Jump to content


Photo
- - - - -

<> The UV Sticky #2: UV Lenses 2014 <>


  • This topic is locked This topic is locked
No replies to this topic

#1 Andrea B.

Andrea B.

    Lost in the Desert

  • Administrators
  • 11,034 posts
  • LocationNuovo Jersey
  • Edit my pics?:Yes

Posted 27 November 2011 - 16:37

The UV Sticky #2:  UV Lenses 2014
by Andrea G. Blum for Nikongear.com

Last Update:  25 February 2014

Note from Editor:
This is a joint effort by the members of Nikongear who hang out in the Invisible Spectrum section. Thanks to everyone there for their suggestions, comments, proofreading, lists, links, measurements, experiments and all round good fellowship.

Please PM <annedi> on Nikongear with any corrections, additions or suggestions.

Abbreviations:

  • IR = infrared
  • UV = ultraviolet
  • UVIR = ultraviolet and/or infrared
  • <screen-name> = Nikongear member's screen name

*******************************************************************

UV LENSES
 
Measuring UV Transmission of a Lens
I asked Nikongear member Shane Elen what was needed to accurately measure the UV transmission of a given lens. He wrote:  Ideally you need a CCD spectrometer, or spectrophotometer (preferably in a dual beam configuration) with a monochromator, an integrating sphere, and a stable output UV-V-IR source. The integrating sphere helps ensure that the readings are independent of the incoming light ray angle. This will provide you with wavelength specific transmission response.
 
To informally test UV lens transmission, several folks have gathered a set of narrow UV bandpass filters, mounted them on a board and estimated a lens UV transmission by taking a photo of the filters. Here is one example shown in an article by Enrico Savazzi (which contains additional links to other such experiments): http://www.savazzi.n...estfilters.html
 
UV Focus Shift
Focus shift between the Ultraviolet & Visible wavebands in a lens is a form of axial chromatic aberration that occurs because shorter, higher frequency UV lightwaves refract more in typical optical glass than do longer, lower frequency Visible lightwaves.
 
Such wavelength-induced focus shift is a topic of particular interest in UV photography when using an external filter and a camera that has no Live View. First you must focus the lens in Visible light before mounting the dark UV-pass filter. After mounting the filter you might have to adjust your initial focus if the lens has not been designed to bring the UV rays to the Visible plane of convergence. With a bit of trial and error you should be able to determine the proper correction and note it for future reference.
 
UV focus shift is less of a worry with an internal UV filter because during conversion the auto-focus can be adjusted a bit to compensate for UV for most lenses at most apertures. Focus shift is not problem at all when using LIve View if you have sufficient UV illumination. Attaining sufficient illumination to use Live View for focusing in the UV case is not always easy.

Diffraction
In photography, diffraction is the spread of light waves caused by their passage through a lens aperture. The narrower the aperture, the more the diffraction. In UVIR photography, a key fact to note is that longer IR wavelengths spread more at a given aperture than shorter Visible or UV wavelengths. Thus IR shots are more prone to the effects of diffraction and UV shots less so.

So, for example, if you make a Visible light photo with a sensor & lens combo that begins to show diffraction blur past f/8, then you will have to open up your lens to f/5.6 (or larger) to shoot a sharp IR version of the same photo. But on the UV side, you could stop down to f/11 (or smaller) and still stay sharp. The rule of thumb is there is approximately a 1-2 stop aperture variation around the diffraction limit of a given sensor & lens combo.

When diffraction is recorded by a digital sensor, it shows up as a loss of sharpness in an image.

About the UV Lens List
For a lens to be on our UV Lens List, it must have at least one Nikongear member who has either used it or tested it to confirm that the lens is UV-capable in some portion of the UV bandwidth. Our lists are by no means exhaustive, so please experiment and let us know of your discoveries.

Please Note:

  • UV-Capability ?
    The amount of UV-capability of the lenses on this list varies.
    We have tried to list lenses that reach at least 350nm, but not all lenses have been formally tested.
    Investigate before purchase!
     
  • Nikon F-Mount ?
    Many lenses on this list do not have Nikon F-mounts.
    Modification of the lens mount and the use of focusing helicoids and/or bellows may be necessary for use on a Nikon camera body.
    Investigate before purchase!
     
  • UV Focus Shift ?
    Most of the lenses listed below have some degree of the UV focus shift discussed below.
    Lenses without such focus shift are noted.
    Investigate before purchase!

Contributors to the UV Lens List

  • annedi = Andrea Blum
  • anon = Anonymous
  • brianc1959 = Brian Caldwell
  • kds315 = Klaus Schmitt
  • nfoto = Bjørn Rørslett
  • overmywaders = Reed Curry
  • RKPhotog = Bob Kerr
  • Vivek = Vivek Iyer

Lens info for each brand includes: Focal Length & Speed, Description, User/Mount/Filter and Remarks, if any.
 
UV/IR Lenses: Excellent UV Response with No UV-Vis-IR Focus Shift
These lenses have no focus shift between UV, Visible or IR wavelengths.

Asahi Pentax 85mm f4.5 Ultra Achromatic Takumar

  • No longer manufactured.
  • Rare and expensive in the "collectible" market.
  • M42 mount, 49mm front filter size, 45.46mm flange focal distance.
  • Tester: kds315.

Coastal Optics 60mm f4.0 Apo Macro

MegaVision 120mm f4.5 Macro UV-IR Apo

UV Lenses: Excellent UV Response with No UV Focus Shift
These lenses were designed as UV-dedicated lenses that have no UV focus shift .
They may be useable for IR, but would have some IR focus shift.

 

Attached File  NoUVShift.jpg   456.66KB   1 downloads

 

 

UV Lenses: Excellent UV Response with some UV-Vis Focus Shift.
Although some of these lenses have ‘UV’ in their name, they all have some UV focus shift. They will need a final focus adjustment if initial focus is made in Visible light prior to mounting a UV-pass filter. They may be useable for IR, but would have IR focus shift.

The lenses here are listed separately from the UV-capable lenses that follow this list because these transmit more deeply into the UV band.

 

Attached File  SomeUVShift.jpg   342.71KB   2 downloads

 

 

UV Lenses: Good UV Response with some UV-Vis Focus Shift
These lenses all have some UV focus shift. They will need a final focus adjustment if initial focus is made in Visible light prior to mounting a UV-pass filter. They may be useable for IR, but would have IR focus shift.

 

The presentation order here is Nikon lenses first, then the remainder of the list in alphabetical order.

 

Attached File  nikon-micro.jpg   275.86KB   0 downloads

 

Attached File  ELNikkor.jpg   301.2KB   1 downloads

 

Attached File  FaxNikkor.jpg   140.22KB   1 downloads

 

Attached File  a-j.jpg   434.87KB   2 downloads

Attached File  k-o.jpg   404.97KB   1 downloads

Attached File  petri.jpg   555.65KB   0 downloads

Attached File  p-r.jpg   442.82KB   0 downloads

Attached File  s.jpg   420.31KB   0 downloads

Attached File  t-z.jpg   250.56KB   0 downloads

 

 

UV LENS LINKS


Andrea B.
UltravioletPhotography.com





0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users