Using Luminosity for Highlight & Shadow Detail

How did you make that image?

Started with the one from the camera (on left) which I really like. Made at the edge of a mountain stream in the Great Smokey Mountains. Used a Nikon D300, Nikkor 105mm 1:1 macro lens (good for more than just macro; it’s a 105mm prime lens and one of Nikon’s best of any focal length); 1/2 sec. at f/29, ISO 640 (640 to help keep the stopped-down lens’s shutter speed reasonable as it was breezy & raining) and circular polarizer.  And a tripod, of course. A little post processing gave me the one on the right.

While experimenting with Silver Efex Pro 2 B&W conversions I found a nice way to bring out color detail from both ends of the histogram – shadow & highlights. In the before/after above, look at the rocks on the far bank and the almost pure white foaming water. You’ll see there’s a lot more detail in the “after” version (click to enlarge). Let’s see how that was done.


Post Processing

Step 1 – B&W Conversion. I mentioned in an earlier post that SEP2’s default B&W conversion result is the HSL color model’s luminosity layer (not a simple desaturation or grayscale). For reference, the SEP2 default luminosity conversion is shown next. Note the histogram which spans almost the entire tonal range.

For comparison next is a conversion made solely to reduce the luminosity range (by making tones as equal to one another as possible – compare this histogram with the one above; it’s much narrower). If you click and expand this version you can see the SEP2 Global Adjustments used to reduce the contrast (Contrast & Soft Contrast all the way left). The image is flat and not a good B&W conversion, but a good B&W wasn’t my goal – equiluminance was.


Step 2 – Combining the B&W image with the original color using Photoshop’s Luminosity blending mode.

  • If the SEP2 default  conversion is combined with the original color image using Photoshop’s Luminosity blending mode there is no change to the color version. This is because luminosity combines the original layer’s Hue & Saturation with the blended layer’s (B&W) Luminosity. So – if the B&W layer is SEP2′ s default (which is simply the original image’s luminosity), then no change is exactly what we should expect.
  • It’s only when we change the B&W image’s Luminosity that we should expect to see changes to the original color after the blending step.

Here’s the result of the Luminosity blending using the reduced contrast B&W –

It’s washed out, reflecting the overall flatness of the reduced luminance B&W half of the blend. But, what if we reduce B&W layer’s opacity – say to 25%? That give us the final version with its improved shadow and highlight detail.

Here’s our final. It may or may not be your preference as compared to the original which reflects the mood of the dark rainy day.


There are many ways to pull out highlight/shadow details. This is just one more tool to add to your arsenal – (but please, please, please – I implore you, please >> don’t use HDR on a scene like this. It’s totally unnecessary & screws up image quality in the same sense as putting a crappy cheap filter in front  of your expensive lens. What’s with all of these broad daylight HDR shots?? I keep seeing posted on line – even from “pro’s”?? OK- Get my soap box out of here!)