I am tossing up whether to buy the lovely Olympus mZD 40-150mm f/2.8 Micro Four Thirds lens and leave my old favorite, the Olympus ZD 50-200mm f/2.8-3.5 SWD Four Thirds lens for certain niche uses such as 800mm telephoto reach with the EC-20 teleconverter.

So my past 2 bushwalks have been with ONLY the Four Thirds lens mounted on my Olympus OM-D E-M1, to see if I can do without the faster focusing, more compact Micro Four Thirds lens.

The Four Thirds lens gives me more telephoto reach but in low light or poor contrast, the PDAF of the E-M1 still is a bit slow and for these sunset shots when contrast in the distant trees was low, I decided I was better off resorting to manual focus. Now I am not sure if the Micro Four Thirds lens optimised for CDAF will do better but I suspect it does.

The other lovely aspect of the Micro Four Thirds lens is that the lens does not extend on zooming – this aspect makes the Four Thirds lens look very long and intimidating indeed, particularly with the big lens hood attached. However, it does sit reasonably well on my waist belt – although I certainly wouldn’t want anything much heavier than this on my waist while bushwalking.

Here are a couple of hand held low light dusk sunset shots with the Four Thirds lens:

Olympus E-M1, Olympus ZD 50-200mm f/2.8-3.5 SWD Four Thirds lens at 112mm f/5, ISO 800, 1/160th sec. I chose f/5 instead of f/3.2 just to give me a bit more background depth of field.

Flock of birds flying home to roost.

Olympus E-M1, Olympus ZD 50-200mm f/2.8-3.5 SWD Four Thirds lens at 182mm f/5, ISO 800, 1/80th sec – yes that’s right 360mm effective focal length hand held at 1/80th sec, not bad – that’s why I use Olympus gear. If I had the Micro Four Thirds lens, I would have had to add in the 1.4x teleconverter to get this telephoto reach.

So, I am still undecided both lenses have their pros and cons – if I didn’t already have the Four Thirds lens, the Micro Four Thirds lens with 1.4x teleconverter would be a no brainer for me – but can I really justify having both?

	Olympus mZD 40-150mm f/2.8	Olympus ZD 50-200mm f/2.8-3.5 SWD
Price at Amazon.com	$US1399	$US1199 but perhaps half price used on Ebay
focal length range in 35mm terms	80-300mm	100-400mm
1.4x teleconverter	112-420mm f/4	140-560mm f/4-4.9
2x teleconverter	N/A	200-800mm f/5.6-7
length	160mm fixed length, collapsible lens hood	157mm but extends on zooming and bulky bayonet lens hood
diameter	79.4mm	81mm
weight	760g (880g w tripod mount)	995g (1070g w tripod mount)
CDAF optimized	Yes, silent dual linear voice coil motors, face detection AF	No, requires PDAF (eg. E-M1)
close focus	0.7m giving 0.42x macro	1.2m giving 0.42x macro
filter size	72mm	67mm
diaphragm blades	9 circular	9 circular
optical formula	16 elements in 10 groups (1 aspherical ED lens, 2 aspherical lenses, 1 SED lens, 3 ED lenses, 1 HD lens)	16 elements in 15 groups (3 ED lenses)
image sharpness in centre (my testing)		At 200mm marginally sharper than the 40-150mm with MC14 at 150mm and comparable apertures. At 150mm marginally sharper than the 40-150mm at 150mm and comparable apertures.