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Marko

Sun Sept 24 2006, 03:51PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

Meh. What lightning pics could I get if I could expose for 5 minutes..

Guess it needs to be shorter, maybe 1min max, to get good pics.

HV Enthusiast

Sun Sept 24 2006, 07:24PM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068

TDU,

Cool. See, your camera is just fine. For star trails, the easiest way is just the same as with sparks. Limit your exposure to about five minutes, assuming you don't overexpose the sky, and repeat this for about an hour or two. Limit time between exposures to about 5-10 seconds.

Now take all the exposures, and combine them in photoshop using the LIGHTEN blend method. This keeps the background the same intensity as a single exposure, yet stacks the star trails on top of each other.

Here is about an 1.5 hours of exposure from my place in Ocean City, MD. The sky is pretty bright here, so its not too spectacular.

Also, the best shots for star trails are centered around one of the poles (south in your case), so you get nice concentric rings.

Steve Conner

Sun Sept 24 2006, 09:01PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Wow, that's pretty neat! What is the long streak at the horizon, is it lights on a boat or something?

HV Enthusiast

Sun Sept 24 2006, 09:41PM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068

The streak is a boat. This was a quickie, so i didn't correct it. To correct it, i would simply make another layer (blend NORMAL) and erase that light using the eraser tool.

Tesladownunder

Sun Sept 24 2006, 11:58PM

Registered Member #10 Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424

EastVoltResea wrote ...

... Limit your exposure to about five minutes, assuming you don't overexpose the sky, and repeat this for about an hour or two. Limit time between exposures to about 5-10 seconds.

Now take all the exposures, and combine them in photoshop using the LIGHTEN blend method. This keeps the background the same intensity as a single exposure, yet stacks the star trails on top of each other...

My camera takes at least 5 minutes to compute the noise reduction after a 5 min shot. Should I not be using the noise reduction?

As to Photoshop, I have resisted getting it so far. My distorted logic is that I can't "cheat" with my photos if I don't have it. I guess I will have to get over that.

Peter

HV Enthusiast

Mon Sept 25 2006, 01:03AM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068

wrote ...

My camera takes at least 5 minutes to compute the noise reduction after a 5 min shot. Should I not be using the noise reduction?

I never use the in-camera noise reduction. You probably don't need it. Its basically only for getting rid of non-random noise such as hot pixels etc...

wrote ...

As to Photoshop, I have resisted getting it so far. My distorted logic is that I can't "cheat" with my photos if I don't have it. I guess I will have to get over that.

Yes, your logic is definitely distorted. Using photoshop to post-process images is NOT cheating and the techniques you would be using would really be no different than if you were in an actual darkroom manipulating negatives and film. Of course, if you cut an image from the Hubble Space Telescope and plopped it into your image, that would be cheating, but standard processing techniques such as sharpening, noise reduction, levels, curves, etc... are basically the equivalent of similar techniques used on real film in the darkroom.

Dan

BTW, here is another Milkyway image I took this past week.

The following link is for an original sized JPG image (WARNING - BIG FILE)
http://www.danielmccauley.com/milkywayroad01.jpg

Enjoy!
Dan

Bjørn

Mon Sept 25 2006, 04:10AM

Registered Member #27 Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058

My camera takes at least 5 minutes to compute the noise reduction after a 5 min shot. Should I not be using the noise reduction?

The camera takes another 5 minute exposure with the shutter closed and subtracts in from the first image. If you don't do that in camera you have to do it manually because there are some issues with noise and CCD heating. If you do it manually you can just keep a few dark frames on your PC as long as the temperature and exposure length are about the same.

As to Photoshop, I have resisted getting it so far. My distorted logic is that I can't "cheat" with my photos if I don't have it. I guess I will have to get over that.

Since you are thinking that you are not likely to be tempted to cheat. The camera uses processing that is based on an algorithm created in a dark basement in Tokyo, since it is just a computer program it does not understand the image and will sometimes do it completely wrong. Correcting those mistakes are never cheating.

I always have my camera set to take JPEG+RAW, that way I can use the JPEG files for normal use and when the white balance turn out wrong or the JPEG file does not have the dynamic range required I load the RAW file and adjust that. The RAW file contains a lot more information both in colours and in details.

Steve Conner

Mon Sept 25 2006, 02:00PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Photoshop rules, TDU! The way I think of it is this: If you shoot JPGs with your digital camera, it's like shooting slide film with an old-fashioned film camera. The dynamic range is quite limited, and the camera does its best to fit the scene into that range, like BjÃ¸rn explained.

If you shoot RAW, it's like negative film: it captures more detail than can be shown on a print. (often 12 bits per colour, whereas JPEG files can only store 8.) You can then use Photoshop to "print" your "negative" to a JPEG file (or to a printer) using all the same fancy tricks, like dodging and burning, that people used to do in "real" darkrooms.

99% of the time I just shoot JPEGs, but at least I know what I'm missing

HV Enthusiast

Mon Sept 25 2006, 02:38PM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068

Sort of. Regardless of the ISO, RAW or JPG mode, the camera always captures the exact same information at the sensor. Changes in ISO does not affect the sensitivity of the camera and does not change the amount of information recorded by the camera. Also, whether you are in RAW or JPG mode, the camera still captures the same information. However, in JPG mode, the camera's processor will automatically stretch the information as captured by the sensor to match that of the sensitivity of film. So in actuality, shooting JPG is more closer to that of negative film than RAW mode. In RAW mode, you basically get out exactly what the sensor records.

For most photos, JPG is absolutely fine as most of the information is distributed across the histogram, centered about the middle. However, when the processor stretches this data, data recorded at the extremes (highlights, and shadows) is usually tossed away. Again, with normal daytime photos, this information really isn't revelevant anyways.

However, with astronomical images, or even spark images, there is a lot of information which is recorded at the left end of the histogram (black) which is important to the photographer where JPG mode will simply throw this info away (due to the auto stretching by the processor). With RAW mode, this information is saved, and by manually stretching the histogram using photoshop for example, you can redistribute this important data over a large portion of the histogram which can then be readily seen by the eye.

For regular photography, this is most important for shadow recovery or highlight recovery. For astrophotography, this means tweaking out every bit of detail from very dim nebula for example.

Noelle

Fri Oct 06 2006, 10:38PM

Napoleonic Powermonger
Registered Member #2 Joined: Thu Jan 26 2006, 05:10AM
Location: Meadville, PA
Posts: 70

Holy cow, those are some amazing pics, EVR. What sort of camera do you use?

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