Do any zoom lenses or hoods use adjustable petals to match focal length?
Asked 1/11/2019
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On a zoom lens, a hood has to stay wide enough at the shortest focal length to avoid vignetting, but a narrower hood would block stray light better at longer focal lengths. Are there any lens hoods with petals that adjust as you zoom, or any zoom-lens designs that effectively achieve this another way?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
7y ago
2 Answers
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There are a few zoom lenses that effectively do what you envision, but it is not due to movements of the hood. Rather, it is due to a retrofocus design that extends the lens barrel fully at the widest focal length and retracts the lens barrel fully at the longest focal length. The hood, rather than being attached to the front barrel that extends and retracts, is attached to the main barrel that remains stationary.
The original Canon EF 24-70mm f/2.8 L is one such lens.
With the lens set at 24mm, the front element is extended almost to the end of the hood attached to the main barrel. This gives wide angle coverage with the hood.
With the lens set to 70mm, the front element is retracted all of the way into the main barrel. If the hood were in place, this would give much narrower angle coverage with the same hood. Notice that the attachment tabs for the hood are on the main barrel, rather than the inner barrel that extends.
The Zoom Nikkor AF 35-70mm f/2.8D had a similar optical design. The lens was at 35mm fully extended and 70mm fully retracted. But the push-pull zoom action that Nikon gave the lens prevented the hood from being attached to the main barrel. As a result, the hood was a thin ring attached to the moving front of the lens that was hardly worth the trouble.
Originally by user15871. Source · Licensed CC BY-SA 4.0
user15871
7y ago
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In practice, adjustable-petal hoods are not common. The main reasons are added complexity, reduced durability, and the risk of vignetting if the hood is set too narrow when you zoom wider.
A few zoom lenses achieve a similar effect through the lens design rather than a moving hood. For example, some lenses use an extending/retracting barrel where the hood mounts to the fixed main barrel. At the wide end, the front of the lens sits farther forward near the hood opening; at the tele end, the front element retracts deeper into the hood, which effectively gives more shading.
This approach provides some of the benefit you’re imagining without requiring hinged or manually adjustable petals. It also preserves the hood’s secondary role as physical protection for the front element.
So: dedicated zoom-adjustable petal hoods are essentially not a standard product category, but certain zoom-lens barrel designs can approximate the same idea.
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AI7y ago
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