That does help, thank you @jankaiser. Regarding the slider for focusing, I’ve bought a few different kinds and mostly they’re the dovetail type meant for DSLRs. I did, however, just get this microscope 2-axis piece in yesterday and will try that as well.
Regarding the first question, optically I think there is no difference between the 42mm adapters and the C mount adapters.
The use of one type or another would be determined by availability and price, although in my opinion, mechanically and aesthetically, 42 mm adapters are better.
As for the second, in my assembly I do use a helical adapter with a variable extension between 17 and 31 mm. All my adapters are inexpensive, Chinese in origin, but of pretty good quality.
Specifically, the helical adapter works very smoothly, without harshness throughout its travel.
With this optical system I have recently digitized two complete reels of 120 m each without problems.
Once the focus was adjusted, I didn’t have to retouch it at any time.
It is true that the mechanical operation of my machine is very smooth. In my opinion, to avoid vibrations, it is essential to adjust the stepper motor to operate at very high resolution, with small microsteps. In my device I use 32 microsteps per step, 6400 microsteps per revolution, in this way the vibrations are minimal.
I take this opportunity to comment that the final assembly of my optical system is not the one that appears above in this same thread, but rather the one that appears in this other thread https://forums.kinograph.cc/t/my-telecine-machine/ 2054/9.
The reason for the change is the impossibility of focusing with the first montage.
If observed, with the first mount the distance between the lens and the sensor varies, but the distance between the lens and the film also varies, which prevents focus.
With the final mounting, the distance between the lens and the film remains constant, only the lens - sensor distance changes and with the helical adapter it is focused with great ease and precision.
Greetings.
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I have to agree with @Manuel_Angel that the M42 solution looks a lot better. That said, M42 is really only chosen for convenience because of the availability of M42 components. Ideally, one would want to go straight from C-Mount to M39 (if you are using a Componon-S or similar). M39 components are not quite as easily found, though.
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Another vote for using the M42 heli. I also have a c mount version, but it’s a lot stiffer to move with less range. The Unifoc12 made by Schneider Kreuznach is very nice, and has a thumbscrew for locking. But it’s very expensive unless found 2nd hand on eBay. I use the cheap 36-90mm generic version on eBay as I can pull out for 16mm, and also punch in for 8mm. I haven’t noticed any vibration changing it.
Thanks for the guidance, everyone. I ordered a variety of parts to try out and should have all of them by next week. I will post tests on the social media pages and the results will be in the monthly update. You all saved me hours of research.
Maybe someone here can give me some insight into something I’m observing with my lens setup, and that others might be seeing as well.
Depending on the aperture I’m setting on the 50mm Componon-S, I’m seeing substantial changes in sharpness, to the point where f4.7 is perfectly sharp, but f16 is notably lacking in sharpness. This is in line with this test on the 50mm Componon-S that states that the lens is sharpest at f4.7.
I think I remember @cpixip mentioning in one of his posts that mounting the lens this far away from the sensor is taking it somewhat out of its design working range. I imagine then that in this case the strong difference in sharpness is the result of the rather strong magnification which simply makes the difference in sharpness that much more visible? I’m assuming others are seeing the same effect with other lenses in similar setups?
@jankaiser: well, what you have observed is a general behaviour of normal optical systems. It’s pure physics and engineering.
Basically, any lens will underperform with the aperture wide open. The reason is that even today most optics are based on spherical lenses. They are easy to manufacture.
However, a spherical lens is a good approximation to a perfect lens only close to the optical axis. Lightrays which pass noticably off-center do “notice” the deviation between the spherical surface one can manufacture and the theoretically optimal lens shape. The image gets blurry.
The simple solution: one closes the aperature, which cuts off these “bad” off-axis rays. The image gets sharper.
However, there is another challenge hiding here: optics are usually calculated based on the assumption of light propagating along straight lines (“light rays”), getting bend appropriately by the curved surfaces of the lenses. In reality, light is an electromagnetical wave. And that means (among other things) that light gets bended around sharp corners or tiny holes located in its propagating path. This results in the so-called Airy disk phenomenon: the further you close an aperature, the larger the Airy disks of that lens gets. Or, to word it differently, the image gets blurry with smaller aperatures.
Now, as both effects are at work simultaniously, it is clear that for every lens there exists an optimal f-stop where you get the most out of the lens. For the Schneider Componon-S, this range is around 4,7-5,6.
Actually, nowadays one is able manufacture not only spherical, but also aspherical or even freeform optical surfaces, mostly by using single point diamond turing machines. Lenses produced by these means are performing better even with wide open aperatures. However, most lenses today are still based on spherical optics and feature one or two aspheric lens elements at most.
In the Super-8/Raspi HQ camera setting, the Schneider Componon-S 50mm is operating quite close to a 1:1 mapping (distance between gate and lens = distance between lens and sensor = about 100 mm), and that is actually within the design range of this lens.
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@jankaiser @matthewepler
This website was a great source of information on lenses. Cannot speak to the particulars of the Componon-S, I have been using the Nikon EL-Nikkor 50mm.
What @cpixip explained is clear on this chart. When one has the depth of field thinking, it is not intuitive why the higher F stop would not produce better results, and light physics is the explanation.
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This is a great resource. Thank you for posting, @PM490. I was glad to find that the author found the Componon-S the best 50mm enlarger lens. He also recommends mounting it in reverse, which I believe at least one forum member has also said was his preferred method.
This is all good timing as I hope to get the lens on in the next few days.
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Makes sense to mount enlarger lenses reverse, it basically keeps the film on the side of the lens it was intended to (for small film). Instead of projecting to paper, it projects to the camera sensor. In my case the film is smaller than the sensor (8/Super 8 to a DSLR 23.2x15.4 mm sensor). @matthewepler If the film is larger than the sensor, as it could be the case in 35 mm, I wonder if reverse mounting is needed/best.
@PM490 - citing from the website you linked to above: “The Schneider 50mm shows sharpness varying from outstanding below 1:1 to good at its highest magnification.” I think you do not need to go through the hassle of reverse-mounting that lens (at least in the Super-8 case I am concerned with). However, be sure to cover the internal light path for the f-stop “display” when using this lens.
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Thanks @cpixip. I don’t have the Schneider (although have been thinking about it). Agree that for 35mm reversing the Schneider may not be needed.
For the Nikkor EL 50mm 2.8 (the one I use), I did mounted it in reverse. I use a bellow and a fotodiox Reverse to 52mm, and then a 40.5 to 52mm, it worked perfectly.
The Bellow has its challenges, it was an Ebay find. So considering replacing it for a tube, and working a rig for focus, but not there yet.
Thanks for the tip on the Schneider, I may switch lenses and it is on the top of my list.
I don’t know what I am doing here, so forgive my stupid question, but…
Looking at ebay for the Schneider lens, and it seems there are a few without the manual focus adjust handle on, is that problematic?
https://www.ebay.co.uk/itm/165205109570?hash=item2676fdeb42%3Ag%3AescAAOSwYKRholA8&LH_BO=1
On an enlarger, you use the bellows to focus, not the lens.
I now have a Schneider Componon-S without a handle. I suspect the ones with a handle are a later type.
I wouldn’t worry too much about the handle. The one you’ve linked looks to simply have more of a slider in place of the handle. On this page you can see that the newest version also has more of a stub than a handle. I guess the design was just changed a couple times over the years. I would stay away from the fixed aperture versions and maybe be careful around the very old metal barrel ones, but other than that, as long as the condition is good, I think you can get any version.
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As mentioned above, none have focus, and there are some changes in design over the years.
I now have one exactly as the listing you are sharing.
The lens has what looks like a slider-switch, which makes the f-stop ring have a continuous-feeling or a steps-feeling. That model does not have the illuminated window, or the tab.
From what I read, for our application it may be best not to have the illuminated-stop-window (light-pipe), but the work around is to cover it to avoid light ingress. I was not looking for one without the window, but was happy that it didn’t have it (same as your listing).
This post explains it.
As said above there is no focus adjustment on the Componon, only an aperture adjustment.
The length of the extension tube will determine the magnification and it is useful to have a helicoidal ring in the mount.
The focus is done by adjusting the distance between the mount and the film and it is useful to have a micrometer table because it is very sensitive.
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Hate to revive an old topic, but I had a question regarding camera optics. For now, my camera will be a Raspberry Pi HQ. I believe the quality is more than good enough for my purposes for now; I want to get these films scanned as soon as I can. I’ve been looking at an EL-Nikkor lens because it’s pretty cheap and I’ve seen great reviews about it here on the forum. As for extension tubes and whatnot, what would be recommended for scanning 16mm?
I’m not sure about the focal length of your lens, but some time ago I did some experiments using graphing paper to determine the extension needed for 8 mm, 16 mm and 35 mm film when using a 50 mm enlarger lens (Schneider Componon-S). You can find the results of these tests further toward the top of this thread.
If your lens isn’t 50 mm, though, you might need a different length of extension.
Hope this helps!
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