Why do some lenses use fewer aperture blades?

Asked 3/21/2015

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Many budget lenses have relatively few aperture blades, while more expensive lenses often advertise more rounded diaphragms. Since blade count can affect the shape of out-of-focus highlights and stopped-down specular rendering, why don’t manufacturers simply add more blades to all lenses? Does adding blades meaningfully increase manufacturing complexity and cost, or is blade count sometimes also used to differentiate cheaper and premium lens models?

Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0

Photography Stack Exchange contributor

11y ago

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Well, single blade itself isn't very expensive, I guess. But the additional blades require more blade mounting mechanisms and its cost is more likely significant.

Moreover, always take marketing into account. Main goal of lens manufacturer is income, not better quality for lower price. Diversification of lenses helps the business running. Let's consider for example Nikon prime 50mm lenses. You can have the f1.8G with seven diaphragm blades for 200$ and f1.4G with nine diaphragm blades for 350$. If you absolutely want to have nine diaphragm blades, would you pay for more expensive f1.4G if cheaper f1.8G had nine blades too? I doubt.

Originally by user28169. Source · Licensed CC BY-SA 4.0

user28169

11y ago

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Aperture blades themselves aren’t the whole cost issue. More blades also mean a more complex diaphragm mechanism, with extra parts, mounting, assembly, and tighter manufacturing tolerances. So yes, increasing blade count can add real cost and complexity even if each individual blade is inexpensive.

There’s also a product-positioning reason: manufacturers deliberately differentiate entry-level and premium lenses. Features like a more rounded diaphragm can be reserved for higher-end models to justify their place in the lineup.

More blades can improve the shape of the aperture opening, which may make out-of-focus highlights look rounder and less polygonal when the lens is stopped down. But blade count is only one factor in overall image rendering, so makers may choose to keep cheaper lenses simpler and reserve more refined diaphragm designs for pricier options.

UniqueBot

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11y ago

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