Better "Aerochrome" (SD1) with red/yellow/orange filters

Started 3 months ago | Discussions thread
tagscuderia Senior Member • Posts: 1,893
Warning: Down the NIR rabbit hole... !

Hi Christoph, I stopped work on this after our initial discussions because SPP 6.x.x stops the utility that I was using from working but... it's all in the RAW channel gain and colour matrices. Numbers numbers numbers:


i.e. the middle layer (layman's Green, N.B. Merrill X3F RAW is RGB data) is the pivot, with Red's gain being >2 and Blue halved. That sets the white point for the RAW channels for a Daylight illuminant.


That's for a Full Spectrum image, CustomWB taken against an 18% grey card, captured in direct sunlight. The pivot is the same but Red's gain is lessened due to the addition of IR. If you then use a filter, be it: X1, 25A, 099... the white point changes and thus the gain needs to as well.

Basically your use of SPP's Fringe Correction is akin to a Kelvin and Tint White Balancing tool. Whilst the Colour Adjustment tool is additive. Both work on the converted data.



R= 2.84375;-1.71875;1

G=-3.117188; 3.859375;-4.648438

B= 1.273438;-1.140625; 4.648438


R=2.875;-1.71875; 0.9921875

G=-3.15625; 3.851563;-4.648438

B= 1.28125;-1.132813; 4.65625

Taken from the same Full Spectrum shot as above. Only minor differences, probably because it's taken against a non IR reflective 18% grey card... ? It's difficult to know whether it would be worth customising this matrix. Could be like falling down the rabbit hole!










Comparing the 2 shows you how and why FOV Classic Blue works; Ted has mentioned RT, but you can use the Colour Balancing tool in PS.


In order to edit the X3F metadata I've been using ArvoJ's X3FWorkshop, N.B. just the action of opening an X3F in SPP 6.x.x alters the file, making it incompatible with X3FWorkshop (sh*te behaviour from SIGMA, I see no reason for it). All of my NIR X3Fs are now incompatible so I've stopped looking at Infracolour using SPP.

To achieve the rendering that you're after, you'll need to analyse Foveon layer spectral response, that of your filters AND of the Aerochrome film. But using SPP, which is converting for Daylight and at best colour balancing Full Spectrum, will yield sub-optimal results, unless you tell it via metadata what you want to achieve.

So easy, basically

 tagscuderia's gear list:tagscuderia's gear list
Sigma DP3 Merrill Sigma SD1 Merrill Sigma 18-35mm F1.8 DC HSM Art Sigma 50-100mm F1.8 DC HSM Art
Post (hide subjects) Posted by
Keyboard shortcuts:
FForum PPrevious NNext WNext unread UUpvote SSubscribe RReply QQuote BBookmark MMy threads
Color scheme? Blue / Yellow