By remco/Remco (2,432)
on May 1, 2007 5:33:23 PM CDT
Application and some lightsource basics
Size of the lightsource:
Distance of the lightsource:
This is a brief and simple description of controlling specular hghlights in a studio setting while shooting still life or product photos.
Being pretty much a beginner at photography myself, i find it usefull to read tutorials and descriptions about how someone acieved their results. As i have learned a lot from reading turtorials myself, will now try to give something back to the community and share the knowledge i have about this topic. Hope it helps.
During the dark winter days and evenings, a lot of (amateur) photographers like myself are bound to indoor photography. This is why I initially started experimenting with lighting techniques in my attick.
This will be a simple explanation of some lightsources and techniques that might help the beginning photographer.
I have noticed that some photographers struggle with reflections and specular highlights. In this tutorial i will describe how to prevent unwanted reflections and highlights. I'm talking about those areas that will turn up completely white on your photograph. Highlights are not a bad thing, but we want them to retain some of their original colour.
Application and some lightsource basics
The subject matter in this tutorial will be applied to shooting shiney objects in a studio set-up. It doesn't really matter if this studio is a professional studio or your kitchen, any space were you can control the light will do.
In a studio set-up artificial light is used to light the subject. This artificial light could be anything ranging from lightbulbs, tungsten lights, flashes, strobes, or maybe even candle light. The technique being discussed here however can be used in combination with flash or powerfull continuous lightsources. For continuous light, tungsten lights are very suitable and also very budget friendly. They however consume a lot of electricity and produce a lot of heat, wich flashes do not. The advantage of flashes besides the ones of electricity consumption and production of heat are that they are adjustable in intensity and have a more natural colour temperature (e.g. less white balance adjustments needed). The downside of using powerfull flashes however when shooting products from a short range is that you are likely to have too much light, even at the lowest setting and you will have no choice but to use a small aperture.
Using flash, the shutterspeed has no (or very little) influence on the exposure so you have to control exposure with the flash intensity and the aperture.
Using continuous light you can control the exposure with both the shutterspeed and aperture.
In this case i used a 150W/s studio flash (see examples further down the page).
The way to reduce reflections and specular highlights lies in the size of the lightsource and the distance from the lightsource to the subject.
Size of the lightsource:
The common rule is: the smaller your lightsource is, the harsher the light will be and the brighter the reflections off any shiny surface.
Harsh light produces sharp and dark shadows and very bright reflections. This is not allways desirable. Small lightsources produce high contrast.
When the lightsource is larger, the light will be more diffuse, the shadows will be softer, less dark and the transition of light to shadow will be more graduate. When the lightsource is larger, the reflections will be less bright.
Large lightsources produce low contrast.
Ways to make a lightsource larger and more diffuse are using softboxes, screens or bouncing the light off a reflecting surface.
Softboxes are boxes where the lightsource is inside the box and one side of the box is covered with a material the light has to pass through. This material, usually a type of white cloth or semi transparent plastic film, diffuses the light and the light gets evenly distributed across the entire surface thus resulting in a much larger and more diffuse lightsource. Screens work pretty much the same way. Diffused light is often referred to as soft light.
Distance of the lightsource:
The closer the lightsource is to the subject, the larger it will appear to be.
Think of the sun. It's a very large lightsource, it's even larger then the planet yet it appears small and produces very contrasty light. This is due to the distance of the lightsource.
So the closer the lightsource, the larger it will be in effect. This is why not only the size but also the distance of the lightsource matters.
Image 1: This is shot with a bare flash from the right at about 4 feet distance from the subject. You can see that the light is harsh and that there are some unflattering highlights that turned out completely white instead of orange.
Image 2: This is shot with a 60x60cm (2ft) softbox from the left at about 6 feet distance from the subject. The highlights are still bright and unflattering.
Image 3: This is shot again with the same 60x60cm softbox but now at a distance of about 2 feet from the subject. Here you can see that the highlights have retained their colour, wich is the effect we are going for.
Image 4: This is the final result of the image after some digital processing.
This concludes this tutorial about reflections and specular highlights. I hope it helps you in any way. Good luck and happy shooting to all.
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From ranbou/Randy (445)
on June 13, 2007 9:00:02 PM CDT
I am a bit confused (which is nothing new). It looks to me like having the soft box lights closer to the subject produced a less intense highlight than having it further from the subject. Is this correct? If so it is very counter intuitive. I would expect the the highlight to get brighter the closer it gets to the subject.
This was a great article and I appreciate you sharing your knowledge with us. One thing I would add is there are bulbs which are fairly cost effective ($5 - $10) which produce a cooler light and less heat than incandescent bulbs. You can get them at your local hardwares store.
From deleted207185/deleted (13,289)
on July 17, 2007 3:29:34 AM CDT
This is good article.
Highlights (in particular specular) are caused by point sources of light. The further a soft box is from the object, the more it tends to highlight. If you imagine putting it the other side of the room it will be a simple point light source. Getting really close ensures the light comes from a much greater spread.
From remco/Remco (2,432)
on July 17, 2007 4:39:36 PM CDT
Thank you both for commenting.
Indeed a large lightsource at a large distance will yeild the same result as a small lightsource. The closer and larger the lightsource gets the less bright the highlights will become.
Furthermore, when you use some kind of material to soften and diffuse the light, the light source will appear to be as close and as large as the material used, be it a softbox or anything else. So if you would hang a bedsheet between the subject and the lightsource, the lightsource will apear to be as large and as distand as the bedsheet is to the subject, no matter how far away the actual flash or bulb is. However, if the bedsheet is thin and not able to effectively diffuse all of the light, the light will be harscher in the center where the most light hits the sheet. A way around this would be to hang multiple layers of bedsheet some distance apart. The same goes for most other materials. In fact, most commercially available softboxes have multiple layers of white semitranparent material spaced out throughout the box. The 60x60cm boxes i used have 2 layers, one about 1 ft from the flash and the outer layer about 2-3 ft from the flash.
Another way of creating a very large and diffused lightsource is bouncing the light of a white wall or ceiling.
From washer/James (1,506)
on December 6, 2007 12:20:24 AM CST
Actually, there's a little more to it. A specular highlight (direct reflection) is as bright as the lightsource, whereas a diffuse reflection varies according to the inverse square law (see note below).
So, by moving the light source closer, you are lighting diffuse reflection more, while not changing the brightness of the direct reflection (again, see note below).
So, since the rest of the subject is getting brigter and the direct reflection is not getting brighter, the diffence between the two is lessening. However, since the diffuse reflection is brighter, you will be "stopping down" the exposure, which effectively lowers the brightness of the direct reflection. Hence, you can "see" the surface through the direct reflection without "blown highlights"
Note: For you physicists out there.. It's true, the direct reflection does not get brighter, it does however get larger, hence the "total energy" of the light is obeying the inverse square law. i.e. same brightness over a larger area.
From kirbsand/Kirby (5,526)
on March 27, 2008 3:32:19 PM CDT
The brightness of the direct reflection does vary its just that it varies according to the total distance between the light source and the camera. The can occasionally be important because the distance of the camera can make a difference.
If the camera is a fair distance from the subject in relation to the light source, the results are as James says, however if the Camera is very close to the subject in relation to the distance of the light source than the brightness of the highlights will increase when the light source is brought nearer.
Let me put some numbers on this
Example 1. Your doing a portrait - your camera is 12 feet (4m) from the model, and the light source is 6 ft (2m) from the model. Your highlights are too bright, so you bring your light in to 3 feet (1m). Now you are putting 4 times as much light on the model (1/2 the distance with inverse square law = 4 times the light) but your highlights are only 1.44 times as bright (18 feet to 15 feet = 18/15^2=1.44). After stopping down twice, your highlights appear to be gone.
Example 2. Your doing a macro shot from 10 inches (.1m) your light is 12 feet (4m) away, and you find those pesky highlights again. So you halve the distance and stop down twice like you did last time, what happens? Subject light = 12/6^2=4 times as much light. Your highlights brightness: 12.8/6.8^2= 3.5 times as much light in the highlights. You will find in this case that those highlights are only a very little bit dimmer, and they are twice as large now to boot.
Which is why macro photographers usually bring there lights about as close to the subject as there camera is.
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