PDA

View Full Version : Pixel question? (long drawn out, boring question).....



builder24car
12-11-2009, 06:48 AM
I hope I can ask this where it makes sense? I was shooting a church and graveyard last night. When I got the pics on my computer I thought to myself I don't remember any green and red stars in the sky? Then I noticed they were in the exact same spot in every pic. Then it hit me that it was pixels I was seeing. *slaps forehead* :o Is this just a nighttime thing and something I should be concerned about? Best I remember I was shooting at an ISO of 400. I honestly can't remember the F number and shutter speed. All I know is I was freezing and getting pissed off about what seemed like a non stop stream of cars coming by that I had to wait on. I shoot with an Olympus E-500 and that's why I was wanting to ask the Olympus people. :)

jekostas
12-11-2009, 11:43 AM
Yeah, what's happening is that the sensor is heating up because of the long exposure and causing those "spots" to appear. It's quite normal, it happens to all digital cameras, and the bigger the sensor, the worse the problem (heat increases geometrically compared to size).

What you want to do is when you do long exposures (over 5 seconds or so) is turn on the camera option called "Noise Reduction", should be in the first menu. What it does is take a second exposure right after the first with the shutter closed, and compares the two pictures. Any weird lights present in the second picture are automatically removed from the first. It'll double your exposure times (because you're taking the picture twice), but will also save you the time of cloning out the spots in post-processing.

This is a pretty common technique used in astrophotography, called "dark frame subtraction".

If that doesn't work, try pixel mapping again.

builder24car
12-12-2009, 09:45 AM
Thanks jekostas, I appreciate that! I do have my camera set in noise reduction. I've never tried pixel mapping so that's something I'll need to look into I guess. I'll try some other settings as well using a faster shutter speed, etc. :)

TheWengler
12-12-2009, 10:11 AM
I wouldn't worry about it. Use whatever SS you need. I think the default chroma noise reduction setting from Adobe's RAW editor gets rid of those hot pixels anyway.

raven15
12-12-2009, 07:20 PM
Thanks jekostas, I appreciate that! I do have my camera set in noise reduction. I've never tried pixel mapping so that's something I'll need to look into I guess. I'll try some other settings as well using a faster shutter speed, etc. :)
You've never tried pixel mapping? Give it a shot first. I run it on my cameras every few months, or if I see a dead pixel :rolleyes:.



I wouldn't worry about it. Use whatever SS you need. I think the default chroma noise reduction setting from Adobe's RAW editor gets rid of those hot pixels anyway.
Adobe's editor would fix it, except builder24car doesn't have any Adobe products ;).

builder24car
12-12-2009, 09:18 PM
I think tomorrow is going to be a rainy day, so I'll look into that pixel mapping stuff Raven. I always get nervous and worry I might mess something up when doing stuff like that.



except builder24car doesn't have any Adobe products


Like Raven said Lukas, I don't have any Adobe products. For that matter I don't have ANY post processing software. That might be a good thing because if I did I'd never get anything done for messing with pics, etc.

jekostas
12-13-2009, 12:04 AM
I think tomorrow is going to be a rainy day, so I'll look into that pixel mapping stuff Raven. I always get nervous and worry I might mess something up when doing stuff like that..

I swear, it's really, really easy. Pretty well impossible to screw up. Just open up your menu, go to the last list of options, press Pixel Mapping, and "Start". Let it run until status bar finishes and the menu comes back up, you're done. That's it. Takes like, 15 seconds, maybe.

Edit: Okay, just timed it on my E-510 - 12 seconds.

raven15
12-13-2009, 02:59 AM
Yeah, pixel mapping is completely automated and impossible to screw up. No worries there.

I'm almost wondering if my E-410 has a defective sensor, I must have mapped out 50 pixels so far. Only have a little over 10 million left!

builder24car
12-13-2009, 07:59 PM
Ya'll were right, the pixel mapping was a piece of cake and I was worried about nothing. Course now if it would ever stop raining so I can get out at night. :(

TheWengler
12-13-2009, 11:52 PM
Adobe's editor would fix it, except builder24car doesn't have any Adobe products ;).

Oh ok, I'll make a note of it in my book of who has what :p


Like Raven said Lukas, I don't have any Adobe products. For that matter I don't have ANY post processing software. That might be a good thing because if I did I'd never get anything done for messing with pics, etc.

How do you get by w/ no post processing software? It's a pretty big part of digital photography.

builder24car
12-14-2009, 11:54 AM
How do you get by w/ no post processing software? It's a pretty big part of digital photography.


I haven't been into photography long Lukas. I really don't know that much about it. I read and lurk a lot hoping to find answers to my questions. The only post processing I do/have done is cropping, some shading, etc, nothing major. Just doing that little bit made me realize I don't like post processing very much at all. I try and get the shot close to right when I take it so I don't have to mess with it after I upload it. That's why if I take a 100 pics, I might delete 98 of them. I'm learning by reading, listening, and by practice. When people are talking about post processing software it's all greek to me. Not to mention that stuff costs money. That's how I get by for now...............

jekostas
12-14-2009, 01:52 PM
Well, if that's the case post-processing will probably be the next big frontier for you. There are some decent free software packages around that you can mess with, a few of them are pretty powerful as well.
The ones I've tried are:

Photoscape (www.photoscape.org, very good)
Paint.net
GIMP (if you feel like doing some deeper level editing).

Picasa is a good starter program, but it does have that very annoying feature of wanting to catalogue your entire hard drive whenever you start it up, though.

builder24car
12-14-2009, 09:06 PM
Thanks jekostas, I'll look into the Photoscape. I'll need to start out slow. I've had my feel of Picasa. Never again as I've said before, it found EVERY pic I had on my puter and that was not good! :eek:

pip22
12-15-2009, 02:10 PM
You can also process raw shots with Olympus Master which comes with the camera, though it's relatively slow when you make adjustments. It won't scan your PC for images either, which will be good news to you. It just has a folder pane on the left side which you navigate yourself to find your pictures folder. You might want to give it a try.

The great thing about shooting raw is it gives you a "second chance" if somehow you got the exposure wrong or if there's excess noise in the picture. Both these are almost impossible to correct if it's a jpeg file in a regular photo-editor.

builder24car
12-15-2009, 06:43 PM
Thanks pip22! I have messed with my Olympus software, though not much at all. I tried downloading that photoscape and it wouldn't do it for me. Norton even said one of the downloads had several viruses?