Luminosity Blending – in Context

The past few posts looked at luminosity blending as a post-processing step to enhance color & detail. That step usually is not done in isolation. Most often it’s just one step in a workflow. This post illustrates such a workflow beginning at image-capture where the most critical decisions are made – post-processing can only help so much.

Capturing a Snow Image

REQUIRES ATTENTION TO

EXPOSURE AND COLOR

The Basin

Franconia Notch State Park, New Hampshire


Start & Finish


Technical

RAW is essential because of the several stops of extra dynamic range it provides

This means more shadow & highlight detail is possible than with JPEG or TIFF & once that detail is gone because you failed to shoot RAW, it’s gone forever

RAW also allows easy “tuning” of the White Balance – difficult in JPEG

This image’s exposure, as measured by the histogram’s size & location, was nearly perfect (see screen shots below)

Even though the exposure is good – per the histogram – the upper left area’s shadows are too dark. We’ll fix that using the approach described in this post.

The captured image’s color has a blue cast which some viewers like with snow, but I’ll remove it in this image

Exposure notes for snow –

A positive exposure compensation (maybe over 1 full stop) is often needed

This is because the camera meter attempts to make the overall image tonality middle gray

If the scene is mostly white and you leave EV set to zero, your snow will be gray

Not a problem in this image since the snow was a small part of the overall image

Composition

Not many options, especially given the icy conditions which required me to slide on my butt on several stretches just to reach this spot in one piece. Not as agile as I used to be.

Post-process

1. RAW conversion in Capture NX2; the critical 1st step is WB correction and then shadow recovery

1a. The first step was to remove the blue cast as shown in the following screen captures; click to enlarge & see details

Before


After


1b. Followed by shadow recovery using NX2’s D-Lighting

The above NX2 WB & shadow recover steps provide the input to the next step.


2. Tonal & color contrast adjustments in Color Efex Pro 4 using my custom designed recipe for basic image post processing

  Step-by-step detailed illustration in this post


3. B&W conversion in Silver Efex Pro 2

3a. This step was solely to get a B&W version for use in step 4

3b. SEP2’s default conversion does not change the image’s luminosity. If you use this as your B&W conversion you will see NO difference in the final result after doing step 4. You must change luminosity.


4. Blended #2 & #3 in Photoshop using Luminosity Blend at 33%

4a. I try this with most images because, used judiciously, it often brings out beneficial details & colors that I can’t achieve otherwise

4b. Here’s what PSE’s layers look like after changing the SEP2 layer’s blending mode from normal to luminosity


Here’s the beginning to end –

Capture…………After WB……….After Shadow Recovery

After Step 2………………B&W Conversion……………Final

Click to enlarge


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Luminosity Blending Magic, 3

Here’s a step-by-step wrap up on the process of blending a B&W image with a color image using luminosity blending. The emphasis here is luminosity blending (NOT luminosity as a B&W conversion technique). In fact, as shown yesterday, if you use a B&W that was converted via the luminosity method you will see NO change between the before & after blending step. Today it’s about blending & not B&W conversion. Sorry if it’s confusing.

Luminosity Blending provides the potential for

A quick 1-step processing technique

To bring out detail in an image


A step-by-step example:

1. As Captured                                      2. RAW>JPEG

    3. Silver Efex Pro                       4. Luminosity Blend of 2 & 3

Washington National Cathedral

RAW>JPEG included white balance adjustments and shadow recovery


This is an overview. The details are in the previous posts.






The final result is dependent mainly on the characteristics of the B&W image.

There is no panacea – experiment and you’ll discover what works best for you.

REMEMBER

  • Do not use a B&W conversion that is itself a luminosity conversion
    • If you do, there will NO change to your image – and you’re looking for change (refer to the previous post)
  • “what is best” is “what YOU want”. It’s your vision, not someone else’s.

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Luminosity Blending Magic, 2

Here’s more on using a B&W image blended with a color image. Yesterday’s post showed if the B&W was a luminosity conversion, color image improvements were possible in a single quick blending step. How does that compare to the results from using desaturation or grayscale images in the blend?

B&W CONVERSION ALTERNATIVES –

What’s the difference?

For Luminosity Blending – A Lot

and for regular B&W prints – maybe even more so


 

Textures, Shapes & Lines


This is part of a series on Luminosity Blending –

A simple effective single processing step

for improved color, contrast & detail


Which conversion technique is best?

A viewer commented yesterday and questioned my stating that luminosity is the “best” conversion technique. He was right, of course, as what I meant is that in-my-opinion it most often produced the best B&W conversion. What is actually “best”? Here’s what I wrote on this exact question three years ago.

It depends. Depends? On what?

On which technique provides the result that YOU want.

That’s all that matters.

Myself, I see no redeeming virtue in desaturation and would never use it.

Between the other two I tend to prefer the luminosity technique.

I’m still researching details on grayscale vs. luminance when it comes to human vision considerations – something for a later post.

Regardless, I do 100% of my B&W in Silver Efex Pro 2 and the preset conversions are nothing more than starting points in my use of SEP 2.

(As an aside – the luminosity result is what Nik Silver Efex Pro 2 uses as its default neutral starting image – Preset 000. Take that for whatever it’s worth.)

As you should know by now – using that SEP2 default as your luminosity blending layer will

Result in no change to your original image (see example below)

If the reason isn’t clear, go back to the earlier luminosity conversion post & read it again

For comparison, try using SEP’2 Preset 005 instead (as a starting point) – or others


Conversion technique comparison examples:

AND – if the original is blended with each of the three above conversions we get the results shown below –

To conclude, if we used the B&W produced by SEP2 Preset 005 (left below) and blended that with the original we’d get the lower right image.


Tomorrow,back to the real world and real photographs  and real luminosity blending examples to wrap up luminosity blending.


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Luminosity Blending Magic, 1

The past few posts examined several approaches to B&W conversion. A case was made for an approach that is based on image luminosity. These next several posts will explore luminosity further – not just as a means of B&W conversion.

A Simple Processing Step Based on Luminosity

CAN BRING OUT COLOR & DETAIL

BETTER THAN ALMOST ANY OTHER SINGLE STEP

Luminosity Blending (top – before)

Click to enlarge for details

Main Altar, Washington National Cathedral

From the viewpoint of a prostrate sinner ;-)


This was done simply by –

  • Opening the original image in Photoshop
  • Adding a B&W version in the layer above the original
    • NOTE – not just any B&W
    • One converted using luminosity B&W conversion
    • TIP – The Silver Efex Pro default setting is a straight Luminosity B&W conversion.
    • Save a SEP default result and voila – Luminosity-based B&W
  • Changing the blending mode of the B&W layer to luminosity
  • Done in about a minute

You can used an image that’s been post-processed first. This example used the in-camera captured version.

If you enlarge the sample

  • You’ll see an amazing increase in detail
  • Please ignore the noise
    • This is one of the images from “Oops! The ISO is 1600, dummy!” shoot discussed here
    • (An interesting read if you have the time)

This is just one example of the use of luminosity in image processing. A powerful tool that doesn’t get the recognition it deserves.

Tomorrow – Part 2


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Taking a Day Off from B&W Art

Back to the art of B&W tomorrow. Today I’d like to share something that I found fascinating – from many perspectives, just one of which is photography.

Scientists at the University of Tubingen in Germany, used an artificial intelligence based neural network to create artistic images when provided with a photo and an example painting to learn a style from. They presented this paper on August 26th. Five “learned-by-example” painting are shown below.


Don’t peek at the text beneath these examples until you decide how many of the five famous artists (B through F) you recognize through their paintings. OK – now you can look. I didn’t recognize B.

To see these images LARGE, click on the link above to the paper, go to page 5, it’s a PDF page so use your PDF reader’s size option to enlarge it.

neural net art


I spent six months (many years ago) on a sabbatical doing artificial intelligence research. I love art and study books on art (including a reference on all of the paintings in the Louvre) to guide my photography. These two pieces of trivia only begin to describe why I found this paper and its results fascinating.


Tomorrow – Luminosity Tips


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B&W Conversion 3 – Luminosity

Today we’ll look at the 3rd of three B&W conversion techniques, Luminosity.

sharps lane cades cove

Cades Cove, Great Smoky Mountain NP

Misty Dawn Scene


This technique produces what I call a “luminosity” B&W.

  • It can be done with any editing program that uses layers and has a Luminosity blending mode. The method (using Photoshop Elements) is shown in the following screen shot:
    • Make a copy of the original image
    • Place a white layer beneath it
    • Change the blending mode of the copy to Luminosity
    • You’re done

The result derives from how Luminosity blending works.

  • Luminosity takes its hue & saturation values from the 2nd layer (the white layer below the luminosity blend layer) and its luminosity values from the top layer.
  • Since the 2nd layer’s H & S value are zero (neutral) the result, as shown on the left, is pure black and white (gray tones) whose lightness values match those of the original image.
  • Voila – we’ve extracted the luminance channel.

For the 4th & final time, here’s the comparison of all three conversion techniques

2015-08-29_7-37-21


It’s unfortunate that image editing software programs offer desaturation and grayscale, but not luminosity – unfortunate because, of the three, it’s the best. There is an easy way to make a luminosity-based B&W without going through the PS routine described above. Tune in tomorrow,


Tomorrow – Luminosity Tips


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B&W Conversion 2 – Grayscale

Today we’ll look at the 2nd of three B&W conversion techniques, grayscale.Tomorrow it will be luminosity.

_DSC7420_nx2 cep bw2

Portland Head Light

Dark (well before sunrise) misty scene (the kind I love)


How is Grayscale computed?

  • Grayscale attempts to take into account how our vision perceives color.

We do not perceive all colors as being equally bright

  • Green is seen as being brighter than red which is brighter than blue.

In order to convert colors to match the colors the way that we see them (more or less)

  • We can’t simply average all three colors equally as in the desaturation method
  • We must weight each color proportionally to how our eyes see them
  • The accepted weightings are:
    • 30% of the red value
    • 59% of the green value, and
    • 11% of the blue value
    • Not equal weights as in desaturation

The weighted average gives us the grayscale shown in example below.

  • Often, it is hard to see a difference between luminance and grayscale
  • This RGB test panel example shows that there is one – especially the green

2015-08-29_7-37-21


Tomorrow – Luminosity


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