Light tent lighting/white balance

[Freedbaby]

I do a lot of product photography but am having white balance problems. It seems that I am never able to get the background white white. I using custom white balance and am shooting on several different white backgrounds.

If you look at my latest, this is the best I have been able to do.

I am using a light tent that comes in a Smith Vector package with two 5000k lights and I know I could post process these, but I just don't have time during the day to do so.

thank you,

Freedbaby

[Daniel W.]

Could you give us a shot that you think is off?

Part of the white is a bit of overexposing the background. What wattage are the bulbs? 5000K is the color temp, and that's pretty close to the 5500 range of sunlight/flash, you should be able to mix these lights and flash but honestly the little S-V kits with continuous lights can often provide not enough power. Two cheap manual flashes (like a Vivitar 285, Sunpak 383, or Canon flash if you have it) instead of the S-V lights would do better, allow you to stop down your lens for sharpness and get the pure white look.

Take a look at this:
http://strobist.blogspot.com/2006/07...to-studio.html

[jgooding]

Nice link, Dan. Thanks for sharing that. Jay, I noticed you're using different "white" backgrounds. My first thought is to use a single background. Since that may not be feasible in this case, here's an idea:

Set up and take some test shots (using each of your several "white" backgrounds) under your normal conditions. Play with the Kelvin value in PP to see what Kelvin gives you the consistent white that you want for each background. Make a note of those values so that thereafter, all you have to do is set your camera to value appropriate for each background.

Of course, this assumes consistent shooting conditions and lighting and involves a small amount of time up front. But, the idea is to save you much more time in the long run.

As Dan noted, you might consider alternative lighting. From what I've seen of those kits, the lack of power from the kit lights seems like it might be a limiting factor.

[Freedbaby]

I used the "insert image" feature to add the pictures but they didn't show up in the thread?!?!?!?

Try this:
http://www.flickr.com/photos/22474714@N07/

[Freedbaby]

ok....i just added to my flickr a quick picture of my setup. The bulbs are 26w and 5000k is the temp. I couldnt show you a picture of it, but I am using the flash on the camera on a tripod. I set the timer and hold a home made diffuser in front of the flash. If I crank up the power on the flash then I notice that the piece of jewelry is way over exposed. The camera I use here at work is a Rebel XT.....I have a 430EX that I use at home on my 40D but I have no off camera flash at work.


Jgooding, I use PS Elements but do not know how to look at the Kelvin scale in it. Do you have a link to a tutorial?


Freedbaby

[merock]

We just got finished shooting some diamond rings and jewelry for a pretty high end client here in Austin. We rigged up some vellum paper and shot through that to get the even lighting throughout the jewelry. We also shot a grey card to get proper white balance. I think in order to get the really white whites, you're going to have to create a path and cut out each image individually. Also, after talking to some other high end jewelry shooters, we found out that (and we did this as well) people are actually taking multiple focus shots in order to get sharpness throughout the entire ring. After our shoot, I found out about this software as well:

http://www.heliconsoft.com/heliconfocus.html

Haven't checked it out yet, but seems pretty cool. I hope this helps.

[Daniel W.]

Holy cow, 26w? Household bulbs would be an improvement on that (60-100w).

I would really consider getting a few strobes, if you can sell it to the folks at work. You could get 2x Vivitar 285's, stands, and radio sync triggers for under $300, or if you were feeling generous, buy an off-camera cord for your 430, hold it through the box and light with that, reflector on the other side of the box (inside).

[Freedbaby]

Remember that these are flourescent bulbs, I think a 26W is the equivelent to a normal household wattage.

Daniel W, do you have a diagram by chance of how you would set up the strobes? If I was going to spend the money would I be better off with AC strobes and a soft box on top, or the two vivitars that you spoke of?

Also, as I was mentioning previously, when I use the on camera flash and crank it up enough using my diffuser so the backround is white the piece of jewlery starts getting a bit over exposed.

sorry have so many questions but I have been battling this for a while and it seems that I am in need of some more equipment to solve the problem

Freedbaby

[jgooding]

Yeah, the light output of the 26W CFL bulbs is approximately equivalent to that of 100W incandescent bulbs.

You shouldn't need powerful AC strobes. Some battery powered flashes like the Vivitars or the like should be fine. What are the dimensions of your light tent? You could use one flash on each side of the tent and a third (not on camera) to blow out the background.

Regarding the white balance/Kelvin in post, are you using Adobe Camera Raw in Elements? I don't use Elements, but it's my understanding that ACR is also a free plug-in for Elements, not just the full PS. ACR has a simple Kelvin slider tool that you can use to adjust the white balance.

[ramblinray]

To get really white blown out backgrounds, you have to be able to illuminate the subject seperately from the background. Then you can put some serious light onto the background. The problem is that your subject is right there at the background. You can't get the light at different levels when they are so close together. If you can raise the ring or whatever up some so that you can get more light on the background and not on the subject I think you will get the effect you want.

[SpeedRacerSlots]

I had that same problem with 5000K bulbs, so I changed to 6500K Tungsten bulbs.
Oddly enough a 6500K Tungsten and a 6500K CFL ... dont have the same output levels if used together. I can tell which side the CFL was used on.

I fought it, then went the strobe route.
The room is cooler to working without the hot lights.
The colors are white.

The one thing I would recommend tho is to back the lights off the sides of the lightbox a little tho, so you dont have hot spots. Light the whole thing evenly if possible.

Good luck, and as with anything else...its experimentation to get what you want out of it....While I can shoot 1/32 scale slot cars with my box all day, if I shoot custom cut aluminum wheels with the same setup and settings...you can see the impurities in the metal of the wheels (in macro mode).