Removing Hot Spot for IR....

Started Jun 5, 2014 | Discussions thread
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Albert Valentino Veteran Member • Posts: 6,492
Removing Hot Spot for IR....

I revised the possibility of removing the hot spot from lenses, particularly the Fuji 18-55 lens, for use with near IR shooting. I played with various methods last year but was never pleased - a lot of work with less than optimal results unless the contaminated area was cloneable. One of my first tricks was to start with Nik Viveza control points and work from there. Again, it is often a lot of work to get results that were far from perfect, especially when viewed closely.

Anyway, now that Photo Ninja is my main converter I decided to play around and was glad I did since the results on the several tests were excellent. So far it worked on every image I tested - no artifacts or halos... Ideally this method, outlined below, should work with any RAW converter but I only tried with adobe ACR (not obsessively) and could not get to work as well. Perhaps it is an X-trans interpretation, I do not know and you are welcome to try. Of course we have many Raw converter options so below I will simply describe my 'simple' method using Photo Ninja.

Below is my recipe. The pictures below are not optimized (exposure/contrast...) for an end result, just the first step, WB correction, and the second step (hot spot correction) in the work flow.

Step 0: Shooting

I shoot with a Hoya R72 filter on my XE camera in RAW with WB set to Custom. The Custom WB is set by pointing at something green and setting to make that neutral (or close to neutral). This is a much better starting point than using Auto WB and trying to correct in post since you might now have enough latitude to completely fix.

Step 1: Correct WB

Simply use the WB eye dropper tool on the area you want to neutralize, cloud, trees, grass. (If clouds and trees it is often best to click on the clouds so you can play with faux color in the trees doing more advanced methods like channel swapping.

Step 2: Hot Spot Correction

In Photo Ninja go to Color Enhancement (similar to Hue/Saturation in adobe).

A) Click on the Blue box

B) Move Saturation slider to left

C) Move Reference Hue slider around until you see the least amount of blue - this indicates you are working with the correct shade of hot spot blue. Then, move the Hue Affinity slider a bit to the right until you the greats color diminishment.

D) Play around with the Saturation and Lightness sliders to fine tune

That's it!!!

It has worked great with my 18-55 so it should work as well with other lenses. Give it a try

Note: The hot spot itself will be lighter and wider at wider apertures. As you stop down the spot gets smaller but more concentrated.

White Balance Corrected

Hot Spot Corrected

Default Settings for Color Enhancement - clicked on Blue

Corrected settings for the above picture.

White Balance Corrected

Hot Spot Corrected

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Fuji Silver XE1 w/14, 35, 18-55, 55-200, Rokinon 8mm Fisheye & Tamron 90mm f/2.8 Macro

 Albert Valentino's gear list:Albert Valentino's gear list
Olympus E-M1 Olympus M.Zuiko Digital ED 9-18mm F4.0-5.6 Olympus Zuiko Digital 1.4x Teleconverter EC-14 Tamron SP AF 90mm F/2.8 Di Macro Olympus M.Zuiko Digital ED 40-150mm 1:4-5.6 R +12 more
Fujifilm X-E1 Ricoh Caplio R7
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