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They aren't! Years ago they used to be common on the backs of cars, so you could look where you were parking. Vans and estate cars invariably had them. But no
by Theodores 7y ago
They aren't!
Years ago they used to be common on the backs of cars, so you could look where you were parking. Vans and estate cars invariably had them.
But now?
Backup cameras.
Same with the original lighthouse application. They don't use Fresnel lenses any more.
The lighting tech used for aircraft has superceded the Fresnel tech of old. So lighthouses are done differently now.
Even in home applications Fresnel lenses don't last the distance, You don't have hacky Fresnel lenses in products to make up for them having a naff CRT for the image.
But then again, Fresnel lenses do live on, but in better ways. There are many compound lenses for lights that are not a classic Fresnel lens but work nicely.
- rangibaby 7y agoNikon makes fresnel telephoto lenses, and they save size + weight vs their classic counterparts
- Theodores 7y agoIn practice though most lenses and applications move away from being Fresnel. The lights get better or a camera or other screen technology replaces it. Fresnel lenses are like motorbike sidecars, they are a cheap hack. But if I was to post 'you don't see motorbike sidecars these days' then some nitpicker on HN would Google search a new Kickstarter project of a motorbike sidecar and - two seconds later - mod me down for being generally but not universally correct. As I understand it the Nikon lenses are not 'Fresnel' as we know it. The idea is to combine a regular lens with a Fresnel lens to remove chromatic aberration. The weight saving isn't what it is about since there is still a regular lens that the Fresnel lens works with.
- i_am_proteus 7y ago> In practice though most lenses and applications move away from being Fresnel. Tungsten fresnel lights (and now LED fresnel lights) are very common in videography. The lens provides a simple spot/flood mechanism.
- rangibaby 7y agoThe fresnel element version of the 300mm f/4 lens reduces the weight by half and the size by one third compares to the non-fresnel version
- hug 7y ago> But if I was to post 'you don't see motorbike sidecars these days' then some nitpicker on HN would Google search a new Kickstarter project of a motorbike sidecar and - two seconds later - mod me down for being generally but not universally correct. I'm of course not going to downvote you, but just to help you out with your point IMZ-Ural still manufacture motorcycles with sidecars to this day, and in fact are working on a fully electric model.
- maxxxxx 7y agoTrue! "Proprietary Phase Fresnel technology" on the 500 PF. It looks very different though.
- ISL 7y agoCanon makes them too -- look for the DO lenses.
- buserror 7y agoFor many years now I've owned a 70-300 DO very very compact zoom lens and always been happy with it. There are some rare optical artifacts, in some lights, on some subjects, but it's never been a problem in real life.
- pmyteh 7y agoVery common in theatrical lighting, where a somewhat-focused beam is wanted but the not-quite-crisp edges characteristic of a Fresnel lens are an asset rather than a liability. For example: https://www.strandlighting.com/global/products/rama-led-fresnel-mkii https://www.strandlighting.com/global/products/rama-led-fres...
- djmips 7y agoVive (SteamVR) headsets use fresnel lenses. (vive vs vive pro comparision) https://i.imgur.com/SvxVRUL.jpg https://i.imgur.com/SvxVRUL.jpg