[EXPERIMENT & TEST LIST] Updated & Revised

[Andrea B.]

Update and revision of the proposed Experiments and Test list.

Anyone is free to perform these Experiments or Tests or those of their own devising to add to our general knowledge of filters, lenses, gear and methods used for reflected UV photography.

 

 

All comments and suggestions welcome!!

[Andrea B.]

Group comparison of typical UV-pass filters used for reflected UV photography.

 

Scene

Shoot a sunlit summer outdoor scene with the typical UV-pass filters and filter stacks currently available.

Hurry, summer is passing quickly!

 

If you do not have all these filters, that is OK. Just show us what you've got. It is always interesting.

 

Filter List

List filter designation peak and bandwidth. List manufacturer.

The UG-5 and U-330 filter glass are used for UV+Blue+Green transmission, so will not be included here.

• AndreaU2
  
• BaaderU
  
• KolariU
  
• LalaU
  
• LuvU2
  
• MoonU
  
• StraightEdgeU
  
• UG-1 ??
  
• UG-11 (2mm) + S8612 (2mm)
  
• U-340 ??
  
• U-360 (2mm) + S8612 (2mm)
  
• ZBW1 (1.5mm) + S8612 (2mm)
  

[Andrea B.]

Long UV & IR Exposures at Night in Ambient Light

 

Background: Is there much UV at night in the ambient lighting near a shopping center with street lights and traffic? Is there much ambient IR at night in the same place? In a long night exposure would ambient IR or Visible light contaminate a UV shot? We have had some examples of such UV night photography, but I have not yet tried it myself.

 

Reference: Add links to topics here on UVP featuring UV night photography.

 

Subject: Shopping center with street lights and traffic.

 

UV-Pass Filters and Filter Stacks

TBA

 

IR-Pass Filters

TBA

[Andrea B.]

Red Leak in UV-Pass Filters

 

Background: Most of the glass substrates used in UV-pass filters are UV+IR dual-bandpass. The IR transmission is so high as to thoroughly contaminate the recording of UV characteristics without the addition of strong IR-block coatings or IR-block glass layers. There is also some transmission of red light around the 700 nm mark by some of this glass. Given that not all UV-pass filters made from these dual-bandpass substrates completely suppress the leakage, how much of this observed leakage is near-IR leak; how much is red leakage? While we may not be able to quanitatively determine the answer to this question, we might be able to trap the red leakage with the right filter stack.

 

Filter List:

• UV-pass filters and filter stacks.
  
• IR-blocker: S8612 and/or BG glass.
  
• Red+IR and IR longpass filters.
  

[Andrea B.]

Violet/blue Leak in UV-Pass Filters

 

Background: Some of the glass substrates used in UV-pass filters pass a small amount of light past 400nm in the violet to (possibly) the violet-blue range. Such violet leakage is generally not considered damaging to a UV photogaph in small amounts because the division between the end of UV light and the start of Visible light is somewhat arbitrary, although typically taken to be 400 nm. Indeed, a bit of visible violet can enhance certain artistic results in reflected UV photographay.

 

Some recent work with longpass filters gave me some insight as to how I might test for violet/blue leakage in UV-pass filters. I also have some Baader blue bandpass filters which might be useful in such a test.

[Andrea B.]

Compare raw composite version of the the same scene across different cameras using a fixed filter and a fixed lens.

 

Background: A raw composite made in the Raw Digger app illustrates the demosaiced raw capture before any white balance has been applied. I'm always curious about what that looks like. What channels are recorded in? How does that affect the white balance result?

 

Scene: Hard to choose. We would want something with some visual interest other than just sky and foliage. The garden scarecrows at a local park are always useful for such experiments. "-)

 

Lens: Use one UV-dedicated lens, probably the CO60.

 

Filter: Some typical UV-pass filter.

How do I pick just one without offending anyone?? :lol:

 

Standards: Must use Spectralon to record a white balance measurement.

 

Exposure: f/8 or f/11 @ suitable ISO between 100-400.

 

Illumination: Sunlight

 

Broadband Cameras:

Compensate for sensor size by moving rig?

• Lumix GH1
  
• Nikon D610
  
• Pentax K5
  
• Sony a7R
  

[Andrea B.]

Chromatic Aberration in UV-dedicated and UV-capable Lenses

 

Scene: Crumpled Foil and Shiny Metal Objects

I've done this informally and it is quite revealing.

 

Filters: Don't overthink it.

 

Lighting: Try both UV-Led and UV-Flash

 

Lens: UV-Dedicated, Corrected

• Coastal Optics 60/4.0
  
• Nikon UV-Nikkor 105/4.5
  
• Zeiss UV-Planar 60/4.0
  
• Asahi Ultra-Achromatic-Takumar 85/
  

Lens: UV-Dedicated, Uncorrected

• Zeiss Jena something
  
• Asahi whatitsname, the old one
  

Lens: UV-Capable

• Novoflex Noflexar 35/3.5
  
• El-Nikkors
  
• whatever else
  

Lens: Just for comparison's sake, also try some typical kit lens and/or an old manual Nikon 35/1.4.

[Andrea B.]

Green Leak in UG?

 

Suggested by Cadmium. Thanks!

 

Filters:

U-340 (1mm)

U-340 (1mm) + S8612 (2mm)

UG-11 (1mm)

UG-11 (1mm) + S8612 (2mm)

 

Light: Must be a fluorescent which outputs green? Tungsten does not work.

 

Have done this informally. Saw the greenish or greenish-cyan.

Need to figure out how to show it.

Can green be trapped with other filters?

VG9 or Baader Greenpass?

 

VG9 (1mm) PEAK 525nm

490 (48%)

560 (50%)

[Andrea B.]

LINEAR GRATING EXPERIMENT

^{Suggested by UVP Member Cadmium}

 

Purpose: Obtain informal spectrum for given camera+lens+filter+sunlight combination.

 

Mount UV-pass filter and linear grating filter.

On tripod, aim at about 45° angle to sun.

Observe long "rainbow" line.

Adjust rotation of linear grating filter for maximum rainbow length.

 

Example from Cadmium.

[Andrea B.]

MONOCOT vs. DICOT Foliage Fluorescence

Suggested by UVP Member Damon

 

Damon has observed that, generally speaking, monocot foliage fluoresces blue tones while dicot foliage fluoresces red tones.

More examples are needed together with lens, filter and lighting details.

[Andrea B.]

MINERAL FLUORESCENCE

 

While well-represented across the web, photographs of mineral fluorescence often fail to provide details of camera, lens, filter and illumination used. Also, there has been little attempt to standardize the colour outcomes for purposes of comparison. So I suggest a 365uvLed used together with the Target Grey for such standardization. A companion rendering of the colour in a typical Daylight white balance would be useful to include.