Maximum Bulb time

[tkerr]

H





What I was planning is :


( not sure if this is the correct english )


Make a picture of the night sky, were you will see the stars form a line ( half of a circle )


( Was thinking of starting with an exposure time of 15 minutes, not sure if this will be long enough though ? )

That's called Star Trails. You can do it with long exposure, use ISO 100 with the largest aperture for your lens and let it go for as long as you want.
(1 Hour = 15° of arc.)
However, you can also do it with Shorter exposures as well. Something along the lines of just 2 to 4 minutes is plenty with a very short interval between each, and then you stack them all together..


If you have Photoshop you can load all your shots into Layers and change the blending mode for each to lighten. Or Select all the layers and convert to Smart Object. (Layer > Smart Objects > Convert to Smart Object)
Then you use Maximum Stacking Mode (Layer > Smart Objects > Stack Mode > Maximum)

Or you can download a application for making star trails using multiple exposures that is called Startrails. http://www.startrails.de/

[freelanceshots]

Good information tkerr on the brief photoshop how to. What other kind of shots is stacking good for?

[BelGer]

.


I have used "some kind"of stacking with this picture.


Although I did it a bit more time consuming :-) ( since this was one of my first experiments with Photoshop )


What I did was take all the shots into photoshop, Took 1 picture as the basis, and then "cloned" parts of the other picture in this "Base" picture. This is of course a bit of a puzzle.


I also have made something like this of a man who is attacked by a German Sheperd. ( not sure what the correct English is ) in Dutch it is called "Pakwerk" Maybe a Dutch reader can help me with this ? Anyway, it is not attacked in a bad way, but this was for police dog training :-)

[tkerr]

.


I have used "some kind"of stacking with this picture.


Although I did it a bit more time consuming :-) ( since this was one of my first experiments with Photoshop )


What I did was take all the shots into photoshop, Took 1 picture as the basis, and then "cloned" parts of the other picture in this "Base" picture. This is of course a bit of a puzzle.


I also have made something like this of a man who is attacked by a German Sheperd. ( not sure what the correct English is ) in Dutch it is called "Pakwerk" Maybe a Dutch reader can help me with this ? Anyway, it is not attacked in a bad way, but this was for police dog training :-)

You can achieve the same thing loading all your images into Layers, select all the layers and convert to Smart Object just like I described above. Instead of Maximum Stack Mode you might have to choose Minimum Instead. Saves you from all that cloning.

[freelanceshots]

I have plenty of experience with the multiple images joined into one image to give the effect of progressive movement where I've even gone a step further and done it with a panning image. At first that is what I was kind of considering image stacking to be but when I read on the Internet I learned that its best for photographing the sky at night.


Found this webpage (http://keithwiley.com/astroPhotography/imageStacking.shtml) and it helped me to understand better. Simple right?!?!

[tkerr]

I have plenty of experience with the multiple images joined into one image to give the effect of progressive movement where I've even gone a step further and done it with a panning image. At first that is what I was kind of considering image stacking to be but when I read on the Internet I learned that its best for photographing the sky at night.


Found this webpage (http://keithwiley.com/astroPhotography/imageStacking.shtml) and it helped me to understand better. Simple right?!?!

It's been a while but I am familiar with that web site and the information contained within.
Simple?
Well, If the conditions are right and you have all the right equipment it can be. Capturing all the image data, (Light Frames, Dark Frames, Bias, and Flats) is relatively easy, but time consuming. Then you need the right stacking software! One popular application is Deep Sky Stacker. That makes things easy as far as Calibration and Stacking of everything goes. The hard part comes when you need to process all that stacked image data to bring it to life. Unfortunately just stacking a bunch of shots isn't going to do that for you.

[BelGer]

Hi Tkerr.


Thnx for the tip.


At that time I did not know this was possible, I will try that method again on the same image, maybe I can also see some change in quality.


Again thnx for tips.


( By the way )


Coming back to my first question this post started with :-)


I also have send Canon an email asking the same question about the maximum Bulb time.


They told me that the camera should turn off automatically when it starts to overheat, or when it detects damage may come due to overheating.


Well.... keep my fingers crossed lol :-)


I have planned this weekend a trial of my long exposure project. Hopefully the weather gods are with me :-)


Ger

[tkerr]

Good information tkerr on the brief photoshop how to. What other kind of shots is stacking good for?

It's a common practice for most Astrophotography. Stacking multiple exposures vs a single or only few longer exposures improves the S/R(signal to noise ratio).


Camera: Canon EOS 50D
Exposures: 45x 180 seconds at ISO 800

[Jon Ruyle]

Stacking multiple exposures vs a single or only few longer exposures improves the S/R(signal to noise ratio).

Many people make this claim, but it is not true. There are several good reasons to stack, but improving SNR is not among them.


Photon noise is not affected at all by stacking (ie, 10 one minute exposures stacked or one ten minute exposure will have the same photon noise and same signal, and thus the same photon noise / signal ratio). Read noise is actually worse when you stack.

[tkerr]

I don't care to start an argument about it here, but there are numerous other more experience photographers than I who would. Shooting does increase the s/r but won't remove every kind of noise. For that is the reason you also shoot and use Darks, Bias/offset frames, and Flats for proper stacking and calibration.


This is just one resource, I can supply hundreds more.


http://www.astropix.com/HTML/J_DIGIT/COMPEXP1.HTM





You go ahead and shoot a 10 minute exposure and compare the level of noise to 5 x 2 minute exposures stacked and tell me which has less.