Olympus 12-40 vs 12-45: Is One Stop Worth the Weight?

Choose the Olympus 12–40mm f/2.8 PRO if you want one standard zoom for daylight, indoor people and evening photography. Choose the 12–45mm f/4 PRO when a smaller walking or hiking kit matters more than the extra stop of light.

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The 12–40mm is the more versatile default; the 12–45mm earns its place through portability. For indoor family photography, the 12–45mm’s limitation is its f/4 maximum aperture: it requires roughly twice the ISO or twice the exposure time compared with f/2.8. Neither lens deserves a blanket warning against buying it—the right choice depends on whether you need that aperture often enough to carry the larger lens.

These figures come from the original 12–40mm specifications and the 12–45mm instruction manual. The newer OM SYSTEM 12–40mm f/2.8 PRO II retains the same aperture, focal range, dimensions and weight, so the central comparison applies to both generations.

Indoor people make the 12–40mm worth carrying

The difference between f/2.8 and f/4 is one photographic stop. As an exposure example, a scene requiring approximately 1/125 second at f/4 and ISO 3200 could use 1/250 second at f/2.8 and the same ISO. Alternatively, keep 1/125 second and reduce ISO to approximately 1600. These are exposure calculations, not measured transmission results for these particular lenses.

That choice matters when children turn their heads, guests gesture across a table or a pet moves through a dim room. Image stabilization compensates for camera movement; it cannot stop the subject moving during the exposure. A sharp handheld photograph of a building at night does not demonstrate that the same shutter speed will work for people.

For a stationary landscape, you can often accept a longer exposure. For moving people, you usually need to protect shutter speed. That distinction is more useful than simply asking whether you shoot in low light.

At matching focal length, framing and focus distance, f/2.8 also produces shallower depth of field than f/4. Choose the 12–40mm if subject separation matters, while remembering that one stop is a useful difference rather than a guarantee of a heavily blurred background. For video with a fixed shutter speed, the wider aperture similarly gives you more room to reduce ISO.

Travel and hiking favour the 12–45mm

The 12–45mm saves 128g, calculated from the manufacturers’ stated weights. That is about one-third of the 12–40mm’s lens weight, although the percentage saving becomes smaller once you include the camera body. Its barrel is also 14mm shorter.

Those differences matter when the camera hangs from your shoulder all day or must fit into a small bag. If you normally photograph streets, landscapes and buildings at f/4 or smaller apertures, the 12–40mm’s extra aperture may spend most of the trip unused.

The 12–45mm also reaches a little farther. Its 45mm endpoint gives 12.5% more focal length than 40mm, calculated as 45 divided by 40. That is useful for slightly tighter framing, but it does not turn either lens into a long telephoto. Both begin at 12mm, so neither gives you a wider view for interiors.

A small camera body strengthens the portability argument. If you are building around an E-M10 IV, the E-M10 IV travel-kit guide covers the body considerations alongside the lens choice.

If you already carry a fast prime for evenings, the 12–45mm becomes especially sensible: the zoom handles daylight flexibility and the prime handles darker scenes. That recommendation assumes you are willing to change lenses. If you want the zoom to stay mounted from morning through dinner, choose the 12–40mm.

Close-up photography has a surprising winner

Do not choose the 12–45mm solely because its minimum focusing distance is shorter. It focuses down to 12cm at the wide end and 23cm at the long end, while the 12–40mm focuses to 20cm. Those figures describe focusing distance, not how large the subject appears in the photograph.

Olympus specifies the 12–45mm’s maximum magnification as 0.5× in full-frame equivalent terms across the zoom range, corresponding to 0.25× actual reproduction. Both 12–40mm generations reach 0.3× actual magnification at the telephoto end, or 0.6× equivalent. The 12–45mm figures appear in Olympus’s launch announcement reproduced by DPReview; the newer 12–40mm figures appear in OM SYSTEM’s specifications.

The 12–40mm can therefore reproduce a subject about 20% larger linearly at maximum magnification, calculated from 0.3 divided by 0.25. The 12–45mm’s particular attraction is achieving its close-up magnification at the wide end too, letting you show a small subject with more surrounding context.

Neither figure means true 1:1 macro. For flowers, food and travel details, both are useful; for maximum subject size on the sensor, the 12–40mm wins this comparison.

Sharpness does not justify a universal winner

OpticalLimits measured 6.2% barrel distortion at 12mm without correction on the 12–45mm, falling to 1.1% with correction. Its resolution testing found excellent centre performance at f/4 and f/5.6 throughout the zoom range, with weaker wide-angle borders associated with the stretching required for distortion correction. These findings come from Klaus Schroiff’s OpticalLimits review.

The practical implication is to keep the intended lens corrections active when judging wide-angle files, especially photographs of architecture. An uncorrected RAW preview can give a misleading impression of the result you will actually export.

Those measurements support the 12–45mm as a capable compact zoom. They do not establish that it is sharper than every 12–40mm at every focal length and aperture, and they should not be presented as measurements of the newer PRO II. Choose primarily around aperture and carrying weight; a universal sharpness ranking overstates what this evidence resolves.

Original 12–40mm or PRO II: check the suffix

The original Olympus 12–40mm f/2.8 PRO and the OM SYSTEM 12–40mm f/2.8 PRO II are separate versions. The II retains the core specifications but adds IP53 protection and a fluorine coating on the front element. OM SYSTEM also describes revised coating placement and manufacturing improvements intended to reduce flare. These changes are documented in its PRO II launch release.

The original 12–40mm has an IPX1 splash rating with a compatible splash-resistant body. Do not transfer the II’s IP53 specification to an original lens simply because both say PRO. Likewise, weather protection depends on the camera-and-lens combination; a sealed lens does not seal an unprotected body.

Handling also separates the two focal ranges. The 12–40mm design provides a pull-back manual-focus clutch and an L-Fn button; the 12–45mm omits those controls. The II’s operation is described in OM SYSTEM’s feature documentation, while the 12–45mm manual identifies its simpler controls. If you frequently switch manually between autofocus and manual focus, that difference can matter more than the extra 5mm of reach.

If you already own either focal range, change only to solve a specific limitation. Moving from the 12–45mm to a 12–40mm gives you one stop and the additional controls. Moving the other way removes 128g. For a first versatile standard zoom, choose the 12–40mm; for a deliberately compact daylight kit, choose the 12–45mm.