Silly question: one lens lens?

duckrider · Joined: 11 Dec 2013 Posts: 437 Location: Germany

It's boxing day and presents are all packeted out, have nothing to do....

So thoughts divagate around:

I love simple lens designs! The for me most impressing one is the 3 lens Hologon design from the early 1970's:

http://www.mir.com.my/rb/photography/companies/nikon/nikkoresources/RF-Nikkor/Contax_RF/Zeiss-Hologon/index1.htm

Three lenses for a perfect ultrawidewide angle!

Now we're 4 decades later and aspheric design is used in cheapest consumer cameras, new glass types of optical dispersion and diffraction are found.

But most lenses are zooms with so many lenses in there.... Crying or Very sad

Is a fixed focal length with only one (or maximal 2) lenses possible?
Using glass of different refraction zones melted together in one lens, aspherical design and of rectangular shape (different diffraction in the corner regions), especially fitted to the film or sensor. Of course this lens must have straigness of linear guide, must not turn if focused.

Am I crasy?
Wink

Thomas

enzodm · Joined: 11 Sep 2010 Posts: 350 Location: Italy

Meniscus is one kind of single lens lens. Different glass kinds in the same "lens" maybe could be better described as single group, more than single lens (e.g., achromatic doublet).

Attila · Expire: 2025-11-18

Novoflex 40cm f5. 6 is a doublet, it has two lenses only and pretty good.

iangreenhalgh1 · Expire: 2014-01-07

In long lenses, there are many that are achromatic doublets.

In 'normal' lengths, there was the Periskop type, which was two elements arranged around a central stop.

You could also use half of a dialyte, which is a 4/4 lens, so the half is 2 elements in 2 groups.

luisalegria · Expire: 2018-01-18

There are many types of achromatic doublets of many focal lengths in the Edmunds catalog if someone wants to experiment.
Also some of the better closeup lenses are doublets. For that matter all closeup lenses would work as camera lenses also.
Not good ones, but maybe interesting.

bernhardas · Expire: 2017-05-23

Edited

danfromm · Joined: 04 Sep 2011 Posts: 576

Well, if you can live with small coverage and are willing to work at small (and smaller) apertures, there's nothing wrong with simple lenses (meniscii, doublets). If you want large coverage, a large aperture and well-tamed aberrations then you'll need a lens with more elements. If you want all that and zooming too, still more elements are needed. The minimum for reasonable coverage, reasonable speed and reasonable corrections seems to be three elements. Reasonable people can disagree reasonably with reason about how much coverage, speed and corrections are reasonable.

Its all a question of your resources and your preferences.

I want good corrections, can live with relatively slow lenses. So the lenses I use most have no more than eight elements in four groups and most are simpler. This wasn't always true, my cine cameras' zoom lenses are incomprehensibly complex, but I no longer use them.

I've had and used two achromatic doublets, still have one. Both Century Tele-Athenars, both lousy.

enzodm · Joined: 11 Sep 2010 Posts: 350 Location: Italy

tao · Expire: 2015-03-12

Some toy lenses, such as Sima and Portragon, have one element.

Mos6502 · Joined: 20 Jun 2011 Posts: 961 Location: Austin

In the old days when negatives were huge and diffusion was not a worry there were many single and double element lenses.

The achromatic doublet in my VPK is about as sharp as anything made in the era - but the max aperture is f/11! Laughing

Remove the aperture and the lens becomes a nice soft focus job, with a max speed of about f/5.6

Orio · Expire: 2012-12-04

sichko · Joined: 20 Jun 2008 Posts: 2475 Location: South West UK

Orio · Expire: 2012-12-04

sichko · Joined: 20 Jun 2008 Posts: 2475 Location: South West UK

ForenSeil · Joined: 15 Apr 2011 Posts: 2726 Location: Kiel, Germany.

+1 for Novoflex 400/5.6 and 600/8
Both are doublets and quite good.

There are also some more modern "semi-Apo" ED doublets used for telescopes in focal lengths from ~400mm to ~2000mm with prices ranging from a few hundred to many thousands � in telescope shops. They are outstanding in terms of resolution and CA control but have a slightly curved field of sharpness without further correction elements. There are dedicated correctors for that available for (astro-)photography with large sensors (APS-C and larger). Another problem is that they are mostly produced in China with bad quality control - sometimes recalibration of the lens assembly on an optical bench is necessary to get everything out of the lenses (Here in Germany there are several companies are offering such a service, starting at 50�)

luisalegria · Expire: 2018-01-18

Thats what I also understood.
Gluing two pieces of glass together with different refractive indexes seems like a rather crude and inelegant solution.
I don't think there is a practical alternative yet however. There are quite a few patents filed on this.

duckrider · Joined: 11 Dec 2013 Posts: 437 Location: Germany

calvin83 · Joined: 12 Apr 2009 Posts: 7553 Location: Hong Kong

In the link above, you can find the link to GRIN lens http://en.wikipedia.org/wiki/Gradient-index_optics . Some lens makers do try to put GRIN glass to the photography lens but never make on till now. I heard that theoretically you can make a high quality lens with only two GRIN elements.

enzodm · Joined: 11 Sep 2010 Posts: 350 Location: Italy

David · Expire: 2013-01-25

The simplest single-piece-of-glass camera out there (that I know of and that returns usable results on a regular basis) is the Kodak Brownie Hawkeye Flash. There are other box camera, too, but the BHF is a lot of fun.

So for simple lenses, I've been experimenting with this a bit the last month and plan to try and get at least one good pictorialist-style photo this year. So that end, I picked up a plastic half-sphere cabochon (which is basically a 75mm 1:1.5 lens) and three lenses from Surplus Shed (plano-convex, Meniscus, and one other I forget the type of.) Each has a positive focal length that ranges from about 80mm to 100mm (making them all about f1.5, too.) I've not tested the image circles yet, but they're probably large enough to at least cover medium-format.

Anyway, single lenses can provide good results -- the BHF being an example that provides good (if slightly low-contrast) images with sufficient detail. The cheapest thing to do if you are really eager it to pick up a positive meniscus lens from Surplus Shed or eBay. Make sure it has a focal length at least double your camera's flange to prevent it from contacting the mirror, etc. Then grab some black plastic (such as the bags that film or photo paper come in) and tape a skirt around the lens. You can then free-lens without light entering the space between the lens and camera. More intense would be a tube-in-tube structure that allows focusing and possible even some removable aperture rings. The results won't ever be Zeiss-like, but they may produce interesting results.