IQ of cropped image, M4/3 vs. dSLR

[Richard Stern]

Hi,

I have been shooting with Oly. OM-D E-M5 micro-4/3 and (for birds) Panny 100-300 lens for several months now, and I also shoot with Nikon D7000, 300 f/4 AF-S, and 1.7x TC. For images that need little or no cropping, the IQ of the Oly is excellent - sharp, good contrast etc., but for images that need a lot of cropping, the IQ is invariably better with the dSLR with its APS-C sensor - with more detail, less need to introduce sharpening artefacts in post, etc. Always Raw, processed in LR and sometimes in Elements as well, and usually hand-held.

I have recently tried taking some pictures of the same bird with both sets of gear, one immediately following the other, and it seems a consistent finding even allowing for differences in technique, hand-holding, different shutter speeds and apertures etc. So my dSLR setup has gone back to being my go-to gear for bird photography despite the much higher bulk and weight, and less convenience. Is this just a function of sensor size, or pixel density, or something else, and if so, would a larger sensor camera (e.g. full frame dSLR), but which might require a bigger crop to achieve the same result, do even better?

Always tying to learn, and improve my images --- Richard

[David Stephens]

In the case that you cite, sensor size is an important factor, but the focal length of 300mm plus a 1.7x TC is also huge vs. 300mm max with the Panny.

Canon's recent firmware upgrade to my 5D MkIII has allowed me to routinely use a 2.0x TC on my full-frame camera. It's addictive and even my wife noted an improvement in my average IQ afforded by the extra reach vs. my 500mm +1.4x TC.

I also own a crop sensor 7D, with much denser pixels than the 5D MkIII. Its IQ gets limited as the ISO get raised over 800, but it's excellent up to that point. If it would AF at f/8 I'd be tempted to use it instead of the 5D3, but it's AF is not near as accurate, consistent and reliable, so I use the 5D3, despite the less dense pixels. My keeper rate is much higher with the 5D3.

You can't just count and measure pixels and predict relative IQ. If all other things were equal (DR, high-ISO performance, etc.) you'd want the highest pixel density possible for focal length limited shooting. The reality is that not all pixels are equal and manufacturers trade off one quality against another to meet different target audiences.

[John Chardine]

Hi Richard- Your Olympus sports ca. 3.7 micron sensor sites and therefore samples the light falling on its sensor at about the same rate as the Nikon D3200 and D7100 (3.9 micron sensor sites), which are by all accounts excellent cameras. All other things being equal, your camera should perform as well as these do, but of course all is not equal. Your D7000 has larger sensor sites (4.8 micron) so comparing the two is a little like apples and oranges. With the smaller sensor sites your Olympus is capable of sampling more detail on the subject than your D7000, but obviously image quality is more than about this aspect of sensor performance.

[Richard Stern]

Thanks for the replies. The problem really only occurs with big crops, so I suspect that the difference between the 100-300 Panny "FF equivalent" at 600mm., and the D7000 gear (equivalent 765mm) is indeed responsible for some of it, as I would have to crop less for the same main subject size on the D7000 than on the OM-D. The OM-D should theoretically be shaper if lens quality is equal, at the same ss, as the image stabilisation is excellent, and the D7000 +300 etc. has none. Lesson - probably - as alway, is to get closer to the subject and crop less.

Richard