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Blame
Joined: 14 May 2010
Posts: 212
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 Posted: Sat Jan 29, 2011 5:50 am Post subject: |
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| Charles Krebs wrote: | | I think a key attribute of these would be the ability to get the "tube lens" diaphragm very close to the objective; something that is not easy to do with SLR lenses. |
That is certainly a problem. One of the options I am considering is a 135mm f/2.8 Pentacon. The early "bokeh monster" version. I have the 200mm version and it's diaphragm is right out at the front. Zoom and the diaphragm moves out with the front lens. Coated but not multicoated. Amateur reviews show it to be sharp stopped down a little, but I have no certainty regarding corners.
I am also thinking of the 135mm f/3.5 Zeiss on the grounds that is has reviewed as very sharp corner to corner and wide open. As good as the best modern lenses. It has a very similar design to the Pentacon but diaphragm at the back. No real certainty that it will give such excellent results as a tube lens.
I have ordered a Morfanon, but god only knows how long all the adapters and extension tubes will take from China. Morfa showed it working well down to 160mm but it struggled a little at 120mm. Finite objectives are not usually happy run with seriously shortened tube lengths so I am just amazed it worked so well. Would the the "perfect" short tube lens do better? I figure it is worth trying.
Morfa added further confusion to the mix with the possibility that a thin lens might be the way to go. The morfanon is probably an example of trading a more primitive design against a better fit to the required characteristics, and now you are advising process lenses that trade the other way.
Arrrgggg. None of these options is demonstratively or clearly ether perfect or just the best available. Worse, there is no hope of any other solution than trial and error. I could also very likely be after something that just can't be done. |
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ChrisR
Joined: 14 Mar 2009
Posts: 3051
Location: Near London, UK
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| Posted: Sat Jan 29, 2011 6:25 am Post subject: |
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Does your 200mm Pentacon with its "diaphragm right out at the front" give a large image circle?
You speak of Morfa using his tube lens down to 120mm - not possible, it's a longer lens than that, so I don't know what you mean.  |
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ChrisR
Joined: 14 Mar 2009
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Location: Near London, UK
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Blame
Joined: 14 May 2010
Posts: 212
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| Posted: Sat Jan 29, 2011 7:02 am Post subject: |
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ChrisR
Morfa's lens is a 172mm, but he used it with various tube lengths. The shortest gave a 6x magnification with a 10x lens. It is perhaps technically incorrect to say he reduced it to 120mm, but think of it as zooming.
I am going to stick to fixed focal length options as they tend to give better results but I am certainly considering projector lenses. The big catch is finding out how good they are before parting with my money.
The Pentacon 200mm is no test. Just about anything works at 200mm. The trick is getting lower. I am not even going to bother until I have the morfanon lens + adapters to compare it with. |
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ChrisR
Joined: 14 Mar 2009
Posts: 3051
Location: Near London, UK
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| Posted: Sat Jan 29, 2011 7:51 am Post subject: |
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| Quote: | | Just about anything works at 200mm. The trick is getting lower. |
Not what I've found. |
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dmillard
Joined: 24 Oct 2006
Posts: 456
Location: Austin, Texas
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| Posted: Sat Jan 29, 2011 8:12 am Post subject: |
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| Blame wrote: |
Morfa's lens is a 172mm, but he used it with various tube lengths. The shortest gave a 6x magnification with a 10x lens. It is perhaps technically incorrect to say he reduced it to 120mm, but think of it as zooming.
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"When I use a word," Humpty Dumpty said in rather a scornful tone, "it means just what I choose it to mean -- neither more nor less."
"The question is," said Alice, "whether you can make words mean so many different things."
Sorry . . . I couldn't resist! 
David |
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Oskar O
Joined: 13 Dec 2010
Posts: 242
Location: Finland
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| Posted: Sat Jan 29, 2011 9:17 am Post subject: |
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I'm kind of skeptical about a projection lens producing the desired quality, but I don't mind being proven otherwise 
There are plenty of decent 135 mm small format lenses, especially when performance stopped down is considered. They also don't cost so much. My intent is to start testing a bit with my 135/2.8 Nikkor once I get more adapters, but it's a fairly simple lens, nothing fancy. |
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Blame
Joined: 14 May 2010
Posts: 212
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| Posted: Sat Jan 29, 2011 10:25 am Post subject: |
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| ChrisR wrote: | | Quote: | | Just about anything works at 200mm. The trick is getting lower. |
Not what I've found. |
Damb. You mean I may have spent a whole £5 on a lens and it might not work? Sigh. I might be reduced to using it for taking pictures.
Anyway, right now the adapter is somewhere between here and china, so I guess I will have to wait & see. |
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Blame
Joined: 14 May 2010
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| Posted: Sat Jan 29, 2011 10:28 am Post subject: |
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dmillard.
Humpty Dumpty?
I really should put more effort into this diet. |
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conkar
Joined: 18 Dec 2010
Posts: 189
Location: Sweden
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| Posted: Sat Jan 29, 2011 12:35 pm Post subject: |
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I wonder one thing about this......., or two.... 
A Zoom objective have more lenses and groups than a prime, so is it an advantage or disadvantage with more or less of lenses and groups in the objective?
In my own theory of the ray of lights it should be an advantage to use a prime objective together with a infinity microsopic lense.
Had anyone done a test with a polarizing filter between the microscopic lense and the camera sensor?
Regards,
Conny |
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Blame
Joined: 14 May 2010
Posts: 212
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| Posted: Sat Jan 29, 2011 1:58 pm Post subject: |
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Hi conkar.
From reports of users, you appear to be correct. Generally primes work better. They vignette less. Exactly which lens is best is still a matter of heated debate and frantic testing.
A polarizing filter is something I had on the "to do" list. It has been used by others here with great effect on shiny insects. You do need another filter on the light source so as to cross polarize. That way reflected light is cut. |
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Chris S.
Joined: 05 Apr 2009
Posts: 1088
Location: Ohio, USA
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| Posted: Sat Jan 29, 2011 2:06 pm Post subject: |
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| conkar wrote: |
Had anyone done a test with a polarizing filter between the microscopic lense and the camera sensor? |
I do it a lot, but so far only with finite optics. Works great. NB, I'm using an "analyzer" from a microscope, rather than a polarizer marketed for general photography. Same idea, but since some folks have suggested that an analyzer may offer higher extinction and better color fidelity when cross polarizing, I went with one.
--Chris |
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dmillard
Joined: 24 Oct 2006
Posts: 456
Location: Austin, Texas
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| Posted: Sat Jan 29, 2011 2:55 pm Post subject: |
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| conkar wrote: | I wonder one thing about this......., or two....
Had anyone done a test with a polarizing filter between the microscopic lense and the camera sensor?
Regards,
Conny |
Hello Conny,
I have been playing with an inexpensive rotating 52mm polarizer between a 5X infinity objective and a tube lens, along with some polarizing filters on fiber optic light guides, to look at fire agates. I have an Olympus "analyzer" with which I intend to replace the polarizing filter in its mount, but at the moment I've misplaced it  .
David |
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Craig Gerard
Joined: 01 May 2010
Posts: 2600
Location: Australia
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| Posted: Sat Jan 29, 2011 4:12 pm Post subject: |
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| David wrote: | "When I use a word," Humpty Dumpty said in rather a scornful tone, "it means just what I choose it to mean -- neither more nor less."
"The question is," said Alice, "whether you can make words mean so many different things." |
Classic quote! I was only ever familiar with the nursery rhyme. Must be time to read the book
Those analyzers are rather small; you would not believe the size of the box used by the seller to ship the item from the US. It took about 20mins to find it amongst the polystyrene peanuts 
David, check your spare filter containers 
Craig
_________________
To use a classic quote from 'Antz' - "I almost know exactly what I'm doing!" |
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dmillard
Joined: 24 Oct 2006
Posts: 456
Location: Austin, Texas
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| Posted: Sat Jan 29, 2011 5:58 pm Post subject: |
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| Craig Gerard wrote: |
Those analyzers are rather small; you would not believe the size of the box used by the seller to ship the item from the US. It took about 20mins to find it amongst the polystyrene peanuts
David, check your spare filter containers
Craig |
Thanks Craig,
It was in a little plastic bag right next to them! It fits nicely in a Nikon-T-mount adapter directly over the objective, and I've been enjoying playing with it (in incident mode) for the last hour. I really need to crank up the ISO setting on my camera (a more powerful flash may be in order).
David |
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