Personally I think the expression is meaningless and confusing.
Every camera is a "full frame" camera. The advantages or disadvantages of a larger sensor may very well be important....
But it's not meaningless or confusing in the context it is used. If you wish to know the field of view of a lens, you just need to remember for one format in portable cameras. That's become 35mm. From there you apply crop factors to make it easy.
For example, Olympus made a line of "Half Frame" cameras in the 1960s. Everyone knew what that meant. It was half the frame of 35mm film. Today 4/3rd is about the sam, but a different name. You might could claim APS-C to be 3/4 frame cameras. It doesn't matter what you call it but it does have a meaning. Nikon says FX and DX. Again, what's the difference as long as you know how that size crops a larger format.
I just don't think it matters enough to switch from APS to 35mm
I believe the quality of the lens is more important than the size of the sensor.
Even in low light, an APS sized sensor works just fine...
Sure APS works fine. I have a D300 and use it often. Nothing wrong with it. For some, moving to FX is too expensive to consider. To others it might not be. And, of course the lens makes a big difference. But let me tell you. Go get you a D700 for a week or so and come back and tell me what you think. Most are peasantly surprised.
Open up that RAW file in your favorite converter and editor and you'll find headroom, bottom room, living room and maybe a hotel room when your wife finds out what you just spent. Don't do it unless you're willing to make the journey.
As far as bird and wildlife photographers go, I've personally found that most of the seriously passionate ones, the ones that buy the big glass and travel far and wide, use full frame (FX, 35mm) cameras. When I hear through the grapevine that a fairly rare bird can be found on some trail in the Everglades, and I get back in there, I see very few crop cameras. I see Canon 1DS types, 5D types, D700 models with grips and D3s. Now around Anhinga Trail where all the birders mix it up with the tourists and average joes who like to shoot birds, you see everything. But, it's really no big deal. It's just my personal experience in one part of the country. Elsewhere might be different.
I think the myth about bird and wildlife photographers preferring APS-C for the supposed reach is more of an Internet Forum tale.
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Cheers, Craig
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