Ya thats what you told me and thats what im agreeing with now.
What are the advatanges? its not clearly stated. What 4/3 does it forces you to shoot further from the subject by doing so you are actually increasing DOF. And this is not just about justifying whether i should go FF, this is a place where im learning. Plus i cant simply agree with everyone can i? i process the information and determines what is right and wrong.
I think this is the failure of the 4/3 system marketing as well as the success of Canon marketing. Canon have marketed so well and everyone is psychoed into larger sensor better performance. But really, it is hard to market the benefits or advantages of the 4/3 system. It is too technical and even for me, took me some years to actually start to appreciate it.
In any case, you need to be clearer - do you want to be further away or nearer to your subject? Or do you want narrow DOF? Or do you want less or more background-foreground separation? When you talk about perspective, I thought that you were talking about foreground-background separation.
There is no system that can do everything. Every system has its strengths and you choose the system that best matches your requirements. It is just the physical limition of each system. Larger sensor, narrower DOF, better IQ, better noise control. What they never tell you is that narrower DOF, more out of focus shots. What they never tell you is that narrower DOF, means for group portraits or landscapes etc, you cannot shoot at larger apertures and so have to shoot at smaller apertures. This means that ISO has to be higher, which affects dynamic range etc. Shutter speed also has to be lower, which means that if you have no IS, you need tripod etc. Narrower DOF means that for action shots, if your subject moves a little out of your focus plane, your shot OOF. ie. a very narrow DOF means that your tolerance for focused shots will be lower.
As an example, for me, I want more DOF. And I like nice bokeh, and this may seem like contradiction to many, but its not. And I want my portraits to look pleasing. I hate to take photos of people, and only one face is sharp and the rest is blur. As such, I want more DOF, not less. Already on 4/3 system, aperture of f2 is just about enough for single person portraits. If you are shooting groups, at least f2.8 or even 3.5 or more is needed. If you want to shoot group portraits at f2, then you need to buy an even smaller sensor system eg. X10 or the XZ1. In 135 FF system, if you are shooting groups, your ultra-expensive and large f2.8 L lens, is useless. You cannot shoot at f2.8. YOu have to shoot maybe f5.6 or so to get everyone's face in focus. In 4/3, the DOF of equivalent aperture is roughly doubled that with comparable 135 FF focal lengths. The important advantage of being able to get adequate DOF in 4/3 while shooting at larger apertures or low F numbers, is that you can use much lower ISO values (100-200 is what I consider low ISO values). This is a significant advantage too but this is something that I only appreciated after years of shooting.
Large sensor, large aperture, and long focal lengths does not mean that your bokeh is nice. Bokeh is largely determined by lens construction, the glass and the diaphragm of the aperture. I find that my portrait lenses on 4/3 particularly 50 mm f2, 45 f1.8, 150 f2, have one of the best bokehs around. Super smooth and silky. The other lens factor is closest focusing distance. On the 4/3 HG lenses, they all are made to allow close focusing. Sometimes even down to 1-2 cm or 10 cm. You do not even appreciate this until you go and buy a $10000 leica lens and realized that you need to stand 1 m away to shoot that salt shaker on the table instead of shooting it from a sitting position. A closer focusing distance allows you to narrow your DOF, and thus allows you to blur the background more. So, having a lens with a very close focusing distance allows you to get more blurring. This is something that many people are now aware of. Finally, the subject background distance is important. The more, the more background blurring. So you see, Its true you need to be close to your subject to get narrower DOF but you also get more foreground-background separation. But also, too close, you get perspective distortion - and I think this is your concern right?
So in general, for portraits, it is recommended that you shoot further away so that you get LESS foreground-background separation. This is to make the nose look less big and prominent and to flatten facial features which apparently is more pleasing.
4/3 systems and now the m4/3 systems ticks all the above boxes for me, as well as giving me a compact system that is easy to carry around. There are other advantages too, which are not mentioned here because this is about perspective etc. The other advantages are punchy colours from the OOC JPEGs. The second is that the JPEGS are so good, RAW development is rarely necessary. The third thing is that the lenses are very good and a capable of producing super tack sharp images. Sharp to me means that in a head shot, you zoom in and see the blood vessels in the white of the eye and the details of the eye lashes. If the lens cannot do that, it is not sharp. Also, the lens should be able to do that at wide open maximum aperture. There are many lenses non 4/3 lenses out there which are f1, f1.8 or f2, but are soft wide open and to get decent sharpness, you need to shoot at f2.8 or more. So...defeats the purpose. Remember, a longer focal length lens, or a larger aperture lens, is exponentially larger in terms of size and weight. So, 4/3 has this advantage because I only need to carry the size and weight of a 50 mm lens which can achieve a 100 mm lens effect.
) Hope this can help you justify to your Minister of Finance to get that beautiful FF DSLR. 