[quote name='Walid' timestamp='1331025877' post='16434']
What happens when you use DX lenses on ff cameras? What is 300mm f4 performance on ff? I mean is it fx
What is the difference between ff camera and not ff cameras?
Sorry for my ignorance
There are 135 format (otherwise known as 35mm film, which is actually 36mm wide <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/wink.gif' class='bbc_emoticon' alt='
' /> ) sensors, they are called "full frame". Then there are cameras with a bit smaller sensor, they are called "APS-C" size. APS was a smaller film type introduced in the 1990's.
SLR lens makers, obviously, used to make lenses which have a big enough image circle to work well with the FF sensor and film size.
But in the digital age, making big sensors is difficult and expensive, that is why smaller sensors started to appear, the APS-C size sensors.
Lens makers responded to that by making lighter, cheaper lenses with a smaller image circle.
To differentiate between full size and smaller size image circle lenses, they use different codes in the lens names.
Nikon adds "DX" to APS-C lenses.
Canon uses "EF-S" instead of "EF" for APS-C lenses
Sony adds "DT".
Pentax just makes a mess of the naming.
Tokina uses "DX", like Nikon.
SIgma uses "DC" for APS-C, "DG" for FF.
Tamron uses "Di II" for APS-C, "Di" for FF.
Nikon started relatively late with full frame sensors. Confusingly, Nikon felt it necessary to think of an equivalent name like DX....
So now, instead of normally talking about APS-C, Nikon likes to say "DX", and instead of talking about FF, nikon likes to say "FX".
Any Nikon F-mount lens which has no "DX" in its name is a full frame lens. In that sense it is "FX".
If you use an APS-C lens on full frame, you get dark (black) corners, which is called vignetting. If you use an APS-C zoom lens, it may be that on the widest settings, you can actually use it without getting dark corners.
Examples for that are the Nikon 12-24mm f4 DX and Tokina 12-24mm f4 DX which work without vignetting from about 18mm to 24mm on full frame. And the Tokina 11-16mm f2.8 DX, which works without vignetting at 16mm on full frame.
The 300mm f4 from Nikon is not an APS-C lens, so works as designed on a FF camera.