Stacking Schott BG3 with KG3 and KG1 filters

[Cadmium]

You know that straight out of camera blue and yellow look that LifePixel calls 'Super Blue IR', and what people have come to equate with Schott BG3,

well, I have never been able to make BG3 work the way I have seen it shown to work by others.

First of all, with my Nikon cameras it isn't possible to do an in camera custom white balance with BG3, the camera just sees that filter as too dark to CWB in camera,

so my only way of optimally white balancing BG3 is to use CNX2 or NX-D and white balance from RAW/NEF.

However, I don't get the nice yellow/blue, I get more of a dirty tan, not very strong foliage color (as illustrated in the first photo below).

 

Along comes Schott KG3, etc. (see graph below).

The KG type glass attenuates the NIR (IR) range, still transmitting IR, but reducing the volume gradually more in the higher IR/nm.

Here are example of Schott BG3 2mm alone, and stacked with KG3 and KG1. I white balanced all of these in CNX2, full frame marquee WB.

KG filters are very useful, something I hadn't ever realized before, and they can be used to attenuate other filters also.

 

BG3 2mm alone

 

BG3 2mm + KG3 2mm stacked

 

BG3 2mm + KG1 2mm stacked

 

Schott KG filters

 

[Ninjin]

Great pics, very beautiful yellow!

 

I saw yours, and I made a comparison for my BG3, if it works with weak IR block.

And yes, yellow - all like you said!

 

In test, BG3 - 2 mm, Сзс 24, Сзс25, Сзс26 - IR block filters are all 3 mm thick. White balance NX-D for all, completely the same:

[Cadmium]

Evgeniya, Very nice, thank you. Do you have a comparison between BG3 and CC4, each alone, and maybe more?

Nice clouds.

[Ninjin]

Yes, I did a comparison with CC4.

But I don't understand - why there dependence of blue from IR suppression..

 

With BG3, the sky is to more turquoise IF

IR is blocked strongly. If I understood correctly, sky color is: residue visible turquoise? -> blue -> pink from UV.

 

If IR blocked very strong for BG3 - the sky is to pink+turquoise and leaves to the red-brown, and then further to black-brown?

OK, but If the IR is weakly blocked, or no blocked, the sky is visible dark blue.

 

May be, for add blue in sky with BG3, need to cut off the UV + add only a very weak IR shield. It can do yellow for the leaves + add blue to the sky, without pink.

But why if IR strong suppressed = more turquoise in the sky? I do not understand about turquoise, at all.

 

I tried the test BG3 with GG420 + CЗC26 for. Maybe someone also tried any landscape with BG3 + GG 420 + KG3 comparison vs BG3 + KG3?

[Cadmium]

Thank you Evgeniya, very nice tests! :)

Clouds left... :(

First of all, your shot using BG3 alone is much stronger than I ever get using BG3 alone, and it may be closer to what most people get when using it alone, than what I get, I don't know.

Regardless of that, I can't say for sure what the exact difference is with the sky color, but given the graphs, I would say that there is less violet in the GG420 filtered stacks,

and that the white balance may change based on the difference in ratio of blue vs yellow in the total mix.

 

You are using the Russian filter C3C26, which is like Schott KG1 (if I am not mistaken).

KG1 = C3C26, KG3 = C3C24