in the grove at sunset

[photoni]

A photo with 25A red filter (~ 580nm red + IR)
a photo with blue filter BG25 (Jena glass 2mm)+ BG39 (Chinese Glass 1mm)

 

the warm and contrasting light of the sunset disappears with the cold-toned filters

Toni

 

 

 

 

 

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[Andy Perrin]

Now subtract them! 

[photoni]

34 minutes ago, Andy Perrin said:

Now subtract them! 

 

I don't understand ... the photos are not in register :)

[Andy Perrin]

Obviously I did not mean those literal photos, you would have to re-shoot it with the camera held stationary. You also would have to adjust the exposure probably. But you could extract just the shadows and it might be interesting.

[photoni]

my intent was to guess what I don't see

(the extreme north and the extreme south of the sensor)

 

the Raw of the photo with 25A has all the information in the shadows (ISO 100)

if I lighten it I lose the three-dimensionality

[Andy Perrin]

Your intent was clear above.
 

I was making a suggestion for a different experiment. If one filter shows shadows and the other doesn’t, subtracting the (registered) images should show shadows only, which might be fun to see. I think you would have to make both images monochrome first though. 

[Nate]

The elimination of shadows is fascinating, great comparison of filters.

[colinbm]

41 minutes ago, Nate said:

The elimination of shadows is fascinating, great comparison of filters.

He doesn't have these BG25 + BG39 filters, so we don't know what he is using ?

[Nate]

1 hour ago, colinbm said:

He doesn't have these

Ah ok, I totally misinterpreted this post then. Great wooded scene anyway

[Andy Perrin]

9 hours ago, Nate said:

Ah ok, I totally misinterpreted this post then. Great wooded scene anyway

No, you were fine, what Colin meant was that Photoni is using Schott names for Chinese filters that are meant to be similar (but which we know do not exactly reproduce the Schott spectra). Photoni does not actually own those Schott filters, only Chinese ones. So we don’t know what the spectra are that we are seeing here exactly, only “in the ballpark.”

[Nate]

Gotcha Andy, thanks

[photoni]

2 hours ago, Andy Perrin said:

Photini is using Schott names for Chinese filters

Andy you're right, I corrected the title and specified thickness and origin.

My curiosity concerns the "contamination" of a part of the visible in IR and UV

I didn't want perfect black and white

I didn't want a color split

Now that you got my brain cells spinning I think I'll be back with a tripod and wratten 87c 800nm

Toni

 

Andy ...what does Fotini mean?

maybe I prefer the translation of PHoToni = photons

or like the old Nikon photonics :-)))

[Kai]

Nice comparison, Toni!
I find it exciting how well you can see the effect of the wavelength-selective light scattering through the sky!
In the short-wave half of the spectrum, it is mainly the scattered light from the sky that illuminates the scene and shadows can hardly be made out. The sunlight from the low-lying sun hardly has any short-wave components to produce shadows.
The opposite shows the long wave part. Here practically only the sunlight illuminates.
So far I have only ever seen this effect when comparing UV-A with NIR. It is interesting that you show us that this is also the case with the inclusion of the (half) VIS area.
And aesthetically I like the pictures too;) 

[Andy Perrin]

7 hours ago, photoni said:

Andy ...what does Fotini mean?

maybe I prefer the translation of PHoToni = photons

or like the old Nikon photonics :-)))

Ah, I see, I will correct it. 

[photoni]

On 11/24/2021 at 11:40 AM, Kai said:

Nice comparison, Toni!

Thanks Kai, You've got the theme right.
I didn't expect such a big difference.
It amazes me that the azure blue filters remove 95% of the warm sunset light ... as if a heavy white cloud had passed over the sun.

[photoni]

in the grove I have not found the same light
but at sunset I saw this row of trees covered with ivy.

 

in black & white,  IR 750nm and red 580nm are similar,

the one with Chinese BG39 1mm is similar to that with + BG25 Jena 2mm glass