Hot pixels on a D-Rebel?

[RGM-79(G)Pilot]

ok, i now have a nice shiney new Digital Rebel, and i love it. much nicer to use than my V1, though i still have a long ways to go in developing technique.

i was doing some low light shots this AM, taking pictures out my window into total darkness and having a long exposure time. when i took these pictures into photoshop, and adjusted the levels, i thought i could see stars, but then to my dismay i noticed that these spots were on the houses, and trees... everywhere. lots of them.

when looking at the un adjusted photo, you cant see them, but making the picture brighter, and then ading a sharpen filter... you can see hot points everywhere. i'd upload a pic, but when its sized down you cant see them hardly at all. though on a poster sized print, it would be ruined.

any help here? should i send my new baby to canon?

 

[ambientZ]

hot pixels are a fact of life at long exposure times, and when you are adjusting levels it only makes them worse.

Some people have cameras that they show up visibly at 30s, yours dont show until you do levels, so it sounds better than most.

You could start to use dark frame subtraction or something.

How long is "long" anyway? posting a picture with the levels manipulated wont tell us anything.


Canon is most likely going to tell you its within spec, and to stop wasting their time.

 

[RGM-79(G)Pilot]

damn man, chill. i was just asking. i havent ever dealt with this before.

just spend 1k$ on this stuff. want to make sure it isnt broken.

 

[maw]

damn man, chill. i was just asking. i havent ever dealt with this before.

just spend 1k$ on this stuff. want to make sure it isnt broken.

i don't think ambientZ was being unreasonable in telling you that what you are seeing is perfectly normal and that Canon will tell you the same thing.
you are basically pushing your equipment way beyond the norm, then adding fuel to the fire by sharpening afterwards. if you ask me, i'd be surprised if you DIDN'T see hot pixels in those circumstances.

 

[HorsePunchKid]

Can you post a crop (maybe an 800x600 or so) of the original image in a region where you're finding hot pixels? That would definitely help.

 

[[TQ]]

damn man, chill. i was just asking. i havent ever dealt with this before.

just spend 1k$ on this stuff. want to make sure it isnt broken.

WTF

 

[HorsePunchKid]

WTF

I think RGM-79(G)Pilot chose to ignore all of ambientZ's post except the "stop wasting their time", and additionally interpret that as what ambientZ was saying to him. Simply not what was said, but people around here love to jump to conclusions.

Still hoping you can hook us up with at least a crop, RGM-79(G)Pilot. There are too many factors left open for us to be able to give you good advice. If you're not used to it, you might be surprised how blown-out stars can be in a 30" exposure or so (if that's what you mean by "long").

 

[Joves]

Actually sounds more like noise to me. Are the pixels diffrent colors or, the same? Most digis do not like long exposure times and, will show a helluva lot of noise. Also what did you set you ISO speed at as, higher ISO settings tend to be much more noisy.
You are going to have, to clean up the pixels in PS or, whatever program you are using, either way. Is the Rebel point and shoot, I dont know my Cannons that well.

 

[HorsePunchKid]

Is the Rebel point and shoot, I dont know my Cannons that well.

I don't know my Canons either, but Google does. It's definitely a step up from P&S. I think that's why he's worried about hot pixels, but without more information, it's hard to tell whether or not it's anything to be concerned about.

 

[RGM-79(G)Pilot]

ok i apologise for over reacting.. was a little disappointed with my camera.

but there is a crop of a section. the stars are circled, as are the hot pixels.. the suspected pixels are not stars since it was cloudy.

the suspectes also are in groups down lower in the picture, across the homes and trees. but that is a sample.

 

[ambientZ]

damn man, chill. i was just asking. i havent ever dealt with this before.

just spend 1k$ on this stuff. want to make sure it isnt broken.

i wasnt trying to be rude, i was just impersonating canon tech support
actually they'd probably tell you to send it in, charge you for shipping, and ship it back and say its in spec.

Can you give us some technical details? shutter speed, ISO, an crop that wasnt leveled (or post processed otherwise), we can give better information then.

Astronomers with million dollar ccd's still get noise, and they have extravagant liquid chilling systems to reduce the sensor noise.

 

[PS-RagE]

Another test you can do is take a long exposure pic with the lens cap on

 

[RGM-79(G)Pilot]

i dont have that pic that isnt leveled. but i did take several 30" 7.1 shots and i dont see this problem anymore.

maby it had somtinng to do with the ammount of light coming in from out side, and not total darkness. and doing that adjustment to other pictures taken of the same place using my v1 dont have those spots.

maby im just expecting too much.

the pic in question was iso 400, 30" not sure of the Av, i changed it alot. fyi

 

[ambientZ]

the aperture wouldnt matter for hot pixels.
For legit long exposures youd want to use RAW instead of jpeg.

hot pixels should be red green or blue, not white... might be an artifact of the levels adjustment.

 

[misan-thrope]

At higher ISO settings, it gets more and more noisy due to the pixels being locked on for longer to absorb more light.
One way to help decrease this is to keep the camera colder, the colder it is the less likely it is to have that noise.
My rebel has a few hot-spots at higher ISO settings (800+), good way to test is like was mentioned, with the lens cap on.

 

[RGM-79(G)Pilot]

ok thanks for the help.

i just had questions, since i have taken alot of long exposures of the mountains when the sun was down, with my v1...and i never got those white spots on the pictures.

i'll try not to worry so much about this.

i did take some with the lens cap on, and i dont see them without adjusting the levels. so maby i am seeing a byproduct of adjustment and compression?.

 

[maw]

i did take some with the lens cap on, and i dont see them without adjusting the levels. so maby i am seeing a byproduct of adjustment and compression?.

i'd say this is probably the case. too much sharpening or too much contrast will often produce noise.