[Brightcolours]

Wooow, relax, no need to be so agitated.

 

All I'm saying is extremely simple:

An f/4 lens on MFT will meter the same as an f/4 lens on FF. That's what I meant when I said "sensor size is irrelevant". Nothing more, nothing less.

I this context, if you set a D800 with a f/4 lens (no matter the focal - that's not the point here) at ISO 400 and 1/200 for instance, you will get the same exposure as with an E-M1 with a f/4 lens at ISO 400 and 1/200.

I don't care whether ISO 400 on FF is roughly 1-2/3 stop better than on MFT. That's not the point. I was just talking about exposure.

I used to own a D800 and I switched to MFT, so I perfectly know the tradeoffs I made by doing so. To me, the IQ difference *in real life* is not significant.

 

Now, regarding the 600mm equivalent lens.  Yes, you can sure use the combos you mentioned. However, the 300mm f/4 Oly lens will probably have much better IQ than any of the solutions you suggest. Also, as you mentioned, there is no 600mm f/8 lens in existence in the FF world (and if it did, it would lead to AF issues anyway).

Bottom line: to reach 600mm on FF, you need to carry something huge and heavy. That's the whole point of my previous replies.

So what you are saying is that ISO 100 film at f4 gets exposed the same as ISO 400 film at f4.

Because according to you, all that matters is how much light falls on a square millimeter.

 

And not sure why you are starting to talk about the quality of the lens again, apparently you do not read what I have said about that. Understanding lens equivalency (in this context) is not about which lens is the sharpest. Or fastest focussing. Or something like that.