These two lenses give a similar field of view – that of the “Standard lens” or 50mm in full frame terms.
I have posted similar DOF and background blurring comparisons for full frame 85mm f/1.8 vs Olympus 45mm f/1.8 and also full frame 85mm f/1.8 vs Olympus 75mm f/1.8 taken twice as far away.
This blog post is to demonstrate the slightly shallower depth of field (DOF) and more background blurring that a full frame camera can attain over a Micro Four Thirds camera – but does it make the image more aesthetic, and is the difference really worth losing all the fantastic benefits of Micro Four Thirds – smaller, lighter, less expensive kit, easier to take traveling, to social events and hiking, better weathersealing, better image stabilisation, touch screen AF, closest eye AF, more fun and versatility, and the list goes on.
Only you can decide if you really need to go shallower DOF – and of course on both cameras you can get even more shallow DOF – the full frame allows use of 50mm f/1.4 lenses (and even a Canon EF 50mm f/1.2L), while on the Olympus OM-D, you can use the wonderful superb Olympus micro ZD 25mm f/1.2 lens, and if you want, you can go to f/0.95 lenses but currently only in manual focus.
The Canon EF 50mm f/1.8 II lens is known as the plastic fantastic – perhaps one of the worst build quality of any modern AF lens, and a cheap price to match but it has reasonable optics – although, not the sharpest tool in the shed wide open, and has lots of vignetting on the Sony a7II, plus lots of coma aberration and the bokeh is quite busy and often annoying – but this comparison is just to show DOF and degree of background blurring at f/1.8. When used with the Sigma MC-11 EF-Sony lens adapter, you do get fairly fast AF but no Eye AF, BUT it is very frustrating to use as you must re-mount the lens every time the camera is turned off or goes to sleep, and sometimes AF is a very slow stuttering experience. For some reason, the Sony a7II under-exposes this lens at f/1.8 but not at f/2.8 – very strange indeed!
On a full frame camera such as the Sony A7II mirrorless camera, the Canon EF 50mm f/1.8 ii provides the user with a further 1.3 stops of shallow depth of field options when compared to an Olympus OM-D E-M1 II with the old, now discontinued, Panasonic leica D 25mm f/1.4 Four Thirds lens but will this really matter for most people and will the many benefits of the Olympus system outweigh the DOF benefits of the full frame system?
Note that this Four Thirds lens is one of the few that is compatible with CDAF, but for some reasons, AF is stutteringly slow on the Olympus OM-D E-M1 mark I but works fine on the mark II camera. This lens was replaced with a smaller, lighter, less expensive Micro Four Thirds version. Neither are weathersealed but the new Olympus mZD 25mm f/1.2 lens is.
Real world lens tests:
Let’s have a look at some jpg images straight from camera (just resized for web viewing) with both lenses wide open as I walked around some gardens yesterday, not really looking for great shots, but shots to show difference in depth of field and image quality between the two systems when taken from the same camera position.
The Panasonic 25mm f/1.4 lens is first then the Canon 50mm f/1.8 lens, both taken from same camera position:
Note that the severe mechanical vignetting of the Canon EF 50mm f/1.8 II lens on the Sony a7 II is causing much more annoying “cat’s eye” shaped bokeh near the edges – note the sky highlights, as well as much darker corners. In addition, the longer aspect ratio of the full frame system makes it harder to exclude distracting skies in portrait orientation than it is with the wider Micro Four Thirds 4:3 aspect ratio – another reason I prefer Micro Four Thirds for portraiture.
The greater blurring capability of the full frame is well demonstrated here but the near out of focus leaves on the right are far more annoying with their distracting bokeh compared to the less blurred but less distracting bokeh of the Panasonic image.
When the focus point is farther away, the difference of the degree of background blurring becomes less between the lenses – as demonstrated with my previous posts.
For this image, the 25mm lens gives adequate subject isolation and background blurring, and I think it has much nicer bokeh, plus if you look at the highlight area of the statues’ head, the cheap and nasty 50mm lens has much more flare, softer, less contrasty imagery – that’s one of the resons why you may want to pay more for a higher quality lens!
Again the 25mm gives adequate background blurring and it is less busy – look at the branches of the birch – but this bokeh issue is not a full frame versus MFT issue but a lens design issue.
The larger out of focus circles of the 50mm are actually much more distracting and annoying – sometimes the more background blurring is actually worse for aesthetics!
Again the 25mm gives adequate background blurring and it is much less busy with nicer bokeh.
This closer image of grapes, looks nicer with the 50mm lens to my eye as the much larger out of focus bubbles make it less busy.
The 50mm lens here is giving too much background blurring making it hard to work out what is in the background which can work against the aesthetics by making the viewer work too hard – of course, the 50mm could have been closed down to f/2.8 to address this.
The bridge looks busier on the 50mm lens – the 25mm to my eye is giving nicer bokeh and sufficient background blurring.
Moral of the story:
Just buying into a full frame system does not guarantee you nicer looking, shallower depth of field, more aesthetic bokeh – you do need to choose your lens carefully, and lens design is always a trade off between wide open sharpness vs wide open bokeh:
The superbly sharp, big, heavy, expensive, Sigma 50mm f/1.4 Art lens has busy, distracting bokeh – sort of defeats the purpose of having a shallow DOF lens.
The Canon EF 50mm f/1.2L lens has buttery smooth bokeh but is soft (not that sharp) wide open with lots of aberrations.
The Canon EF 50mm f/1.4 lens is soft wide open with lots of aberrations and often busy bokeh but at least it is relatively small and inexpensive.
The Sony FE CZ 55mm f/1.8 ZA is sharp across the frame, relatively compact but has busy onion ring bokeh and costs $AU1150.
The Sony FE 50mm f/1.4 ZA has nice bokeh and is sharp in the centre wide open but is soft half way to edges and will set you back $AU2250!
See also my comparison table of the high end 50mm AF lenses for a Sony full frame.
And here we have the full frame conundrum – which is the lens that suits your needs best and can you afford the cost and weight?
If you are going to have stop it down to f/1.8 or more for adequate image quality or depth of field, then perhaps you are not really gaining much over an Olympus 25mm f/1.2 lens which is weathersealed, compact, relatively light, has almost zero aberrations and minimal distortion, probably better edge-to-edge sharpness wide open, can focus twice as close, has a lovely manual focus clutch, and has by far the best image stabilisation of 5EV 5 axis IS when used with Olympus OM-D cameras, which also allow fast, accurate AF almost anywhere in the frame (not just near the middle and which can be activated rapidly by using the touch screen or even the touch of the Live View screen on a wifi tethered smartphone) and with ability to accurately AF on the closest eye – just awesome! And that’s not all – on the E-M1II you get continuous AF at 18fps and silent shutter, not to mention the unique Olympus Live Composite mode for doing star trails, car headlights, etc at night, and for static scenes with tripod, the ability to shoot 50mp Hi Res shots.
ps… I didn’t do this comparison with the Olympus 25mm f/1.2 lens as I don’t own one ….. yet! 🙂
In the end, do you really need the extra shallow DOF that full frame affords when you are giving up so much to have it?