40d problems - no idea what though.

Hello from Australia, no one in this country seems to know the answer to my problems (even Canon), and from a fair bit of reading on this site, there seem to be alot of knowledgeable people around. Sorry for this being my first post

Alrighty, the other night i decided to take a long exposure at night and found that my camera (or maybe something im doing) is causing a "christmas tree" effect on the images i take.

I have tried each and every mode (M, SP, AP), ISO changing, white balance settings, however when the shutter is opened more then 1 second, this happens. The darker the image is, the less i get the effect. So bright images come out as below.

The spots are in the same spot each time.

100% crops of two different photos, i have 100 with the same effect.

Byte size: ZERO | Content warning: NOT AN IMAGE

Byte size: ZERO | Content warning: NOT AN IMAGE

Seems to me as if you have a sensor issue. I see the second was one a 30 second exposure on ISO 1600. Some strange spots can be expected with such an exposure, but I wouldn't expect the ones (or the amount) shown in those photos. I would send it back for a check up.

HOT PIXELS due to high ISO and exposure length

S2000 wrote in post #4093028
HOT PIXELS due to high ISO and exposure length

Does that look like a normal amount to you though?

No, it looks like the good candidate for replacement!

PAFC2004 wrote in post #4093043
Does that look like a normal amount to you though?

Don't know if it's normal, but it's what it is.

I would try ISO 200 for an extend exposure and see what I get though.

S2000 wrote in post #4093076
Don't know if it's normal, but it's what it is.

I would try ISO 200 for an extend exposure and see what I get though.

The OP has a camera that is useless at ISO 1600 though.

you can test it with this just for fun.

http://www.photo-freeware.net/deadpixel​test.php

I think it's pretty reasonable to expect some hot pixels at high iso for long exposures (how many, I don't know). That is one of the reasons people that do this kind of shooting stack exposures.

at ISO100 the results are 99% the same.

I ran that test last night, and it said it found alot...

twofruitz wrote in post #4093188
at ISO100 the results are 99% the same.

I ran that test last night, and it said it found alot...

Now I would say take it back.

Been a while since I did long exposures but I am sure I recall a setting on my 350D - no doubt somewhere on all of the EOS dSLRs - for making "dark frame" subtraction' exposure this is intended to remove such hot pixels and reduce the noise found in long exposures ~ or am I totally off the wall with this understanding

If they are hot pixels... why do they take up more than one pixel? Are hot pixels often localised like that?

Also, just for my interests sake, do several rounds of 'clean' now using the built in cleaning system (go to the menu). I've heard that it can remap hot pixels, adn was curious to know if it worked.

Remember - the final JPEG is the result of combining the different colour values of adjoining pixels. The effect of a single hot pixel will "spill over" to adjoining ones. And if it's truly hot, it'll heat up adjoining ones too. Hot/dead pixels are essentially extreme examples of sensor noise. The longer the exposure and the higher the ISO the worse it'll be. ISO 1600 for 30 sec. and you'll have a lot of noise. If it's at all warm to begin with, expect still more.

PAFC2004 wrote in post #4093081
The OP has a camera that is useless at ISO 1600 though.

No, but he might have a camera that isn't great for 30 second exposures at 1600...

Jon wrote in post #4094994
Remember - the final JPEG is the result of combining the different colour values of adjoining pixels. The effect of a single hot pixel will "spill over" to adjoining ones. And if it's truly hot, it'll heat up adjoining ones too. Hot/dead pixels are essentially extreme examples of sensor noise. The longer the exposure and the higher the ISO the worse it'll be. ISO 1600 for 30 sec. and you'll have a lot of noise. If it's at all warm to begin with, expect still more.

I see. Thank-you.