andyptak wrote:
I just got a a6000 converted to 850 nm and used it for the first time yesterday. Very surprised at the dull and flat dng. I played with various settings in LR and improved it quite a bit, but still lacking compared to the samples I see here. Any processing tips anyone?
I have never shot an 850nm filter but assume it is similar to 720nm but just even less permissive.
Step 1, when shooting, you need a lot of light…not because of shutter speed, necessarily but to bring out the differential ziR reflection in the scene. Overcast skies require a lot of post. Ideally, you have a partly cloudy sky with the sun not behind a cloud.
Step 2, choose your subject. As a rough approximation, assume everything green reflects the same degree. Assume yellow/dry grasses will be a bit less and that red leaves may be yet darker. Look for scenes where you have elements expected to reflect varying amounts of light as well as some that will not likely reflect at all (dirt, tree trunks, metal, blue sky, some stone) and try to shoot from angles wherein the light areas are broken up by dark ones. It is perhaps easier to describe what not to shoot. For instance, if you shot a densely leafy tree from above that was sitting in a dense green field of grass, it would be a big white nothing. The dark elements need to break up the lighter ones to pull them apart from each other.
Step 3: expose to the right. Increase the exposure until you start overexposing the whitest elements…and then reduce 1/3 stop. Generally, do not have the sun in your image…ideally behind you or directly above.
Step 4: process to improve the contrast. If you followed the steps above, then your scene should already be fairly high contrast but still may need the black point darkened. For starters, pull the Blacks slider to the left in LR until the histogram starts to touch the left wall. You can always tweak more or less. Your White edge should already be close to the right wall. Take it all the way there with the Whites slider. This is now the max (unclipped) contrast. Better? You can now decide where the middle tones should be and how steep your curve should be.
Many images essentially only will need the black point set. Others will require more work, but far IR has less intrinsic contrast from a single subject, so composition and exposure are really important.
Jim
Jul 10, 2022 at 10:22 AM
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