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The simplest vintage formulas?
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PostPosted: Fri Mar 10, 2023 11:00 pm    Post subject: The simplest vintage formulas? Reply with quote

Hi there!
So after trying on a Sears 135mm from the 70's, I realized how simple that thing is.
4 elements in 4 groups, and outstanding optical performance.

What are some of the best, SIMPLE low element-low group count builds that produce stunning images?
I would like to start to collect the simple ones Smile


PostPosted: Fri Mar 10, 2023 11:15 pm    Post subject: Reply with quote

Triplets are 3e/3g

tessars are 4e/3g

dialytes are 4e/4g

don't be fooled though, almost all 135mm lenses are good, but the same cannot be said of other focal lengths.


PostPosted: Sat Mar 11, 2023 12:46 am    Post subject: Reply with quote

You may start collecting simple [2/1] achromats. They often were used in ultra-long lenses since their main disadvantage is field curvature. Notable examples are the Novoflex Noflexar 400mm f5.6 and 600mm f8. Leitz also sold similar [2/1] long lenses such as the Telyt-R 400mm f6.8 and the the Telyt-R 560mm f6.8. [2/1] achromats (of lower quality) were produced by several Japanese companies during the 1960s and 1970s.

Slightly more "complicated" is the Leica Tely-S 6.3/800mm lens. It's a [3/1] construction. Using a special glass with anomalous partial dispersions it is nearly apochromatic.

The Novoflex Noflexar-T 5.6/400mm is even more complicated ... a real [3/2] construction with surprisingly good performance on 24 MP FF (not as good as the Canon 2.8/400mm L but clearly less CAs than the Canon FD 4.5/400mm). Biggest problem - again - is field curvature.

The more complicated triplets [3/3], Tessars [4/3] and Ernostar [4/4] designs were mentioned already by Ian.

If you look for for complicated 3 element lenses the Zeiss Sonnar type (by Bertele) is very interesting. Slower Sonnars such ast the 4/135 were [4/3] constructions, the slightly faster ones were [5/3] (e. g. Sonnar 2.8/180mm), and the fast f2 anf f1.5 ones were [6/3], [7/3] and even [8/3].

Simple lenses would be [1/1], and they have really stong aberration problems. One can "minimize" those problems to a certain extent. Using e. g. a 6:1 relation of the radii of the lens minimizes the spherical aberration, and low disperions glass would minimize the aolor aberrations (but at the same time increase spherical aberration and other monochromativ aberrations due to low refraction index). Some pretty nice tutorials about simple lens construction are available, e. g. from Kingslake (Kodak) or from current Japanese lens designers.

S


PostPosted: Sat Mar 11, 2023 1:38 am    Post subject: Reply with quote

Here is the list of triplets I recommand from my personal experience:

Steinheil Cassar S 50/2.8
Voigtländer Color-Lanthar 50/2.8

Leica Elmar 90/4.0 3-element
Meyer Trioplan/Diaplan 100/2.8


PostPosted: Sat Mar 11, 2023 6:40 am    Post subject: Reply with quote

There are also some pretty good triplet projection lenses, like the Braun Ultralit PL B-MC 90 mm f/2.8 / Reflecta Agomar B-MC 90 f/2.8:

I select you! by simple.joy, on Flickr

as well as very good industrial/enlarging lenses, particularly from Steinheil, like the V-Cassarit 50 f/3.5:

Jester single moment by simple.joy, on Flickr

or this Steinheil Optronic lens:

Tea partly by simple.joy, on Flickr

I certainly was more than impressed by that kind of IQ from a triplet, even though it is pretty limited to certain magnifications with some of them.


PostPosted: Sat Mar 11, 2023 10:31 am    Post subject: Reply with quote

As already well said, triplets are simplest anastigmats.

But the ernostar-derived 135mm lenses should get credit. A reasonably narrow angle of view I'm guessing allows the lack of symmetry to work, although there are far more non symmetrical designs out there...


PostPosted: Sat Mar 11, 2023 10:45 am    Post subject: Re: The simplest vintage formulas? Reply with quote

Coyote23 wrote:
Hi there!
So after trying on a Sears 135mm from the 70's, I realized how simple that thing is.
4 elements in 4 groups, and outstanding optical performance.

What are some of the best, SIMPLE low element-low group count builds that produce stunning images?
I would like to start to collect the simple ones Smile


The number of elements is just one aspect of complexity in a lens design. The different glass types per design another one. More aspects: Whether all element surfaces have different curves. How asymmetric a lens is, up to retrofocal or tele asymmetry. Short radii of the curves on both surfaces of one element can be tricky in manufacturing. For example the Unilite, Biometar, Xenotar 4th element in what is called a simplified Planar as it has 5 elements instead of 6. Elements or groups can shift independently of another. Which can exist in the front cell focusing of simple Triplet and Tessar designs while focusing the total unit is seen as delivering better IQ. Floating elements in more complex designs however improve IQ for more subject distances.
Modern aspherical surfaces of elements (some on both sides) can reduce the number of elements and still correct for all kinds of aberrations. The lenses in the Kodak disc cameras, your phone camera, for example.
To keep the costs low and the challenge meaningful I would suggest to look for the 50mm standard lens on FF format in all its design variations. Then there still is a list of what describes the quality of an image made with them. Center IQ, overall IQ, vignetting, bokeh, etc.

BTW, which Sears 135mm 2.8?


PostPosted: Sat Mar 11, 2023 11:06 am    Post subject: Reply with quote

I must give a shout out to on-axis, mirror-based lens designs as the simplest and cheapest way to achieve large aperture performance across a wide field.

For a lot of photography applications, the effect of the central obstruction is not relevant.

I'm on my phone at the moment, so don't have all the resources, but there's a reason people start out there... it's easy! Make lens elements concentric with each other, place elements at the centre of the mirror's curvature, etc...

For example - the lensless Schmidt camera, which in diagram below is operating at f/5 with only one mirror (and aperture stop of significance):



Pictures from one: https://www.cloudynights.com/topic/474788-lensless-schmidt-camera-updated/

How does it work? To quote MKV:

Quote:
It's a matter of simple geometry. An aperture stop at the center of curvature of a mirror, forces all incoming ray bundles to encounter the mirror surface squarely, that is -- orthogonally. One can say all incoming light into a Schmidt camera is technically "on-axis." And since coma is an off-axis aberration, it will be zero for all incoming angles of light. is zero There's no astigmatisms either since that, too, is an off-axis aberration. The only aberration remaining is its the spherical aberration and that depends on the size of the clear aperture. The smaller the aperture relative to the ROC the smaller the SA. An aspheric corrector is a zero-power optic and only affects the optical path difference across aperture. This permits larger apertures relative to ROC and increased photographic speed for which such cameras are well known.


Well worth reading the full thread on them https://www.cloudynights.com/topic/692091-lensless-schmidt-camera-for-astrophotography/

So what are the issues? The aperture stop has to be at the centre of curvature for the spherical mirror, which in this instance will be twice it's focal length -

in telescopes of long focal length, that will be a very long instrument!!

Secondly, the field is not flattened. So if you want to take pictures, you will need a film plane curved in '3D' - difficult. And finally, most importantly -

The focal plane is inside the instrument, hence why it is called a "camera". You can take pictures there, but how do you observe?
You'll see in the linked thread someone modified it to use a fold mirror.

Now - as for simple optical designs, the idea of not needing a flat film plane can be quite a significant aid to the design.. and not to those intending to use it. As already mentioned, many cheaper cameras with single or two element lenses can often have a curved in one dimension film plane (which still isn't perfect).


PostPosted: Sat Mar 11, 2023 5:10 pm    Post subject: Reply with quote

Another factor to watch out for on a lot of these earlier lenses, especially those without an automatic aperture, is the number of aperture blades.
For instance, my M42 Tessar 50mm f/2.8, with the auto-aperture pin and an a/m switch, has only five blades, a somewhat earlier (1950's?) pre-set Exakta-fit Tessar has eight blades, whereas my (early '60's?) aluminium-coloured pre-set M42 Tessar has 12 blades.
Wide open, they're all much of a muchness, but close down a few stops and introduce a bit of backlight and you'll really notice the difference!
Horses for courses, obviously … some people struggle with pre-set mechanisms, I grew up with them Wink


PostPosted: Sat Mar 11, 2023 6:16 pm    Post subject: Reply with quote

I love the Zeiss Jena 13.5cm Triotar f/4 - the old slim version that looks like a lightsaber.


PostPosted: Sat Mar 11, 2023 6:32 pm    Post subject: Reply with quote

If I understand it correctly, telescopes are often based on simple doublet schemes, and the rendered image quality is quite high. Are not there longer photo lenses which also keep the doublet base?


PostPosted: Sat Mar 11, 2023 9:38 pm    Post subject: Reply with quote

alex ph wrote:
If I understand it correctly, telescopes are often based on simple doublet schemes, and the rendered image quality is quite high. Are not there longer photo lenses which also keep the doublet base?


Telescope doublets are corrected for a much, much narrower 'image circle' than a 35mm film frame, which is considered 'wide' in astrophotography.

This doesn't mean they're unusable, but it's best to bear in mind just how many degrees of freedom a doublet offers to correct aberrations, what it's best suited to because of this, and why it had to be departed from to achieve certain designs.

A cemented doublet has three degrees of freedom with which you can mostly correct spherical aberration, coma and axial chromatic aberration. Having an air space adds another which from what I've read is good to control coma better. Correction for spherical aberration and coma makes it an aplanat, as your link mentions.

This then leaves out the following, in order of significance - astigmatism, field curvature and distortion. These are all defined as off-axis aberrations, away from the optical axis.


Sooooooo... we can see why telescope doublets have a narrow field of view. It is restricted to that.

In general [...] with refractors, field curvature is still primarily related to focal length. Short [focal length] refractors tend to have greater curvature than long refractors.

As a (field) curvature has a radius, we can see the smaller the radius, the greater the (field) curvature is, as demonstrated here:



So we can see why long focal lengths help, but honestly - they have to be quite long. I wonder if the older tele lenses banked on shooting subjects where things might be less bothersome.

Here is a 420mm f/6 doublet ED refractor on an APS-C camera, without and with a field flattener:




Now just imagine on a full frame camera...


PostPosted: Sat Mar 11, 2023 10:43 pm    Post subject: Reply with quote

Thank you for a very interesting piece of explanation. It works well for my technically underprepared glance, as I associated the issue of doublet undercorrection (thus the need for the narrow angle) with projector and CCTV lenses which resolve fine in the center, with optical correction dramatically falling towards the edges.

How does your field flattener look like?


PostPosted: Sat Mar 11, 2023 11:54 pm    Post subject: Reply with quote

alex ph wrote:
Thank you for a very interesting piece of explanation. It works well for my technically underprepared glance, as I associated the issue of doublet undercorrection (thus the need for the narrow angle) with projector and CCTV lenses which resolve fine in the center, with optical correction dramatically falling towards the edges.

How does your field flattener look like?


The simplest field flattener is a single negative lens at the rear, towards the film/sensor. To improve it (color correction!) one can use an achromatic doublet or even more complicated designs.

Many of the long "Wundertüte" lenses (often something like 6.3/400) from the 1970s/1908s have an achromatic doublet in fromt
(as the main lens) and a small single negative lans at the rear end ("field flattener"). That works pretty well, and I'm a bit puzzled Novoflex
didn't add one to its excellent T-Noflexar 5.6/400 lens ...


The Tair-33 for instance has a triplet in front plus a simple additional field flattener, while the Tair-3 consists of a doublet plus field flattener. The Tair-33 is for 6x6cm film, while the Tair-3 covers jusr 24x36mm:
https://allphotolenses.com/lenses/item/c_1027.html#prettyPhoto
https://allphotolenses.com/lenses/item/c_857.html#prettyPhoto

Images taken with the Tair-33 look pretty OK at f5.6, but not as good as a fully corrected lens such as the Mamiya Sekor C 5.6/300mm:

http://forum.mflenses.com/tair-33-vs-nikkor-ed-if-4-5-300mm-vs-mamyia-sekor-5-6-300mm-t80908.html

S


PostPosted: Sun Mar 12, 2023 12:31 pm    Post subject: Reply with quote

simple.joy wrote:
...as well as very good industrial/enlarging lenses, particularly from Steinheil, like the V-Cassarit 50 f/3.5:

Jester single moment by simple.joy, on Flickr

Cool, Distagon type aperture.


PostPosted: Sun Mar 12, 2023 1:10 pm    Post subject: Reply with quote

kypfer wrote:
Another factor to watch out for on a lot of these earlier lenses, especially those without an automatic aperture, is the number of aperture blades.
For instance, my M42 Tessar 50mm f/2.8, with the auto-aperture pin and an a/m switch, has only five blades, a somewhat earlier (1950's?) pre-set Exakta-fit Tessar has eight blades, whereas my (early '60's?) aluminium-coloured pre-set M42 Tessar has 12 blades.
Wide open, they're all much of a muchness, but close down a few stops and introduce a bit of backlight and you'll really notice the difference!
Horses for courses, obviously … some people struggle with pre-set mechanisms, I grew up with them Wink


I love to use preset lenses on digital cameras. Focus can be done easily and accurately at full aperture in live view, then stopping down is just a quick flick of the aperture actuator, no need to count aperture click stops as that has been pre-selected already. Those early aperture blade configurations do give a much nicer bokeh.

The only fly in the ointment with those older preset lenses is if the lens has significant SA and there is an apparent focus shift when stopping down.


PostPosted: Mon Mar 13, 2023 11:29 am    Post subject: Reply with quote

RokkorDoctor wrote:
kypfer wrote:
Another factor to watch out for on a lot of these earlier lenses, especially those without an automatic aperture, is the number of aperture blades.
For instance, my M42 Tessar 50mm f/2.8, with the auto-aperture pin and an a/m switch, has only five blades, a somewhat earlier (1950's?) pre-set Exakta-fit Tessar has eight blades, whereas my (early '60's?) aluminium-coloured pre-set M42 Tessar has 12 blades.
Wide open, they're all much of a muchness, but close down a few stops and introduce a bit of backlight and you'll really notice the difference!
Horses for courses, obviously … some people struggle with pre-set mechanisms, I grew up with them Wink


I love to use preset lenses on digital cameras. Focus can be done easily and accurately at full aperture in live view, then stopping down is just a quick flick of the aperture actuator, no need to count aperture click stops as that has been pre-selected already. Those early aperture blade configurations do give a much nicer bokeh.


I like them too but these 10 or more blades of the older vintage lenses are usually reflecting more which sometimes make them incompatible with sensors. The reason later lenses reduced the blades number was mainly that the auto functions could not cope with the extra friction of more blades. Modern lenses again have light, low friction polymer blades with low reflection and there is some freedom again to increase the blades number.

The Olympus OM lenses are not of the preset type but I do like to have the aperture ring close to the body which they do not have (some exceptions). So I 3D printed a kind of preset ring that is close to the body and when turned it presses the DOF preview button of the OM lenses. BTW that button is also in an awkward place.



PostPosted: Tue Mar 14, 2023 3:14 pm    Post subject: Reply with quote

Pancolart wrote:

Cool, Distagon type aperture.


Thank you! I try to celebrate this beautiful shape (I know not everyone likes it Wink ) as much as I can:

Rust suspect busted! by simple.joy, on Flickr

You‘ve finally match your master! by simple.joy, on Flickr


PostPosted: Tue Mar 14, 2023 7:18 pm    Post subject: Reply with quote

simple.joy wrote:
Pancolart wrote:

Cool, Distagon type aperture.


Thank you! I try to celebrate this beautiful shape (I know not everyone likes it Wink ) as much as I can:

Rust suspect busted! by simple.joy, on Flickr

You‘ve finally match your master! by simple.joy, on Flickr


Back in the late 80's and early 90's you could have sold pretty much any of your photographs to 4AD records; they used to love such images on their album covers & inside the CD booklets (maybe they still do) Like 1 small