I've been looking forward to the Olympus ZD 25mm f/2.8 lens for a long time now. A pancake lens maximizes the most obvious strength of the Four Thirds format, the small form factor. Despite blogging about rumors of just such a lens, I gave up waiting and sold my E-410. When the ZD 25mm lens was announced, I ordered the E-420 and patiently waited for the lens to become available.

The E-420 and ZD 25 make a far more compact package than any other DSLR combination available, prompting Björn Utpott to write about the Shrinking Gap Between DSLRs and Compacts. Now that I have the lens in hand, I thought I'd post some size comparisons with other cameras, including both compacts and SLRs.

To begin with, here is a comparison with the Ricoh GRD II:



The difference is more pronounced when thickness is taken into account:




The GRD II is compact enough to slip into most pockets. It is an easy fit in a Lowepro D-Res 8:



Here is the comparison with the Sigma DP1:





The DP1 will also fit in the D-Res 8, though without any room to spare:



Taking the DP1 along with spare cards, batteries, and/or a viewfinder, the Lowepro Edit 100 becomes a good option. At this point, I'm looking at a bulky belt case with a shoulder strap. An easy tote, but no longer a "go everywhere" solution like the D-Res 8:



As the following photo shows, my trusty Olympus OM-2n with OM 40mm f/2 pancake lens is shorter and longer (wider) than the ZD combination:



The OM camera will snugly fit into the Edit 100:



The top panel of the E-420 bears a striking resemblance to that of the old. Yet look at all the functionality that has been lost! Intuitive physical controls for aperture, shutter speed, exposure compensation, and ISO are all clearly apparent in the view of the OM-2n from above. From a size standpoint, the E-420 eyecup makes that camera significantly thicker than the OM-2n:



As a result, the E-420 with 25mm pancake will not fit in the Edit 100. It will, however, fit nicely in the Edit 110:



Here are those four cameras again:





The cases compared:





The E-420 and ZD 25 combination is dwarfed by the Canon 5D and EF 50mm f/1.4 combination (shown here with the optional grip):





The Lowepro EX 160 is a nice fit for the Canon:



Do the E-420 and ZD 25mm deliver? I haven't had the lens long enough to say. My very preliminary impressions are mixed. I'll start with the positives. Taken separately, the E-420 image quality, handling, and performance are all very good. The lens is sharp and seems well made, and a 50mm equivalent prime is about right for most of my photography. This camera-lens combination delivers on the Four Thirds potential for compact size. It's great to have the responsiveness and image quality of a DSLR in a form compact enough to, more often than not, take wherever I'm going. The negative impressions come from my inability to avoid making comparisons to that OM-2n and Zuiko 40mm f/2 lens. In no particular order, here are some of the subjective and objective advantages of that old film combination over the young digital challenger:

• Roughly 5 times the total lens light gathering ability, which goes along with the ability to use a much more shallow depth of field when desired. This is a major plus to me.
• Snap on lens cap. It takes me several seconds to remove the ZD 25 lens screw-in lens cap. I've already missed photo opportunities because of this, and a replacement 43mm snap on lens cap is on order. Sure this cost me less than $10 shipped, but the screw-in cap was a bad idea. Minor issue overall.
• Presence of a good distance meter on the OM lens makes it easy to zone focus. The ZD lens not only lacks this but resets to infinity focus each time the camera is turned off. Very inconvenient for zone focusing. Significant issue to me.
• 40mm versus 50mm equivalent field of view. I prefer 40mm, but 50mm is fine too.
• Mechanically linked focus versus focus by wire. I prefer the former.
• Physical dials for control of aperture, shutter speed, ISO, and exposure compensation. What I would give to have these on my digital cameras!
• Brighter, larger viewfinder with a focusing screen that is sensitive to changes in focus.

Both lenses are sharp with pretty good contrast and colors. Both show moderate barrel distortion. Unfortunately, the ZD 25 suffers from moderate lateral chromatic aberration (color fringing). Though not bad from a bokeh standpoint, my preliminary feeling is that the ZD lens does not render out-of-focus areas as well as the OM lens. Here are a few bokeh samples from the ZD 25mm lens. The first two are at f/2.8, the third at f/4.5.







Overall, I can tell that the E-420 and ZD 25/2.8 combination is going to be a good fit for my needs, possibly more so than any digital system I've used to date. However, it falls short of the digital OM system I'd like to have.

Addendum - Realizing that the bokeh examples above aren't the greatest, I asked Christopher Lulic whether I could use one of his photos as an example. His photo, shown below with permission, demonstrates both foreground and background out-of-focus rendering with the ZD 25mm f/2.8 lens:

Click image for intended viewing size.

Chris, who goes by Chris in Osaka in the DPReview forums, did a nice comparison of the Leica D Summilux 25mm f/1.4 and Olympus Zuiko Digital 25mm f/2.8, which you can find here.