|From left to right - Sony NEX-5N, Canon S95, Nikon V1|
So it just so happens I have my hands on three cameras with different-sized sensors (I actually had four, but sold my Canon 5D before I could do this comparison!) and thought I would try a little practical exercise.
The depth-of-field/Bokeh/"blur"/Isolation Test
The fake situation I've put myself in is rather simple. I'm standing at point A, aiming at subject B, and I want a framing of C. Given the cameras and their respective kit lenses, how do the photos turn out?
A few more details:
- All cameras were shot in RAW then exported as JPEG using Adobe Lightroom 4 and the default profile. this prevents any of the blur (bokeh) being affected by different contrast curves the cameras apply to JPEGs.
- I mounted each camera on a tripod and tried to adjust framing to be as similar as possible (harder than it sounds). I came close, but it's not perfect.
- I made a moderate effort to get exposures as similar as possible, but I didn't pour a whole lot of time into this aspect - any differences were adjusted in LR4 beta.
This was just a quick exercise into just how much blur is "lost" due to using a smaller V1 sensor as compared to the NEX-5N's sensor. Also, just how much smoother is the V1 going to be over a good point and shoot, the Canon S95?
|Image 1 - Sony NEX-5N|
So here we have the first candidate, the NEX-5N. In case you're not sure, I'm focusing on that awesome hot-pink Kitchen Clip. Pay attention to the background - I've placed some random objects to simulate a "busy" (non-pleasing) background. The distance from the clip to the objects in the back was approximately 5-6 feet.
|Image 2 - Nikon V1|
|Image 3 - Canon S95|
There are really a few ways to conduct this test, but I decided to simulate a "what if" scenario: if I were walking along and found a subject I wanted to photograph, and that subject was both close to the background and to my camera (which was about 3-4 feet away in these samples), what would the results look like?
As can be seen, due to the larger sensor size of the NEX-5N, it naturally has a more shallow DOF than the other two cameras. While the V1 isn't bad, it certainly shows a degree of definition in the background that isn't found in the 5N. Still it does a reasonable job.
Of course once we step down to the S95, we're looking at a pretty distracting, almost in-focus background. Poor subject isolation means it "runs into" the background and you lack a sort of 3-D effect that the NEX-5N gives you.
Unfortunately I don't own a full-frame camera any more, but if I did, we could see an even smoother background than the 5N's image.
The take away from this is that given all else equal (almost*), when it comes to framing the photo and taking the shot from the same location, the larger sensor is going to yield a smoother background.
Fret not, though - there are actually other ways to blur out the background even with smaller sensors - it just becomes much more difficult.
As an extreme example of what the larger sensors can do, here is a Nikon D700 shot using an 85mm lens set at f/1.4 (big sensor + fast lens + close subject = bokeh paradise!)
Nikon D700 with Rokinon 85mm at f/1.4
*Now, some caveats - I realize the apertures aren't the same between these photos - that's because I was doing a "real-world" experiment in that I was shooting wide open on all three cameras.