Originally posted by crewl1 I don't think there is any magnification going on, rather you are recording a smaller section of the viewed image onto your sensor.
it is acknowledged that a focal length somewhere in between 35-50mm equivalents to what we see in the viewfinder. I guess there is a reason PENTAX made a 43mm lens(other story) Try to set your lens to app. 40mm or so. look through the OVF. and look with your other eye straight ahead and close the eye in front of the OVF. On viewfinders like the ones in K-5 and K-3, it will be hard to tell a real difference, other than that there is a frame around what you see when you look through the OVF.
The result what you see through this viewfinder with a 43mm lens mounted on an APS-C body would be app. the same on a FF camera equipped with the same spec OVF.
A 300mm lens would magnify this result app. 7x
and it does so on FF
and it does the same on APS-C
The difference from APS-C to FF "in the camera", is
(exactly like crewl1 stated) only that you have a bigger frame around your "magnified" picture on a FF lens than you would have on an APS-C camera.
(And
oculararly/ostensible compression of DoF depending on the chosen aperture)
So in that point crewl1 is right. In reality there is no real magnification going on from FF to APS-C and that is exactly what i wanted to hold on with this writing. BUT(t):
if you turn the coin, there is. Because: one normally would take the output and only enlarged to 1.56 times he would compare it to a shot of a FF camera in the real world.
looking at a 9x13 cm print of a shot taken with 300mm on a full frame body and comparing it to app. the same shot taken with 300mm on an APS-C body, the result of the APS-C is in the end indeed "magnified", because the APS-C sensor took out a smaller frame of the same proportional reflexion that lands on the sensor layer... but gets printed on the same sized paper or ends up on a webpage with the same proportions (AxB) as a FF picture would.
this is the reason why i want to remind you, that i clearly stated "
magnification may be equivalent" and not "
magnifies to"
again reason of posting: Focal length stays focal length.
A FF-capable lens (a lens that projects a reflection of what you see in your viewfinder, over the whole area of 24x36) like the DA*300(actually a original FF design) on a FF-DSLR body, gets you nearly(may be a difference in -->IQ) the same as an FA*300 on a FF-DSLR body, given that you use the same aperture stop.
Only to avoid misunderstandings or misreadings.
---------- Post added 03-04-16 at 01:24 PM ----------
THX VoiceOfReason. Field of View. That is what explains a long story short and avoids misunderstandings.