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Old Jul 2, 2005, 3:36 PM   #1
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I am trying to test for dead/hot pixels with this program.

"Firstly I'm guessing really, you should get the area as black as possible. As it has no manual shutter, when I put it in black it puts itself on a 16s exposure.

"The first time I tried this, putting it in a tube in a pitch black room (or what I thought), the end result looked like a fireworks display when zoomed in.

"It's just I hope to sell the camera, but don't really want to sell it with lots of dodgy pixels.

"So does the 16s exposure matter? The camera has no lens cap, so how do I make it pitch black?Also the camera has no Tiff mode, does that matter?and secondly are hot pixels a problem, and would selling the camera used with them be wrong?

Also in the program, how do you get the histogram to show?

Thanks for any help

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Old Jul 6, 2005, 6:01 PM   #2
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I am trying to make sense out of your post. The only thing I really understand is that you have a camera you want to sell and you want to test for bad pixels.

First off, what kind of camera are you talking about? You say it has no shutter so it must be a point'n'shoot.

Second, what is this 16s you are talking about?

Third, what does zooming have to do with it?

Fourth, what is this program you are talking about.

A dark room would be a good place to test for hot pixels. For dead pixels, try shooting something that is bright white and fill the frame. You shouldn't have to do any zooming. You may need to select manual focus in order to take the picture since auto focus probably will not work in either the white or dark case.

I don't understand your reference to tiff mode. Tiff is an image format that eats up a lot of storage space but the only reason I can think of that it relates to bad pixels is that there is no compression so every pixel is recorded in the image file.

You refer to program again when you ask about histograms. If you are referring to a histogram display on the camera, I refer you to the camera manual. If you are referring to a computer program, I am puzzled. A histogram will probably not provide any information on a few bad pixels. They probably wouldn't even register.

Pleas provide more information on what you are trying to do, how you are trying to do it and what software you are using (if any).

Cal Rasmussen

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Old Jul 7, 2005, 11:12 AM   #3
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Oh, thanks for your reply Calr. I'm sorry if some of my points weren't very clear: I'll try and explain some things more clearly.

I am talking about the HP photosmart 935, which does not have shutter control so is a point and shoot.

The 16s is the exposure it picks to shoot in pitch black. For eome reason I thought the scene had to be totally black, using something that's totally white would seem a better trial.

Sorry for not being clear on the zooming: I meant playback zoom as when I magnify the image there are so many dodgy bright pixels I think I must have done somethign wrong.

THe program I am talking about is DeadPixelTest. It is a well-known program that analyses a shot to test 'hot/dead' pixels. I'll give you the URL in case you're interested:


Thanks for the point about dark for hot, and White for dead, I realise why that would be useful. I guess for the hot I just have to amke sure it's so dark, no light will be picked up in a 16s exposure. I think that's what happened when I tried it last time.

When I asked about Tiff, I was referring to the fact DeadPixelTest default format is Tiff pictures, I was just wondering whether the fact my picture from the HP935 would only be Jpeg so that the dead/hot pixels would be affected.

Sadly the HP 935, doesn't have manual focus. Will that majorly affect the test?

Sorry I wasn't very clear about the program and the histogram. If you look at the program, there is a space for the histogram to appear. (where you can zoom inon the histogram). However when I use it with an image, it doesn't work. I was just wondering why.

Hope I have made this more clear, I am sorry that you found my original post diffucult to understand, thanks for replying!

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