Forums
New posts
Search forums
What's new
New posts
New media
New media comments
New profile posts
Latest activity
Media
New media
New comments
Search media
Members
Current visitors
New profile posts
Search profile posts
Log in
Register
What's new
Search
Search
Search titles only
By:
New posts
Search forums
Menu
Log in
Register
Install the app
Install
Forums
Lenses
General Lenses
Technical question about a zoom lens
JavaScript is disabled. For a better experience, please enable JavaScript in your browser before proceeding.
You are using an out of date browser. It may not display this or other websites correctly.
You should upgrade or use an
alternative browser
.
Reply to thread
Message
<blockquote data-quote="Revet" data-source="post: 387225" data-attributes="member: 17612"><p>Just trying to understand whats happening with a zoom lens regarding the variable lens speed. Lets take for instance my Tamron 18-270 (f/3.5-6.3). So as I understand it, the lens speed at 18 mm is 3.5 and at 270mm, 6.3. Now lets do some math:</p><p></p><p>At 18 mm and f/3.5, the aperture would be 5.14 mm (18/3.5=5.14)</p><p></p><p>At 270 mm and f/6.3, the aperture would be 42.9 mm. (270/6.3=42.9)</p><p></p><p>I assume these are effective apertures and not actual correct?? I would assume that the aperture is the exact same opening (its max) whether it is at 18 or 270 mm at the fastest f value for that focal length, Correct??</p><p></p><p>Any insight or corrections to my logic would be appreciated.</p></blockquote><p></p>
[QUOTE="Revet, post: 387225, member: 17612"] Just trying to understand whats happening with a zoom lens regarding the variable lens speed. Lets take for instance my Tamron 18-270 (f/3.5-6.3). So as I understand it, the lens speed at 18 mm is 3.5 and at 270mm, 6.3. Now lets do some math: At 18 mm and f/3.5, the aperture would be 5.14 mm (18/3.5=5.14) At 270 mm and f/6.3, the aperture would be 42.9 mm. (270/6.3=42.9) I assume these are effective apertures and not actual correct?? I would assume that the aperture is the exact same opening (its max) whether it is at 18 or 270 mm at the fastest f value for that focal length, Correct?? Any insight or corrections to my logic would be appreciated. [/QUOTE]
Verification
Post reply
Forums
Lenses
General Lenses
Technical question about a zoom lens
Top