What type of Bahtinov mask works best for a 200mm f/2.8 Micro Four Thirds lens?
Asked 11/7/2022
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I want to use a Bahtinov tool to focus stars with a Panasonic Leica DG Elmarit 200mm f/2.8 on Micro Four Thirds. I’ve read that the ideal Bahtinov geometry can vary with the lens, and I’m unsure whether I need a custom-calculated pattern for this photographic lens or if a different style works better. What kind of Bahtinov mask or focusing tool is most suitable for a 200mm camera lens?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
3y ago
2 Answers
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I don't know how to calculate the ideal Bahtinov mask for a particular lens, but in my experience, the filter-style Bahtinov masks (etched polycarbonate plastic, very dense line pattern) work much better for photographic lenses than the laser-cut lower-density line patterns that are typically used over telescope objectives.
Generally, for camera lenses, think "filter" instead of mask. Those from Kase, LonelySpeck, and the like, are great for photographic lens purposes. E.g.: Kase 100mm × 100mm Night focus tool (Bahtinov); Kase Wolverine circular Bahtinov 77mm; LonelySpeck Sharp Star 2.
For telescope optics, use the appropriate "mask" (occluding) style Bahtinov.
Originally by user11924. Source · Licensed CC BY-SA 4.0
user11924
3y ago
0
Generated from our catalog & community — verify before relying on it.
For a photographic lens like a 200mm f/2.8, you generally don’t need to calculate a custom Bahtinov geometry. Community experience suggests that dense, filter-style Bahtinov tools work better on camera lenses than the larger, laser-cut occluding masks commonly used on telescope objectives.
In practice, think “filter” rather than “front cap-style mask” for a 200mm camera lens. These are typically made from etched plastic with a finer line pattern, which suits photographic optics better. Traditional telescope-style masks are more appropriate for telescope apertures, where the mask sits over the objective.
So the practical recommendation is: use a photographic Bahtinov focusing filter sized to your lens/filter thread or front diameter, rather than trying to derive a custom telescope-style pattern for the lens.
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