The Great Full Frame vs Micro 4/3’s Debate

If you want to start a firestorm in camera circles, just state that shooting with an f1.8 lens on a full frame camera is not the same as shooting with f1.8 lens on a micro 4/3 camera. Say that on the 4/3 camera, because of its crop factor, that f1.8 lens in fact becomes the equivalent of an f3.6 lens in full frame terms. And then stand back and watch the fur fly.

I am an enthusiast and have no pretensions to being an expert; however, I have done a fair bit of research on this. As the owner of both a full frame camera and a 4/3 camera, I have also done a lot of comparative shots. And I can report the following - this is both true and false. Great, you say. Let me explain.

Why do people buy fast lenses? The answer, almost invariably, is right there in the description - speed. If you are shooting, say, a wedding inside a church, you need a fast lens (if you want to avoid using a flash). The bride walking down the aisle can’t be blurry in your pics. So with a 30mm lens at, for example, ISO 400, you would like a shutter speed of about 1/40 second. You also want a usable depth of field, say f2.8.

So if I put 30mm f1.8 lenses on both a full frame and a 4/3 camera (actually, for me, 31mm on the full frame and 17mm [=34mm] on the 4/3) and set both to those settings and take pictures in the church, what happens? Will they both produce pictures with the same amount of brightness and the same ability to freeze the action? The answer is absolutely, one hundred percent, yes. I have done it, over and over again. So if your reason for having a fast lens is, in fact, speed, then you can do this with either camera. It’s quite remarkable how people lose sight of this. Tony Northrup certainly does in a 2014 You Tube video where he goes into great detail on this subject and says he feels sorry for people that spend $1000 on an f2.8 4/3’s lens, thinking that they’re actually getting an f2.8 lens. But in terms of speed i.e. light gathering and the ability to freeze action in darker places (I repeat, the reason one has to expect that most people are getting a fast lens) you are getting exactly and precisely that - an f2.8 lens.

I’m going to go at this from a slightly different angle, because it is here much of the confusion seems to happen. Some things change between shooting full frame and 4/3’s - I’ll review them below. Northrup's video is very thorough in covering these things as well. However, speed doesn’t. On both systems, the only way to freeze action in low light is with a fast lens. And on both cameras, with the same settings and shooting in the same place, I will have exactly the same amount of light and the same lack of blur from movement in my shots. If you feel the need to argue this point, you need to spend some time with both cameras. And to repeat one more time - if speed is why you bought your fast lens, then with either system, you have got it.

Then what is different? Two main things; depth of field and noise. Depth of field does change from full frame to 4/3’s; with the settings we mentioned above, using the 4/3’s camera will have an equivalent depth of field of a full frame camera shooting at f5.6 rather than f2.8 (not always a bad thing by the way). This is because the sensor on the 4/3’s is half the area of the sensor on the full frame. In the end what this amounts to is this: slightly clearer Bokeh with the 4/3 camera. Both can be smooth and buttery, but the full frame will be somewhat more blurry. If this is what makes it or breaks it for you, then full frame is your ticket. It doesn’t for me, especially for the times I want to shoot as fast as possible but have more depth of field. Let’s say you want both the flower girl (who is 10' ahead of the bride) and bride in focus as they walk up the aisle, but still need a minimum of f2.8 aperture to get to your desired shutter speed, for example. I like having the option of more or less within the same light gathering parameters.

The key here I think (and the point Tony Northrup misses in my view) is that we mostly define lenses in our minds by speed. Lower f stops on lenses means that they are 'faster' lenses. They aren't defined as lenses with more Bokeh or less noise. So in labeling a lens, I think it is best to keep this in mind - let f2.8 define the speed, the criteria most people care about. Whether that's completely scientifically correct isn't really the point - it is what people are looking at, and for, when they buy.

Which brings us to noise, the great quantum mystery of digital cameras. Those photons are just plain weird. Mathematically, because of its smaller sensor, there should be more noise in a 4/3 camera. Is there? The honest answer is, yes and no. We will look at some sample pics a bit further on to illustrate what I mean.

When I magnify pictures taken with both cameras to 2:1 in Lightroom (most camera and lens test enlargements are done at a 1:1 setting, so we are double that), I will see some more noise on the 4/3’s shots. The first thing to point out is that this doesn’t mean much when you’re shooting at ISO 400 or less (where I do most of my shooting) - you literally can’t tell the difference unless the print is 10 feet high. But there is more to it than that.

My Pentax K1 with the 31mm f1.8 limited lens on it is a truly magical combination. It takes often stunning pictures and I love using it. My Olympus OMD EM1 with a 17mm f1/8 lens on it is also terrific, and probably half the weight of the Pentax. Choosing between them is often just a matter of feel. What it rarely is for me is a matter of noise, because the Olympus also has some magic tucked away in there, and that magic is how it handles noise.

I use Lightroom to process my pictures. Anyone who uses Lightroom knows about the Noise Reduction box near the middle of the right hand strip. A lot of people shy away from it because they know in reducing noise, they are also reducing image quality. It’s why I almost never noise correct on the Pentax. But not on the Olympus; I now, without even thinking about it, slide the Luminance setting (under Noise Reduction) to 20 on all my Olympus shots (I do one and then sync it to all). And the results are quite remarkable; the noise goes away, but the detail doesn’t! The pictures below will let you have a good look at this. This is consistent across all the lenses I have for the Olympus.

There is nothing that stunned me more after I got my Pentax than discovering that the picture quality of the Olympus could go toe to toe with it, one of the highest rated full frame cameras out there. It has given me a huge amount of respect for the 4/3’s system. With my EM1 and my tiny little 17mm f1.8 lens I can be a camera ninja, sneaking shots all over the place; with the 12-100mm on it I am a travel guru. And with my Pentax, I can pretend to be a real, full frame, actual 'photographer'. Alright.

In the end, for me, there is no battle. I use and love them both.

Olympus OMD EM1 camera with 17mm f1.8 lens. ISO 200, f1.8, 1/640 sec.

Pentax K1 camera with 31mm limited lens. ISO 200, f1.8, 1/640 sec.

Screenshot of Olympus at 2:1 without noise filter applied

Screenshot of Olympus at 2:1 with 20% luminance applied (the noise in the background is gone with almost no effect on the bird - ctrl + on your keyboard will zoom you in)

Screenshot of Pentax K1 without noise filter applied

Screenshot of Pentax K1 with 20% luminance applied (a very slight difference)

As a small aside, can you get the same Bokeh from both lenses with the same settings? Well, in fact you can. The first answer is a rather obvious one - shoot from 1/2 the distance to your main subject with the 4/3. There is an interesting twist to this though; full frame lenses by their nature, can't shoot as close as 4/3 lenses. In fact the norm is about 1/2 as close (double the sensor area). So if you go to the minimum focusing distance with each lens (i.e. as close as you can get and still focus) - and notice we are no longer choosing what to do but rather taking as much as the lenses give us - then the Bokeh is now the same with both systems. Here are two pics below showing this (please forgive the truly awful shots - I was just trying to get a feel for the background.) The Bokeh is essentially identical.

Olympus OMD EM1 with 17mm f1.8 lens. ISO 200, f1.8. 1/3 sec. at minimum focus distance (about 5").

Pentax K1 with 31mm limited f1.8 lens. ISO 200, f1.8, 1/4 sec. at minimum focus distance (about 10").