A dead pixel checking simple test

[LinhLe]

I just used this simple test to look up for dead pixels of my new S2.

- Set for a high resolution.
- Set ISO 100.
- Any lens
- Set for Manual Focus.
- Set Mode M, Any Speed, any Aperture.

- Take a picture with the lens' cap on
- Load this picture to your computer, open it with Photoshop or any graphic editing program (Paint, Corel...)
- The "photo" should be all black.
- Zoom in to enlarge the photo as much as posible.
- Use the rectangular select tool to select and check the selected area, the dead pixel should be any white dot, point.
- Delete the checked area and repeat select another area, check and delete piece by piece... until the photo is complete checked
- Remember to save from time to time.
- It takes about an hour to complete.

Lính Lệ

[Tom Nolle]

You could probably use your technique to create a selection mask from your image, with the highlights (the dead pixels) selected. If you saved the mask, then on any shot where you were worried about the pixels you could restore it, shift the mask by a couple of pixels in a given direction, do a copy, shift back, do a paste, and you'd cover the dead pixel with the contents of another nearby pixel.

Tom

[LinhLe]

yes, very good idea Tom.
But, I think it is better for us to send the camera back to Fuji if we have any dead pixel on our CCD so the camera could be fixed.
Lính Lệ

[Tom Nolle]

Unless I had a bunch, I'd probably opt to fix the images. Too much time without the camera!

Tom

[Claude Ollieuz]

Originally posted by LinhLe
I just used this simple test to look up for dead pixels of my new S2.

- Set for a high resolution.
- Set ISO 100.
- Any lens
- Set for Manual Focus.
- Set Mode M, Any Speed, any Aperture.

- Take a picture rith the lens' cap on
- Load this picture to your computer, open it with Photoshop or any graphic editing program (Paint, Corel...)
- The "photo" should be all black.
- Zoom in to enlarge the photo as much as posible.
- Use the rectangular select tool to select and check the selected area, the dead pixel should be any white dot, point.
- Delete the checked area and repeat select another area, check and delete piece by piece... until the photo is complete checked
- Remember to save from time to time.

Lính Lệ,Lính Lệ
I tried the above and found no dead pixel!
As luck(and my natural lazyness) would have it I think I discovered a quicker way to explore the "photo":
after enlarging to the max, use the PS navigator to "scan" the whole surface.
Not finding anything made me doubt my visual acuity, so I applied Autolevels and lo! here comes a view of the innards of the CCD!
Comments anyone?

[LinhLe]

Congratulation,
Your CCD is surely good enough to play around.
Lính Lệ

[mmaathuis]

Shutterspeed!
there's a difference between dead and hot pixels! All CCD's will have hot pixels, hopefully yours will have no dead pixels.

Dead-pixel or stuck pixel - Is really broken and will not work again
Hot pixel - Is a pixel that leaks power

Using the a long shutterspeed in the test above will get you a picture with hot-pixels. Hot pixels are pixel that leak energy and will therefore always be a brighter color than the rest.

Since leakage is an issue you should always remeber that heat is a factor in this. A warm CCD will show more hot-pixels than a cooler CCD.

seanmcclain gave this link in a tread I started:

http://webpages.charter.net/bbiggers/DCExperiments/html/hot_pixels.html


So use the test above but keep in mind the shutterspeed.

Oh, and to save you time in Photoshop: Use Auto Contrast to see the dead pixels at once (Ctrl + Alt + Shft + L)

[LinhLe]

Thank for your test improvement for our test, mmaathuis
So, we should conduct the dead pixel test with a fast shuter. I did at 1/125 for my test.
I'll check my hot pixel sometime.


Lính Lệ

[LinhLe]

Thank to mmaathuis again,
I have read the from the link, It helped me to understand more about the dead, hot... pixel. and the tests given from that site are far more accurate than my simple test.

Lính Lệ

[seanmcclain]

A couple of things that might improve your chances of finding hot pixels:

1. Start with your lens cap on as LinhLe mentioned.

2. As mmaathuis and KeithM mentioned, the hot pixel will become more visible as exposure time and ccd temperature increase. It will also become more visible at higher iso settings because higher iso settings will raise the signal output of all pixels. It will be easier to locate your hot pixels if you shoot a long exposure (30 sec) at high iso (1600 iso).

2. If you look at the histogram for a dark image in photoshop it will only have values at the low end of the scale (unless you have a really hot pixel). Move the white point closer to the dark end of the scale. Don't move it down too far. Just enough to make the hot pixels brighter. You should be able to find the hot ones at 200% magnification. I located all 7 hot pixels on my ccd in about 10 minutes.

3. Don't fret if you have hot pixels. They don't show up easily on prints. They're easy to get rid of. Fuji will map them out if you really find them to be a problem. They did mine last week. It was fairly painless (except waiting for my camera). You figure, if you have 7 hot pixels out of 6 million, that's only .0001% bad pixels. In manufacturing terms, that's a pretty acceptable failure rate.

4. Don't fret about dark pixels. Dark pixels will take on the data from their neighbors during interpolation. You'll never notice them.