White Balance / Colour correction tools

Stefan, I like the Pantone/x-rite stuff and it looks better than just WB alone. The page it suggests looks good and shows how to balance up the full range of greys.

Right from day one video cameras had a button to set the white balance. You just pointed them at what you wanted to balance to and that was it. Pentax cameras don't seem to have that although the *istD might have had it. So screwing a filter on is not much use. I might try it and take a shot and then manually adjust for the next shot it might work?

Indeed.
What the links shows is the manual way of doing it, with the x-rite software it does that automaticly and save it in form as an profile which you can select when working with a RAW file.

Actual the Pentax have it, that you didn't read the manual just kidding.
It's quite hidden away actual if you don't know where to look.

With the K10D you press the Fn button and go to the white balance.
There you set the WB on manual and press right so you can edit the settings.
On the same screen it also shows now the option "shutter" in a box. If you press the shutter the camera takes a photo and with a green box you select an area and the camera takes a WB metering from that.

I believe this function is still in the Pentax cameras and I presume it still works roughly the same.

The Ds could do it, under the WB menu and I'm sure the K20D could too, though I never tried.
Point at something white and set the custom WB. It was very easy to do.
The manual tells you how to do it, but it is in fact pretty easy even without the instructions.

Stefan beat me to it

I seem to remember reading that, I'll have to have a look at the manual for the K20D. It must be 4/5 years ago that I bought the Expodisc and basically gave up with it when I found that there wasn't a button like the green button to set the WB.

Just gave it a quick try and for exposure it works OK and I managed
to set the WB manually.

Quite a few videos on youtube about Expodisc, but non are Pentax related.
This one's quite good.

If you know how to do it, it goes pretty fast.
You can also off course if you shoot in RAW make one photo with the cap on and use that as your base-photo to set the WB and apply it to your other photos.

It works OK in camera. Unfortunately it doesn't tell you what value it's set to so that you can later set in manually or check if it coincides with a pre-set. I'll have to see if I can use it with external flash.

This video shows how to set a WB in Camera Raw from a 1st frame taken off a grey card or Expodisc and then apply it to the following images. Quite good.

The Expodisc works quite well. Just tried it outside, sunny day pointed at the sky, it got the WB spot on. For exposure I had to dial in +0.5 stop. The camera's AWB through the Expodisc was also spot on (probably using the same camera program). Set to Daylight WB on camera had too much blue, which might be why some non-Pentax lenses show a blue cast.

The Expodisc gets the full frame to the same shade of grey which isn't possible with a grey card. Still worth including something grey in the first shot.

Thanks for the comments so far, I'm not sure about the Exodisc as I tend to use far to many different sized lenses, although the X-Right looks interesting. Any other suggestions.

Spyder has now a X-rite clone on the market. link
And they have something called a Cube link

But if you want to be colour accurate, correct WB and exposure than the colour checker passport is the best all in one package.
For the rest I don't know of in products.

Thanks Stefan, I may put this on the xmas list for the family if I start getting my act together over the portraiture.

The Expodisc gives the best results in my opinion, and to help you avoid the mistake I made, by the biggest you need for your largest (filter thread) lens. Then by cheap step down rings for the others.

It's not something you can do quickly though if you have to change a ring to suit the lens in use at the time.

By far the simplest, easiest, and quickest to use is a Photographers Grey Card. It's 18% grey one side, white the other. Simples.

Just keep in mind that for each change in lighting, you'll need to make another reference shot.

After that, it's all done in post processing.

My Expodisc is 58mm and I have 2 step down rings. To use it I leave the rings on the lens and just push or pull the Expodisc off. It isn't threaded it has ball bearing type catches that fit into the filter thread.

The grey card is difficult to set up and take accurate readings from.
On the computer you get different readings from different parts of it.
The Expodisc is very accurately calibrated even comes with a test certificate.

Mine is correct to 00R 01G 01B the white density rating is 0.74
18% would be 0.745 An error of +/- 1/6th stop would be in the range
0.695 - 0.795 So my incident manual metering should be spot-on.
If I set the camera to +0.5 stops in Av mode I get a grey (RGB)
value of about 115 which is only about 4 out.

So does the Expodisc work when the camera is in shade and the subject is in bright light? I assume it does, but have to ask.

You use it like an incident light meter where you take the camera to the subject and point it back to where your going to use the camera from. Press the green button to get a manual exposure setting and then set the WB using manual capture as per the camera manual. It just means pressing the shutter to capture the WB and then OK on the camera back. Then go back to where your taking the photo from. You can change the exposure again if need be.

I tried it before pointing the camera at a table lamp that had a largish 20w energy saving bulb in it of unknown colour balance. The exposure and WB I captured were spot-on. It actually read on the computer screen 117R 117G 117B which is exactly right...... I was surprised it was so close.

I also tried a shot at the same lamp with the Expodisc on and the camera set to AWB.... I was surprised to find that it wasn't right.

It's a lot of money though for such a simple item.

The videos on the site are quite good.