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memetph
Joined: 01 Dec 2013 Posts: 940 Location: Poland
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Posted: Sun Jan 03, 2016 9:54 pm Post subject: WA with floating element and adapter |
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memetph wrote:
I have a technical question.
Many WA and UWA have a floating element to improve quality with focusing.
If I use an adapter which allows focusing beyond infinity . Do I loose some quality from such a lens in that case?
I have an adapter nex fd which is very precise and I have no problem with my fd 20mm and 24mm.
I struggle with a Rokkor MC 24 and my adapters go beyond infinity. is there a connection ?
Of course when I will have time I shall try to modify a nex md adapter but I would be interested by the opinion of competent people. |
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blotafton
Joined: 08 Aug 2013 Posts: 1621 Location: Sweden
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Posted: Sun Jan 03, 2016 10:18 pm Post subject: |
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blotafton wrote:
Interesting questions. I'd like to know as well. |
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visualopsins
Joined: 05 Mar 2009 Posts: 10981 Location: California
Expire: 2025-04-11
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Posted: Sun Jan 03, 2016 11:17 pm Post subject: |
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visualopsins wrote:
Please, get a precise adapter & tell us! (I am guessing there will be no difference!) _________________ ☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮ like attracts like! ☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮
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Lightshow
Joined: 04 Nov 2011 Posts: 3666 Location: Calgary
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Posted: Mon Jan 04, 2016 2:55 am Post subject: |
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Lightshow wrote:
I think it depends on how the lens was designed, on some lenses the rear element is in a fixed position, I think these are more sensitive to adapter thickness than lenses that have elements that move at different speeds through the use of helicoids.
I'm always looking for nuggets of information passed along from those that do know, so, if you do know, please share. _________________ A Manual Focus Junky...
One photographers junk lens is an artists favorite tool.
My lens list
http://www.flickr.com/photos/lightshow-photography/ |
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calvin83
Joined: 12 Apr 2009 Posts: 7555 Location: Hong Kong
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Posted: Mon Jan 04, 2016 3:57 am Post subject: |
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calvin83 wrote:
You have to take the glass in front of the sensor into account.
BTW, may I ask what FD->NEX adapter give you precise infinity? If it is a cheap one, it will be good to let the us know to save our time and money on trying different adapters. _________________ https://lensfever.com/
https://www.instagram.com/_lens_fever/
The best lens is the one you have with you. |
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memetph
Joined: 01 Dec 2013 Posts: 940 Location: Poland
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Posted: Mon Jan 04, 2016 7:01 am Post subject: |
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memetph wrote:
It is a no name adapter.
I don't think that the problems which I have with my Rokkor are connected with the thickness of the sensor glass. |
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calvin83
Joined: 12 Apr 2009 Posts: 7555 Location: Hong Kong
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Posted: Mon Jan 04, 2016 7:31 am Post subject: |
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calvin83 wrote:
memetph wrote: |
It is a no name adapter.
I don't think that the problems which I have with my Rokkor are connected with the thickness of the sensor glass. |
Any photos or links of the adapter?
The thickness of the adapter(and sensor glass) have a greater impact of the corner performance than the center performance of a lens. If anyone want to make a test, here is the MD helicoid for E mountClick here to see on Ebay or a cheaper one with EOS mount Click here to see on Ebay. _________________ https://lensfever.com/
https://www.instagram.com/_lens_fever/
The best lens is the one you have with you. |
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WNG555
Joined: 18 Dec 2014 Posts: 784 Location: Arrid-Zone-A, USA
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Posted: Mon Jan 04, 2016 7:59 am Post subject: |
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WNG555 wrote:
The answer to your initial question is no. _________________ "The eyes are useless when the mind is blind."
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memetph
Joined: 01 Dec 2013 Posts: 940 Location: Poland
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Posted: Mon Jan 04, 2016 2:32 pm Post subject: |
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memetph wrote:
Why ? |
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memetph
Joined: 01 Dec 2013 Posts: 940 Location: Poland
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Posted: Mon Jan 04, 2016 2:50 pm Post subject: |
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memetph wrote:
calvin83 wrote: |
memetph wrote: |
It is a no name adapter.
I don't think that the problems which I have with my Rokkor are connected with the thickness of the sensor glass. |
Any photos or links of the adapter?
The thickness of the adapter(and sensor glass) have a greater impact of the corner performance than the center performance of a lens. If anyone want to make a test, here is the MD helicoid for E mountClick here to see on Ebay or a cheaper one with EOS mount Click here to see on Ebay. |
Yes , I have some experience with this.
When I have time I will simply increase slightly the flange to get infinity.
I always thought that I have a bad sample of the MC 24.
Nevertheless, I am interested to understand if a lens with a floating element works as good with a wrong infinity position . In that case the element is not where it should be. |
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paulhofseth
Joined: 05 Mar 2011 Posts: 575 Location: Norway
Expire: 2018-06-28
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Posted: Mon Jan 04, 2016 5:49 pm Post subject: mismatched adapters |
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paulhofseth wrote:
With the adapted lens at infinity and focus point behind the plane of the sensor, the adapter is too thin. Short focus lenses need a fairly small extension to cover its focus range. A wide-angle will need to be a nominally much closer distance than a long lens in order to bring the plane of focus forward, but with a solid block lens, this does not change its intended performance at that nominal distance -even if in reality the object is at infinity.
A lens with a moving element is designed to compensate for the errors introduced with the changing distance between object and sensor plane. If it has to be set at 1 meter distance when the object is at infinity, it performs as it should with the object at 1 metre, not as it is designed to do with the object at infinity.
An example from longer lenses; the Zeiss S-Planar 60mm is designed for a reproduction ratio of 1:10 and does not have moving elements. Zeiss informs users of the design criterion, adds that it can be used over its full range and provides the differing MTF curves for the different conjugates. The Leitz Macro Elmarit 100mm has a variable distance inside in addition to the main helix. This allows it to perform well all the way down from infinity. To make a discernible difference for this length, a fraction of a millimetre would not matter, but Leitz does not advise using the ordinary -much longer - extension rings on the M-E 100.
p. |
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DConvert
Joined: 12 Jun 2010 Posts: 921 Location: Essex UK
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Posted: Mon Jan 04, 2016 6:04 pm Post subject: |
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DConvert wrote:
WNG555 wrote: |
The answer to your initial question is no. |
My experiences suggest otherwise! The more comprehensive answer by paulhofseth gives some indications of why it might be.
I've come to the conclusion that adapting UWA lenses is unlikely to give great results. When focal lengths are in the region of 10mm minor errors in the adapter, that are not significant with standard 50mm lenses, are significant... |
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