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UltravioletPhotography

Schott IR-Pass Filters: 15 Views of the Raw Color


Andrea B.

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See also: Schott IR Filters: 15 Views of the Color Checker Card ...and More

 

Experiment: Investigate the raw color of 15 IR-pass filters.

 

Gear: D610-mod + UV-Nikkor 105/4.5 and 15 IR-pass filters.

 

Filters: The 15 filters are listed in the link above and also labeled on the composite below.

 

Subject: Color Checker Card together with a 99% and a 75% reflective Labsphere Spectralon white standards. In this topic only the 99% standard is used. Here's the OG515 raw color file so you can see what I was working with. The 99% standard is on the left.

d610_uvNikkor_og515_sun_20180626shoreCottageSwhME_10571_nef.jpg

 

Processing:

Each IR file was converted in Raw Digger and exported with RD default autoscaling and contrasts but with no color profiling so as to preserve the raw colors recorded by the D610-mod under each IR-pass filter. The exported TIF was then given a tweak in NX2 to set the white point and black point. (This step is performed only on the Luminance of the file and does not change the hues.)

 

After cropping for the 99% reflective Labsphere Spectralon white standard, the raw color hue was sampled. The fully saturated, fully bright version of the sampled hue was overlaid in a square on the standard with an RGB label and color wheel location.

 

Labeling and composites were made in PS Elements 11.

 

Notes:

There is a hue cluster for the RG610, RG630 and RG645 filters whose sampled hues are 16°, 16° and 17°. It makes sense that these 3 filters would record similarly given that they are not very far apart with their transmission peaks. There is another such hue cluster for the RG665, RG695 and RG715 filters whose sampled hues are 19°, 20° and 20°.

 

BTW, I did couble-check the sampling. But we shouldn't read too much into these hue clusters. There is also the matter of intensity to be taken into account. If you refer back to the white balanced IR series in the initial link above, then you can see, for one example, that the RG715 result has less colour over all than the RG665 result.

 

Another observation: While we all think of the RG830, RG850 and RG1000 IR-pass filters as giving us monochrome results, you can see that the white balanced monochrome of these filters derives from a raw, almost magenta hue.

 

 

 

This compsite is 960 x 1575 px. The forum software resizes it to a max of 1200 px.

d610_uvNikkor_irRawColorsComp_2018.06.26proof.jpg

 

 

 

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