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[Filter Test] StraightEdgeU OD5-OD6 Wins IR Forcing Shootout!

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#1 Andrea B.

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Posted 26 August 2016 - 16:44

Editor's Note: To save you from having to read all this, here are the results up front. :D
Rankings
#1 StraightEdgeU
#2 U360 (2.0mm) + S8612 (2.00mm)
#3 U360 (2.0mm) + S8612 (1.75mm)
#4 BaaderU




[31 August 2016 UPDATE]
After finding a light leak in my D600, I performed the IR-Forcing Test again with the light leak blocked. See Post #4 below for those results. In all the 30-second IR-Forcing Tests, 4A [not shown], 4B and 4C, the StraightEdgeU was the best performer showing no IR-leak even when the converted file was severely pushed.




[26 August 2016]
INTRODUCTION

As UV photographers we are always looking to suppress that pesky IR leakage. It is well known that the BaaderU does not completely suppress IR around the 715 nm range although the amount of leakage is very minor and does not interfere with typical UV exposures. Under long exposure times, however, some UV photographers have had valid concerns about the BaaderU's possible transmission of contaminating IR.

UVP member Cadium (also the UVIROPTICS vendor) has paved the way to excellent IR suppression with his use of Schott glass S8612 as an IR-blocking filter. When stacked with UV-pass filters, the S8612 combination can give us between OD3 - OD5 IR supression depending on the thicknesses of the filters in the stack.

Now we have from UVP member Reed Curry (also the UVR Optics/UVR Defense Tech vendor) a new IR-suppressing dichroic UV-pass filter, the StraightEdgeU, which achieves IR suppression between OD5 - OD6. I recently received a test copy of the StraightEdgeU for testing and review. Some other test topics involving the SEU are found here: DISCLAIMER

Hang in there while I offer up UVP's usual little disclaimer.
Neither Bjørn nor I, as Owner/Admins of UltravioletPhotography.com, receive any income from any manufacturer or seller of photographic equipment. We do accept some gear items for testing. When not under a non-disclosure agreement, we share the results of the testing with the UVP membership.
The UV photography world is a very small one, isn't it? I personally think it is very cool that someone with an interest in UV photography goes on to research, manufacture and sell needed items of UV gear like UV-pass filters, as Reed and Cadmium have done. UVP keeps member-vendors under some rather strict rules about what they can discuss on UVP's pages but does permit sharing of any factual information. And we do permit an approved announcement of a new product.

TEST NOTE 1: f/11 @ ISO-400 for 30"

I set up this particular IR-Forcing Test to mimic the way I typically shoot UV outdoors in good sunlight. So the results naturally reflect my chosen f/11 aperture and, for this test, an ISO-400 setting. (I typically shoot UV between an ISO of 100-400.) All exposures were of length 30-seconds. Other UV photographers may want to use other testing parameters for an IR-Forcing Test, but this test should pave the way. Full details of my IR-Forcing Test are found in the next post.

TEST NOTE 2: Discovery of a light leak in the D600-BB !!

Finding a light leak in my old D600-broadband maybe should not have been a surprise, but it was. I have pondered mightly over whether the light leak interferes with the test results? I've decided to present the test results anyway with the thought in mind that I will repeat the test when I can nail down where that blasted light leak is coming from. You will see the light leak in the cropped photos as a streak on the upper left of the photo.

TEST NOTE 3
Tested UV-Pass Filters (in alphabetical order)
  • BaaderU
  • StraightEdgeU
  • U360 (2.0mm) + S8612 (1.75mm)
  • U360 (2.0mm) + S8612 (2.00mm)
Stacked IR-Pass Filters
  • B+W RG9: an old bandpass filter
  • B+W 092: cuts in at xxx, reaches at xxx
  • B+W 093:
RANKINGS
#1 StraightEdgeU
#2 U360 (2.0mm) + S8612 (2.00mm)
#3 U360 (2.0mm) + S8612 (1.75mm)
#4 BaaderU

Visual Reference
Here is the Sunflower used as a test subject. Just before I photographed the 4th set, the sunflower, which was feeling a bit frisky, rolled off its prop. I let it have a bit of a frolic and then re-posed it. So my 4th set had a slightly different view of the test flower. [That set was made with the U360 (2.00mm) + S8612 (2.00mm).]

For best view, click up to 1000 pixels wide in an expanded browser.
Attached Image: forceTest_visSun_20160825_MidtwnNJ_13003960.jpg

Photo Presentation
The first strip in each set shows the 30" exposure as shot. The second strip shows the Raw Digger raw composite of each file. In some cases, this reveals a bit more of what is lurking in the file. The third row shows the result of applying Auto Levels in NX2 to each file. Auto Levels is a hard push on any file, so we should not over-interpret that result. It simply shows that in the original As Shot file there is some evidence of IR leakage with certain UV-pass filters. Such leakage may or may not contaminate the UV file depending on your particular UV shooting parameters.


#1 StraightEdgeU 30" IR-Forcing Photos for f/11 @ ISO-400
Each photo strip may be clicked up to 1200 pixels wide in an expanded browser.
Attached Image: SEU_AsShot_strip.jpg
Attached Image: SEU_raw_strip.jpg
Attached Image: SEU_lev_strip.jpg


#2 U360 (2.0 mm)+S8612 (2.00 mm) 30" IR-Forcing Photos for f/11 @ ISO-400
Each photo strip may be clicked up to 1200 pixels wide in an expanded browser.
Attached Image: U360S8612thick_AsShot_strip.jpg
Attached Image: U360_thick_strip.jpg
Attached Image: U360thick_lev_strip.jpg


#3 U360 (2.0mm)+S8612 (1.75 mm) 30" IR-Forcing Photos for f/11 @ ISO-400
Each photo strip may be clicked up to 1200 pixels wide in an expanded browser.
Remember the first row shows the actual photos.
The 3rd row is severely pushed.
Attached Image: U360S8612thin_AsShot_strip.jpg
Attached Image: U360thin_raw_strip.jpg
Attached Image: U360thin_lev_strip.jpg


#4 BaaderU 30" IR-Forcing Photos for f/11 @ ISO-400
Each photo strip may be clicked up to 1200 pixels wide in an expanded browser.
Remember the first row shows the actual photos.
But for the BaaderU + BW 092 stack, the actual photo is rather leaky.
The 3rd row is severely pushed.
Attached Image: BU_AsShot_strip.jpg
Attached Image: BU_raw_strip.jpg
Attached Image: BaadU_lev_strip.jpg
Andrea G. Blum
Often found hanging out with flowers & bees.

#2 Andrea B.

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Posted 26 August 2016 - 16:45

Test 4B: Infrared Forcing Test
Date: 25 August 2016
By: Andrea G Blum, UltravioletPhotography.com, Middletown, NJ, USA
Location: Middletown, NJ

Filters:
Baader UV/IR-Cut Visible-Pass Filter
UV-Pass
Baader Planetarium 48mm BaaderU UV-Pass Filter on 48-52mm StepRing
UVIROPTICS 52mm Schott glass U360(2.0mm)+S8612(1.75mm) UV-Pass Filter Stack
UVIROPTICS 52mm Schott glass U360(2.0mm)+S8612(2.00mm) UV-Pass Filter Stack
UVR Optics 52mm StraightEdgeU UV-Pass Filter
IR-Pass
B+W 52mm RG9 IR-Bandbass Filter
B+W 52mm 092 IR-Pass Filter (xxx nm)
B+W 52mm 093 IR-Pass Filter (xxx nm)

Gear: Nikon D600-Broadband + UV-Nikkor 105/4.5 + RRS Groundpod

Subject: Potted sunflower on lawn.

Conditions: Sunny, wispy clouds and hot with high humidity. Some breezes.
Solartech Solarmeter 5.0: approx. 4.1 mW/cm2 (for UVA/UVB between 280-400 nm).
The sun was behind and to the left of the photographer. Photos were only made when cloud wisps were not passing over the sun. The breezes probably caused some motion blur in the long UV+IR stacked exposures but it cannot be seen.

Exposure: f/11 @ ISO-400 with shutter speeds as described next.
The ISO was increased in this test to avoid using bulb mode. The shutter speed for the visible and UV reference frames was first set to the metered value and then at 1/3 and 2/3 stop over the metered value. For the UV+IR stacks, all shots were made for 30-seconds.

Other: As noted, the D600's ISO was raised to 400 so that long exposure would not require using bulb mode.
LiveView: Viewable meter needed because the viewfinder must be closed for UV work.
Picture Control: Monochrome, for exposures of maximum luminosity without misleading false colour.
ADL: Low, for a slight dynamic range boost without affecting shutter speed.
Metering: Matrix
Mode: Manual

Test Procedure: Make 30-second exposures with UV+IR filter stack to force IR leakage.
Focus was made on one of the petals at the top of the LiveView screen. A visible reference photograph was made. For each of the four UV-Pass filters, a UV reference photograph was made. A 30-second exposure was made for each of the four UV-pass filters stacked with each IR-pass filter in turn.

Comment: I set up this particular IR-Forcing Test to mimic the way I typically shoot UV outdoors in good sunlight or in sunlight combined with a UV-flash boost. So the results naturally reflect my chosen f/11 aperture and, for this test, an ISO-400 setting. (I typically shoot UV between an ISO of 100-400.) All exposures were of length 30-seconds. I rarely need a UV exposure longer than about 5-seconds (unless done deliberately for some reason). Thus my evidence about IR leakages through the four tested UV-pass filters only extends to conditions of good UV illumination and exposures less than or equal to 30-seconds at a moderate ISO level using a stopped down lens. For a UV photographs made under other circumstances where there might be a different kind of illumination or where very much longer exposures are required, the results obtained in this test might not hold.

Conversion: Raw Digger 1.2.6 v447 (x64) Profile Edition
Each UV+IR file was rendered in Raw Digger as a raw composite in which only demosaicing, auto-scaling and gamma was applied. The raw composite was exported from Raw Digger as an uncompressed TIFF with 3-channel RGB (G1 and G2 are combined). No white balance is applied in this procedure, so the actual raw colours (for the given Bayer filter) can be seen in the TIFF subject to its assigned colour space.

For the visible and UV reference photos complete edits were applied following TIFF conversion to obtain fully finished, sharpened photographs. For the sake of uniformity, a D600-broadband custom visible color profile was also used for colour profiling of the UV photos. An average white balance was applied to each UV photo by dragging the Photo Ninja white dropper from upper right to lower left. Photo Ninja's Scenic colour enhancement was applied with full saturation of 100.
A second set of visible and UV reference photos was made using an alternate white balance.

Each TIFF was subsequently cropped (to remove un-necessary details), resized and converted in Photo Mechanic to an sRGB JPG. This final JPG conversion may alter some colours.

D600 Light Leak: In IR-Forcing Tests 4A [not shown] and 4B [photos shown above], I discovered I had a light leak through the upper LCD of the D600-broadband. This leak shows up in the photo as a bright streak in the upper left of some of the raw composite and auto-leveled ("pushed") versions. A subsequent IR Forcing Test 4C [shown below] proves that this camera IR-leak did not affect the results of IR Forcing Test 4B.

TEST 4B RESULTS:
In order from no IR-leak to most IR-leak, we have:
#1 StraightEdgeU (best)
#2 U360 (2.00mm) + S8612 (2.00 mm) (close second)
#3 U360 (2.00mm) + S8612 (1.75mm) (not far behind)
#4 BaaderU (worst)

TEST ANALYSIS:
The StraightEdgeU has no IR leakage detectable in 30-second long exposures even when the file is severely pushed with auto-levels.
The BaaderU can transmit some IR in long exposures. So, if long UV exposures are required in a scenario with lots of ambient IR, choose another UV-pass filter or add an IR blocker to the BU.
For filter stacks, in addition to considering the UV-pass filter thickness, be sure to choose an IR blocker of sufficient thickness to prevent IR contamination.
Andrea G. Blum
Often found hanging out with flowers & bees.

#3 Andrea B.

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Posted 26 August 2016 - 16:45

The photos for Test 4C are in the next post.

Test 4C: Infrared Forcing Tests: REPEAT
Date: 26 August 2016
By: Andrea G Blum, UltravioletPhotography.com, Middletown, NJ, USA
Location: Middletown, NJ

Filters:
Baader UV/IR-Cut Visible-Pass Filter
UV-Pass
Baader Planetarium 48mm BaaderU UV-Pass Filter on 48-52mm StepRing
UVIROPTICS 52mm Schott glass U360(2.0mm)+S8612(2.00mm) UV-Pass Filter Stack
UVR Optics 52mm StraightEdgeU UV-Pass Filter
IR-Pass
B+W 52mm RG9 IR-Bandbass Filter
B+W 52mm 092 IR-Pass Filter (xxx nm)
B+W 52mm 093 IR-Pass Filter (xxx nm)

Gear: Nikon D600-Broadband + UV-Nikkor 105/4.5 + RRS Groundpod

Subject: Green shrub.

Conditions: Sunny, windy and hot with high humidity.
Solartech Solarmeter 5.0: approx. 3.7-3.8 mW/cm2 (for UVA/UVB between 280-400 nm).
The sun was behind and to the right of the photographer. The wind caused much motion blur in the long UV+IR stacked exposures. However the goal is simply to either record IR light or not.

Exposure: f/11 @ ISO-400 with shutter speeds as described next.
The ISO was increased in this test to avoid using bulb mode. For the UV+IR stacks, all shots were made for 30-seconds.

Other: As noted, the D600's ISO was raised to 400 so that long exposure would not require using bulb mode.
LiveView: Viewable meter needed because the viewfinder must be closed for UV work.
Picture Control: Monochrome, for exposures of maximum luminosity without misleading false colour.
ADL: Low, for a slight dynamic range boost without affecting shutter speed.
Metering: Matrix
Mode: Manual

Test Procedure: Make 30-second exposures with UV+IR filter stack to force IR leakage.
Focus was made on a leaf in the middle of the shrub. A visible reference photograph was made. For each of the three UV-Pass filters, a UV reference photograph was made. A 30-second exposure was made for each of the three UV-pass filters stacked with each IR-pass filter in turn.

Comment: I set up this particular IR-Forcing Test to mimic the way I typically shoot UV outdoors in good sunlight or in sunlight combined with a UV-flash boost. So the results naturally reflect my chosen f/11 aperture and, for this test, an ISO-400 setting. (I typically shoot UV between an ISO of 100-400.) All exposures were of length 30-seconds. I rarely need a UV exposure longer than about 5-seconds (unless done deliberately for some reason). Thus my evidence about IR leakages through the four tested UV-pass filters only extends to conditions of good UV illumination and exposures less than or equal to 30-seconds at a moderate ISO level using a stopped down lens. For a UV photographs made under other circumstances where there might be a different kind of illumination or where very much longer exposures are required, the results obtained in this test might not hold.

Conversion: Raw Digger 1.2.6 v447 (x64) Profile Edition
Each UV+IR file was rendered in Raw Digger as a raw composite in which only demosaicing, auto-scaling and gamma was applied. The raw composite was exported from Raw Digger as an uncompressed TIFF with 3-channel RGB (G1 and G2 are combined). No white balance is applied in this procedure, so the actual raw colours (for the given Bayer filter) can be seen in the TIFF subject to its assigned colour space.

For the visible and UV reference photos complete edits were applied following TIFF conversion for the best presentation (even when motion blurred). For the sake of uniformity, a D600-broadband custom visible color profile was also used for colour profiling of the UV photos. An average white balance was applied to each UV photo by dragging the Photo Ninja white dropper from upper right to lower left. Photo Ninja's Scenic colour enhancement was applied with full saturation of 100.

Each TIFF was subsequently cropped (to remove un-necessary details), resized and converted in Photo Mechanic to an sRGB JPG. This final JPG conversion may alter some colours.

D600 Light Leak: In IR-Forcing Tests 4A [not shown] and 4B [photos shown above], I discovered I had a light leak through the upper LCD of the D600-broadband. This leak shows up in the photo as a bright streak in the upper left of some of the raw composite and auto-leveled ("pushed") versions.

For this IR-Forcing Test 4C, the top LCD was covered with a folded towel while shooting this Test 4C. This seems to have supressed the worst of the leak. In the auto-leveled ("pushed") photos, there is still evidence of yet another small light leak. [So I will have another go at tracking that one down.]

TEST 4C RESULTS:
In order from no IR-leak to most IR-leak, we have:
#1 StraightEdgeU (best)
#2 U360 (2.00mm) + S8612 (2.00 mm) (close second)
#3 BaaderU (worst)

TEST ANALYSIS:
The StraightEdgeU has no IR leakage detectable in 30-second long exposures even when the file is severely pushed with auto-levels.
The BaaderU can transmit some IR in long exposures. So, if long UV exposures are required in a scenario with lots of ambient IR, choose another UV-pass filter or add an IR blocker to the BU.
For filter stacks, in addition to considering the UV-pass filter thickness, be sure to choose an IR blocker of sufficient thickness to prevent IR contamination.
Andrea G. Blum
Often found hanging out with flowers & bees.

#4 Andrea B.

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Posted 30 August 2016 - 19:45

IR-Forcing Test 4C Photographs

Reference Photos
Attached Image: ref_block.jpg


#1 StraightEdgeU 30" IR-Forcing Photos for f/11 @ ISO-400
There is no evidence of IR reflective leaves in any of these shots.
Attached Image: seU_asShot_strip.jpg
Attached Image: seU_raw_strip.jpg
Attached Image: seU_lev_strip.jpg


#2 U360 (2.0 mm)+S8612 (2.00 mm) 30" IR-Forcing Photos for f/11 @ ISO-400
There is very minor IR leakage which only shows up when the exposure is severely pushed.
Attached Image: u360_asShot_strip.jpg
Attached Image: u360_raw_strip.jpg
Attached Image: u360_lev_strip.jpg


#3 BaaderU 30" IR-Forcing Photos for f/11 @ ISO-400
IR leakage is evident.
Attached Image: baadU_asShot_strip.jpg
Attached Image: baadU_raw_strip.jpg
Attached Image: baadU_lev_strip.jpg
Andrea G. Blum
Often found hanging out with flowers & bees.