BaaderU, KolariU and UVBplus, ZWB1x8.0: Red Bluets

[Andrea B.]

Some time back I got two new filters:

• Ulf's ZWB1 x 8.0 mm 325fwhm75, LINK1, LINK2
• UVR Optics UVBplus 331bp75

 

I finally was able to test drive the new filters and thought I'd show you some results from photographing a little flower near our house. This flower is a Houstonia rubra. Flowers in that genus are commonly called Bluets, because they are blue (yeah...). I thought it a bit funny that this Houstonia's common name is Red Bluet. It was interesting to see this pincushion of rosy flowers popping up in the middle of all the sandy dirt. I actually carried water to it a few times to try to keep it going during the heat wave, but it's gone now. I hope it reappears next year.

 

For all photos, white balance was measured on Spectralon.

 

Visible:  f/11 for 1/125" @ ISO-100

Baader UV/IR-Cut + B+W BG38 on UV-Nikkor

 

 

Here are two reference reflected UV photos to compare to the photos from the new filters. Both the Pink Bluet's flowers and leaves are very UV-absorbing. But the plant does stand out against its background.

 

UV:  f/11 for 1" @ ISO-400

BaaderU on UV-Nikkor

 

 

 

The KolariU photo looks almost the same to me as the BaaderU photo.

UV:  f/11 for 2" @ ISO-400

KolariU on UV-Nikkor

 

 

Now the photos from the two new filters.

 

UV:  f/11 for 2.5" @ ISO-400

UVBplus 331bp75 on UV-Nikkor

 

 

I'm not entirely sure, but there might be a bit of flare from this one.

UV:  f/11 for 3" @ ISO-400

ZWB1 x 8.0 mm 325fwhm75 on UV-Nikkor

[Andrea B.]

300° = magenta

330° = cerise (equal amts of magenta & red)

360° = red (aka 0°)

30° = orange (equal amts of red & yellow)

60° = yellow

 

I measure areas of averaged color simply as a way of informally noting differences between the filters and how they record in our camera's Bayer RGB channels (in full, cloudless sunlight in this case). It's probably not a good idea to regard these measurements as anything at all absolute, OK? 

 

Note that the UVBplus and ZBW1 x 8.0 do not have much raw color "spread". That correlates, perhaps, with their relative lack of false color when compared to results from the BaaderU or KolariU.

 

 

BaaderU Raw Composite (demosaic/autoscale/gamma. but no white balance)

 

 

UVBplus Raw Composite

 

 

ZBW1 x 8.0 mm Raw Composite

 

[Fandyus]

Does UVBplus pass mainly UVB?

[Andrea B.]

Maybe about half UVB and half UVA? Although we do need to take into account that there is more UVA in sunlight than UVB.

 

Wikipedia sayeth thusly: 

UVA 315-400

UVB 280-315

 

 

Here's the UVBPlus chart from UVR Optics website.

[Andrea B.]

P.S.  I like the UVBplus for its 330 nm peak with no violet/blue/green visible leakage. And my results from it are nicely sharp. I have not tested for IR passage. Looks like it is OD 3+ in the usual bump area which is pretty much what the BaaderU is. I also haven't tested it with an IR blocker yet.

[ulf]

The transmission graphs for the ZWB1, 8mm:

The blocking is OD 4+

Linear

 

Log

[ulf]

17 hours ago, Fandyus said:

Does UVBplus pass mainly UVB?

No it passes mainly UV-A, but includes UV-B and little UV-C.

The peaks of both filters above  are in the UV-A range above 315nm.

That makes the bell shaped transmission contain more UV-A than UV-B + UV-C.

 

With just that filter or a ZWB1, 8mm or a UG11, 8mm combined with the sensor sensitivity of a camera sensor in a FS-converted camera, the UV-A will dominate the image of you are not using a light source lacking most UV-A.

 

Maybe the labels of the different UV-bands, UV-A, UV-B and UV-C are less important than the actual transmission ranges?

Some years ago there were a discussion about if a filter had a pure UV transmission around 400nm, that IMHO did not make sense either, especially as there are several differing definitions of the wavelength for different bands.

[Andrea B.]

Ulf, thank you for the transmission charts! 

 

I want to make some more photos with both the new filters. Naturally I started with flowers. 

 

[LarsHP]

On 7/27/2023 at 7:09 PM, Andrea B. said:

...

I want to make some more photos with both the new filters. Naturally I started with flowers. 

 

Hi, Andrea. Considering the ZWB1 in 8mm, did you find out whether the filter is fine, or is there some issues with it?

The sample you share (last image in the first post) looks a bit blurry to me. (You mention possible flare.)

[LarsHP]

On 3/10/2024 at 3:56 PM, LarsHP said:

Hi, Andrea. Considering the ZWB1 in 8mm, did you find out whether the filter is fine, or is there some issues with it?

The sample you share (last image in the first post) looks a bit blurry to me. (You mention possible flare.)

Never mind. I have ordered it.