Seen elsewhere

This link was given on another web site I use.

Seems quite interesting but the final bit says roughly 'I didn't like the results it gave so I changed them'. Umm that isn't maybe the best recommendation I have ever seen.

Nonetheless it looks like it might be a useful device although too expensive for me to justify.

Mike

Not sure why it has to be a cube, and not flat.

G

Looks as though it might be useful - but £50 !!!

I think the cube shape allows you to arrange the light to fall on different angles and it looks nicer!

I agree 50 quid!

Mike

If you go so far getting the white balance right then you also need a card to make a colour profile for the camera or else the WB is perfect but all the colours are still off, quite a shame if you ask me.

I thought that all these cards etc tended to use an 18% grey to allow the software to calibrate against a known value. If that's right then all the colours have to fall into place - that's what I thought the theory was.

Mike

The grey card is only to get correct exposure and WB.
In truth the camera meters 12% grey but it's easier to print 18% grey since that's 50% lack and 50% white I believe.

But it doesn't do anything for the colours, just like monitors they also all act differently. Some display the colour red differently and so on.
With the K20D you even have settings to control the colours.
The calibration device makes an image on the monitor and reads that and correct till it is right.
With the camera you make a photo of a colour card. since the colours are know what they need to be you can make a accurate profile for your camera colours.

This a colour card used to make a profile link
And this a simpler version link
The last one is simpler and can so far as I know not been used to calibrate or make a profile. here is an explanation how to use the simple one link

The grey card has 18% reflectance as this is the value that an "average" scene has been found to average out to. It is also Zone V on the Zone System, a mid tone.

In the case of the camera, this is the "K value" or the point to which the metering is set. Some cameras actually have a K value of 10%, intended to improve shadow detail in auto exposures with negative film.

I doubt that this would help with slides or digital, so I suspect that the Pentax is calibrated to the standard 18% which is why sometimes it is accused of "under exposing" compared to other marques.

Here is a little read about the grey card link

Thanks Stefan, but bear in mind that it's referring to the calibration of Nikon cameras, and the calibration of Pentax ones is clearly different.

But John it's also referring to the ANSI standards and that's worth something.
And to be honest I don't know if it's really different, never seen comparison were a grey card is used.