Getting black backgrounds

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colohank
Posts: 113
Joined: Sat Jul 24, 2021 6:07 pm
Location: Fruita, Colorado, USA

Getting black backgrounds

Post by colohank »

In photography, black isn't a color; it's the absence of light. I've found that the best way to achieve a dark background is to rely on the Inverse Square Law. In other words, position your shot so that the background is many multiples of the distance between lighting and subject. Assuming that's the only light in the workspace, it doesn't take many multiples to produce a fall-off in exposure that far exceeds a camera's dynamic range and registers as black on the sensor. Fewers multiples of distance will yield something a bit lighter, if desired. Most of my black backgrounds are actually the inside surface of a white garage door which is just too far away, when poorly illuminated, to appear as anything but black. If I want background color, I can aim a speedlight with color gel at the white door.

As a rule, I can get rid of unwanted halos and other such stacking artifacts using the black and shadow sliders in LR6. Attached are before and after halo-removing shots of a Cheerio. If memory serves, the fill light at left was set at half the intensity of the key light at right.

For many macro subjects, I've begun relying more on LED panels for illumination. Mine (branded as Dazzne on Amazon and about 8.5" X 13") are adjustable for both color temperature and intensity. They produce a soft, enveloping light and few shadows. No need for fussy diffusers.
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Gearhead
Posts: 14
Joined: Tue Mar 23, 2021 12:11 pm
Location: Indianapolis, Indiana, USA

Re: Getting black backgrounds

Post by Gearhead »

Judging by your images you are pretty successful using the techniques you describe. My approach is a bit different. When I’m setting up a photomicrography I watch Live View on a large monitor. I have my Nikon Z7 set to display the histogram on top of the image and I use it to be certain I don’t clip important details in highlights or shadows. I try to keep the exposure towards the left side of the histogram, the black side. I shoot in NEF format, Nikon’s RAW format. I process in Photoshop. On of the first things I do in PS is to open CURVES and try the eye dropper tools. The left hand eye dropper will set the black point, where ever you click everything with that value will become completely black. Next I use the right hand dropper to select a white value. Thus the curve is stretched between those values. If things get really messed up I click cancel and start over. I find that curves eyedroppers are very valuable in giving me the black background I want and the white highlights. Sometimes it’s astonishing! When in doubt, click the box for SHOW CLIPPING. That way you can see if you are clipping anything you don’t mean to.

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