Robert , here is the only shot I have of the disc . After you set WB it will be within 1/4 stop of 18% gray. I will take some more for you later and post them.
J1000 wrote:
I'm not sure I understand what that disk does.
I believe it gives your camera something that is a shade of 18% grey so that your camera can callibrate and adjust the WB for the lighting condition you are in at each given moment. Did you ever see a professional photography shoot, and they have one of those black cards with a bunch of colors on them, and also a card with just black and grey, well that is what they use to get the colors and white balance correct during professional shoots (correct me if I am wrong, please) I have never used one, but I believe that is what they are for, just from reading other posts and such.
This is Tom's homemade version of the commercially available Expodisc, which costs well over $100. You place it in front of your lens and take an exposure through it. Then you use that shot to set your custom white balance.
Tom, I've been trying to find the instructions for making the Hickspodisc. From what I've been able to dig up through searching, you sandwich three sheets of 3M N95 respirator material between a glass UV filter and some kind of acrylic diffusion material? Which side faces out? What are the details of the acrylic? Can you use the acrylic on both sides?
The Hickspodisc as it was dubed is a product like the expodisc, or a CWB tool that I made from old components for about 5 $. I made it out of a 3m R95 respirator replacement filter , the 3m is the only R95 that will work right , the other brands although labeled R95 don't use the same components, and won't give you the right reading .
The ones I used were round in shape , those are disc. and now are of a tapered rectangular shape , you will have to cut them to fit . the filters are made from 3 different materials sandwiched together. the easiest way to make one is to get two UV filter put the material between them and screw them together.
Hold the disc if front of the lens blocking out the ambient light take a pic and set it to CWB .
msalvetti wrote:
This is Tom's homemade version of the commercially available Expodisc, which costs well over $100. You place it in front of your lens and take an exposure through it. Then you use that shot to set your custom white balance.
Tom, I've been trying to find the instructions for making the Hickspodisc. From what I've been able to dig up through searching, you sandwich three sheets of 3M N95 respirator material between a glass UV filter and some kind of acrylic diffusion material? Which side faces out? What are the details of the acrylic? Can you use the acrylic on both sides?
You can use either side out all the glass does is protect the material from dirt , the acrylic material I got at home depot it was cheaper and easier to cut that a piece of glass.
These types of devices are not going to be as accurate as taking a reading off a grey or white card. Whether you use the original $100 Expodisc, or this reasonable $5 version, the camera meter will still be measuring reflected light from your subject matter. The problem is you don't have much control over the color of that reflected surface - It could be a yellow wall, red cape, pink elephant, orange hippo, etc. etc.
But in contrast, by making a measurement from an 18% grey card or even a cheap white coffee filter, your camera is obtaining proper value from a known variable.
Try this experiment;
Use one of these disks and make a reference image by pointing it at a bright red or blue object like a shirt that someone would be wearing. (That's how these devices are supposed to be used, it even says so in Expodisc manual). Once you have your white balance measurement take a photograph.
Next, use a standard 18% grey card or true white surface and make a white balance measurement and take a photograph of the same subject.
Now compare the two images and see which one is more accurate.
My grey card cost $5 and takes the same amount of time to use as one of those discs, but with higher accuracy over white balance and has paid for itself even more.
AJ Nadershahi wrote:
My grey card cost $5 and takes the same amount of time to use as one of those discs, but with higher accuracy over white balance and has paid for itself even more.
I also have one that was made by Jobo. Nice thing about it is that it is flexible plastic material and very durable. One side is grey and the other a standard color chart. It's available here.
Here are some samples , shot with the cam's auto wb , wb set with cam's incondecent setting , wb set with white side of gray card , wb set with hickspodisc and Nikon D2H WB set with cameras CF .
come to your own conclusions Cause I really get tired of having to defend myself.
Auto
Edited by Tom Hicks on Jul 20, 2005 at 05:35 PM GMT
Cause I really get tired of having to defend myself. 