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 Replies: 15 / Views: 1,552 |
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Pillar of the Community
United States
3076 Posts |
Hi all its been a long time...I recently got this lens, but am not sure just what it is as I can't seem to find any details for the P designation....
any one have any info or ideas of what this lens is or used for? I had to reload my computer to many times, so some time this week I hope to take a few pics with it....still downloading software.. thanks...G
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Moderator
 United States
23522 Posts |
Is it a piece with a difficult-to-adjust aperture, consisting of a slot you have to put something pointed in to adjust it and a little setscrew to hold the setting? If so, it's a lens designed for printing machines (where you won't be adjusting aperture except for initial dial-in), and you can expect some pretty excellent results from it.
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Pillar of the Community
United States
4038 Posts |
Got a picture of it? What is the max aperture? Is that all it says on the lens, 105mm Rodagon P, or is there more?
Contact me for photographic equipment or visit my home page at: http://macrocoins.com |
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Pillar of the Community
 United States
3076 Posts |
I think its like F5.6 to 32. 39mm connection which is ok for mounting...I will try to get a photo..
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Pillar of the Community
United States
3076 Posts |
here is a pic of the lens as far as the f/stops...  |
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Moderator
United States
23522 Posts |
That's the one I'm thinking of.
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Pillar of the Community
United States
3076 Posts |
so do you dial in? what...the lens to the set up../ focal point for focus, and then dial in the F/stop for the best results?
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Pillar of the Community
United States
3076 Posts |
it is supposed to have an adjustable diaphram.. not sure what that is....any ideas what this means or why its adjusments are for this diaphram...what does or is the diaphram?
this sounds something slightly beyond the norm of lenses adjustmentys...I mean.. most lenses simply shoot for focus,
shoot for the f/stop for the best overall picture.. whats different about this lens
?
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Moderator
United States
23522 Posts |
The "diaphragm" is the mechanical part of a lens which opens a hole in its' center. We call that hole an "aperture."
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Pillar of the Community
United States
3076 Posts |
Thanks Dave, I had thought the term "diaphram" was indeed the aperture, however was wondering why is not adjusted by the normal means... with this lens, as it seams one must manually unlock and adjust the aperture from the inside of the lens itself...I guess as its a printing lens of sorts...yet my
research of "Rodenstock" does not acknowledge the "P" designation for the Radagon series.....WIKI shows the radagon, the Radagon D series,
the radagon N and the Radagon WA..
the "P" is not listed as I am to think its not a general population production lens...
My other question would be.......in general, most lenses have a low and high side to there operating qualities, quality of the outcome .. the quality of the picture... meaning the effect of the lenses aperture opening values we call the F/stop../.Without going into all the details of lens design and there intended purposes the F/ numbers seems to be....for any lens in general...F/1.8 for instance. to say f/16
SO before I loose people why I am asking such a question....If one notices any lens the f/stop numbers can be quite different...The Aperture "lets more or less light on to the cameras sensors"....the effect is quite amazing when you test this part of the big 3...
yet for most lenses.... there true color shines(pictures)
within few degree's of there overall adjustment values....say F/1 to F/32
Many articles always tend to say "stop down".....1 or 2...for the lens to be at its best...for lenses aperture....settings a lens "SAY'S" F/5.6 values.... would the lens be better or best at say F/8? many know of the arburations or CA and outer perifials of the picture are not as even as the center..... its all a combination...but
I would like a little deeper understanding of what the F/stop,
the Aperture is one of the big three as you know....
AND is one of the biggest differences in many of the lenses that can be found.....they can be from f/1.4 "TO" like my mirror lens F/8 (solid mirror Cat lens) To F5.6 to 45.....any comments? as always its enjoyed...I have been away but I have never read any discussions in detail of this subject. its considered already understood...yet every lens is subjecked to these F ratings.....What is the intention...of having a low F/stop like F/1:8 or another lens which might have F/5.6
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Moderator
United States
23522 Posts |
Without getting into a boring dissertation on the physics behind all of this....
The place your thinking must start is the camera's sensor. The pixel pitch of the camera's sensor (the size of each individual pixel; the distance between the centers of those pixels) has a bearing on the point where diffraction starts and costs you sharpness. Smaller pixels (smaller pixel pitch) tolerate less-tight (numerically larger) apertures before the onset of diffraction. So the 18MP sensor of a T2i sees the onset of diffraction at a wider aperture (numerically smaller number) than the sensor of a Rebel XT (8MP on the same sensor size).
And don't forget, magnification changes the actual aperture, regardless of the number you set on the lens. The more magnification, the smaller the effective aperture you're offering the sensor.
So with the 18MP sensor of a T2i, you'll be hard-pressed to find an aperture that will both prevent diffraction and still give you enough depth of field to avoid focus-stacking.
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Pillar of the Community
United States
4038 Posts |
So the lens looks like a Rodagon lens without the normal aperture adjusting mechanism and with an aperture lock screw. Interesting.
I'd suggest checking to see if the lens is good wide open and if it is lock it in place...
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Moderator
United States
23522 Posts |
I managed to run down a couple of informal reviews from people who were quite happy with it.
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Pillar of the Community
United States
3076 Posts |
Thanks guys, I just got home and received the lens, looks perfect.. It has the mini bolt that looks like the lock down nut and set at about F13/14 with a centered mark where it now sits...hardly wide open..but I think after I load up the software I hope to get some shots and then take some at wide open F/5.6 and then around f/8 and see whats what..G
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Pillar of the Community
United States
3076 Posts |
Its been to long in taking pictures, like starting over... I was trying some Morgan shots and the Jansco LED's have so much color reflection on the silver surface so I did a quick fake out by putting some "plastic foam" over the lenses which seemed to help on short notice...I took some shots of a Lincoln Penny here with the Radagon P at F/5.6 wide open, and haven't yet tried it at other settings...And I can't beging to tell you all who already know lighting is so critical in getting the right shot...even balanced deatail or contrast over the entire coin...I think its close now, but the reverse wasn't quite there but close...here's a couple of shots..   Strait shots and crops....I'll try a Morgan next... let me know what you think of the lens... |
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Pillar of the Community
United States
3076 Posts |
The plastic foam worked well in keeping the speckled colors out,,the OBV is a toned Coin as a result in a crack in the Redfield holder..though it has many surface marrings/scratches you can see....I really need to bust this coin out of the holder for some better shots....   |
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Replies: 15 / Views: 1,552 |
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Posted 04/17/2013 12:17 am
