day use I use a Minolta 24-85mm lense, but also use a Tokina 19-35mm lense, a Cosnia 100 to 400mm lense and (for when I feel strong enough to lift it) a Sigma 50-500mm lense (which certainly would be expensive to replace).

I am mainly looking at the Sony Alpha 550 or 850, but also considering the Alpha 700. What I'm really keen to understand is the effects of the smaller sensor on the 550/700 compared to the full frame sensor on the 850.

I understand that one of the effects of the smaller sensor (on the 550/700) is that my lenses zooms will effectively increase by 1.5. So whilst this sounds good for wildlife/aviation photography with my higher zoom lenses, it would mean I would lose the wide-angle effect of my wide angle lense - so would need a new lense to cover that "zoom range" (although with the cost saving from the 850, that may be affordable). But what I don't know is what other negative effects will there be from using lenses designed for a full frame camera on a camera with a smaller sensor? Presumably the effect of now having up to ~750mm zoom is that I will have to operate at much higher ISO rating, move to using a tripod earlier and/or have greater risk of suffering from camera shake? Or is that not the case? Also, are there any risks with distortion by using the smaller area - I know some magazines (WDC included) refer to the risk - but will I really see it?

I know that makes it all sound like I've made my mind up that the alpha 850 is a better bet - but I would sooner avoid the additional money as not really sure I need everything it has to offer, but I just can't quite get to the bottom whether the above issues are really issues.

And as one last query (which might sound blindingly basic), my only real experience with digital up to now has been with Panasonic and Olympus compacts, where the standard image size is slightly squarer than that I am used to from 35mm, which can make cropping rather irritating - as to fit alongside 35mm images in album means cropping - whcih makes composition a bit of a guess from the screen. I notice that the sensor ratio for the Sony (and I expect other DSLRs) is as for 35mm (ie. width divided by height is 1.5 - so consistent with 6x4 prints) - I assume that means that the image is of that ratio too (unlike the compacts)?

Many thanks, and apologies for going on rather!