14 replies to this topic

[GaryR]

Some shots from the Michigan Central RR bridge, now converted into an Elevated Park. Not much color this time of year, but I thought I'd try some CIR shots with the sdQH+KG3.







Some rusty relics along the trail.

[microbat52]

These are so beautiful!
How do you get so much colour on long wavelenghts if you dont mind me asking?

[Cadmium]

Gary, You posted this in November? I have not seen it before.
Very beautiful photos.
I really like the tractor photo a lot!

[Andy Perrin]

microbat52, on 16 December 2020 - 22:58, said:

These are so beautiful!
How do you get so much colour on long wavelenghts if you dont mind me asking?

This is a Sigma Foveon camera with KG3. Foveons do not have a Bayer array like our usual cameras, instead they use the depth that light of different wavelengths penetrates silicon to derive the color information. The KG3 seems to be a blue-green filter that does not completely eliminate IR, while the Foveon is expremely sensitive to IR, with the result that the KG3 balances the visible and infrared contributions to the resulting image with the gorgeous results shown above. GaryR has put more photos back in this thread, and Cadmium posted the KG3 spectrum also, at the link:
https://www.ultravio...dpost__p__36170

Edited by Andy Perrin, 17 December 2020 - 00:51.

[Cadmium]

I have actually never tried KG3 alone myself. It is a very handy filter for attenuating IR without removing it.
It is very different than BG filters (BG = Blue Green).
KG filters are basically full spectrum filters, flat transmission for the visual range, tapered attenuation in the infrared range.
It looks practically clear, with some slight gray/silver/green tint.
Schott calls it a Shortpass filter / Heat protection / cold light filter.
Here is a photo of Schott KG3.

[Andy Perrin]

Well it is certainly not a Schott BG series filter and I can see it passes quite a bit of red also. I was using the “blue-green” description informally based on your spectrum Cadmium. I’ve never seen the actual filter until now.

[Cadmium]

Yep.
It kind of looks a little blue in that photo, but to my eyes it looks more like green/gray, basically clear.
Here is what the Schott catalogue says:
Color: nearly clear
(light greenish tint)

I hope you all have Happy Holidays everyone,
and let's all stay safe this season and beyond.

[dabateman]

I remember these images and other comments here.
This must be the doing of the reset back up of December 6th.
Also google has been buggy and down over the last 2 days.
I have been getting messages a day late. One Pm from here came 12 hours after sent.

[microbat52]

Thanks for explaining Andy, i just learned something new

[GaryR]

hmmm, I hadn't realized that anyone replied to this post. Thanks for explaining Andy and Steve, and yes the KG3 is extremely helpful to attenuate the excessive reds on the sdQH.

For comparison, I recently took this set of images at the same location with my FS Sony a7R. Sigma has the advantage of SOOC CIR, but unfortunately no EIR-style color switches.

Instead of the KG3, I thought I'd try my recently acquired DB850 (thanks Andy!) with a Y12. The DB850+Y12 combo seems produce more red than the orange tones of KG3. I'll have to try another comparison in better weather.

Yellow weather vane - Sony a7R+DB850+Y12


Bright red planter - Sony a7R+DB850+Y12


Sony a7R+DB850+Y12


Sony a7R+DB850+Y12


Sony a7R+DB850+Y12


Sony a7R+DB850+Y12


Sony a7R+KG3

[colinbm]

These are looking fantastic Gary.
Could you do a comparison shot with both the Sony a7R Bayer & Sigma sdQH Foveon with this filter combination Please ?

Edited by colinbm, 09 February 2021 - 02:51.

[Cadmium]

Gary, Much improved. I especially like that second shot of the little tree in the yellow pot!

[GaryR]

Colin, It's a bitterly cold -20C lately, but I'll try it with both cameras when the weather improves.
Thanks Steve. I never get tired of that red to yellow/green color switch.

[dabateman]

The difference is striking. The china container goes from Foveon blue the A7R magenta. But I like both tractors. The amount of sunlight IR maybe playing a role.
I like the last A7R kg3 shot. Looks like a gathering for some science fiction movie.

[GaryR]

David,
Some blues, shift to purple with the sdQH, but aside from red foliage, most colors remain the same.
The last shot is a group people looking for the elusive Mystery Monolith in Toronto. It lasted one day after being vandalized, but that didn't stop hundreds of people looking for it the next day.