Hot Pixel Test?

[MediaMagic]

Okay, I've been searching through the forum again and I've been reading about a hot pixel test with the lens cap on in manual mode. I never thought to do this but now I am interested in trying it for the hell of it.

So, I take it that the test is to use different ISO settings and shutter speeds? does aperture value affect hot pixels as well? or is it just the ISO along with length of time the light is hitting the sensor?

How many hot pixels are considered acceptable at the various settings? I'm gleaning this "test" from posts, but I never could find a post where instructions for the test were given.

Thanks.

[robertwgross]

For one thing, with the lens cap on, there won't be any light hitting the sensor!

If you have faulty pixels on a sensor, then shoot darkness (with the lens cap on), and you may see some red, blue, or green micro dots on the image.

If the sensor is good, you will get almost pure blackness, with nothing brighter than a very dark gray dot.

---Bob Gross---

[MediaMagic]

robertwgross wrote:
For one thing, with the lens cap on, there won't be any light hitting the sensor!


---Bob Gross---

LOL Yeah, I guess that would make a good addition to the "So I'm Stupid" thread. Um, I use a lighted lens cap when my transparent L glass lens cap isn't available.

It also seems like for the test, a lens wouldn't be necessary at all, but just the dust cover.

[bnpndxtr]

Right you can do the test on the body only. This what I did at Best Buy when I took my original 10D back to exchange it for one that had minimal hot pixels. You can take a program like DeadPixelTest.exe with you on a CF card and then run the test right there after taking a dark shot long exposure. My first 10D had a noticeable blue hot pixel (really they appear as a small cluster rather than a single dot) with a 10 sec exposure at ISO 100. Deadpixeltest said its luminance was around 30. This was very noticeable to me- partly because I had already gone through this exercise with my G2 last year so I knew what to look for. The camera I ended up with (after looking at 4 of them!) had nothing above12, and I had a hard time seeing anything at all.

By I saw a lot of variance. One body had a hot pixel cluster with luminance of 178! I was disappointed with Canon’s quality for this reason. It could be that Canons in general have fewer hot pixels than other brands- I don’t know. But if I’m going to spend that much money, I don’t want hot pixels.

If Canon would like to defend themselves here, be my guest- but I was astounded with the out of box defect rate I experienced. I saw two with irritating hot pixels and one in which the focus servo was nutty- it would just run back and forth between the stops sand never stop at the focus point.

http://www.starzen.com/imaging/deadpixeltest.htm
.

[perfectpixel]

bnpndxtr wrote:
You can take a program like DeadPixelTest.exe with you on a CF card and then run the test right there after taking a dark shot long exposure.

How does the program work? did you take your laptop along? I doubt Bestbuy let you load an exe file on one of their PCs for you to check this.
Sounds like a useful thing to do, but exactly how did yuo do it? The link you gave has no directions on how to use the program.

[bnpndxtr]

You run the program, load the file, and start the test. The program displays a list of hot pixels that are brighter than the threshold you input in the box. The default threshold was 60, so I changed it to 20. I put the program on my CF card prior to going in to Best Buy. So after I took the 10 second exposure, the image and the program were sitting there on the CF card together. Then we used the PC in the camera department to open up the directory on the card and run the program. When I found no hot pixels at 20, I reduced it to 10. A few showed up at 11 or so, but I could not see them visually using a viewer.

I became a pest at Best Buy because I had already bought the camera once. I don’t know how receptive they are to doing this if you haven’t already bought the camera yet.