Compact vs. dSLR (Resolution)

A compact camera owner raised the question on a camera forum whether a dSLR necessarily has better resolution than a compact camera at the same number of megapixels. This person's thinking centred around lens quality, but in my experience compact camera lenses are surprisingly good. They have to be given the intense competition, not only with other brands but with previous generations of the same brand.

But let's see for ourselves. A couple years ago I did a backyard test of four different digital cameras I happened to have available at the time:

Pentax DS, a dSLR with the standard Sony 6 megapixel CCD. And the 18-55 Pentax zoom. Not the most expensive glass, but at F/8, no problem.
Panasonic LX1, an 8 megapixel compact with an excellent Leica-designed lens.
Fuji E550, a 6 or 12 megapixel compact depending on how you count.
Nikon E7600, a truly consumer-grade 7 megapixel compact.

Here are the test shots I took. Clicking on any image here will take you to the full frame from the camera, which varies from 2.5 to 4 megabytes per download. Both the Pentax DS and the LX1 are RAW-capable, so I took RAW shots then converted them with the default setting in RawShooter, except for sharpening being at (supposed) zero. The other two cameras only produce JPEGs; for them I used the least aggressive settings and highest JPEG quality, such as that was.

Fig. 1. Pentax DS + 18-55 zoom at 33mm. F/8

Fig. 2. Panasonic LX1 at 10mm, F/4

Fig. 3. Fuji E550 at 11.9mm, F/4

Fig. 4. Nikon E7600 at 12.7mm, F/3.5

I worked from a tripod, which I didn't move throughout the shoot. But because of the difference in aspect ratio, lens perspectives, and most of all the impoverished control sets of the Fuji and Nikon cameras, All I could do was try to approximate getting the same coverage in all shots. I used what I considered to be the optimal F/stop for each camera, but with the Nikon one doesn't even have that much control. We can argue 'til the cows come home whether there is any point of comparison between the above shots; but the bottom line is I didn't take these shots for publication, and they're all I have to offer.

In terms of resolution, the Panasonic is an 8 megapixel camera for the full glory of its 16:9 frame, but 7 megapixels if cropping to the 2:3 aspect ratio of the Pentax, and 6 megapixels if cropping to the 3:4 aspect ratio of the Fuji and Nikon. So in fact there is very little difference in megapixel counts here, and resolution will have much more to do with other variables, including lens quality.

Another question entirely is the general and ultimately indeterminate question of IQ (image quality). A point raised on the forum is that compacts may not fair too badly when compared to dSLRs so long as one sticks to ideal shooting conditions. One reason I like to use this scene for testing is because it covers both poor and ideal exposure in the same frame. The shadows are dark, the highlights are hot, and the entire latitude of the scene exceeds 7 stops. For these shots I deliberately set exposure to just blow the pure white areas in sunlight, so the drainpipes, for example, are deliberately blown. This tells us how deeply each camera can dig into the shadows.

We can see that the inexpensive Nikon simply blows highlights, imposes its own idea of sky colour, smears fine detail in the shadows with in-camera noise reduction, and degrades everything with a combination of crude sharpening and JPEG artifacting. The Fuji doesn't blow highlights but otherwise suffers from the same faults. (The Fuji had RAW output but there wasn't a converter available to me at the time.) The Panasonic is noisier in the shadows, but otherwise trumps the dSLR in resolution and acutance, and holds its own in other areas. (To judge resolution I suggest you add some USM at 0.3 radius and amount to taste.)

Those, in any case are my own conclusions. Hopefully, the full frame shots will help you to draw your own, as well.

Incidentally: the Panasonic, not the Pentax, wins for most accurate colours, but that has nothing to do with the camera and everything to do with the camera profiles in RawShooter.