Sunday, August 4, 2013

Dark Field Lighting


A friend of mine recently asked me about dark field / light field lighting and at the moment I didn't have enough time to give what I thought would be a thorough explanation.  So after thinking about it (when I did have some spare time) I thought I would just set up something quickly and post how I did it.  Sometimes pictures can say a lot more than words.

Dark field / bright field lighting is simply about creating good edge light or shadow on your subject and is often seen in photographs depicting glassware such as wine glasses, bottles etc.  This technique works really well for glassware because since glass is so reflective it will literally mirror anything in front of it, including you, your camera and your light source.  So in order to light something that reflective, sometimes its better to not actually light that subject, but rather to rim light it to show its shape and physical characteristics.

First off there are two important things to consider when lighting any piece of glass.  First off, make sure its CLEAN... and I mean as spotless as you can get it.  Any little spot or imperfection will show up like a lighthouse through fog.  You can easily take this out in post, but you could spend a lot of time "fixing" things when if you just take a little time before hand, it could save you a lot of effort after the fact.  With stemware, I usually hand wash it, dry it slightly with a towel then polish it with a paper towel.  You don't want any lint left over from cloth towels so that's why I finish with paper towels.  Also, watch those paper towels because cheap ones can wear out quickly and leave little bits of paper on your glass.  After you clean it, inspect it thoroughly for any blemishes and if you find one, simply hit it again.  Like I said, you can also take care of this in post, but one advantage to cleaning your subject is that it makes it very shiny which will also add to the final effect of the image.

The next thing to consider is, since glass is convex and has a mirror like surface, it will literally reflect everything in front of it.  So if you want to do this from a perfectionist stand point, the best way to get good results is to hang up a large black sheet between your camera and your subject then cut a slit in the sheet and point your lens through that.  That way, the only thing the glass will see is black, which in dark field lighting is what you usually want.  I set my shot up quickly and didn't bother to do this step though, I simply cleaned the final image up in post which was basically a curves adjustment layer and a little clone stamping... 5 minutes top. 

Another thing to consider is that when you are aiming a light source back toward your camera, you are going to get some flaring or areas that are washed out with light (usually on the edges of your image).  To prevent this, the black sheet will help immensely, or you can position more black cards on either side of the glass hanging parallel to the softbox.  This cuts down the flares almost completely.  I just chose to clean up the image in post as the flaring was minimal.  Both ways work, it just depends on how much time you have.  Normally, I use the black cards to do this.

Also, because of the glass's reflectiveness, make sure no windows or overhead lights are on as, believe it or not, even with fast shutter speeds these can still show up in the glass.  For these types of shots I also use radio triggers because as much as I love Nikon's CLS system, the preflash will show up in the glass even if you have the output set to "--" or zero.  Again, glass is very, very reflective so considering this upfront will save you time in post.  My AF assist light even showed up in a shot or two so eventually I started holding my hand in front of it for the final image.

With these two considerations out of the way, lets take a look at how this was lit.  There are several ways to do this, but after shooting these for years I've found two different ways I like to do this depending on how big the subject is.  For the shot above, I simply put a 24" softbox with a single speedlight (flash) behind the glass pointed back towards the camera.  Then, in between the softbox and the glass I placed an opaque black card, this is the background for the glass and also prevents the softbox from shooting right through the glass.  The black card behind the glass only needs to be big enough to fill the frame of your camera and to just be slightly bigger than the glass itself.  That way, the light from the softbox can literally wrap around the black card and rim light your glass.  You can experiment with different distances of the glass to the softbox but in this situation I find that having the glass as close as possible to the black card usually gives the best result.  If you move the glass further from the black card the rim lights on your glass will become thicker, but light will also start to spill in through the glass leaving sort of a "foggy" look.  You can experiment though for what gives you the look you want.  In this first setup shot (taken with my iPhone) you can see what it looks like from the perspective of the camera.  You can click on any image for a larger view!

For this shot again, I simply had the black card that was the background resting against the softbox and had another black card underneath the glass for a base.  You can see that in this next setup image.  Also note that I have the glass setting on a stool instead of a table.  You can use a table but it seems I get better edge definition when I use a stool, or even better, using a piece of glass as the base resting on two sawhorses (or stacks of books or whatever else you can find).  I simply didn't want to take the time to get out the sheet of glass and set it up.  However, it does create a different look and gives a reflection of the wine glass (or in this case a martini glass) in the base.  If you have a pane of glass, you should experiment with that as well, it does create a nice effect.

Keep in mind this was done with one off camera flash and not even anywhere close to maximum power.  Another way to do this (and the method I prefer for larger items) is to hang up a piece of white paper, and instead of using a softbox, simply fire your flash in to the white paper and use that as your softbox.  The white paper can be as large or as small as you wish and is a cheap and easy way to create a large light source.  I keep a piece of white seamless stapled to the wall in my studio simply because I use it so often.  By having it literally on the wall also keeps me from having to use stands for support which in turn, frees up floor space in my studio.  It also comes in handy for head shots and myriad of other projects.  You can see how this "thrifty" set up looks in this other iPhone pic.  This method does require a little more power from your flash though, but still not enough to stress it to the point of overheating, and wine glasses don't move that fast so you don't have to worry about those quick recycle times. ;)

As far as camera settings go, unless I'm going for a more creative look (like using limited depth of field) I tend to stop my aperture down quite a bit as it seems to give more detail in the final image.  I think for the shot at the top of the post, I used f/18 at 1/250 sec ISO 800.  If I had paid attention more to my camera settings, I would have dropped the ISO to 200 and used an aperture of around f/16 or f/11.  That's what I get for being in a rush.  The flash power in the softbox was set to 1/4 power.

Once you have this set up and after you get the initial shot you were looking for, play around with it a bit, shoot odd angles, add some liquid to the glass, shoot horizontal and vertical just to see what you come up with.  Just because you have a good thing, don't give up on it.  You might find that you will get an even better image that you weren't expecting and also, you may learn a couple of new tricks in the process.  You can mix up your aperture and flash settings for different looks.  You can flag off one side of the subject with another black card so that you're only lighting one side of the image.  You can use gels for a different color effect, the possibilities are endless.  Once you learn this technique, it really yields a lot of other cool effects and ideas.

Next time on the blog, I'll do a bright field lighting.

Hope this helps a few folks and inspires you try this out for yourself.  If anyone has any questions about this technique, just sound off in the comments!


Mark n Manna said...

Very informative post,John. Thanks for sharing

Anonymous said...

Glad I just found this John, I've been trying to do this all day!! I can have another go tomorrow now following your instructions - many thanks


John said...

Anonymous - very welcome, hope it helps!