DOF question. DSLR or MFT?

Started Aug 18, 2011 | Discussions thread
Erot
Junior MemberPosts: 42
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Re: Nononono
In reply to agc1976, Aug 20, 2011

agc1976 wrote:

Bilgy_no1 wrote:

Let's not, because like many trueisms, yours is FALSE but often repeated, and that's why people get confused about it. DOF is a function of the Lens (focal length and aperture), as well distance to subject.

Let's consider the practical side indeed. Say I want to shoot a 24mm equivalent perspective with NEX or a m43. The NEX will use the 16mm f/2.8, the m43 the 12mm f/2. The NEX lens is longer, but the m43 lens is brighter. DOF will be very similar, but you see that sensor size is not the determining factor. Especially between APS_C and m43, the differences are simply too small, and the lens line-up differences too big, to make such general statements.

what I do ignore here is the effect of 'circle of confusion'. The captured image on the sensor is magnified to produce the final image. This affects the appearance of sharpness and thus the DOF. Because you magnify the image from the smaller sensor more than the image from a larger sensor, this means that you get more shallow DOF with the smaller sensor. Go figure!

Jeez... I don't understand why people insist on trying to make the sensor size a non-issue when it really is. It's getting tiring already. Sensor size is just as important as focal length because SENSOR SIZE FORCES YOU TO USE A DIFFERENT FOCAL LENGTH TO GET THE SAME ANGLE OF VIEW .

Comparing the Sony 16mm f2.8 with the Oly 12mm F2, how convenient... Why don't you compare the Oly 12mm F2 with the Nikon 24mm F1.4 on a D700 then? You can even stop it down to F2.8 and still have less DoF on the full frame system.

Same field of view
+
Same entrance pupil (= focal length / f-stop)
=
Same DOF (regardles of sensor size)
+
Nearly same noise (regardles of sensor size, same shutterspeed, different ISO)

Same field of view
+
Same f-stop
=
Large DOF with small sensor and small DOF with large sensor
+

More noise with small sensor and less noise with large sensor (same shutterspeed, same ISO)

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