Like any camera format, Micro Four Thirds format has its strengths and weaknesses.
To me the strengths outweigh the weaknesses by more than a little bit, but some things have to be taken into account when looking seriously at the format*.
1) Visible Image Noise is mathematically more likely.
Simply put, a smaller sensor, all things being equal, will produce more noise at the same pixel count (same number of pixels on each sensor, not density per inch). This is physics, undisputable and on record. The answer to me comes in software advancements balanced with real world needs. There are already phones out there doing the near impossible, so bigger sensor cameras of all types will benefit here a bit like Formula One technology trickle down, but backwards.
For me, using ON1 combined with C1, I now consider ISO 12800 my upper limit for good quality images and do not think twice about using ISO 32-6400 files mixed in with better quality ones.
Is it the best noise performnace around? No, of course not, because all sensors are playing on the same field, but it is good enough to take my images, even those taken at ISO’s beyond my wildest dreams (and needs), into the “good enough for fine-art sized prints” category. Something I have noticed when given the chance to try a bigger format again, is that the difference is not as big as you might believe.
Being able to use a very long, f4 lens hand held for action subjects in poor light is my “stretch point” and ths format, with all its performance enhancers is well and truly enough.
Tight portraits from well outside of the subjects awareness range, using a 600mm equivalent lens in less than ideal light is now an expectation and this was before ON1 came into my life.
The reality is, arguments over small differences in sensor size have been less and less supportable for a while now and hypocracy in this space is rife, as it has been since the film era. For a time when the EM5 mk1 first came out, these little cameras were even kicking the big guys around the block, forcing them to lift their game in most areas (I had FF Canon and changed to MFT to follow the quality and performance).
2) The other full frame feature often cited as “superior” to MFT is depth of field control, namely shallow depth without the advantages inherent in the other direction compared.
The “you cannot get good Bokeh with MFT lenses” gripe is uneducated, innacurate and often ignores the practical application of depth of field (and what “Bokeh” really means). A full frame shooter with a super wide aperture portrait lens can produce the softest and most incoherent blur in the same situation at the same distance, but so can the MFT user with exactly the same lens, the lens just has twice the reach, which when you think about it, is actually a bigger benefit. When shooting Canon, my Bokeh king was the 85mm f1.8 used wide open. Never a fan of even faster apertures, this was enough and totally practical when that exact look was wanted. The Olympus 75mm f1.8 is effectively the same lens, but gives me the added benefit of greater reach and is by most measures, a better lens.
Now re-visiting this statement, what practical use is this super soft Bokeh? If you have a background that needs to be blurred out or the actual point of the image is to demonstrate Bokeh in all its (often miss-understood**) glory, then fine, but this can also be done with lots of software after the fact (again phone and compact camera tech). Now ask yourself how many images you want to take like this before it grows tired? The only area FF users can win without much effort is wide angle-shallow depth portraiture, an odd sub-genre really and one that MFT can still do with some effort applied.
The reality is, most FF users use f2.8 zooms for good reason. They offer versatility, good light gathering and a practical aperture range, which is why they are often the most popular flag-ship lenses in a range. A practical amount of DOF is shallow enough to softly bur out backgrounds, while keeping some context, but also guarantees enough depth to get the whole subject sharp.
In my own kit my 75 f1.8 is my Bokeh king (150 f2.8 equiv). It does not get a heap of use, the 40-150 Pro (F2.8 at 40-150 actual focal length-see below) being the work-horse. When I need it, it does the job as well as any lens out there.
Often the equivalency cited when describing an MFT lens, with terms like the 40-150 Pro being an 80-300 f5.6 equivalent, is missleading. The lens is still an actual F2.8 lens at 40-150, but it has double the magnification, so when multiplied out, the DOF is also magnified, but it is still actually an f2.8 150mm any day of the week. It is also a 300 f5.6. Sometimes when using my slow 4.8-6.7, 75-300 (truly horrifying/impressive FF specs), I do not get enough DOF!
How much less DOF would have been desirable? This was taken with the equivalent of a 150mm lens, quickly, quietly and accurately with an old EM5 at f1.8.
Conversely, I have the ability to use any lens in my kit at any aperture on offer without fear of over or under doing it. Basically, my working range is f1.8 for portrait style to F8 for landscapes style and f2.8 does most jobs perfectly. When I shot full frame, my range was f1.8, but only for showing off Bokeh, rarely used for serious work, with f2.8 to f16 for most subjects.
If I need more DOF, then I can get it at a setting 2 shutter speeds faster (or 2 ISO settings lower) than FF. In other words, depending on who you talk to, I have a DOF and/or light gathering advantage.
Ok, what else?
That’s really it.
The benefits of extra reach, smaller form factor and a fully developed system, including one of the more respected video systems now come to the fore. I can have a fast super wide that goes into a pocket, a top tier 600mm equivalent for the price of a mid range tele in FF and regularly have a speed advantage at the same cost/size ratio. My favourite Canon lens, the 135 f2L, was replaced by a 75mm Olympus that is at least its equal in quality, 15mm longer in actual reach, a little cheaper and half the size and weight.
Equivalent of 600mm f13+ and the wing and tip of the beak are a little out.
Looking at MFT from a brand to brand perspective, Panasonic and Olympus have been putting out one excellent lens after another, in a format that actually makes edge to edge sharpness easier to achieve. The big boys on the block have recently overhauled their systems, not once, but twice. First they lifted their game in their SLR stables, then, after tasting the winds of change, re-hashes them all again in mirrorless.
My issues with this system come in the form petty annoyances like having to buy smaller adapter sets to attach a Smallrig Mat Box, difficulty buying rarer super small filters, loosing lenses in the bottom of my bag, carrying too many options because I can etc. A friend was complaining yesterday about the limits of his bag with a FF body and two f4 FF lenses. I had four cameras (2 stills, 2 video), 3 pro zooms, a long tele and room for lunch.
What does the future hold?
Logically, smaller sensors should be on the rise, but the perceptions reinforced over the last couple of decades, cheaper sensor manufacture and the fear of losing ground to an opponent (especially a phone brand) has pushed the ever declining top tier of the industry in the other direction. Nikon is the only brand with a direction that to me makes sense. By using a larger lens mount than standard FF, they actually reduce DOF by another stop compared to FF, meaning you can buy cheaper and lighter f4 lenses with f2.8 depth characteristics.
I just hope MFT and 1” can hold on long enough to ascend to their rightful place as the true workhorse formats of the industry, not the perceived whipping boys.
*
*I have not looked into the new OM-1, so there may be even more to look forward to. We will see.
**Bokeh is a measure of the quality of focus transition at any aperture, focal length or lens to subject distance, not just f1.2 on a long lens.