11 replies to this topic

[UlfW]

Today we had the winter solstice just before noon and I begun shooting at 1 P.M.
I have considered doing this for some days to test if UV-photography still was doable.
Today it was overcast, rather windy, with a humid biting wind just above freezing.

As this is rather extreme I also wanted a very old motif.
I chose an exposed neolithic grave chamber of an old dolmen (dös in Swedish)
It is situated at the coast close to where vikings had a settlement several millennia later.
55° 28′ 56.69″ N, 12° 57′ 34.85″ E

The dolmen is named Eskilstorpsdösen.
According to the information I found it is from ca 4000 B.C., about 1500 years before the great pyramids at Giza was erected.

This dolmen is not very big, just about 3m high and with the top stone ca 3-4m wide.
I have no idea how they managed to move such a big stone with their, at the time, limited resources.
Normally dolmens like this look like small hills of sand or dirt, with the grave chamber buried in the center.

Camera: Multispectral converted Sony A7III
Lens: El-Nikkor 80/5.5 old metal type at f/8
Filerstack: S8612, 2mm + U-360, 2mm
Exposure 5s at ISO 640

[Cadmium]

Ulf, looks great! Very interesting dolmen.

[Andy Perrin]

Nice! You can see the lichen well.

[UlfW]

Two days later the sun was shining and even if there is not much UV with the sun just 11° above the horizon it was enough to try my newly arrived U-340 4mm in a 8mm stack.

Camera: Multispectral converted Sony A7III
Lens: El-Nikkor 80/5.5 old metal type at f/11
Filerstack: 2 x U-340, 4mm
Exposure 2s at ISO 640

I forgot to bring a white balance target so the image is white balanced against the grass i the foreground.

Edited by UlfW, 26 December 2020 - 07:21.

[dabateman]

Interesting yellow sky. Definitely some UV there as the 8mm U340 stack is mostly deeper 350nm to 360nm UV.
You may have captured that yellow band well.
Below that seems to be green and above that seems to be bluish.

[UlfW]

I like this saffron like hue.
It reminds me a bit of the Yooperlite stones glowing in UVIF.

I think the WB is reasonably OK based of that stack's transmission

Edited by UlfW, 26 December 2020 - 09:14.

[Cadmium]

Ulf, Very interesting U-340 8mm photo. I don't know if I have any 8mm shots of the sky.

[UlfW]

I have not found any when searching the forum.
The closest is the specular reflections in the car's window here.
https://www.ultravio...dpost__p__32750
I think that is from clear sky.

[Cadmium]

I guess I need to shoot some that include the sky.
Yes, the link you show has the CNX2 full frame marquee WB, which has the much more yellowish result than Photo Ninja 'full frame' WB or Photo Ninja from Spectralon.
It is a little hard to decide which WB I like the best.
Although I really like the color contrast between the strong reddish colored drapes in the center of the upper windows of the hill side house and the yellowish overall tone of photo #1,
the shot seems to have a little too strong of a yellowish overall cast for me.
The Spectralon WB'ed version (photo #3) looses the strong color of the reddish drapes.
The Photo Ninja 'full frame' WB (photo #2) seems to share a little of each of the other two WB'ed shots, and retains the reddish drapes, although perhaps not as strongly as photo #1.
The Spectralon WB shot was done by shooting a separate close shot of the Spectralon with spot exposure in the center of the Spectralon (at the same time, place, and lighting as the landscape shot),
then WB'ing the center of the Spectralon (in Photo Ninja), and then copying that WB to the landscape photo.

"WB?" is CNX2 full frame Marquee WB.

Edited by Cadmium, 27 December 2020 - 08:56.

[Stefano]

Yes Steve, I am curious too to see if the sky has the usual yellowish color or if it is different. Just take a picture of the sky (if you have a blue sky now, but it could be dark/cloudy now) with Spectralon in the same image, and then white balance it the usual way.

[UlfW]

Cadmium, on 27 December 2020 - 08:50, said:

Yes, the link you show has the CNX2 full frame marquee WB, which has the much more yellowish result than Photo Ninja 'full frame' WB or Photo Ninja from Spectralon.
It is a little hard to decide which WB I like the best.
Although I really like the color contrast between the strong reddish colored drapes in the center of the upper windows of the hill side house and the yellowish overall tone of photo #1,
the shot seems to have a little too strong of a yellowish overall cast for me.
The Spectralon WB'ed version (photo #3) looses the strong color of the reddish drapes.
The Photo Ninja 'full frame' WB (photo #2) seems to share a little of each of the other two WB'ed shots, and retains the reddish drapes, although perhaps not as strongly as photo #1.
The Spectralon WB shot was done by shooting a separate close shot of the Spectralon with spot exposure in the center of the Spectralon (at the same time, place, and lighting as the landscape shot),
then WB'ing the center of the Spectralon (in Photo Ninja), and then copying that WB to the landscape photo.

"WB?" is CNX2 full frame Marquee WB.
U340_8mm_Truck_3_WB_1920.jpg

My feelings about the different WB of your images are the same as yours.
This 8mm stack is definitely more challenging to WB than a U-360 stack.
I expect more influence by the differences in illumination and camera response too, beside how different software do their job for WB.

When I have more sunshine available I'll snap some PTFE-images to use for transplanting WB with this camera.
It was actually the very first times I used it outdoors.

I have had it almost a year, but only used it indoors with my UV-converted Godox flashes, until now.

Edited by UlfW, 27 December 2020 - 09:06.

[Cadmium]

Given a really good broadband deep transmitting lens, the 8mm becomes a different animal than the usual UVA lens.
Removing the upper violet part of the UVA range, and extending the lower range with lower centered peak, makes for a much different range and width.
Just may take on it.
It has a braoder variance of white balance.
I find some of the flower shots I did with it this last summer strangely appealing, but void of the higher blue colors you will see using a U-360 stack or Baader U which do tend to round out the UV false pallet.