Thursday, December 07, 2006

On Assignment: Stainless Steel and Cookies

A while back, we looked at double diffusion as a means for controlling the surface reflections on glass bottles. Having recently talked about the concept of apparent light source size I wanted to revisit the technique and tie the two concepts together.

The assignment was to shoot the winners of the holiday cookie bake-off for the food section at The Sun.

The cookies were all non-reflective and textured, ranging from light sugar cookies to dark ginger snaps. The page designer had chosen as her backdrop a shiny, stainless steel tray. To further expand my range of surfaces, she put the cookies in highly reflective foil baking cups.

This brings up an interesting exercise in light control. The cookies are going to eat the light. The steel is going to reflect it in a predictable manner. The foil cups are going to reflect back every light source in the room.

Before I get into the idea of double diffusion, lets back up to the concept of seeing the light source from the subject's perspective.

If you remember, it's the apparent size of the light source that matters. If you are unfamiliar with this concept, go back to the Dohrn piece to bone up.

Here is the lighting setup. Imagine for a sec that you are a cookie on the tray and that the diffusion material (the translucent sheet tented over the cookies) is not there.

When you look up from the tray, you are going to see a big softbox. I was in the studio, and needed mucho watt-seconds for lots of depth of field, so I was using a Profoto head in a softbox.

This softbox, coming from the top of the frame, is going to define the texture of the cookie as it lights it. All nice and smooth - no problems there.

Now, imagine you are the stainless steel platter. Not only are you going to see the big light source, but you are going to do something extra that the cookies do not do. You are going to reflect it right into the camera like a mirror.

And if the photographer gets out of the line of sight of the reflection, the tray will appear black. Not good.

But technically, the reflection of the softbox is not really a problem for the camera. It looks pretty cool, actually.

The problem comes where, on the steel tray, the reflection abruptly stops. We are talking about a near mirror-like surface, after all.

Again, remembering that you are still the stainless steel platter, try to imagine what you would see if the photographer stuck a sheet of diffusion material - in this case, Rosco Tuff Frost - between you and the light source.

You still reflect everything, and you are gonna throw back that softbox at the camera.

But now, instead of a sharp line where the softbox abruptly stops (within your field of view) you have a fuzzy, diffused edge to the light source. (Think of a window behind a shower curtain if it helps.)

Mind you, your reflective properties have not changed. And you are still going to throw back a faithful reflection of the light source. But the diffusion material has altered the appearance of the light source. So it has altered the reflection you are going to throw into the camera.

The final effect, from the camera's point of view, is to radically alter the apparent surface quality of the stainless steel. It is as if I had sprayed the tray with a dulling matte spray.

The quality of the light on the cookies is unaffected. They just need big, soft and directional. So they are happy.

(Hey, how could they not be happy? They are cookies. Everybody likes cookies.)

So now that we have tamed the (predictable) reflections in the stainless steel, what about the more complicated reflections in the foil?

Well, turns out this is pretty good solution for the foil, too.

You have a big apparent light source - the diffusion sheet itself. Which means that the light is spread out over a large area, so the intensity of the reflection will be modest and easy to manage, tonally speaking.

But also, the edges of the apparent light source are nice and fuzzy. So the reflections (technically, they are called "specular highlights") will have smooth transitions at the edges, too.

Let's back up now.

What we have is one hard light. We diffused it with a softbox to make a broad source. Then we diffused that with a sheet of translucent material to control the apparent edges of the broad light source.

Sounds more complicated that it is. Just look at the setup shoot, imagine you are the tray, and it should all make sense.

Here's the cookie photo at 1024-res, so you can see the light reflections - especially the transitions - more closely. That stainless steel looks like stainless steel should.

On a much sadder note, I had grand expectations for one important aspect of this shoot that went unmet. Tragically, while the cookies looked very good, they had been judged about a week before. So they were terribly stale.

So, all things taken into consideration, I would have to give this session very mixed reviews.

Next: How to Photograph Christmas Lights


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11 Comments:

Anonymous Anonymous said...

For those of us without Tuff Frost, could you have accomplished something similar with a large light panel?

December 07, 2006 12:58 AM  
Anonymous Anonymous said...

i'm a new reader to your blog (since the tree/time lapsed experiment), but must say very well done w/ these cookies!

December 07, 2006 3:02 AM  
Anonymous John Dohrn said...

Couldn't you have just ditched the softbox and used more tuff frost and used it more like a lightbox? Because, from what i can see, the softbox is just eating up more light. I could be wrong, I wasn't there, but that's the way it looks.

December 07, 2006 11:22 AM  
Blogger David said...

@ John-

Good question. But the answer is "not really."

The softbox (which is actually a strip light - could have been any old softbox, but I was too lazy to change it) is the light source. The Tuff Frost becomes the new light source, but with a very special quality.

It transmits the light source, but totally contains it visually from the perspective of the cookies.

This is important, because the whole point of the extra layer of diffusion is to fuzzy up the edges of the "contained" transmitted image of the softbox.

The apparent light source area fades to "unlit" before you get to the edge of the tuff frost.

Just shooting a direct head through the Tuff Frost would not get the same effect. You'd see the edges, well-defined, in the reflections.


@ Anon #1 -

Yeah, you could use about any diffusion material. The key is to have double diffused it. Once for light source size, and a second time to fuzzy the edges of the light source. That's the key.

December 07, 2006 11:30 AM  
Anonymous John Dohrn said...

Thanks David, I just reread it and it makes more sense now. Thanks

December 07, 2006 1:43 PM  
Anonymous Anonymous said...

Nice job, David. In my opinion, though, the page designer made a poor choice with the reflective cups. Even with your nicely-lit shot, my eye goes immediately to the cups and my attention is drawn away from the cookies. Cookies rule! And they should rule this picture.

Nick

December 07, 2006 5:51 PM  
Anonymous chrislaurence said...

David:

Thanks for your explanation (I was anon #1). I "get" your answer that you could have used a light panel as a substitute for the Tuff Frost, but what I was really wondering if you could get a similar effect from having a light panel large enough to fill the family of angles so that you didn't have to worry about the edge of the light source. Maybe the issue is that with the reflective cups, and therefore unpredictable angles, you'd always run the risk of seeing the edge of the light source? Am I thinking through this right?

December 08, 2006 1:07 AM  
Anonymous Anonymous said...

Really good technique, but the subject matter looks like it would be more appetizing to a metal-eating robot than a cookie-eating human.

December 12, 2006 7:55 AM  
Blogger Vika.Valter said...

kind of late for the party but on the lack of Tuff Frost enquiries- wouldn't the white(or natural beige) canvas/bed sheet do the trick?

August 02, 2007 4:52 AM  
Anonymous Anonymous said...

David - love your blog. I've been reading for 2 weeks. Regarding this article and future articles, I think it would help to have pictures of what it looks like in not the 'ideal' setup (instead of just describing it).

Thanks!
eg

May 02, 2008 4:36 PM  
Blogger Daniel Williams said...

Nice technique and good explanation. Is there possible one that shows the example of the edges you were talking about. I think I understand, but visuals always make me understand so much better.

August 25, 2008 10:53 PM  

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