Let's have a glance on size/weight of few recent cameras before getting into this discussion GH2: 442g 124 x 90 x 76 mm GH3: 470g 132.9 x 93.4 x 82 mm (Samy's Camera - Photography, Digital Cameras, Video, Audio) K5: 740g 131 x 97 x 73 mm D7000: 780g 132 x 105 x 77 mm D600: 760g 141 x 113 x 82 mm D700: 1074g 147 x 123 x 77 mm Panasonic DMC-GH3 vs Nikon D600 (Images are not scaled) With shrinking full-frame bodies and expanding micro 4/3 bodies, probably its a time to re-evaluate our camera system's selection criteria on the basis of budget, size and functionality. Being a hobbiest travel photographer, I was always keen in compact and more functional cameras and that is why I swapped my Nikon+Fuji APSC camera gear and lenses (D90, S5 Pro) with Panny GH1 as soon as it was released back in 2009. Since then I stick with that amazing little camera and took it everywhere coupled with an Olympus Pen EP1, without any problem and been waiting for its upgrade. GH2 was an excellent product, but having a GH1 it couldn't inspired me enough to upgrade, then GH3 took a long time to get release and still its not officially announced. However, through its leaked photos and specification at one hand I am tiny bit disappointed on its physical specs and on the other I love its functional specs. As its size is reaching to a small APSC DSLR Physical size domain (like Nikon D7000/ Pentax K5) where exactly a full-frame camera is also landing, the recently announced impressive Nikon D600. I know its not comfortable, but I still want to rethink / analyse these two cameras (GH3 and D600), that belongs to two distant worlds, getting much closer. First of all GH3 is bigger in all three physical dimensions than its predecessor and got an extra 28 grams of weight. Wight wise you can still forgive but in size it's both thicker and taller (marginally) than even D7000 DSLR that also carries a mirror box. Only in height it is shorter but then it is partially due to the hight around the eyepiece and mirror box. Pentax K5 is even smaller. And I am not even considering any entry level DSLR or recently announced Full-frame but Fixed lens smaller Sony. D600 on the other hand got shrink from predecessor Nikon D700, considerably in height and width and gained 5mm of thickness and lost an impressive 300+ grams of weight resulting into a body which is even lighter (20 grams) in weight than Nikon D7000. From the way things are merging together, I am getting strange feeling that in future not too far, we will no longer consider the size of a camera body vs its sensor size when buying a camera system. Having said that, I still believe the two camera system (m43 and FF) have few noticeably Functional Advantages on each other. Even though, we still need to see the IQ tests. Full-frame advantages (D600): - 4 times Bigger sensor surface area means overall cleaner images, noticeably in ISO higher than 1600. - More control over Depth of field. You can arguably consider a variable focal length lens with bright f2.8 aperture over few prime lenses in m43 world (but for DOF considerations only). - Arguably bigger collection of Nikon and third party lenses from Tamron, Tokina, Sigma etc. Though bigger doesn't mean any of my judgement on usefulness. - Dynamic range on Nikon D800 was impressive, it can only get better on D600 considering similar level of advancement in technology and lower density pixels sensor 24 vs 36. Though I am not expecting huge difference. GH3 on the other hand also claim carrying a high Dynamic Range sensor. - Resolution wise a clear advantage in roughly 8 MP over GH3. Again I am not very keen on this aspect as well, as most of the cases lens resolution is not good enough to give a clear advantage on sensor resolution power. - Some prefer Optical Viewfinder over Electronics one, as you can still look into it in much lower lighting situation. Micro Fourthird advantages (GH3): - Even though the size is expanding, its weight is still considerably lighter. - Smaller sensor size advantage is not bound to just camera body. Overall gear with few lenses are still much lighter than full-frame or even APSC (mirror-less or mirrored) system. - Panasonic and Olympus has huge collection of small size lenses, those are ultra sharp on widest apertures with flexible focal lengths or apertures. There are many other innovations with power operated zoom lenses, compact collapsible design, with almost every zoom lens branded with OIS. There is a very good collection of VR zoom lenses in Nikon full-frame family, though few more useful lenses like 24-70mm f/2.8 is still without VR. - Shallow depth of field in Micro-fourthird has arguably some advantages for landscape photography (as hyper focal distance can be achieved more practically with lower exposure times) and recording videos, where switching focuses to various subjects is more forgiving in four third format. Also many existing studios are equipped with lightning more suitable to professional video cameras with sensors more comparable in size with 4/3 standard than any other format. - Though the camera body is reaching comparable in price (expected price of the GH3 body only is $1300 compared to $2000 for D600), overall lenses are still much cheaper. - Fastest Contrast detect Autofocus for Live View and Video recording in Micro-fourthird. GH3 is expected to be much better in this regard. Though DSLRs FF/APSC started offering AF supported in huge number of lens collection, their live view performance is not practical for most of the situations and enthusiast photographer needs. On the other hand Most of the Micro-fourthird cameras are not just incredibly fast, they are also assisted with loads of extra features supporting these operations including touch-sensitive screen focus and shutter release and even in video modes all on a fully Articulated LCD screen. Most of these lenses are specially designed to remain silent to better suit videos. With wide range of recording formats, GH3 also features a special heat-dispersing design for extended recording duration. - Construction wise both systems got reasonable rigid bodies. D600 is getting less durable with maximum tested shutter counts of 150k compare to 200k in D800. With mirror box gone, mirror-less cameras doesn’t have such limitations. GH3 (together with G5) also got a new Electronic shutter release, which operates in a completely silent mode. - I also love the new Wi-Fi(R) function that passes many camera controls to smart phones including shutter and exposure control, GPS sync, time-interval video recording, auto transfer to tablets etc. So there are still quite a few factors when you are considering buying an Enthusiast gear system on the basis of sensor size, however with the passage of time the build quality, controls and size are getting comparable. In nutshell the decision factors are if you want insanely shallow depth of field and marginally better ISO over ISO 1600 (will get better understanding on this after IQ tests) probably you will prefer full-frame, otherwise if functionality, price and weight are your preferences GH3 can still deliver better value and feature-set.