Light and white balance

[WYKnot 0]

I want to learn more about white balance and color temperature, and how they are influenced by light intensity. I am experimenting with diffusers, bounces, and light position (orientation and distance to subject) to assess the impact on fly photography.

 

Any insights with regard to macro photography and light quality would be welcomed. References or web-based tutorials would be appreciated. Perhaps just getting the terminology correct would be a good starting point.

 

Thanks. Russ

[flytire 0]

GOOGLE up "white balance"???

[kargen 0]

Color temperature in photography is talking about the color of your light source. With film you would either buy film compatible with your light source or use filters to correct.

 

http://www.mediacollege.com/lighting/colou...emperature.html

 

That site has a chart showing different light temperatures.

 

White balance most often refers to digital photography and the camera settings correcting for the type of lights you are using.

 

There are a lot of things that can effect the final color of your light. If your difussion material has any color to it that will contaminate your light. So a white light diffused through tan pantyhose will get warmer in color. A white light diffused through a white plastic should remain white, but sometimes it can shift a bit blue. Just because your diffusion material looks white doesn't mean it will not somehow change the color temperature of the light as it passes through.

 

If you use a reflector same thing applies. The light will pick up some color from the reflector as it is reflected. With digital cameras the auto correct setting for white balance should take care of small changes caused by reflectors and diffusers.

 

You can also get something called color bleed. It was worse with film than it is with digital photography. color bleed is caused by colors around your subject. If your fly is to close to something red (background included) it might get a red tint to it that has little to do with your light source. If the object is in your photo it will be more of a problem than if it is outside of the frame.

 

You can take advantage of color bleed though to enhance the photograph. A gold card near the subject can give a warm glow or feeling to your subject. A black card to one side can absorb some light on that side causing a little shadow. Shadows provide depth to your photographs so a bit of controlled shadow is often wanted.

Try to keep the shadows all going one way though so it looks natural. Cross shadows can cause a busy looking photo.

 

If you really need to control color get a nuetral grey card. Always start by taking a photo of your card and then make color corrections to get the photo to match the color of the grey card. You can also adjust exposure to get the density (lightness/darkness) of the card correct. Then after making the adjustments you can replace your grey card with the subject and the colors should all be correct. Some cameras have a slight bias to different colors so a multi colored subject might have one color appear brighter than it really is.

 

If you played pool at all you can almost position lights like planning a bank shot without using English. Light will bounce off a flat surface at the same angle it hits that surface. The camera is where you want the light to end up and the subjext will be what you bank the light off of. A curved or irregular surface you need to adjust a little for. Using reflectors is where this really comes into play. Light will bounce off the reflector at pretty much the same angle it hits the reflector. Knowing this you can swivel the reflector some once you have the light set to control light intensity. If you have the angle right on you will get a brighter relection than if the angle is slightly off.

[WYKnot 0]

Kargen: Thank you for the informative reply and link. I have photographed a grey card in the past, makes sense to use it as a reference for changes made to the lighting set-up. I was unsure what impact diffuser/reflector materials would have in a macro set-up; will definitely play with the warming and cooling effects of colored materials.

 

Flytire: Yep, Google is typically of my first choice for convenient information; spent some time there this past weekend. Regarding white balance and color temperature, there is an overwhelming amount of information, not all of which is in agreement.

 

Thanks for the help.

[WYKnot 0]

Knowing this you can swivel the reflector some once you have the light set to control light intensity. If you have the angle right on you will get a brighter relection than if the angle is slightly off.

How does using the edge of a reflected light source, such as from a mirror of silvered reflector, compare with using the entire reflected light pattern? Would this change the quality of the light? I am thinking of your comment about reducing conflicting shadows, especially if bounced back onto the subject for fill.

[kargen 0]

It depends some on the material being used as a reflector. If you use a mirror you may see a distinct line where there is less light. If you have a subject where one part needs more light and the other does not then this might be something to try. For instance you might be able to lighten up something that is black without making the entire subject lighter. I sometimes use small black cards I tape to the reflector in certain places just to block light on a very specific area. With silver cards or white cards the line will not be as pronounced. With cards you can also bend the card to control the light. Bend it concave to the light source and it will concentrate the light and make it brighter in a smaller area. Make it convex to the light source and it will spread the light more.

 

I'm not sure how it would work with macro, but something fun to play with is glass block. Shine a harsh light through the glass block and you get all kinds of fun things happening. If you put a yellow plastic on the glass block you can get some really warm streaks going through the photo. It can add something interesting to a background

[Will Milne 0]

Russ

 

Hope this helps. I too have been trying to work out some fly pattern lighting . White balance I leave on auto. I work with RAW files so the WB is easily set in the RAW converor if it is off a little.

 

What I have found helps for me is to set up the main light and get it correct first- intensity/angle etc it really helps to check the histogram. Then add fill as needed by looking at the image on the camera LCD. then take away or add more light with the method Kargen suggests- black or white boards.

 

Not a great image but here is the anatomy-

 

 

the "table" is a translucent plastic panel with a peppled surface with the flat side up.

 

Main light slightly to the left of the camera

 

Silver reflector disc to the right to open up the face of the popper and add some fill and contour.

 

Fill light under the panel to open up the shadows.

 

Black card held over and behind the fly to get that fade to black background look.

 

I think the big thing is add one element at a time and look at the result then add the next as needed. It is very easy to get too ambitious and lose track of what needs adjustment otherwise.

 

With this type of photography you are building light/feel etc one element at time.

 

Hope that helps. Keep it going and share your results , I'm sure folks will be glad to help.

 

Will

 

 

[WYKnot 0]

Thanks for the ideas and information. The glass block sounds like a great mid-winter project (in that frozen time between hatches).

 

One problem, of a sort, for me when converting RAW images is never being quite sure what to adjust or, for that matter, why it needs adjusting. Certainly exposure, blacks/shadow, brightness, and white balance are important elements and the histogram helps me understand the impact of the changes made to these parameters. I have found Jon Canfield’s book, RAW 101, to be helpful; but gain a lot of satisfaction from experimenting with the conversion process.

 

Thanks, again. Russ