Friday, October 11, 2013

Recovering from Underexposure - A New Approach


In my last post, I discussed my strategy for exposure for digital cameras, which usually results in images that are underexposed when downloaded straight-out-of-the-camera (SOOC).  In this post, I would like to discuss my current strategy for recovering shadows.  Here I use Lightroom but the same techniques can be used in other post-processing software.




COMPARISON OF THREE APPROACHES

Here is the SOOC version of the image above.


I used the approach I discussed in my last post, relying on ADL to expose for the highlights.  As expected, the SOOC is underexposed.  However, the relevant highlights are preserved:

even the candle highlights are preserved


The highlights in the window on camera right are not preserved but that's ok.  They don't add to the image (it was an overcast day with gray skies) and exposing for them would have led to more noise without much offsetting benefit.

Easy approach

The  easiest approach is of course to use the shadow slider (increase it as needed) and the highlight recovery slider (decrease as needed).  In my opinion it is also the least satisfying way to recover underexposure.  The result looks HDR-ish (but if you like that effect, then this is perfect for you -- boost the clarity slider next to make it look more like HDR).  Moreover, in some sensors like that of the D7100, using the shadow slider is more likely to reveal noise or worse, banding.
Using the shadow slider: HDR much?

Global approach
The next approach is one that I've posted about before.  In brief, instead of relying on the shadow slider, I use the exposure slider.  I do use the shadow slider as well, but only up to about +20 or sometimes +30.  More than that and it looks too artificial for me.  I use as little of the shadow slider as possible.

A +20 or +30 shadow adjustment for a scene that's exposed for highlights will nowhere be enough.  Therefore the heavy lifting ( sorry :) ) is done with the exposure slider which I use as much as necessary.  Using the exposure slider will be more likely to blow the highlights that are actually captured.  To offset that, I use aggressive highlight recovery.  As much as -200 (by using an adjustment brush on top of the highlight adjustment).  Unlike using the shadow recovery slider I don't find any issues with the highlight recovery.

For very contrasty scenes I get a little help by changing the camera calibration to a low contrast picture style and if necessary, by decreasing the contrast as well.

When the midtones look normal, I then work on restoring the oomph because the image will otherwise look very flat / low contrast.  To do that, I increase the white slider (making whites appear more white), and I decrease the shadow slider (deepening the blacks).  Does that effectively negate what I did with the highlight recovery and shadow recovery?  Not at all.  The net effect of those changes is to move the shadows and highlights a little closer to the middle, where it is easier to see them (partly because our eyes can differentiate more midtone shades).

Here is the result:


Here again is the first method for comparison:

This second method produces a more natural and more three-dimensional appearance.  Now let's talk about the third approach.

INTRODUCING THE HOBBY APPROACH

I call my current approach the Hobby approach for two reasons: first, it is styled after Strobist David Hobby's logic of using lights; second, because it is customized for each image, it is probably not usable for event pros who need to edit thousands of shots.  So, it's just for us hobbyists. :)  Well, ok, editorial and portrait shooters too.

Until about a year ago, I was a huge strobist fan.  My lighting collection attests to that (someday I'll review more of my lighting gear).  I'm still a fan, but after having gotten the D600 with its exceptional shadow recovery abilities, I found that I could get results with postprocessing that closely mimic real artificial lighting (lol).  Here's how it works (strobists among you will recognize the logic):

Shadow detail legibility
The first thing I do with the underexposed image is to raise the exposure for shadow legibility.  In strobist-speak that means increasing the exposure to the point where the details of relevant shadows can be seen.  What that exactly means varies depending on your shot and your taste.  If for example you want an intense-looking dramatic scene then the shadow details would be barely visible.  If you want a look that mimics Mr. Hobby's shooting style, you want shadow details that are pretty easy to see (enough that if you print the shot on newsprint with a lousy printer, you will still have enough detail).  I myself prefer something in between.

Here again is the SOOC shot:

And here is the shot with the exposure raised to my desired shadow legibility (in this case +0.36):

Highlights
To tame the highlights, I use the highlight recovery slider, that's all.  I don't mind being aggressive with it, although I watch to make sure the image doesn't become too flat.  For stubborn highlights, I use an adjustment brush or radial gradient to bring them down further.

Midtones
To raise the midtones, I use Lightroom 5's radial gradient.  To me it looks more convincing than using the adjustment brush.  If you're new to LR5, pls. note that the radial gradient can be changed to an oval/ellipse and can be tilted.

I use an inverse mask which means the effect will be within the circle that you apply instead of outside it.  I also increase the feathering from 50 to 75.  This simulates real world lights more closely (unless you want it to look like you used a snoot, in which case you decrease the feathering).  For each gradient I try not to increase more than +0.7 or else the result looks too obvious.

I apply this radial gradient everywhere I want to raise the midtones, starting from the darkest midtones.  For some areas, I apply overlapping radial gradients that are progressively smaller.  For example if I have a portrait shot from the waist up then I'll apply a radial gradient for the head and body, then to highlight the face, I'll add another radial gradient just to the head area.  Note that I don't just use one huge radial gradient to cover the arms as well -- I apply a separate radial gradient to each arm.

From the previous shadow legibility step:

Here are the areas where I applied a radial gradient (see the dots):

Result with midtone recovery:


Contrast
As with the second approach, I add punch to the image using the white slider, black slider, and sometimes the clarity slider.

That's pretty much all there is to this approach.  Note that this method cannot recreate rim lights or kickers or hard lights.  For those I use ambient light sources or flash.

Here are some more samples:








8 comments:

  1. Very funny, that post just came in time. I have shot a headshot session with a friend's D7000.

    During setup I had a few pictures that were almost completely black (occupying half the left-most zone in the histogram), and just for fun, I bumped the exposure to +5 to see what would happen. I was stunned. The picture opened up as if it was well-exposed from the beginning, without any banding and with negligible noise (ISO 100), and with full accurate colors. WOW! It was a first to me to see something like this, I 'll have to try the OMD and the RX100 to see what they would do and post about it.

    However, when I was processing the images, the files did not react to shadow recovery like I am used to, it didn't seem to have much of an effect, and it looked abnormal, while opening up exposure worked much better. So while doing local adjustments, I used positive exposure instead of shadow recovery like I'm used to on my cameras.

    It is really intriguing how each camera reacts to the same adjustments in lightroom. I can see why my usual post processing with Canon RAWs won't work with Nikon, and vice versa.

    ReplyDelete
  2. Hi Mohammad. Yup the D7000 is excellent at recovering shadows which is why I like it a lot and so far is the one I like best among Nikon APS-C cameras. I'm curious to see how well the OMD and RX100 will do since their sensors are also by Sony.

    Best regards,
    Mic

    ReplyDelete
  3. Hi Mic. I have the D600 and use LR5 as well. Lately, in situations like what you show above, I tend to increase the Exposure slider to the right about .33 to .5 and slam the Highlights. Like you, I don't mind being aggressive with it. Next I'll bump the Shadows between 20 and 50 but by now the image can start looking flat. So I move to the Tone Curve where I bump the Lights between 8 and 13 and reduce Darks and Shadows between -2 and -6. These reintroduce some contrast back into the image. Sometimes I employ the Clarity slider but have been finding with people and food I mostly leave it alone. I find, also, that I'm using the Adjustment Brush more and more to make changes only where I want them. I appreciate you mentioning the Radial Gradient. I need to use that more. So far I've mostly used it on some photos of my daughter where she asked for a pink ribbon around her waist to remain pink and make the rest of the photo B&W. It's nice to see how others use LR. I'm still learning and evolving - and to a point I hope that is always the case.

    ReplyDelete
    Replies
    1. Hi Dave. Thanks for sharing your process! Between the adjustment brush and radial gradient i find i get better results with the rgrad. But fyi i use a trackpad. I know others who get great results with the adj brush too. Most of them use a tablet. So it might be one reason why some prefer the adj brush and others might like the rgrad. Thanks again and i totally agree we should be constantly evolving.

      Best regards,
      Mic

      Delete
  4. Mic, no offence, but the final results of your post-processing still look artificial to me, the faces lack that natural glow and sparkle in the eyes that you could easily obtain with a strobe. This is especially evident in the group photo but also visible and detrimental to the other images.
    I believe it is sometimes better to have a lesser camera because it forces you to follow best photo practices. For example, a person forced to shoot at low ISO from a tripod can often take technically much better images (of static objects) than someone relying on the brute force of high ISO and image stabilisation. In the case of your images, if you used Nikon D7000 coupled with an external flash you would get better results than you got shooting with Nikon D600 and fixing the lack of flash with heavy post-processing. Just my opinion.

    ReplyDelete
    Replies
    1. None taken my friend and I think it's great to have different perspectives! Perhaps it's just my laziness or lack of skill with strobes that I would have a hard time lighting all faces and shadows the way I've done here for the group shot. :) Anyhow, I think everyone should try both approaches and see what works for them. Thanks Marcin!

      Best regards,
      Mic

      Delete
  5. that's a good technical approach, however, the biggest problem is that the highlights in the picture do not really serve any compositional purpose. so i would argue that it shouldn't really effect the outcome even if some highlights will be burned.

    ReplyDelete
    Replies
    1. Shalom my friend. There was a time when I didn't care about highlights either. But that changed when I started shooting with film and then later the Fuji S5 Pro. The reason I am very concerned about the highlights is because in my view it is what differentiates film from digital. See here: http://betterfamilyphotos.blogspot.com/2013/10/exposure-for-digital-cameras.html#more When I was growing up, digital was still in its infancy, so I've subconsciously associated the digital look with being "cheaper" and lower quality. That's why I'm a stickler for preserving relevant highlights. :) But I understand not everyone cares about highlights.

      Best regards,
      Mic

      Delete

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