IR images with blue sky and water using a ZWB2 filter

[Kai]

Today I want to share how I occasionally create blue sky IR images.
Strictly speaking, these are UV-IR images.

I use a ZWB2 as a filter. It has a transmission maximum in the IR around 750 nm. I do the white balance against PTFE. IR is then usually rendered color-neutral, UV violet.
The IR portion can occasionally appear greenish or yellowish when the UV portion is very high. According to my observations, influencing factors are: ratio of IR to UV in light (position of the sun, degree of cloud cover); greater sensor sensitivity to IR (broader wavelength range); UV transmittance of the lens ("UV-reach").

 

In landscape photography, the IR intensity is usually so high everywhere in the image that the IR image practically dominates. Wood effect and haze penetration are as usual. Only the blue sky and reflections of the blue sky on water are so IR poor and so UV rich that they appear violet.

I can then either shift the violet to sky blue - depending on my taste or the subject of the picture - or, in the case of a BW conversion, darken it with a yellow filter.

Attached are three sample images for illustration.

 

 

 

 

 

 

 

 

 

 

 

 

 

[colinbm]

Very interesting & lovely results.

[dabateman]

I like the ZWB3 filter for blue skies and whitish to yellowish trees.

That works well on its own at 2mm thickness. 

White balanced off grass or concrete. 

[lukaszgryglicki]

Speaking about a bit similar effects - use Hoya U-340 without IR blocking.... under very strong sunlight you will have two "focus points" and either IR will be kinda sharp and UV will cause blur & haze or the opposite - sharp UV and IR blur/haze.

 

[Andy Perrin]

It depends on how much focal shift the lens has, Lukas. Try it with the UV Nikkor — I think that one has not much shift. 

[Doug A]

Thanks for the great info @Kai

[lukaszgryglicki]

6 hours ago, Andy Perrin said:

It depends on how much focal shift the lens has, Lukas. Try it with the UV Nikkor — I think that one has not much shift. 

It has focal shift between IR and the rest. It doesn't have between Visible & UV.

Great shots @Kai

[Nate]

These look great Kai. I have tried this in the past, but the focus shift was so bad never tried it again thinking it would happen with every lens. Might try again with different lenses.

[Kai]

5 hours ago, Nate said:

These look great Kai. I have tried this in the past, but the focus shift was so bad never tried it again thinking it would happen with every lens. Might try again with different lenses.

My lenses are no "super-apochromats" from UV to NIR. Depending on the focus the pictures show a blurred UV image on a sharp IR image. Since the UV component is "only" used for coloring, the sky and water play little role in landscape photography...
Yes, you should try it again ;)

[Kai]

17 hours ago, dabateman said:

I like the ZWB3 filter for blue skies and whitish to yellowish trees.

That works well on its own at 2mm thickness. 

White balanced off grass or concrete. 

I will test it! :)

[Andy Perrin]

Conceivably one could get rid of the blur by focal stacking…I want to try this now. 

[Wayne Harridge]

17 hours ago, Andy Perrin said:

Conceivably one could get rid of the blur by focal stacking…I want to try this now. 

 

That's a great idea!