Got hold of a not too expensive Tominon 35mm F/4.5 and put it to a little test.
The first subject within reach was an earwig. Framed its last segment and forceps, selection shown at top left.
Maybe not the best of subjects to test a lens, but gave me an idea of its capabilities.
Has anyone ever worked with Tominons? What's the optimum aperture or tube/bellow length?
Are they any good and how do they compare against microscope or enlarger lenses?
Could not find much info about Tominons.
(Comments, advice and critisism about the stack are also welcome...) Tominon 35mm@F/8, sensor to frontlens distance 290mm, probably 10:1. Speedlite 430EXII and 2 Jansjo's. 78 shots in DMap. Removed dustspecks and pixeltrails, upped contrast and clarity a little, slightly sharpened
Took a lot of conversions, an Ihagee tube, a T2, 39mm to 42mm, and 3 small screws were involved to get if fitted on my M42 bellows,
thanks to the great help of Maarten from the vintage camera and lens store.
Edit: Changed title
Last edited by canonian on Mon Oct 17, 2011 4:31 pm, edited 2 times in total.
There have been discussions on the forum concerning the range of Tominon lenses and a number of members own various Tominons; but I cannot find any specific answers to your questions. A forum search for 'Tominon' reveals some of the earlier discussions.
I did a more extensive search, last time I've searched only Charles' midge came up, and he used a 17mm. I know now it should perform best at 5..15 magnification, and it will never be the best tool in my shed. Also max stop of 4.5 made me worried, the result is not as sharp as I wanted or expected it to be and for some reason I think it lost a lot of resolution somewhere in the lightpath. Maybe it is better to concentrate on microscope objectives and leave the cheap enlargers and other vintage lenses for what they are, especially when I look at abpho's results , I feel I've got a long way to go to reach this kind of resolution.
Edit: Typo's
Last edited by canonian on Mon Oct 17, 2011 7:09 am, edited 1 time in total.
I think you're right Fred.
For the highest possible sharpness, seek the largest working aperture you can use at the magnification you're at. Because the physics is right!
For my odds and ends of lenses that means that after about 5x, a scope objective is better. Not necessarily a wildly expensive one*.
But if you want flexibility, without worrying about the corners falling off your picture, and an iris to change dof, and are going to show your stuff at 1000 x 1000 (one whole Magapxel!!) on a monitor, then lenses something like this Tominon (and perhaps its more modern brothers), are a better choice.
*Abpho uses a Nikon 10x NA 0.25 with unusually, a 160mm tube length.
One went through ebay 8 weeks ago, for £23.55 (about $40). The vendor said it looked like it had never been put on a microscope. I can confirm that it looks that way.
ChrisR wrote:Abpho uses a Nikon 10x NA 0.25 with unusually, a 160mm tube length.
One went through ebay 8 weeks ago, for £23.55 (about $40). The vendor said it looked like it had never been put on a microscope. I can confirm that it looks that way.
Sorry, can't grasp this. I'm still a bit of a noob and do not always understand all things written in English.
Google Translate doesn't help either, or even makes it worse.
Do you mean wide open? related to magnfication? euhhh.
I always thought wide open means large DOF/lower res, and shut tight means small DOF/higher res but change of diffraction.
Or you mean the sweet spot between maximum resolution and minimal diffraction, its optimum aperture?
(I begin to wonder if I haven't misplaced this topic, maybe Equipment Discussions would be more appropriate)
lauriek wrote:I'm not sure what Chris meant but in general terms:-
Wide open = Small F-Stop = Large aperture, fast, small DOF, less diffraction, more sharpness
Closed down = Large F-Stop = Small aperture, slow, more DOF, more diffraction, less sharpness.
The word "generally" is crucial.
As I understand the situation, current lenses are likely to be sharpest at some of their wider apertures. This differs from the situation with most of my legacy MF film lenses, which typically (e.g my Tamron SP 2.5 90mm macro) are sharpest at around f5.6 or f8 and my Tamron 400mm at f8 and f11.
Harold
My images are a medium for sharing some of my experiences: they are not me.
Excuse me, Laurie, I've made a common beginner mistake.
Somehow Small Number/Big Hole still doesn't click in my brain, automatically translating it to diameter size.
Harold wrote:As I understand the situation, current lenses are likely to be sharpest at some of their wider apertures. This differs from the situation with most of my legacy MF film lenses, which typically (e.g my Tamron SP 2.5 90mm macro) are sharpest at around f5.6 or f8 and my Tamron 400mm at f8 and f11.
The only experience I have is with an El-Nikkor 50mm that always performes best at F/5.6, and a Componon-S which sharpest aperture is at F/4.7.
Unfortunately there's no rule of thumb on apertures, as the results in Rik's Post on apertures and Mark Goodman's excellent tests show.
I've found more picture made with a Tominon on Flickr and although not bad they're nowhere near as sharp as microscope objectives.
Not in the same league to compare with each other; Apples and Pears ...
Harold wrote:As I understand the situation, current lenses are likely to be sharpest at some of their wider apertures. This differs from the situation with most of my legacy MF film lenses, which typically (e.g my Tamron SP 2.5 90mm macro) are sharpest at around f5.6 or f8 and my Tamron 400mm at f8 and f11.
....Unfortunately there's no rule of thumb on apertures, ...
Not exactly a rule but in general lenses can deliver better resolution at wider effective apertures (Abbe's law) but also are more prone to show aberrations. The optimal aperture is dependant of the equilibre between both factors and is also ralated with the sensor resolution.
The key is the effective aperture, not the f number in the lens. And in high magnification macro and micro photography the effecive aperture is very small, so the better lenses are those that perform well wide open.
This isn't different with film era lenses but now we use high resolution sensors, we can see the pictures at 100% easily and can avoid in some cases the small DOF with stacking software.
a) The manufacturers' specifications for lenses new on the market.
b) Laboratory bench test results conducted for Amateur Photographer magazine, such tests having a very good reputation. In those days the principle measure would mainly be in lines/mm.
I think they've explained my ambiguities Fred!
I would just add that a bigger hole leads to more resolution & sharpness in theory. In practice, aberrations in the lens mean you often have to shut the lens down a stop or two, as you have found, for best performance.
Some lenses (eg longer lenses) tend to need more stopping down. The ones which cost many times more than others at the same focal length, tend to need less stopping down.
That means that a really good lens of smaller aperture, say a 55mm f/2.8 stopped down to perhaps f/4, can easily beat a lesser 55mm f/1.4 lens stopped down to f/2.8 .
Some, like the Olympus 20mm f/2 macro bellows lens, are best wide open, ie at f/2.
With microscope lenses, you don't get the chance to stop down of course, other than with a few oddball objectives which are unspectacular.
Around 40mm - 50mm FL, which in microscope objectives is 5x - 4x or so, there’s some overlap.
A couple of equations:
(changing notation here to eg "f5" instead of f/5, to save confusion with division )
"Fnumber" for a lens is normally given as 1/(2 x NA)
so NA 0.1 is "f5",
(but a lens asymmetry ( pupillary magnification factor) can alter all the numbers a bit.)
The effective aperture in use, is given by
f(effective) = f(marked) x (magnification +1)
So a 5x, NA 0.1 objective will give you
f(effective) = "f5" x (5+1)
= "f30".
Diffraction blur will get you eventually. That's what I meant by "the physics". A pinpoint of light becomes bigger than your pixels.
18MP APS-C sensors like your T2i are affected below (larger number smaller hole) something about f/16 to f/22, 12MP full frame ones about f/32.
So your Tominon was being used at effectively about 8 x (9+1) ="f80"
It wouldn't look great printed full size. But by the time it's reduced to screen dimensions, it's fine, it's as sharp as a much better lens would have looked.
Sorry I've rambled. Perhaps we need a FAQ. There are many faqtors to take in, though.
Guppy wrote:... please let me know something about the camera you took the picture with.
Hello Guppy, I used a Canon 550D /Rebel T2i for this stack.
Thanks Chris, Pau, Laurie, Craig and Harold.
You have given me a lot of information to absorb and I need some time to get my head around this.
I'm more a practical than theoretical guy and I like to learn by trail and error.
Would be nice however to pre-calculate or at least predict results approximately,
which lens or combo will work or not work rather than gambling on time-consuming methods, hoping for good results.
All in all I'm very happy with this lens, price/performance-wise.
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