| Author | Thread |
|
|
12/08/2006 12:10:34 AM · #1 |
| I can't wait to see some really great astronomy shots! |
|
|
|
12/08/2006 12:14:28 AM · #2 |
| Oh great... first experts challenge and I happen to live in one of the most poluted cities in the world... |
|
|
|
12/08/2006 12:22:54 AM · #3 |
Originally posted by Gaby_G:
Oh great... first experts challenge and I happen to live in one of the most poluted cities in the world... |
Certainly that can be used to your advantage, don't you think. Sunsets/sunrises must be rather interesting around there. |
|
|
|
12/08/2006 12:23:07 AM · #4 |
Originally posted by Gaby_G:
Oh great... first experts challenge and I happen to live in one of the most poluted cities in the world... |
Just keep breathing it - it seems to agree with you judging by your self-portraits.
;) |
|
|
|
12/08/2006 12:28:11 AM · #5 |
Originally posted by BradP:
Originally posted by Gaby_G:
Oh great... first experts challenge and I happen to live in one of the most poluted cities in the world... |
Just keep breathing it - it seems to agree with you judging by your self-portraits.
;) |
Jajaja was that good or bad? |
|
|
|
12/08/2006 12:28:58 AM · #6 |
Seems like an odd subject to use the expert rules for. I guess prepare for a lot of oversized moons and heavy use of the flood filter.
Message edited by author 2006-12-08 00:30:02. |
|
|
|
12/08/2006 12:29:01 AM · #7 |
Originally posted by Gaby_G:
Originally posted by BradP:
Originally posted by Gaby_G:
Oh great... first experts challenge and I happen to live in one of the most poluted cities in the world... |
Just keep breathing it - it seems to agree with you judging by your self-portraits.
;) |
Jajaja was that good or bad? |
That was a compliment. |
|
|
|
12/08/2006 12:35:09 AM · #8 |
Originally posted by yanko:
Seems like an odd subject to use the expert rules for. I guess prepare for a lot of oversized moons and heavy use of the flood filter. |
agreed
|
|
|
|
12/08/2006 12:37:08 AM · #9 |
Originally posted by jdannels:
Originally posted by yanko:
Seems like an odd subject to use the expert rules for. I guess prepare for a lot of oversized moons and heavy use of the flood filter. |
agreed |
Multiple exposures opens up a lot though. Night or Day, it's hard to get the sun/moon in good detail without sacrificing foreground and vice versa. Could be cool. Could be some nice HDR without the comic book processing effect. |
|
|
|
12/08/2006 12:42:21 AM · #10 |
I think I'll sit this one out and see what people come up with before I consider entering the next one. I don't see a grunge-textured sky being terribly interesting.
|
|
|
|
12/08/2006 12:49:25 AM · #11 |
Originally posted by routerguy666:
Originally posted by jdannels:
Originally posted by yanko:
Seems like an odd subject to use the expert rules for. I guess prepare for a lot of oversized moons and heavy use of the flood filter. |
agreed |
Multiple exposures opens up a lot though. Night or Day, it's hard to get the sun/moon in good detail without sacrificing foreground and vice versa. Could be cool. Could be some nice HDR without the comic book processing effect. |
That's true. |
|
|
|
12/08/2006 03:20:09 AM · #12 |
Oh, sure, NOW we get a sky challenge....
It is slightly tone-mapped, but from a single image. |
|
|
|
12/08/2006 05:13:46 AM · #13 |
Originally posted by yanko:
Seems like an odd subject to use the expert rules for. I guess prepare for a lot of oversized moons and heavy use of the flood filter. |
I don't know, I would expect anything obvious to be voted down as having lost its photographic-ness. But that would, of course, not include the images done well.
In addition to the non-comic HDR, I expect a lot of stacking to remove noise. It's a standard technique for astronomical photography, but works with any scene ... and can be combined with HDR for even more drasticly stunning results.
I think they chose a good subject for a first run. The sky is definitely one of the harder things to include in any 'interestingly' lit scene.
David |
|
|
|
12/08/2006 06:18:23 AM · #14 |
Originally posted by David.C:
In addition to the non-comic HDR, I expect a lot of stacking to remove noise. It's a standard technique for astronomical photography, but works with any scene ... and can be combined with HDR for even more drasticly stunning results.
David |
David, or anyone really, if it isn't too involved, could you explain the stacking for me please? I'm fairly new to this and haven't heard this before. Many thanks
Nick |
|
|
|
12/08/2006 06:23:29 AM · #15 |
| Yay! I just started my christmast vacation, I have nothing to do for 5 weeks than to take photos and work on a new webpage :) |
|
|
|
12/08/2006 07:14:52 AM · #16 |
Originally posted by nixter:
Originally posted by David.C:
In addition to the non-comic HDR, I expect a lot of stacking to remove noise. It's a standard technique for astronomical photography, but works with any scene ... and can be combined with HDR for even more drasticly stunning results.
David |
David, or anyone really, if it isn't too involved, could you explain the stacking for me please? I'm fairly new to this and haven't heard this before. Many thanks
Nick |
The technique is easy enough to understand. Think of an image as being made up of signal (what you want to keep) and noise (what you want to get rid of). The idea of noise reduction is to increase the signal to noise ratio (s/n). To do this the signal is increased, the noise is reduced or both.
Image stacking works because when two exposures are stacked (layered on top of each other in PS) the constant objects present in both exposures (usually signal) while the random noise is likely only in one exposure at any given pixel. This causes the signal to be averaged against signal, which enhances it -- and at the same time the noise is averaged against signal as well, causing the value of the pixel to move halfway betweeen signal and noise (toward signal!).
With just two exposures there is a fair chance, depending on noise level, of averaging noise with noise -- but this chance decreases with each additional exposure stacked. Also, with more than one exposure stacked, the averaging moves further toward signal (since it is always present).
A quick web search for 'stacking exposures' will turn up much more detailed explainations as well as examples of the noise reduction that can be accomplished.
David |
|
|
|
12/08/2006 07:23:13 AM · #17 |
Originally posted by yanko:
Seems like an odd subject to use the expert rules for. I guess prepare for a lot of oversized moons and heavy use of the flood filter. |
Think astrophotography (often done by overlaying many originals in order to reduce noise). It also opens up HDR/bracketing techniques for landscapes. Time lapse is an option as well.
~Terry
Message edited by author 2006-12-08 07:24:44.
|
|
|
|
12/08/2006 07:28:54 AM · #18 |
could someone please tell me if it's allowed to combine *parts* of other photos? not the whole pictures, but cut some parts of them?
thank you! |
|
|
|
12/08/2006 07:30:19 AM · #19 |
Thanks David that helps me understand how it works, one thing I'm not sure on though, are we talking several separate exposures? and what happens once in PS and layered do you use a blending mode or something?
Sorry for all the questions, thanks again. |
|
|
|
12/08/2006 07:37:24 AM · #20 |
Originally posted by silverfoxx:
could someone please tell me if it's allowed to combine *parts* of other photos? not the whole pictures, but cut some parts of them?
thank you! |
Yes, it is. Remember, though, that if your final image does not look like a photograph, voters are likely to vote it down.
~Terry
|
|
|
|
12/08/2006 07:44:51 AM · #21 |
Originally posted by nixter:
Thanks David that helps me understand how it works, one thing I'm not sure on though, are we talking several separate exposures? and what happens once in PS and layered do you use a blending mode or something?
Sorry for all the questions, thanks again. |
It's okay, I eventually found what I was looking for, it's a very simple technique.
For anyone else interested, this is what I found:
Here's how you'd stack: Say you have 10 shots of a night scene. Pull up the first image as the base layer, then add the second at 50% opacity, the third at 33% opacity, fourth at 25%, etc.. In other words, 1/2 of the second, 1/3 of the third and so on. They must be of the same exposure meaning you don't stack images from different camera settings. At some point you'll reach diminishing returns which from my experience is around 8 images (we're talking common photography) - the next increment would be 16 images to gain an additional 3dB noise reduction.
Nick |
|
|
|
12/08/2006 07:45:19 AM · #22 |
Originally posted by nixter:
Thanks David that helps me understand how it works, one thing I'm not sure on though, are we talking several separate exposures? and what happens once in PS and layered do you use a blending mode or something?
Sorry for all the questions, thanks again. |
The practical side, in a nutshell:
- Take several exposures
- Open the first in PS
- Open the second, place on a layer above the first, and set the opacity to 50%
- Tweak the registration so it is aligned with the first image
- Repeat this process with subsequent images, turning visibility off for all but the first and current images.
- Now everything is aligned. Turn all the layers back on, and set layer opacity as follows (Layer 1 is at bottom:
Layer 1, 100% (1/1)
Layer 2, 50% (1/2)
Layer 3, 33% (1/3)
Layer 4: 25% (1/4)
And so on. For each four images stacked, random noise is reduced to 50% of its original value. |
|
|
|
12/08/2006 07:47:23 AM · #23 |
|
|
|
12/08/2006 08:22:58 AM · #24 |
Originally posted by kirbic:
... For each four images stacked, random noise is reduced to 50% of its original value. |
?!? -- I thought it was for every doubling of the number of exposures the noise is reduced by 50%. I probably thought wrong though. :(
David |
|
|
|
12/08/2006 08:27:22 AM · #25 |
I think I will sit out as well. I hope everybody that participates will put their steps in their comments section. I am not ready for expert editing, but I am anxious to see what those who are experts come up with. But I also want to see some information on the photos. Good luck to the first virgins who participate in this challenge.
Message edited by author 2006-12-08 08:27:55. |
|
Home -
Challenges -
Community -
League -
Photos -
Cameras -
Lenses -
Learn -
Prints! -
Help -
Terms of Use -
Privacy -
Top ^
DPChallenge, and website content and design, Copyright © 2001-2024 Challenging Technologies, LLC.
All digital photo copyrights belong to the photographers and may not be used without permission.
Current Server Time: 04/25/2024 01:26:24 AM EDT.
