[Filter Test SEU Gen2 #10] What good is a filter test without a Rudbeckia?

[Andrea B.]

[Filter Test SEU Gen2 #1] Introduction to the SEU Gen2

[Filter Test SEU Gen2 #2] White Balance, Raw Histogram & Andrea's "White Signature"

[Filter Test SEU Gen2 #3] Filter Speed & A Windy Bull's-eye

[Filter Test SEU Gen2 #4] Dealing with the Usual Dichroic Effects

[Filter Test SEU Gen2 #5] Landscape Interlude

[Filter Test SEU Gen2 #6] Monochrome Museum Comparison

[Filter Test SEU Gen2 #7] Measured Filter Transmission

[Filter Test SEU Gen2 #8] Dichroic Reflection Detour

[Filter Test SEU Gen2 #9A] Longpass Stack Wandering Discussion. See #9B for results.

[Filter Test SEU Gen2 #9B] Longpass Stack Results

[Filter Test SEU Gen2 #10] What good is a filter test without a Rudbeckia?

[Filter Test SEU Gen2 #11] A Fascinating New Rudbeckian View

[Filter Test SEU Gen2 #12] Summary

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RUDBECKIA TEST: Today I photographed a wild Rudbeckia hirta which has a well-known UV-absorbing central bull's-eye.

 

Gear: D610 full spectrum, full frame + UV-Nikkor 105/4.5 + SEU Gen2 + Sun

Exposure: f/11 for 1/10" @ ISO-400

 

Comment_1: Exposure Discussion

When shooting Spectralon to use for a white balance preset the exposure time is usually shorter than is needed for an actual subject. Today I also had some flat, hazy, foggy light to deal with. After creating and saving my white balance preset in Photo Ninja, I rendered this test photo in Monochrome to deal with the hazy light effect which usually necessitates some added contrast - it did for this photo anyway. Then I switched the false-colour on.

 

I also needed to lift the UV-dark tones of the Rudbeckia a bit to provide detail since that part was underexposed due to the need of keeping the 95-98% UV-reflective Spectralon from blowing out. PTFE blows faster than Spectralon, but Spectralon still needs a controlled exposure.

 

Comment_2:

Details are fine and sharp, as expected. Focus was made on the opened florets at the dark base of the rays. The rays (petals) on the left are very slightly in back of the plane of focus. The top of the center disk is slightly in front of the plane of focus. The narrow veining of the Rudbeckia rays is nicely captured.

 

Comment_3:

The black front edge of the Spectralon slab is over-exposed due to the UV-dark midtone lift made for the Rudbeckia center. Typically I would correct that but there's no need to invoke color points and brushes for a test photo methinks.

 

Comment_4:

After white balancing, there is a false-green cast. I do not know if that is caused by the small SEU Gen2 green bump or if this is simply the way the SEU Gen2 shoots and converts. There does not appear to me to be any effect on the tonality of the photo as judged against the numerous UV photos I've made of Rudbeckias over the years.

 

Comment_4:

The Rudbeckia stem is held in place by a small glass bottle and my Solarmeter. When shooting with a filter having a mirrored surface as does the SEU Gen2 or the BaaderU, you will always need to be on the lookout for unwanted flare or reflection artifacts and work around them should they occur. My first shots of the Rudbeckia picked up a bit of reflection off the bottle. A minor rearrangement of the subject matter fixed that right away.

 

 

 

Monochrome Rudbeckia

Monochrome conversion in Photo Ninja.

Resizing in Photo Mechanic.

 

 

False-color Rudbeckia

White balanced conversion in Photo Ninja.

Dust bunny removal and resizing in NX2.

Additional minor sharpening added after resize.

[Andrea B.]

There is a dish of bird seed on the deck for the Song Sparrows. They decided to avoid the eye of the UV-Nikkor but did give me a song or two. Some kind of vine is growing up between the boards of the deck.

 

D610 + UV-Nikkor + SEU Gen2 + Hazy Sunlight

Conversion in Photo Ninja using white balance preset made on Spectralon and D610 color profile.

f/8 for 1/6" @ ISO-400

 

[Andrea B.]

Remember the Somesville Bridge from SEU Gen2 Test #8 ??

 

Here it is again with the nice white balance created from Spectralon on the day of that test.

 

The reflection/flare artifact above the bridge railing was easily removed by selecting the foliage color and brushing over the doubling. Part of the doubling which produced a bright line was just removed with a simple clone drag. (I could have done a better job! Was hurrying a bit.)

 

Of course, there might be situations where reflection/flare artifacts, should they occur, would be less easy to remove. If you happen to see some reflection/flare from an extremely bright reflective subject against a dark background, then move around and re-frame your scene to avoid it. (Please recall that I think my EL-Nikkor 80/5.6 might play a partial role in this problem.)

 

I really find this blue/green rendering very pleasant. Your thoughts??

 

Footbridge in Somesville, Maine

D610 + EL-Nikkor 80/5.6 + SEU Gen2 + Sun

f/11 for 1/1.3" @ ISO-400

[Andrea B.]

Here is the white balance photo made for the Somesville Bridge scene. It does not seem to show as much green, but does show some of the pretty blue. The UV-reflective (very) Spectralon is tilted and has reflected onto my shoe a bit.

 

This is cropped otherwise would be even more boring.

 

 

f/5.6 for 1/50" @ ISO-400

[Andrea B.]

This is a companion photo of the Somesville Bridge made with the (La)²U, which is a 363fwhm50 UV-pass filter stack. The bridge and the little white house are very bright in Visible light, but less so in UV light. For accuracy I have not brightened the bridge and house. For artistry I really do want to brighten them in all the UV photos I made that day.

 

f/11 for 2.5" @ ISO-400

Some motion blur of the trees in the breezes is more evident here in the longer exposure.

[Andy Perrin]

That's a lovely bridge, Andrea. The rudibeckia photos look a bit noisy, I guess because you were trying to avoid the blowouts from the Spectralon (if I understood that part correctly). But you can see the false yellows well enough, despite the SEU2 being tilted toward the 380-400nm range.

[dabateman]

That shoe is great. I like the tail blue glow.

[BruceG]

Hi Andrea, I have SEU version one and AndreaU MKII, on my Sony A7S, when white balanced, their false colors both look very similar to the shot above from Lala U, I found the difference between of SEU and AndreaU MKII to be that SEU gives deeper purple/violet. However, I have not encountered any dichroic effect from SEU, the widest lens I used was 40mm. Does the dichroic effect only happen to the new filter or does it have to do with you camera?

[dabateman]

Bruce,

The dichroic effect is a tricky one and will sneak up on you when you don't want it to. Knock on wood when you say you haven't seen it yet. The Baader venus filter is excellent, but I have had it hit me in an image or two depending on light angle and intensity.

Today with my LP1100 filter, I finally had sunlight. And got nothing good due to glow and angle.

Its something to be aware of and when it comes in. Move your position, use a reverse mount, better hood or just be stuck.

[Andrea B.]

The dichroic effect which might lower transmission rates is not significant enough to worry about.

.

The occurence of concentric false color banding depends on lighting direction, subject chosen and lens used. It has no dependency on the sensor. I think that dichroic banding occurs quite frequently in the periphery of a UV photo, but many times it is not really that noticeable. You will more likely see dichroic color banding in wide view photos or photos made contra jour. I see it much less often in my close up work regardless of lens used. This is probably because there is less light entering at an angle to the main lens axis? Use of a lens hood can sometimes mitigate bad effects of off-axis light.

 

I don't have an observation at this time about about the frequency of dichroic banding for specific dichroic filters like the SEU-1, SEU-2 or the BaaderU. Anyone is welcome to comment on that of course. Is there a dichroic filter which is more prone to UV false color banding than some other?

 

If you want to test to see whether you have some degree of dichroic concentric false color banding, bring your photo into your chosen converter/editor, click-white balance it and then crank up the false color saturation.

 

David's suggestions are excellent when dichroic banding crops up: re-frame, use a lens hood, change the angle of the lighting, try another lens.

Also there are ways to convert the photo to repair some of the dichroic banding when it is strong. One such technique is shown in:

http://www.ultravioletphotography.com/content/index.php/topic/2877-filter-test-seu-gen2-4-dealing-with-the-usual-dichroic-effects/%2B%5Bfilter+%2Btest+%2Bseu+%2Bgen2