Originally posted by starbase218 It's not just the DOF, but also the noise. Crops will show more noise relative to the size of the photo. This is more or less equivalent to having to increase the ISO when you would shoot with that 150mm f/2.4 lens, at least as long as the 24MP resolution holds out.
Offcourse that why small sensors do perform to a lesser level then the bigger sensors. When going down to only using the Nikon 1 series sensor size inside the K-3 you also end up with the sensor performance to that new smaller size.
http://www.dxomark.com/Cameras/Compare/Side-by-side/Pentax-K-3-versus-Nikon-1-S1___914_853
But maybe, comparing to the sensor performance off the Olympus OM-D E-M1 would be better, but then again that sensor is bigger then the sensorsize off the 1 series.
But the advantage is to have that option. Hi-iso performance goes down the drain very fast, but for that I took the superfast FA*85mm with me.
Originally posted by everydaylife I am sorry but I my understanding of the parameters that affect dof must be limited. Can someone explain why the dof changes when an image is cropped?
The Field Of View (FOV) changes with the use off the smaller size off the sensor when the attached lens keeps the same. So the FA*85mm lens has a different angle of viewing the scene on a Full Frame camera (like Sony Alpha 7) then on the crop aps-c sized K-3 or like in this case again different on the only 1 inch used sensorsize that is the same as in the Nikon 1 series. With that change the lightgatering off the lens keeps the same, but the Depth Of Field does change with the different FOV.
So the FA*85mm/f1.4
- On Full Frame: 85mm/f1.4 for FOV and DOF.
- On APS-C: 130mm/f2.1 equivalence to Full Frame FOV and DOF.
- on Nikon 1 series: 230mm/f3,8 equivalence to Full Frame FOV and DOF.
It is not the lens that changes, but the use off the gathered light that changes.
So to come back on my image that was taken with the settings 85mm; f1.8; 1/320th and iso800! So I could have taken my Sigma 70-200mm lens with me (or for those who have the Pentax DA*200mm/f2.8) and use that lens on the long end. For both lenses Sigma and DA*200mm it is wise to use the f3.2 as minimum, since it is better performing then on the starting f2.8 (as is with the FA*85mm that is better performing on f1.8 then on f1.4). So that means that I would use a larger part on my sensor, but hat to crack up the iso to iso 2500 or 3200 (since I underexposed a little, but repairing with hi iso is more difficult). That would give simular image quality I guess with a little less DOF, but probably not noticable. Remember I was expecting half the light that I got for the image, that's why I didn't bring my Sigma-lens.