Weird Color Problem

[HocusPocus]

Hi,

I've had a problem photographing my wife's jewelry for awhile now.
I use a canon eos 400d digital rebel xti and a lightbox. Some of the rings and necklaces look nice and I can make the background white through photoshop (I'm photographing against white paper in a lightbox).

Whenever I photograph the cufflinks, they give a horrible blue/gray tinge to the pictures. I set white balance first and there are three lamps with 100 watt daylight bulbs around the lightbox.

Here's one of the blue/gray pictures:

http://www.steampunkjewelry.ffxoh.com/DarkCufflinks.jpg

And during the same session, one which has come out a little better:

http://www.steampunkjewelry.ffxoh.com/LightCufflinks.jpg

Does anyone know how I can consistently get nice clean white backgrounds? Most of the jewelry looks nice, its just a few which create this horrible blue/gray/murky color.

All the best,
Derrick

 

[Josh66]

Does anyone know how I can consistently get nice clean white backgrounds?

Manual mode. Any time you need consistency - Manual mode is best.

What are you using now? Aperture Priority?

Your lights are putting out the same amount of light for every shot, so once you get the exposure how you want it, there is no reason to change it.

If you're using anything but manual mode, there will be slight variations from shot to shot.

Switch to manual, adjust your settings so you get the nice white background, then leave the settings there (unless, of course, you change the power of the lights, or your aperture or something).

Pretty cool cuff-links, BTW... :thumbup:

 

[HocusPocus]

Thanks Josh and I appreciate the comment about the cufflinks to!

I use manual focus to set white balance in the lightbox, then I switch to auto-focus but I use "Manual Mode" on the canon with my custom white balance set.

I don't change anything through the course of the photographs, I'm wondering if its a light issue, but it seems to be certain pieces of jewelry which cause the blue-gray cast.

The ISO is set to 100, F stop is F 5.6 - does this help?

 

[Josh66]

"Manual Mode" as is for focusing, or exposure?

The main dial on top of your camera should be on M.

If it is, it must be a light issue. The output of your lights must be varying a little from shot to shot. Possibly, they are growing brighter/dimmer the longer they are on.

Do the darker/lighter shots just gradually start creeping in, or is it random?

If none of your settings are changing, it has to be the lights.

 

[Josh66]

It could also be that the color temperature of the bulbs are shifting the longer they burn. If that's what's happening, I would recommend shooting RAW and taking a picture of a WB reference target (I like the WhiBal) every few minutes.

The WB doesn't look the same in the two pictures, but the exposure also looks different which would be independent of the WB...

 

[HocusPocus]

The Camera is set to "M" Manual on the dial, I use Auto-focus on the lens.

I just use a bit of A4 paper for my white balance, I'm unfamiliar with "WhiBal" - I just googled it, is this what you mean? If so, I'll get one.

http://www.bhphotovideo.com/c/product/472220-REG/WhiBal_WB6PK_G6_Pocket_White_Balance.html

It never occurred to me to take more than white balance shot during the photography (which usually goes on for around 30 mins).

Do you think 100 Watt Daylight bulbs are too weak?

I don't change the exposure or anything - same settings all the way through and I 100% agree with you, the two shots look completely different but they were taken during the same "shoot".

 

[Josh66]

Your link isn't clickable - but I'm pretty sure that's the one.

Do you think 100 Watt Daylight bulbs are too weak?

For something like this, the power of the lights shouldn't really matter.
You can shoot from a tripod and let the exposure time be whatever it needs to be for the light output you have.

I don't change the exposure or anything - same settings all the way through and I 100% agree with you, the two shots look completely different but they were taken during the same "shoot".

It has to be the lights.

Either the power, the color temp, or both is changing.

 

[Josh66]

WhiBal:
Light/White Balancing Accessories

Whichever size seems best to you.

 

[HocusPocus]

Thanks Josh, I really appreciate your time and the resources you've shared. :thumbup:
I'll try the WhiteBal and use it throughout the photography and see if this improves things.

 

[Josh66]

I think you'll be happy with it.

You can use it as a neutral reference for both metering and WB.
Not sure what software you're using, but in Lightroom fixing the WB is as simple as selecting the WB dropper and clicking on a picture of the WhiBal card. You can then apply that WB setting to any other pictures that were shot under the same lighting conditions.

 

[Garbz]

If you can spare a few bucks more I suggest getting a Colour Checker Passport instead.

It has a grey card, but if you're every worried about dull pictures you can photograph the colour checker pattern too which will help determine the quality of your lighting. For instance if you white balance a halogen light and a cheap fluro with the same grey card, then yes the grey shades will look the same, however then with the same settings photograph a colour checker card you'll notice that the fluro lit pattern is noticeably duller then the halogen one.

color checker passport

 

[Josh66]

The WhiBal is supposed to be neutral across the entire spectrum (they say it is, but obviously - I have no way of independently verifying that) - would that not solve the problem you're talking about?

Personally, I've never had an issue with the WhiBal - I can't think of one time it didn't perform flawlessly.

Now, the only light sources I've used it under were daylight, fluorescent, tungsten, and halogen - but I think that's pretty typical of most photographers.

I almost bought that color checker passport when you mentioned it a few months ago... I still might. For now though, I just can't think of a reason that the WhiBal needs to be replaced.

 

[Flash Harry]

Looking at the shots I don't think WB is the issue, exposure is, the gray/blue is what you expect to be white? yes, if so these are underexposed, one more so than the other, considering they are continuous lights, and the camera is on a tripod give the shot two stops of SS, so say you took the shot at 1/250th then slow it down to 1/60.

I've just calibrated this screen, its brand new, and I don't see blue, it's grey, which is exactly what your camera exposes for when pointed at a predominatly white area, you need to overexpose. H

 

[Josh66]

^^^ I still think it's WB and exposure. Which means the lights are at fault.

If you look at the actual cuff-links, the WB is quite obviously different between the two shots. The brighter one is much cooler.

And the brighter one does have a bluish tint to the background.

 

[spudgunr]

Is it one of those things that I never thought about, the color of the lamps changing as the cycle of the lights changes? I recently read about that and never thought about it, but the color of the lights WILL change as you go through the cycle of voltage. One hint was to shoot at 1/125 seconds so that you capture one full cycle (assuming 60hz service you'll capture a full half wave).