Night time shots - whats on my lens/sensor?!

[Thiink]

Heres a question for you seasoned digital guys. I went up to Mount Panorama tonight to try and get some shots of the moon for something to do while its cloudy. Anyway I got up there way too late and decided to have a play around anyway. I ended up taking a few shots, got home and put them onto my computer only to notice that all the shots have a little blue dot in around the same place on each shot. Ive attached one of the images including a blown up image of the dot (the dot is roughly just to the left of the blown up version, which was lost in resizing).

Is it noise? Or is it likely to be something on the lens, or something on the sensor?

Image details were 5 second shutter, ISO 100.

[h0ughy]

Oh dear LOL here, you have found Strikers long lost blue dot. You will find that it could be the internal reflection of the very bright moon, other than that it is a hot pixel. take another shot with the lens cap on

[[1ponders]]

Definately take a dark shot Simon at the same time and ISO (preferably at the same temp). Looks like hot pixels. Here's a couple of comparisons

[Thiink]

Ok well I did the lens cap on test, the dot appears in them as well (theres actually two of them!). Happens with or without the UV filter in place. It even happens in lowish light at 1 second shutter.

Is there anything I can do? Its going to be a pain in the (you know what) for lightning shots etc if its there.

Paul: did that come from your 300D?

[[1ponders]]

Yes they are Simon from a 5 min ISO800 shot. You will always get them. It's just part of digital photography. During "normal" photography you won't notice them as much as your images will have lots of different colours and low contrast objects and usually much shorter exposures. But for shots with a lot of black in, it will make the "coloured" pixels more obvious (higher contrast). The down side is that you will see more as you increase your exposure time and as temperature goes up.

[Thiink]

Interesting, I dont know how I havent come across it yet. Ive taken some night time/low light exposures longer than 1s.

They disappear when resampling/resizing so they arent that big of an issue. Thanks to the both of you. :)

[[1ponders]]

There is a couple of options Simon, here's three to think about. If you're doing astrophotography then definately subtracting "darks" are the way to go. If your doing short exposure lightening shots then photoshops clone tool will fix the job fantastically. Or you can do darks for them as well if your really keen, and subtract them in PS. But as you said if you resample and resize them you may loose them anyway.

[Thiink]

Well I just went back into all my day time photos, and sure enough at the same pixel point (around 2312,922) the pixel is there and its blue! When looking at my lens capped image there are three all up across the whole image, but only the main one shows up/is visible all the time.

I have contacted the Canon service center in Sydney to see if anything can be done. I was given a reference number, call can be expected Monday. Its not really an issue, just annoying really! Maybe I am expecting too much.