White Balance - a simple explanation

[Ross]

I thought a quick rundown on White Balance might be appropriate:

White Balance (WB) is the term that we use to refer to the color temperature of a light source, and is measured in Kelvin.

All light sources are not pure white. This is actually easier to explain to you guys as you know there is a huge colour difference between you MH or T5s in your tank. The colour difference is actually the colour temperature of those lights. I actually like to think of MH vs Actinics here... the MH get super hot, but they are almost pure white when you look at them (um, no don't go look directly into them) whereas the nice Actinics are cool blue.

If we start to look at WB as far as digital photography is concerned, mid-day sun is almost pure white at 5500K and Sunrise and Sunset are very yellow at 3500K. Your eyes adjust for this change in colour temperature and colours always look much the same to you. The digital sensor in your camera however is not so clever and can not adjust for this. This is where WB comes in.

Your digital camera needs a reference point which represents white to it, and from this reference point it can now calculate all the other colours. As an example, if you shine a powerful halogen light on a white wall, the wall will look yellow. With the right setting in your camera, the sensor will know that wall should be white and will adjust all other colours to that reference point.

Most digital cameras have a auto WB feature and this is what most people will use. This works by taking an overall view of the scene and then letting the software calculate what it thinks is the right WB reference point. This works most times but it really is a hit and miss situation that can leave you with some rather undesirable results.

Most if not all DSLR cameras today will allow you to choose a preset WB or set a custom one. This will produce a much better result then auto WB but you need to get it right, and you need to remember to change it to suit the shooting situation.

One way to overcome this problem is to shoot in RAW mode on your camera. Then when it comes to post processing of this RAW file on the computer, you are able to play with the preset WB setting or even put in custom ones. I personally never use presets on the camera or on the computer. To me the colour is always to cold and I prefer to make my images a lot warmer. This of course is a personal preference.

Here is a quick table of colour temperature in Kelvin

Color Temp Light Source
1000-2000 K Candlelight
2500-3500 K Tungsten Bulb (household variety)
3000-4000 K Sunrise/Sunset (clear sky)
4000-5000 K Fluorescent Lamps
5000-5500 K Electronic Flash
5000-6500 K Daylight with Clear Sky (sun overhead)
6500-8000 K Moderately Overcast Sky
9000-10000 K Shade or Heavily Overcast Sky

Just a little more info from my personal experiences (you can stop reading here if your head is spinning)

There are many ways to find the ideal WB when actually shooting but probably the most fool proof and believe it or not in this hobby, the cheapest, is to get your hands on a 18% Grey card. This is a cardboard or plastic card that is 18% grey. When you want to find the WB for your scene, you shoot an image with this card in the center of the image. The next step is dependent on your camera and you would have to look it up in the manual, but the low down is you would then tell the camera to use this grey image as a custom WB ref point and it will use this setting until you decided to change it. I am not sure if it would work or even if I would try it (certainly not with cardboard) in a marine aquarium. Something I have done on location a few times is get the card in the scene, don't bother with the custom setting at all and just shoot. As long as you don't change setting to much and the shooting conditions remain fairly constant, when you get these images onto your puter, you are able to select the grey card as your white point and then process all your RAW images with these WB settings. (I am sorry if this sounds way complicated, but I could go on about WB and RAW images for days and each subject could take up huge streams of data.)

The one great thing with our tanks, is once we have found the right WB, it should always be the same until light units or types of lights are changed. Play around with you camera and see what works best for you, then try work with that till you get the image you want.

[Reef Maniac]

Thanks, Ross - Good info

Hennie

[Warr7207]

Cool info, when working with RAW, do you suggest using a program like Photoshop, Corel or the supplied software, IE: Canon etc. ?

[crispin]

thankls for teh write up ross, helps alot. WB is a real hit and miss affair for me, and the presets on the camera really dont do the scene much justice, so a manual setting is whats i need. i'll play around with it, nut as you say a grey card isnt that viable in the reef, which makes things slightly harder

[Tony]

Thanks Ross. I havent heard someone use the 18 % grey card in ages. I thought it was obsolete with digital

[Rory]

WB + shooting under actinics only = frustration...

[Jaco Schoeman]

Hi Ross... I have no DSLR, but my Fuji camera allows to manually adjust settings. Please would you tell / explain to me what the best WB setting (if WB) would be to take photos under actinics. Most Zoa's look best under actinics alone, and then your photo becomes VERY blue. I have plaid around with flash, app, shut speed etc, but still feel the images are a bit blue. I have used Photoshop to "dimm" most of the blue, but even then, it still is VERY blue...

Here's an example:



Note, how nicely the orange is, after adjusting levels and hue's a bit on PS, but still the general image is too blue dont you think?

[Rory]

Jaco does your Fuji have a custom white balance function? I find what worked best on my canon s2 (should be kinda similar to your fuji) was to use this. Usually you need to basically just take a photo of something white, so put something white in your tank (I used an algae scraper) and use that as your "white point" then take a photo of the zoas.

[Jaco Schoeman]

Thanks Rory, that makes sense. Basically you "focus" on the white object, then move your camera onto the zoa's and shoot?

Would you suggest putting on the "white" lights too, and then when you are ready to take the shot, just switch them off again? I just think that under an actinic and pure actinic light, a white surface would be more blue than white, but if the whites are on, that changes the ballgame... mmm...

[Reef Maniac]

The colour temperature of Actinics is far higher than 10 000K, and most cameras have a WB upper limit of less than that, so I doubt if one can actually compensate for actinics.

Hennie

[Jaco Schoeman]

So what do you suggest Hennie? Cause taking that same shot with a flash, or with the white lights on, makes them just another dull brown Zoa.

[Ross]

Originally Posted by Jaco Schoeman

So what do you suggest Hennie? Cause taking that same shot with a flash, or with the white lights on, makes them just another dull brown Zoa.

I think in this case, it depends what you want to show. Under the Actinics, you get the blue and the glow from the zoes. Your camera is actually showing what you see. If they are under your whites, they are a dull colour because that is what you see.

So in this case you have to try find the balance that you want. I am afraid I am not able to comment how to do this on a non DSLR

Ross

[Ross]

Originally Posted by Warr7207

Cool info, when working with RAW, do you suggest using a program like Photoshop, Corel or the supplied software, IE: Canon etc. ?

I would seriously look at Photoshop for this. It can not be beaten.
I have been using a pirate copy for years and only over December decided to purchase a licensed copy. Obviously I could not afford 10K for the full product so I decided to try Photoshop Elements 8 and for photography at our level, it is more than enough. It is defiantly worth the price.

[Rory]

Originally Posted by Jaco Schoeman

Thanks Rory, that makes sense. Basically you "focus" on the white object, then move your camera onto the zoa's and shoot?

Would you suggest putting on the "white" lights too, and then when you are ready to take the shot, just switch them off again? I just think that under an actinic and pure actinic light, a white surface would be more blue than white, but if the whites are on, that changes the ballgame... mmm...

Yes I would suggest some white light, maybe you can jippo it so only one t5 is on or something. If there's no white light your camera can never capture any other colours since colour is merely reflected light, so if you shine a blue light on a red wall it will basically be black. If you shine a blue light on a mix of colours you will only see the blue in each thing.

I can only say how it worked on my canon but you went to find custom white balance in the menus, lined up a shot and pressed the "set" button, it would take a shot of the white thing. Now this white balance stays set until you repeat that procedure or select one of the presets. With that white balance set you just shoot away as normal.

[Ross]

Originally Posted by Rory

I can only say how it worked on my canon but you went to find custom white balance in the menus, lined up a shot and pressed the "set" button, it would take a shot of the white thing. Now this white balance stays set until you repeat that procedure or select one of the presets. With that white balance set you just shoot away as normal.

What Canon is this, as far as I am aware, using the * is for exposure. I have not seen it work for the WB but I am shooting with a 50D so things might have changed.

[Rory]

A "Powershot S2" Ross, not DSLR. If you have a 50D I'm sure you can figure out how to set WB

[Mudshark]

Originally Posted by Rory

I can only say how it worked on my canon but you went to find custom white balance in the menus, lined up a shot and pressed the "set" button, it would take a shot of the white thing. Now this white balance stays set until you repeat that procedure or select one of the presets. With that white balance set you just shoot away as normal.

Works exactly like that on my Panasonic point and shoot as well...... or it did until it broke and now makes custom WB green

[Ross]

Originally Posted by Rory

A "Powershot S2" Ross, not DSLR. If you have a 50D I'm sure you can figure out how to set WB

Custom WB on my cam is take image, load image for camera to find it's 18% grey.
Pointing cam at a scene, pressing * sets the exposure to that scene and then lets you recompose.

Will go look now in the manual though as I might have something similar which would work out great.