Raw EVF megapixels, compared across cameras with different sensor sizes, tells you almost nothing useful about viewfinder quality. Linear resolution ratio is the correct metric: on that measure the OM-1’s 5.76MP EVF on its 20MP sensor achieves 54%, the second-highest in a comparison of eleven cameras, while the Sony A7CR’s 9.44MP EVF paired with its 61MP sensor achieves just 20%.
The OM System settings backup file is unreadable and can only be restored to the same camera model — so when I moved from the OM-1 Mk I to the Mk II, transferring settings meant going through every menu item manually. These spreadsheets, built on BobCS’s 2022 framework and updated by reader MM with full User Guide page references, are the only structured templates on the internet that mirror the complete OM-1 menu system.
Across five tests covering focus accuracy, resolution, dynamic range, noise, and handling, the OM 50-200mm f2.8 matched or exceeded the Sony 200-600mm on every measure while weighing 900g less. The Sony 400-800mm outresolved everything else at 32 LPI with 98% focus accuracy, but at 2.5kg it was impossible to hand-hold for sustained birds-in-flight work.
Using standardised test data from The-Digital-Picture — the only widely available source with controlled lab comparisons of both the 600mm f4 GMaster and the wildlife zooms — the £12,000 prime shows minimal perceptible image quality advantage over the £1,600 200-600mm or the £2,400 400-800mm at 600mm. Independent numerical resolution data comparing exotic primes to wildlife zooms essentially does not exist, because manufacturers provide early samples to YouTube influencers rather than to test houses that might measure the difference.
The rotational inertia index for the Sony 400-800mm is 3.2 times higher than for the OM 50-200mm f2.8 without its tripod collar, which translates directly into how hard each lens is to swing when tracking a fast-moving bird. Neither Sony zoom has a focus preset function, and the Sony 400-800mm’s minimum focus distance of 350cm makes close subjects impractical; the OM 50-200mm with MC20 focuses to 78cm and delivers 2:1 FFE macro capability.
At true ISO 3200, DxO data shows the Sony full-frame sensor has approximately a 1-stop dynamic range advantage over the OM Micro Four Thirds sensor — but the OM pro zoom lenses are 1.3 to 1.7 stops faster than the Sony wildlife zooms at equivalent focal lengths, which cancels or exceeds that advantage. The Sony 200-600mm suffers a further penalty at 800mm: it must be cropped to reach that focal length, reducing the active sensor area to approximately APS-C size and eliminating both the resolution and full-frame dynamic range advantages simultaneously.
Using Visual Extinction (MTF0) testing on a 4x ISO 12233 chart at 18 metres, the OM 50-200mm f2.8 with MC20 at 800mm FFE resolves 23 LPI — matching the OM 150-400mm and out-resolving the Sony 200-600mm at 21 LPI when that lens is cropped to reach 800mm. The OM 50-200mm with MC20 at 800mm loses only one LPI unit compared to the bare lens at 300mm, confirming that the 2x teleconverter is not meaningfully degrading resolution.
Across nearly 11,000 shots on Red Kites at Gigrin Farm, the OM 50-200mm f2.8 + MC20 achieved 93% focus accuracy and the OM 150-400mm achieved 92% — both ahead of the Sony 200-600mm at 90%. The Sony 400-800mm scored 98% but from only 808 shots, because at 2.5kg it was impossible to hand-hold for extended periods; the OM 50-200mm, weighing 1.2kg without its tripod collar, generated more than 2,700 analysable shots in the same session.
FastRawViewer renders true RAW data rather than the embedded JPEG preview, pages through files at near-JPEG speed on a fast SSD, and has keyboard-driven colour labelling that makes it practical to work through tens of thousands of files without importing them into a DAM. At 50fps, one minute of shooting generates 3,000 images; the fine detail view via the Q key is the most reliable tool I have found for checking eye focus on birds during culling.
Testing the OM 50-200mm f2.8 (Little White) and 150-400mm f4.5 (Big White) across multiple sessions, the MC14 teleconverter imposes almost no focus accuracy penalty on the Little White — the combination remained above 90% in conditions where the bare lens achieved 93%. Background type turned out to matter more than ISO: birds against clear sky consistently outperformed the same lens against foliage by a wider margin than raising ISO by two stops.
Three weeks across seven locations in Costa Rica in March 2026 produced 70,000 birds in flight images including Resplendent Quetzals in cloud forest, Scarlet Macaws and hummingbirds using the OM-1 Mk II and OM 50-200mm f2.8 as the primary system. This post records the full itinerary, commentary on each location, and practical notes on transport and accommodation — written in San José airport at the end of the trip for the photographers and birders I met along the way.
OM System’s Live ND stacks up to 128 exposures to give 7 stops of ND equivalent, eliminating the need for physical ND filters in most waterfall and fast-water scenarios, and producing significantly less noise than a single long exposure would. The High-Res shot mode extends this to exposures of up to 8 minutes on a tripod or 12 minutes hand-held, with improved dynamic range and resolution — results I tested against the Nikon Z7 and found superior on every measured metric.
