Depth of field and sensor size
If you read photography or tech web sites you could be excused for thinking “who needs a full frame camera when micro 4/3 camera are just as good?” or “who needs micro 4/3? My smart phone takes great pictures.” I don’t want to detract from cameras with smaller sensors. In all honesty the photos smart phones can capture is kind of mind boggling when you think of the size of the lens and sensor. Also there are some fantastic 4/3 cameras out there, heck I have one. Looking past image size and quality however, is one important factor that always gets glossed over: these cameras do not take the same photos.
I am going on a trip to Europe this summer and am in the midst of planning what camera equipment to take on the excursion. Again, some people would say “leave the camera behind entirely” just shoot with your smart phone. Others would say “all you need is your Olym-uji.” I was skeptical but I am one to question my own beliefs so I thought I’d snap a few photos to see how they differ.
To be honest these three versions of the same scene are fairly similar when viewed small and certainly if your audience is Face-tagram-chatters the difference may not matter to you one whit. But even at this size there is, to me, a stark disparity between them. In the first, the smart phone has a very wide depth of field despite being close to the subject. The 4/3 has somewhat less and the full frame has a very shallow depth of field even though this is a 35mm lens.
Depth of field equivalence
As photographers, changing the depth of field is one of the most amazing tools we have at our disposal. (Yes I know, some of the dual lens smart phones are trying to address this but they really only get part way to 4/3 quality so lets move on.) When people tell you this 4/3 lens is “equivalent” to a 35mm of this focal length they are talking about the “field of view equivalence” (what is in the frame) completely ignoring any difference in depth of field. Depending on your photography style this may not be important to you. On the other hand it may be critically important to you so you should know the difference. These photos are not equivalent!
When considering depth of field you need to ignore “frame equivalence” and focus on physical focal length. On a 4/3 camera a 23mm lens will give you the depth of field of a 23mm lens on a full frame camera. The smart phone will give you the same depth of field as a ~4mm lens on that same full frame camera. Choose whatever works for you but keep in mind how depth of field “equivalence” works as well as field of view “equivalence.”
As for me, it looks like I am going to need to make room for the bigger camera.