Olympus OM manual focus lenses are extremely popular lenses for use on Four Thirds, Micro Four Thirds and Canon dSLRs because they are often readily available on Ebay, are small, light and compact, have an aperture ring, have great image quality and tend to have the common filter size of 49mm.
On Olympus Four Thirds and Micro Four Thirds they gain image stabilisation through the built-in IS in the camera body.
On Four Thirds and Micro Four Thirds cameras the field of view is half that when used on a full frame 35mm camera as the sensor size is a 2x crop. This is very handy when you want telephoto reach, but not so handy for the wide end.
Olympus has recently filed a patent to make an adapter for these lenses which has a 0.5x wide converter optical elements and which also allows these elements to be moved by an SWD AF motor, thereby allowing these lenses to be used at their native field of view and their native depth of field, but with an aperture half of that stated thereby allowing 2 extra EV stops of light to come in.
Thus a 21mm f/3.5 OM lens will function as a 21mm f/1.7 lens but have the same field of view and DOF as a 21m f/3.5 lens on a 35mm camera.
Unfortunately, the price on these lenses has gone up over the past 10 years since Olympus discontinued production and collectors have sort these lenses.
The good news though, is that the lenses that are best used on the Four Thirds and Micro Four Thirds cameras tend to be the slower aperture prime lenses in the 21-200mm focal length range, and these are still at very reasonable prices – usually less than $US200.
In addition unless they are the super expensive APO versions, there will be purple fringing wide open, and are generally best used 1-2 stops down from maximum aperture, furthermore, the exposure system generally requires manual preset compensation for apertures wider than f/2.0.
The faster aperture, more expensive lenses often produce more ghosting due to the larger diameter rear element reflecting light rays back and forth to the shiny sensor.
Lenses with focal length 200mm or more get increasingly tougher to focus hand held when using a 2x crop sensor as you are at 400mm telephoto reach already.
Avoid legacy (and thus OM) zoom lenses – the image quality is generally not as good, and image stabilisation becomes an issue as you have to manually enter a focal length, and this is not practical on a zoom lens with changing focal lengths.
In general, it is probably not worth spending a lot of money on these legacy lenses if a digital lens can be had for a similar price as the digital lens will usually give better image quality, have autofocus, allow the camera to control the aperture and meter more reliably, automatically optimise image stabilisation based on detected focal length, and record the lens settings in the EXIF data of the photo.
The following prices are average Ebay prices as at Feb 2010:
The OM lenses you should consider getting for under $US200 are the following:
- 21mm f/3.5 – the most expensive of this group, but a very nice lens to have unless you bought the Panasonic 20mm f/1.7 which is a must!
- 24mm f/2.8 – highly recommended if you don’t have the Panasonic 20mm f/1.7 or Leica-D 25mm f/1.4
- 28mm f/2.8 – tend to be not as good as the 24mm – softer and more CA wide open – don’t bother getting any OM 28mm lens for use on FT/MFT unless you will be stopping it right down – eg. infrared photography, use a kit lens instead
- 35mm f/2.8 – better than the 28mm but not as good as the 24mm
- 50mm f/1.4 or f/1.8 – really need to be used at f/2.8 but can be very useful lenses
- 50mm f/3.5 macro
- 100mm f/2.8 – nice wide open – a must have compact lens
- 135mm f/2.8 or f/3.5 – excellent – another must have compact lens
- 200mm f/4 or f/5 – excellent but 400mm is getting a tad difficult to manual focus hand held – nice to have – what else gives you 400mm telephoto reach at f/4 image stabilised in such a small package? Can’t do that with any Canon or Nikon dSLR yet!
If you have a particular need or desire, you can look at the next price point of $US300-$700 for mint lenses:
- 16mm f/3.5 fisheye – $US500-800 – usable but some barrel distortion and not fisheye on FT/MFT
- 24mm f/2.0 – $US450-550 – not as good as the f/2.8 version when used on FT/MFT
- 28mm f/2.0 – $US450-550 – not as good as the f/2.8 version when used on FT/MFT – soft and lots of CA wide open
- 35mm f/2.0 – $US225-500 – not as good as the f/2.8 version when used on FT/MFT – soft and lots of CA wide open
- 35mm f/2.8 shift – $US500-700
- 38mm f/2.8 1.7-8x life size (on 35mm dSLR) macro lens for bellows use (2.3-6.7x) or AutoTube (3.1-4.5x) – $US600-700
- 40mm f/2.0 – $US550-700 – variable results wide open – probably not worth it
- 50mm f/1.2 – lots of ghosting wide open though – $US625 -
- 55mm f/1.2 – lots of ghosting wide open though not worth it for MF/FT – $US350-500 (serial no > 1,100,000 is said to be better as no rare earth element which tends to yellow with age)
- 50mm f/2.0 macro – $US500-550 – but may as well buy the awesome Olympus ZD 50mm f/2.0 macro
- 80mm f/4 2x life size macro for bellows or autotube – $US250-350
- 85mm f/2.0 – $US400-550 – usable
- 100mm f/2.0 ED – $US700-800 – excellent but heavy
- 135mm f/4.5 macro for bellows or autotube – $US250-400
- 180mm f/2.8 – $US500-600 – said to produce more CA than expected
- 300mm f/4.5 – $US250-350 – for tripod use only really, handy to have and OK wide open, better at 600mm f/5.6
- 500mm f/8 mirror – $US500-600 – the mirror lens to get if you are going to get one! Tripod use only though as 1000mm f/8!
If you are crazily addicted then here are some nice lenses in the next price point of $US700-$US1200:
- 18mm f/3.5 – $US1100-1500 – but gives barrel distortion
- 21mm f/2.0 – $US950-1300
- 90mm f/2.0 macro – $US650-1200 – excellent on MFT/FT – perhaps the only high end OM worth getting
Collectors and professionals only – the super expensive lenses:
- 8mm f/2.8 circular fisheye – $2500 – not useful on FT/MFT – why bother when you can get the Olympus ZD or Panasonic fisheye instead?
- 24mm f/3.5 shift lens – a superb lens for architecture on a Canon, not so useful on a M43 as you can now get cheap shift adapters – $US 1800-2400
- 180mm f/2.0 – $US3400
- 250mm f/2.0
- 350mm f/2.8 – $US4000-$US6500
More information on Olympus OM here and on using OM lenses on Four Thirds here: