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Specialist white balance cube for getting your photos right
We've been having a look at the new SpyderCube, recently announced at the PMA show.
Exposure and white balance.
Your camera has an exposure meter and can easily select the best exposure and white balance for your photos most of the time.
Why might you need this small gadget, and how can it help your photography?
Manufacturers go to a lot of trouble designing exposure systems to give you correct exposure for your photos.
However, the estimate your camera gives is not always accurate, depending as it does on the contents of the scene you are photographing.
One way round this problem is to use a known object for exposure calculations.
Over the years a common accessory for photographers has been the 'Grey Card', often reflecting some 18% of incident light.
Grey cards are useful too for working out the colour temperature of the light falling on them.
I'll not go into details here, but the white balance setting on your camera is based on whether your subject is lit by a warm light such as from Tungsten lighting (low colour temp.) or a cooler light such as shade under a clear sky (high colour temp.)
Knowing that the cube is a neutral grey allows you to fix white balance when processing RAW camera files, even when your camera was wrong in its own estimate of the appropriate settings.
At about 40mm (1.5 inch) per side, the cube is smaller than most cards, and somewhat more rugged.
The SpyderCube is made of ABS Cycoloy, a hybrid resin that is fade proof, durable, and flame / shock resistant.
In addition, colours are through-pigmented for durability, and are formulated to provide neutral colour values, including an 18% grey.
Note the chrome ball at the top which provides for checking specular highlights in your image.
If you look at the full size image, you can see the lighting setup used for the shot...
There is also a hole at the bottom which is a light trap, and gives a true black reading.
This works even in daylight, where the blackness is very noticeable, compared to any surrounding objects you might describe as black.
The base fits on to a tripod if need be.
The cube also comes with its own storage bag.
I'll start with a simple use for exposure calculation, and processing of a RAW camera file.
I've set the cube up on a small tripod, lit by two lamps (CFL light boxes).
You can see the reflection of the lamps in the ball bearing at the top of the cube.
The display below is a screen shot of the Adobe Camera RAW software I've used to open the photo (and some others for this review).
I've taken several previous photos to get the exposure correct.
One way (with the cube) I can speed up the process of finding optimal exposure, is to look at the RGB values of the different parts of the image.
I've added seven sample points to the image to show the values at those points (I'm using 5x5 averaging for the samples, so as to lessen the influence of camera noise)
With the black point set to zero in the converter (so a pixel of 0,0,0 corresponds to pure black), you get the following seven measurements
You can see that the lighting is stronger on one side (#6 is lighter than #3 for example) and that the pure black of the hole is too high a value.
The reflected highlight is burnt out to 255,255,255, but that's not a problem here.
If you move your mouse over the image below, you will see the effect of moving the black point up (to 6).
This has moved the sample values for point one to zero.
Deep shadow like this rarely contains much but noise, so (in this image) nothing is really lost.
If I start adjusting the various sliders for brightness/contrast then the numbers will alter. Personally I trust to my monitor calibration and eyesight/judgement to get the right look to the image.
If you needed to ensure consistency of exposure and processing (say with different cameras) then the accurate repeatable measurements you can get from a cube are definitely of use.
If you light a scene to record good shots of a SpyderCube, then almost anything you then put in the scene will be correctly exposed.
I dislike energy saving light bulbs. They are great for saving a bit of cash, but from a lighting point of view they (currently) put out a dreadful light that just messes with colour rendition.
However, I do have them in places like hallways, where the picture below was taken.
The glass of pens is one I've used in the past to check lighting, since the bright colours of the plastics show up uneven and low quality lighting very well.
My Canon 1Ds3 has tried to adjust the white balance, but it's quite far out.
Move you mouse over the image to see the results of setting the white balance on one of the grey patches.
Much better, and you can see the true colour of the wall.
Or can you?
I took the photograph at lunchtime, and about 15 feet away (to the left) there is a frosted window above a north facing exterior door.
If you're careful with placing the cube, you can get more information in mixed lighting conditions.
I've some measurements in the conclusions which show why you should use the grey face for white balance rather than the white.
The cube doesn't have to be in sharp focus either, as this shot shows (tungsten halogen lighting on a wooden table).
Move your mouse over the image to see a corrected version.
It's a bright cloudy sky for this shot in my conservatory, which gives an unwanted coolness to the photo.
The adjusted version is better, but I might still choose to cool the adjusted image a bit. It's always worth remembering that the most technically accurate photos are not always the most visually appealing.
Mouse over image to see correct White Balance.
If you look carefully, you should be able to see the black light trap. I've set a sample point and used it to adjust the black point for processing this particular file.
The cube's useful if you were setting up some permanent lighting, where you could experiment and work out optimum exposures and white balance for various configurations.
There are some useful quick intro movies on the Datacolor site, showing examples of the cube in use.
My work conditions are much more variable (I sometimes work in factories for example) with differing light levels and lighting types. The cube covers many exposure and white balance aspects of lighting that I'm likely to want to adjust for when I'm setting up a product shoot (I often work on location).
Something like the cube, just helps bring an extra bit of consistency to my work. It can also help you think about lighting and white balance in a more detached way, without having to think about the actual object you are photographing.
As I showed in the example in the hallway, there may sometimes be different light sources that you'd not thought about, so it's worth taking readings from different faces.
For more precise work I might want to look at a camera profiling setup, but for much of my work, such complexity is not of much benefit.
The chrome ball on the cube is particularly useful for detecting unwanted light sources and reflections that you might not want in your shot.
At higher ISO settings I might want to take white balance reading from the white face, since camera noise might be a bit too strong in the shadow and grey areas, however the white is a slightly warm white and not as spectrally neutral as the grey. I'd suggest a specific over-exposed shot to raise the brightness of the grey face if you are setting white balance at high ISO.
The spectral response for the cube is plotted below. It was measured with my spectrophotometer (non UV cut) covering wavelengths from to 380nm to 730nm.
The blue line shows a slightly less even response from the white surface.
The green line is the grey surface, and looks pretty neutral to me.
The brown line at the bottom is from pointing the spectrophotometer (with its light source) into the light trap and is reassuringly zero right across the range...
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My only (slight) reservation with any product like this, is that all too many photographers think that gadgets and gizmos will improve their photography.
Usually the key to improvement is taking more photos, and learning to decide which are good and which are bad (and why).
That said, this is actually a useful device to have in the camera bag for those times you need it.
I've had the original calicube for some time and have already replaced it in my bag with the SpyderCube.
The tripod mount on the bottom will make it easier to use on location.
Simple, easy to use and no batteries to ever replace ;-)
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