Backwards Zoom Lenses?
Posted 13/05/2019 - 13:36
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It all depends on the optical design.
For example, most front elements are convex, but a few are concave. I concur that the 16-45mm is an excellent lens.
For example, most front elements are convex, but a few are concave. I concur that the 16-45mm is an excellent lens.
Best regards, John
Posted 13/05/2019 - 19:05
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Working that way round can cause shadowing issues using the onboard camera flash at wider angles.
John K
Posted 14/05/2019 - 00:22
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I think most of my zoom lenses are shortest at intermediate focal lengths, usually extending slightly for the shortest FL & more for the longest setting. This is certainly the case for at least half a dozen around the 'normal' focal length.
I'm sure it's a consideration that comes quite a long way down the list of priorities in lens design, in fact probably so far down it's not even on the page.
I'm sure it's a consideration that comes quite a long way down the list of priorities in lens design, in fact probably so far down it's not even on the page.
Mike
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Pentax:K5ii, K7, K100D, DA18-55, DA10-17, DA55-300, DA50-200, F100-300, F50, DA35 AL, 4* M50, 2* M135, Helicoid extension, Tak 300 f4 (& 6 film bodies)
3rd Party: Bigmos (Sigma 150-500mm OS HSM),2* 28mm, 100mm macro, 28-200 zoom, 35-80 zoom, 80-200 zoom, 80-210 zoom, 300mm M42, 600 mirror, 1000-4000 scope, 50mm M42, enlarger lenses, Sony & micro 4/3 cameras with various PK mounts, Zenit E...
Far to many tele-converters, adapters, project parts & extension tubes etc.
.[size=11:].Flickr• WPF• Panoramio
.
Pentax:K5ii, K7, K100D, DA18-55, DA10-17, DA55-300, DA50-200, F100-300, F50, DA35 AL, 4* M50, 2* M135, Helicoid extension, Tak 300 f4 (& 6 film bodies)
3rd Party: Bigmos (Sigma 150-500mm OS HSM),2* 28mm, 100mm macro, 28-200 zoom, 35-80 zoom, 80-200 zoom, 80-210 zoom, 300mm M42, 600 mirror, 1000-4000 scope, 50mm M42, enlarger lenses, Sony & micro 4/3 cameras with various PK mounts, Zenit E...
Far to many tele-converters, adapters, project parts & extension tubes etc.
.[size=11:].Flickr• WPF• Panoramio
Posted 14/05/2019 - 08:19
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There are a few lenses with unusual designs like that. The M 75-150mm f/4, while it doesn't get any longer or shorter when zooming as the zoom ring moves along the barrel, is at 150mm with the zoom ring closest to the camera. This seems to me to be good design as it adds stability when the lens is at it's longer focal length, which is where it's most needed.
I remember being surprised to find that, while the lens lengthens when focusing closer to the subject, the rear element of the DA 35mm limited stays in the same place always and doesn't move with the rest of the lens elements.
I remember being surprised to find that, while the lens lengthens when focusing closer to the subject, the rear element of the DA 35mm limited stays in the same place always and doesn't move with the rest of the lens elements.
Pentax hybrid user - Digital K3, film 645 and 35mm SLR and Pentax (&other) lenses adapted to Fuji X and Panasonic L digital
Fan of DA limited and old manual lenses
Fan of DA limited and old manual lenses
Posted 14/05/2019 - 09:01
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I remember seeing a lens test for the M 75-150mm f/4 in LPMM and it showed the lens to be sharper at the 150mm end than the 75mm. Normally it's the other way round.
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Half Man... Half Pentax ... Half Cucumber
Pentax K-1 + K-5 and some other stuff
Algi
Pentax K-1 + K-5 and some other stuff
Algi
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2518 posts
16 years
South Dorset
- How backwards zooming works optically.
- Why Pentax (or other designer) would use a backwards design for a zoom lenses.
- Whether there any other fairly common zoom lenses that are backwards.
- Whether the DA 16-45mm and Q-02 are related optically.
Steve