Basics

The first thing to mention is that the M4/3 line uses the same sensor size as the 4/3 DSLR line of cameras. Just the mount bayonet size is smaller and the distance from mount to sensor is reduced on the M4/3 cameras due to having no flip-up mirror.

The name "Four Thirds" stems from the fact that the sensor size in industry terms is sized at 4/3 inch (1.333 inches). This is an old method of rating sensor sizes that stems from 1950's Vidicon imaging tube technology where 4/3 inch was the size of the vacuum tube containing this sensor size of 17.3mm x 13mm.

This sensor size when compared to the standard of 35mm film frame size has about half the diagonal measurement and one quarter the surface area.. The net result is that a, say, 14mm lens on an M4/3 camera covers the same field of view as a 28mm lens on a 35mm film camera. This is an advantage with tele lenses in particular when a 300mm lens on an M4/3 camera behaves like a 600mm lens would on a 35mm film camera.

So the basic kit lens 0f 14-42mm covers the same field of view as 28-84mm would in 35mm film camera terms. The optional kit tele lens of 40-150mm covers the equivalent of 80-300mm. The superzoom 14-150mm covers the equivalent of 28mm to 300mm. The wide angle 9-18mm zoom covers the equivalent of 18-36mm.

The E-PL1 is the first of the "Light" version of the Pen line of M4/3 cameras. The initial Pen line started with E-P1 followed by E-P2 and the later E-P3. In the PL line the E-PL2 and E-PL3 now exist, my comparison chart of the PL series is here. Many ideas first tried out in the E-PL cameras do make it into the main E-P stream of bodies.

In making the E-PL versions, some simpler methods of construction have been used plus some features on the regular P series are not on the PL series.  Against that the E-PL1 and E-PL2 have a pop-up flash for more versatility plus that also enables the Olympus RC remote slave flash system to work with the Olympus R series flashes.


Lenses

With the advent of the E-M5 there seems to have been a large increase in the numbers of people starting in the M4/3 forum on DPReview, many converting over from heavier DSLR systems, or at least buying the M4/3 system as the light weight casual system and keeping the DSLR as the work system. This preamble brings up the fact that there has been a sudden increase in the number of people who change a lens and the LCD/viewfinder is black and nothing works. Read the manual.... early on (page 6 in the case of E-M5) it says "Do not press the lens release button" [when mounting a lens]. The reason being that holding the button in allows the lens to rotate just a little past the proper home position and when you release the button the lens locating pin does not drop into the hole in the lens, thus shutting down live view. The instant fix is to take your finger off the release button and rotate the lens back a bit until the pin does click into place, or of course never to hold the release button when mounting a lens. It will happen on my E-PL1 as well when I tried it, so is a common "problem" that is not a problem.

The kit lens for the E-PL1 is the Mk1 version of the 14-42mm lens which is a compact multiple barrel lens to keep the overall size small when stored. It has front barrel focus so the focus is a bit slow and the barrel rotates, thus making it a slight pain when using a polariser.

The Mk2 14-42mm lens sold with the E-PL1s (the 's' model was only intended for Japan but can be found elsewhere) and later cameras has a simpler and more robust barrel construction and by using internal focus it focuses faster and quieter than the Mk1 lens. Both lenses will fit on either camera. This Mk2 lens accepts these Olympus attachments.

WCON-P01 two element wide angle converter takes the focal length to about 11mm
FCON-P01 three element fisheye converter takes the lens to about 10mm but with a typical curved fisheye field of view
MCON-P01 single element +2.5 dioptre lens gives better close focus. 

The Mk2 R lens sold with E-PL3 has had a cosmetic upgrade but behaves the same as the earlier Mk2 and accepts the same add-on lenses.

The early twin lens kits added the 4/3 version of the 40-150mm lens plus the MMF-2 adapter that allows 4/3 lenses to fit the M4/3 body.

Later E-PL1 twin lens kits included the revised dedicated M4/3 version of the 40-150mm lens thus eliminating the need for the MMF-2 in the kit. Its bayonet mount at the front accepts the MCON-P01 where it will enhance close focus ability.

From E-PL3 an R version of the 40-150mm is supplied, same function as the original M4/3 lens but with cosmetic upgrade.

For the E-M5 an optional kit lens is the 12-50mm which is weather sealed to match the weather sealed E-M5 body and the lens also has internal focus and internal zoom so does not change size when changing focus or zoom.

Later kits sold are a box with the E-PL1 or E-PL2 and the very convenient super zoom 14-150mm lens which does not lose much in quality to a twin lens kit, but makes an amazingly convenient travel camera outfit.

Slowly other dedicated M4/3 lenses will appear and a number of manufacturers have become involved. See the available M4/3 lenses here.

Lens reviews and tests and interesting interactive displays of quality in a graph of aperture vs focal length is available (if indicated as "Tested") for many lenses here.

The older 4/3 line of lenses can be used by using the MMF-2 adapter or the Panasonic DMW-MA1 adapter that does exactly the same task as the MMF-2, either adapter can be used on Olympus or Panasonic M4/3 bodies. The auto focus may be a lot slower with some of the 4/3 lenses. The latest version of this adaper is the MMF-3 which is weather proof to suit the weather proof E-M5 camera. The MMF-3 of course can be used on a Pen body but does not cause any weather proofness as the Pen bodies and lenses have no weather proofing.

Try the simulator here to see any lens on any body.

Olympus make an adapter to fit the old Olympus OM film lenses to the M4/3 bodies, plus some other adapters as seen on that same link.

Panasonic M4/3 lenses can of course be used on Olympus bodies with the restriction that if the lens has no switch for OIS (Optical Image Stabilisation) then when on an Olympus body the lens defaults to no OIS. The Panasonic lenses with OIS switches allow the choice of lens stabilisation or body stabilisation or none at all. It is advised not to use both lens and body stabilisation at the same time. The Olympus bodies do not correct for chromatic aberration (purple fringing) so Panasonic lenses on Olympus bodies lose that correction. The usual barrel and pincushion distortion is corrected.

Many third party adapters are found on eBay and the like to enable fitting of many old lenses to the M4/3 bodies. The lens best needs a separate aperture control ring, so your favourite Leica lens on your M4/3 body is possible, it's just of course a smaller field of view behaving as though the focal length had doubled when compared to that lens on a 35mm film camera. See my links page for a few suppliers of adapters.

A summary of lenses available in M4/3 mount now on separate page.

Stabilisation

Image stabilisation is in the body with Olympus and involves a dynamic mechanical shifting of the sensor to combat shake for stills. With video, on the Pen series to avoid overheating the mechanism and to avoid noise in the recording, a pixel shifting method is used to lessen shake. This contrasts with Panasonic where the OIS stabilisation is in various lenses, but not all of them.

The newly announced OM-D series E-M5 model now has a sensor that rotates as well as provides the usual X-Y movement, allows better movement correction, it is effective with video now, and does appear to work better than any lens stabilisation method. A new feature on the E-M5 is to optionally have the stabilisation working at half press so as to get a stabilised view for framing or focus.

If using a Panasonic OIS lens with a control switch on the lens itself, the stabilisation can be controlled via either the lens OIS or the in body stabilisation (IBIS). The effect is roughly the same in terms of improved minimum shutter speeds attainable, something in the order of 3 stops or 10x shutter time period.

If using video then the OIS stabilisation is the better method. Any Olympus owner who is a very keen video user should probably choose to buy a Panasonic OIS stabilised lens, but make sure it is one with a switch on the lens, as the OIS lenses that have no switch on them disable OIS when on an Olympus body.

In practice on the E-PL1 the IBIS does add some minor blur to nearly all images taken at what may be considered safe shutter speeds. If your hand-holding technique is generally shake free, then leave IBIS off for daylight use and only turn it on when shutter speeds do get below the generally accepted 1/(35mm equivalent focal length). I find that I can shoot reliably shake free with IBIS off at the recommended minimum shutter speeds (such as 1/300 sec for 150mm) and with care most times can go as low as 1/160 sec with 150mm with no shake. Below that shutter speed I  turn on IBIS, or OIS if using an appropriate Panasonic lens.


Menus

The Olympus Pen models have a very complex menu system allowing a great variety of customisation options, so it takes careful reading of the manual to sort them out. The E-PL1 manual is poor in many places at explaining the features and the E-PL2 manual often is better to read to sort out some of the common features. Find all Pen body manuals from here.

The very first thing to do with this camera (or any Pen or OM-D camera) is to turn on the optional custom menus (the gear wheels item in the menu list) by....
 Menu ► Wrench/Spanner Menu ► Menu Display = ON.

Next is to enable the extremely useful SCP (Super Control Panel) by....
 Menu ► Custom Menu (Gear Wheels) ► D DISP/x/PC ►  Control Setting ► then go though the iAUTO, P/A/S/M and ART/SCN settings to set the way things display on the LCD when the Start/OK button is pressed.

The choices for each are Live Guide, Live Control and SCP. I have only the SCP turned on for all three modes. If two or three options are turned on for any mode, then when the OK button is pressed then you may need to press the INFO button to cycle to the control screen desired.

The SCP allows easy access to all the usual functions needed during a day's shooting and saves delving into menus to make changes.


Auto Focus

The Pen series of cameras, because of no mirror and thus no phase detect auto focus method, have to rely on the slower contrast detect method of auto focus. This is good in daylight and with good contrast subjects but starts to get slow and hesitant in lower light with the small maximum apertures of the kit lenses. Using a lens with f/2.8 or better vastly improves the low light focus performance. Many buy the Panasonic 20mm f/1.7 lens for this purpose, the lack of zoom is somewhat balanced by the greatly improved low light performance.

In experiments in poor light I have found (with camera in normal landscape position) that a contrasty edge in the focus box makes focus more reliable. At a certain low light level horizontal edges fail to focus, but twist the camera so the edge is not exactly horizontal and then the camera will focus reliably. At a certain lower amount of light (depends on the aperture of the lens) the auto focus fails completely.

The magnify button can be used to enlarge the focus box area of the screen by an optional 7x, 10x or 14x in order to check auto focus accuracy or to make manual focus more precise, see here. A  tip found on the DPReview forum  is to set the Red video button or the Fn button for depth of field preview and then when the commonly used manual focus assist magnification sometimes make life difficult for framing, then hold the Red (or Fn) button while doing the manual focus and then there's no magnification.

Many ask "why can the lens be focused past infinity?" and that has to be the case for contrast detect focus. The lens needs to hunt each side of the highest contrast point to find the proper focus. If aiming at a distant object then the lens has to focus past it (past infinity) and then back closer in order to zero in on best focus point.

Using an older 4/3 lens adapted to the E-PL1 via the MMF-2 adapter you can clearly hear the focus motor making the appropriate steps to attain focus. The dedicated M4/3 lenses work much faster so the steps are not so obvious.


Preview and Histograms

Some are dismayed that in preview the histogram does not change when the exposure compensation is moved plus/minus. Ditto the highlight/shadow blinky warnings don't change. 

This is due to the camera being in Live View Boost = ON.

Turn Live View Boost = OFF and now the histogram and blinkies will obey exposure compensation changes in preview. The Live View Boost setting is found in Menu ► Custom Menu (gear wheels) ► D ► Live View Boost ► ON/OFF. Live View Boost tries to always brighten the display in dim conditions to allow easier framing.

The histogram and blinkies highlight and shadow limits can be changed by a small amount to better suit your post process RAW converter or print results, find that also in Menu ► Custom Menu (gear wheels) ► D ► Histogram Setting ► Highlight (245-255) & Shadow  (0-10).

Blinkies = Highlight & Shadow, setting buried in Menu ► Custom Menu (gear wheels) ► D ► Info Setting ► and set it ON/OFF for preview, playback etc. "Blinkies" name because on review the highlights and shadows blink, but on preview they don't blink.

To my mind preview blinkies are easier to use than peering at the histogram. Make sure Live View Boost = OFF and then wisely use Exposure Compensation  to get just maybe a minimal amount of insignificant red highlights blown. This may be hard to do in some places with washed out white polluted skies. Keeping an eye on the highlights and attempting to "expose to the right" lowers the overall noise and improves shadow areas. The desired exposure to get the correct look to the image can be adjusted later in post process.


Flash

The E-PL1/PL2/P3 have a pop-up flash deemed by some as "unprofessional" but indeed it has the serious advantage of being the controlling flash for the Olympus RC remote slave capable flashes so makes it a more "professional" flash creature than the flashless models of E-P1 and E-P2. Up to three groups of flashes can be separately controlled and each group can have three flashes in it. Nine slave flashes controlled in a choice of modes by an "unprofessional" body.

The normal maximum flash sync shutter speed is 1/160 second but the camera can be tricked into using any shutter speed and I find the true maximum  flash sync speed is 1/320 second. To use a faster shutter speed then a flash capable of high speed sync is needed. More on the flash page.

The E-PL3/PL5 now has no flash in the body but an accessory FL-LM1 is in the box and that slides into the hot-shoe and takes power via the accessory port. Its functions are basically the same as the pop-up flash. The E-PM1/PM2 model has the same accessory flash device while the E-P3 body has incorporated a pop-up flash.

The OM-D line starting with E-M5 camera also has a  small accessory flash FL-LM2 in the box but this one is weather proofed, both FL-LM1 and FL-LM2 will all work on any model that needs that accessory flash. Flash compatibility tables are here.

The Olympus accessory flashes sold are:
FL-600R new in 2012, same output as FL-36R, uses 4xAA batteries for faster recycle, has extra features over older FL-36R.
FL-300R small flash, takes 2 x AAA batteries.
FL-36R medium size, suits M4/3 bodies, takes 2xAA batteries.
FL-50R large size, unwieldy on M4/3, takes 4xAA batteries.

Panasonic has lately adopted the same RC flash control method.