Lens diameter

Started Jun 20, 2011 | Discussions thread
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kebwi Regular Member • Posts: 213
Lens diameter

My understanding is that the Sony 18-250mm has a 62mm diameter while the Sigma 18-250mm and the Tamron 18-270mm have a 72mm diameter. Is this as clear-cut as it sounds? Does the Sony lens (I know it's an older Tamron lens) actually have a small surface area with which to collect light?

On the same camera, all other settings identical, would one expect a photo taken with the Sony lens to actually be darker than one taken with the Sigma or the Tamron? The difference in surface area between 62mm and 72mm is about 75% or half a stop (give or take and to the best of my understanding, which may be flawed). Is the Sony lens half a stop darker than the Sigma and Tamron at otherwise identical settings? That should be visually discernible.

I'm more of an astronomer than a photographer and I am used to the astronomers being super duper gung-ho about the diameters of their telescopes because the more light they can scoop in (they call big telescopes light "buckets") the brighter they can make faint objects like galaxies and nebulae.

Maybe I'm really wrong about all this. I'm open to such a suggestion.

Thanks.

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Personal website: http://keithwiley.com

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