This guide compares the older 75-300mm f/4.8-6.7 II and the newer 100-400mm f/5.0-6.3 IS within the context of your OM-1 Mark II system and birding activities in West Cork.
1. Technical Specifications Comparison
| Feature |
M.Zuiko 75-300mm f/4.8-6.7 II |
M.Zuiko 100-400mm f/5.0-6.3 IS |
| Status |
Older lens |
Newer addition |
| 35mm Equivalent |
150–600mm |
200–800mm |
| Max Aperture |
f/4.8 – 6.7 |
f/5.0 – 6.3 |
| Weight |
423g (Lightweight) |
1,120g (Professional heft) |
| Length |
116mm |
205.7mm |
| Stabilization |
Camera IBIS only |
Built-in Lens IS (Supports Sync IS) |
| Weather Sealing |
None |
Dust, Splash & Freezeproof (IPX1) |
| Focus Limiter |
No |
Yes (Physical switch) |
2. Optical “Sweet Spots”
Understanding where these lenses perform best ensures maximum detail for your birding shots.
M.Zuiko 75-300mm f/4.8-6.7 II
- Sharpest Aperture: f/8.
- Performance: Excellent between 75-150mm. Noticeable “softening” occurs at the full 300mm extension.
- Pro Tip: To maximize results at 300mm, always try to stop down to f/8 if light allows.
M.Zuiko 100-400mm f/5.0-6.3 IS
- Sharpest Aperture: f/6.3 to f/8.
- Performance: Remarkably consistent across the entire range. It remains very sharp even at the 400mm (800mm eq.) limit.
- Pro Tip: This lens is optimized for wide-open use. In your C4 (Birds in Flight) mode, you can safely stay at f/6.3 to maintain the fast shutter speeds required for action.
3. Teleconverter Integration (100-400mm Only)
The 100-400mm can be extended using M.Zuiko teleconverters for extreme reach.
| Configuration |
Effective Reach |
Max Aperture |
Recommended Use |
| Lens Only |
800mm |
f/6.3 |
General birding / Flight |
| With MC-14 (1.4x) |
1120mm |
f/9.0 |
Distant shorebirds |
| With MC-20 (2.0x) |
1600mm |
f/13.0 |
Static subjects (Tripod required) |
4. Usage Recommendations for West Cork
- For Hiking/Casual: The 75-300mm is the winner when portability is key. Its low weight makes it ideal for long walks where photography is secondary.
- For Dedicated Birding: The 100-400mm is the superior tool. Its weather sealing is essential for the Irish climate, and the built-in IS provides significantly steadier handheld shots at long focal lengths.
- Diffraction Warning: On the OM-1 Mark II, avoid shooting at f/11 or narrower whenever possible, as diffraction will begin to soften the fine feather detail.