Tuesday, July 17, 2007

Lighting 102: Unit 2.2 - Specular Highlight Control

Summary: The fourth lighting zone on a given photographic subject is the specular highlight, or reflection of the light source. This can be manipulated in both size and intensity to allow total control over the tonal range of a portion of your subject.
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Last week we talked about the diffused highlight, the shadow and the diffused highlight to shadow transfer area. But there is a fourth area, which is usually brighter than the diffused highlight.

The specular highlight is nothing more than the reflection of the light source in the object you are lighting. This reflection is an often overlooked control in lighting design. In it's most basic form, it is simple to grasp and to predict. Explored more fully, it allows you to completely manipulate the tonal structure of your subject.

Take a look at the ball up above, lit with a single soft box. It's a frame grab from the excellent lighting DVD's compiled from the 1980's Finelight tapes by Dean Collins. What tones do you see?

You see the true tonality of the ball, which is your mind's visual anchor for judging color and tonal density in the photo. This is noted by the blue circle, and is called the diffused highlight. You see a dark shadow, in the unlit area of the ball. And you see a soft, transitional area between highlight and shadow.

And you see the reflection of the soft box -- or the specular highlight -- inside the diffused highlight area of the ball. (This soft box has been broken into fourths, probably by the use of gaffer's tape strips, to better simulate a window light source. Neat trick.)

Your brain processes all of these relative tonal densities to tell you much about the ball and its environment. You know the color, of course. You know the shape, as revealed by your off-camera light source. You know the approximate size of the light source by the nature of the highlight-to-shadow transition area.

How would your brain discern the surface quality of the ball, without your touching it, just by looking at the photo? By processing the quality of the specular highlight. The specular highlight reveals not only the size and shape of the light source, but the surface quality of the object.

What if the ball were lit by a point-source light, and not a soft box? How would it look different?

Well, the specular would be much smaller. And much brighter. All of that lighting energy would be coming from a small source, so it would have a lot of intensity per square inch. It would be a point-source specular that would almost certainly blow out in term of the brightness.

But the soft box specular is well-contained on the tonal scale because all of that lighting power is spread out over a larger area. As the size of the light source decreases, the intensity of the specular highlight increases. And vice versa.

Light sources can be manipulated to gain control of the specular highlight. I placed my glasses on a pillow and bounced a speedlight off of the ceiling for a light source. With the zoom head set on tele, you can see a decent-sized light source (the partially lit ceiling) reflected in the glasses. But the reflection is distracting in its size and too bright in its intensity.

Now look what happens when I zoom the flash head out to 17mm and light the whole ceiling area above the glasses.

First, the specular fills the whole lens area, making for a far less distracting tone. But on further examination, you can see that the intensity of the specular has been lowered to the point where you can easily see through it. Now it reveals both the surface texture of the glass and detail underneath it.

You can see a couple of really good examples of using specular highlights selectively in these watch photos.

So, when is a glasses reflection not a bad thing? When the intensity of the light is spread out (from a very large light source) such that you can see right through the reflection. The surface texture of the lenses are defined, but detail is still visible through them.

To prove the point I flew in a supermodel at great personal expense and photographed him wearing his (purely cosmetic) glasses in my living room. The illumination was from a speedlight fired into a nearby wall and zoomed to make a huge light source.

See how you can see the surface quality of the glasses, and yet still lose yourself in those devastatingly handsome eyes?

You get the point: Light, spread out over a large enough area, becomes less intense per square inch. So much so, that it can both illuminate and offer partial transparency in the reflections.

Here is a shot from one of the London seminars which featured a student against a darkish room divider. We used the light (in an umbrella) to illuminate Ray. But we get double duty out of it by lining the specular highlight off of the background in such a way as to separate Ray's shadow side (tonally) from the background.

You can see another version of this technique here, where the specular is used to form a halo, of sorts. (From the Rhode Island seminars, scroll down the page.)

This is one of my favorite one-light portrait techniques. Such an elegant result from such a simple setup. Executives in dark-paneled boardrooms or offices look like a million bucks with this soution.

If you are still with me, let's go this one better. (And this was another one of those "Aha!" moments for me when I first learned it.)

Let's try a little mental exercise. What if you could use the specular highlight of a large light source to introduce a new, artificial tonal area in a very dark-skinned subject?

Here's a scenario: You have for a subject a Caribbean islander. And to say that his skin is dark is an understatement. The man looks like blued steel. He shows up in a white shirt just to piss you off. And you need to reproduce him in your paper (as in, printing on Charmin) and hold detail everywhere.

What do you do?

You light him with a soft source from the front is what you do. This creates a three-tone structure for his face.

First, is his true tonality, which your paper can probably not even reproduce if he is properly exposed. And you have to properly expose him to keep the white shirt from blowing out anyway.

Second is the shadow area -- even darker -- which you can only define by separating it from a light background. But third is a tone that you can totally control by varying the angular position (and the distance) of your big light source.

You are lighting him, but fat lot of good that does for you with a very dark diffused highlight. But you are also creating a nice, much lighter tone -- where you want it -- on his face by exploiting the specular highlight from your light source. This is what will reveal your detail and create a beautiful tonal structure which could even reproduce on a old photocopier.

You are not shooting his skin. You are shooting the reflection of your light source on his skin.

When shooting a dark object, form is revealed by specular highlights. When shooting a very light object, form is revealed by the shadows.

And when shooting a highly reflective object, you are basically shooting a reflection of your light source. The stainless steel and cookies On Assignment was a good example of this. The double-diffusion technique described there allows you to define the light source and its edges separately.

The Light Science and Magic book has a tremendous amount of info on specular highlights in chapters four, six and seven.

There is so much you can do with this layer of control.

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Your exercise this week -- the last before we move onto a few full assignments -- is to choose a 3-d object that is reasonably reflective and explore what you can do by manipulating a specular highlight. I am not being too specific on this one, because I want you to have some room to explore.

You do not need to use an umbrella as a soft source. You can bounce a flash off of the wall of a ceiling to get a soft light source. Or diffuse it through some paper.

Billiard ball, apple, face, whatever. Just create that specular highlight and play with it.

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Tag your pix with:

strobist
lighting102 (note no spaces)
specular

You can see all of the completed exercises here.

Please use this Flickr thread for discussion and showing off your pix.

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NEXT: Discussion: Specular Highlights


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23 Comments:

Anonymous Anonymous said...

Neat article.

And, incidentally, that first model looks (a little) like Edward James Olmos.

July 17, 2007 5:42 AM  
Blogger Rafa Barberá said...

Hi David, when you say "You know the approximate size of the light source by the nature of the highlight-to-shadow transition area." what you really mean is "You know the apparent size of the light source from the ball's position, by the nature of the highlight-to-shadow transition area." isn't it? Because size don't matters and anyway you can't know the real size from this image, as you didn't know the size of the ball.

July 17, 2007 5:43 AM  
Anonymous Anonymous said...

when i look up the book "Light Science and Magic" von Amazon.de
I get 2 different versions, a "Focal Press" version, and a paperback.
Where's the difference?

July 17, 2007 5:44 AM  
Blogger Alan said...

There is a great Nature article on the perception of specular vs diffuse highlights and our interpretation of surface properties here. It appears that glossy perception is due to skewing of the luminance histogram. This suggests that manipulation is pretty straightforward in image editing and the authors demonstrate this with some examples.

Alan

July 17, 2007 10:24 AM  
Blogger Craig Patchett said...

Unfortunately, the Nature article Alan refers to is available to paid subscribers only (or for $18 to non-subscribers.

Craig

July 17, 2007 2:02 PM  
Blogger Alan said...

D'oh! Blast that IP-regulated subscription model. My academic network just takes me straight through to the article. I thought that the commentary article would be freely available at least. Sorry.

If anyone really wants a look at it I will send you the PDF - email me: a.huett@gmail.com

Alan

July 17, 2007 4:24 PM  
Blogger Aaron said...

David, is it possible to control the size of the specular highlight and the size of the diffused-highlight-to-shadow transfer area independently?

Put another way: can I have hard light as well as a large specular highlight?

Intuitively, (and from playing around with the assignment) the answer seems to be no, since increasing the size of the specular highlight necessitates increasing the apparent source size which would force the light to be softer.

Thoughts?

July 17, 2007 4:38 PM  
Blogger David said...

Rafa-

You are correct.

Aaron-

I would listen to your intuition.

July 17, 2007 5:16 PM  
Anonymous Will Hore-Lacy said...

Unfortunately this I couldn't find this photo in flickr but is shows somewhere it is importatnt to have a specular highlight:
http://www.photo.net/photodb/photo?photo_id=3402894

July 17, 2007 7:17 PM  
Blogger Zey said...

Really a great article which helps me in photographing highly reflective subject such as a car. Please visit http://www.pbase.com/zey/accord , I've tried to bounce some light on the wall to create specular highlight on the car doors.

July 18, 2007 2:16 AM  
Anonymous Pamela Vasquez said...

David...in the pictures at the seminar of the gentleman you were portraying as a tech guru...did you use two lights? One for the background and the other for his face? Curious because with one light how can you blur the background so effectively and have his exposure right?

And on the other photo of the man with the dark wood wall behind him....did you only use one light there too? I was trying to mimic that, but had a really hard time getting a highlight that was bright and obvious on the background without over exposing my subject. Thanks. I have learned so much from you..Pam Vasquez

July 22, 2007 4:46 PM  
Blogger Poca Long said...

David,

Is there a side menu to navigate L 102 or am I missing it? It's good to have to work your way through each section but it gets a little old after a while trying to read the current section.

July 23, 2007 8:52 PM  
Blogger Photography Luna said...

Ok, the specular highlight thing is quite ok for me, but the mind-exercise with the caribean dude is a little too much at this time (I admit, I only slept 2 hours last night). Is it ok if I imagine it being an eskimo? ;-)

Cheers,
Bjorn
http://photographyluna.blogspot.com

August 01, 2007 7:11 AM  
Anonymous Anonymous said...

Is there an index to Lighting 102? It seems to end with this entry and I can proceed no further.

October 09, 2007 2:43 PM  
Anonymous Anonymous said...

Yeah, not sure if there is, but the next part is about balancing flash indoors at

http://strobist.blogspot.com/2007/09/lighting-102-33-balancing-flashambient.html

Catcha

November 12, 2007 7:00 AM  
Anonymous Anonymous said...

Anonymous said...
Is there an index to Lighting 102? It seems to end with this entry and I can proceed no further.

October 09, 2007 2:43 PM

Remember when you arrived late to class.So it is with me and Lighting 101 - 102 . I really wish there was an index. It's a wonderful course but playing catchup can be a little difficult.

Hope there is an index or will be.

thanks

Paul

November 25, 2007 3:52 PM  
Anonymous Anonymous said...

This session leaves me a little confused. You go from a specular highlight being an obviously reflected light on a cue ball and reflected light on your glasses to a specular highlight being light on a backdrop behind the model in a headshot. Obviously except when backlighting a subject, all the light which reaches our eyes or the camera's lens is reflected light. In the picture of the young woman it would seem to me that the specular highlights are on her cheeks, chin, and forehead rather than on the background. What am I missing here?

January 01, 2008 6:24 PM  
Blogger David Ziser said...

Hi David,
I just posted an article that speaks to your Lighting 102 article. I had an oportunity to spend a week with Dean when I was just starting out in the early '80s - he was a wealth of knowledge. We shared the platform several times over the next several years. Check out my piece and see if it doesn't round out your diccussion on "specular" reflection. Here is the link:
http://digitalprotalk.blogspot.com/2008/03/technique-tuesday-specular-vs-diffuse.html

Thanks, David Z.

March 25, 2008 12:28 PM  
Blogger Alex Russel said...

I know I'm late, but I've been working through the Lighting 102 courses. One of the comments on the Flickr thread mentioned the idea of Specular to Diffuse Highlight transitions. I've noticed that different surfaces can have a strong effect on the specific quality of the specular highlight.

Take a look here: http://en.wikipedia.org/wiki/Specular_highlight to see an interesting description of how this is caused by microfacets on the surface. The microfacets cause what they refer to as "blurring" that affects the edge detail of the specular highlight, resulting in a transition zone.

The article also describes why some specular highlights pick up the colouration of the surface, and why some remain white.

Next step: Figure out how to control this phenomenon.

August 21, 2008 4:32 PM  
Blogger Aino said...

These are really really good articles!! I am loving this. I have to take one article at a time and take time to "digest" it.

I am not really getting the tonality thing about the darkskinned guy... but I will try to figure it out.

Thanks a lot for these phenomenal series.

November 20, 2010 7:22 AM  
Blogger Tina M. Neely said...

"When shooting a dark object, form is revealed by specular highlights. When shooting a very light object, form is revealed by the shadows."

This is a very good quote and i would like to repost it (and remember it forever).

Just found your blog - and i love it. Thanks for all your down-to-earth helpful hints and tips. Also, thank you for taking us through the processes. It's discouraging when people are too vague - then you feel like you'll never really know what to do. So yeah, thanks :)

April 13, 2012 1:40 PM  
Blogger bronney said...

David,

You keep wowing me. That halo portrait trick is so neat I did my noob wow 3 times.

Thanks again, I finished 101 and is on 102 now and will sure to put these to practice.

btw, I stared into the eyes of that model you flew over and couldn't get out of the trance, is that bad? :D

April 23, 2012 6:05 AM  
Blogger Andrew Davies Photography said...

Hi , Completed 101 and all went well , so far so good with 102 till now. A little lost with exactly how to control specular highlights, after two hours of watches and glass balls all i am getting is very small differences with the spec high which is also due to moving the umbrella around i dont seem to have much control zoomed the flash from 24 to 105 and still not that great a deal. Nothing has clicked need some more help. Using a single flash 580ex2 on stand through umbrella from 1 foot to 4 foot away shooting a watch and a small glass paperweight, any advice ? thank you www.andrew-davies.com

April 26, 2014 3:12 PM  

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