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Archive 2013 · Night/Star Photography - A Question
  
 
Lisa_Holloway
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p.1 #1 · Night/Star Photography - A Question


So I'm a portrait photographer but dabbling in landscapes, and have an image in my head that includes a silhouette of some saguaro cacti with some of the last colors of the sunsets, with the stars above. I am assuming a photo like this would only be possible by blending 2 different exposures? One with the sunset/silhouette, and the other of the stars? Is there a special way these 2 photos are combined in Photoshop? My husband and I are going to take a drive to a nice dark area tonight and want to test this out. I've got my wide angle, a tripod and remote, and am excited to try something new. I'd really appreciate any tips or tutorial links you guys might have! Thank you!


Feb 16, 2013 at 06:08 PM
Tuan Le
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p.1 #2 · Night/Star Photography - A Question


Lisa,

You'll want to take at look the excellent tutorial that Floris has put together. He's posted here on FM before but you can also find it here:

http://www.naturephotographers.net/articles0509/fv0509-1.html

Good luck!



Feb 16, 2013 at 06:44 PM
JimFox
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p.1 #3 · Night/Star Photography - A Question


Hey Lisa,

That sounds like a fun little project. Yeah, the sunset colors will be gone before the stars appear. What you are asking is actually pretty easy and would just require a pretty simple layer mask. It just depends on how high the Saguaro is in the scene as to how difficult it might be to blend, but if you are letting it silhouette, then that will help too.

So, if possible once you find your sagauro cactus and get your sunset shot, ideally, you would leave the camera in tact in that spot, don't move or touch a thing, especially the focus, as getting the shot focused at night is actually one of the hardest parts, and where those new to shooting stars mess up the most in my experience.

Okay, so you shoot the sunset... don't move the camera, what I would do then is after the sunset fades, keep shooting occassionally, especially as twilight fades.. As I am thinking this through (and it depends on what cloud coverage you have) you would want to blend above the color of the sunset, where the sky is turning blue again, and then with the stars. The closer you shoot the stars towards sunset, rather then say at midnight, the WB of your camera will more easily keep the sky a blue... which will make it easier to blend...

For your star shots, not sure what experience you have with that. If you just keep taking the occassional shot after the sunset you will keep adjusting your exposure. First key really, well you can try it different ways, but if you want your stars still, don't let your shutter exceed 30 seconds. So as the sun fades, I would keep increasing the length of the exposure to about 20 seconds or so, at that point I would start opening up the fstop until you got down to about f8, at that point then start increasing the ISO until you get to about ISO 1600. Don't trust your LCD anymore, the shots will appear okay but will be too dark as the LCD in the dark will make underexposed shots look okay. For stars, make sure your histogram is showing about 2 stops underexposed, that will work. Again, trust the histogram, not the LCD screen at this point.

So depending on how long you will be staying to shoot the stars, when the sky is pretty dark, my ending settings on shooting the stars is usually around f4, ISO 3200 and a 30 sec shutter. For fun... when you are done, before you move the camera... try a star trail shot or two... You can drop the ISO to ISO 400, go to f5.6 and then do a 5 minute exposure, and then maybe try a 10 minute if you are adventurous... but that's up to you. The simplest is the sharp stars with keeping the exposure under 30 secs like I described.

Now back at the ranch... Convert your raw images. Then open up both images in PS.

1. While Holding down the shift key, drag the Sunset shot on top of the star shot. (Holding the shift key will auto center the layer on top of the background)
2. Use the Lasso around select the top of the sky down just into the sunset area.
(Make sure you are on the top layer)
3. Go to the Select Menu, choose Refine Edge.
4. Adjust the Feathering. You might have to try this step once or twice to get the right feather amount, but start at 250 for a feather amount.
5. Hold down the ALT key and click on the Make Layer icon in the Layers adjust panel. It will be a small rectangle with a circle in the middle.
6. This will automatically generate a layer mask from your Lasso selection, allowing the star part of the sky to come through.

And there you go... that's it basically... you might after seeing the look, decided what you selected with the lasso should be more or less... so just undo the couple of last steps and reselect, etc... if the Saguaro is pointing up high into your photo, you can go back with the paint brush and with the color white, click on your Layer Mask screen in the Layers Adjust window, and then paint some of it away, etc...

I hope that helps... And I am pretty sure you have a good handle on PS from seeing your other work, but I still wanted to go through the PS steps with the Layer Mask just in case.

Have fun,

Jim



Feb 16, 2013 at 07:12 PM
voltaire
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p.1 #4 · Night/Star Photography - A Question


Hi Lisa,
I've tried a hand at night photography and this is what I've learned so far. To answer your question, you'll probably need two shots, combine and blend somehow or you can shoot the stars and light paint your foreground but it won't have the sunset silhouette.

It'll be awhile before the stars come out after sunset and given that its the waxing gibbous, your best bet to get bright stars is after midnight tonight which is when moonset happens. Your experience in a dark sky might be different. Whatever it is I recommend shooting a dark frame which is the equivalent exposure of your star exposure with the lens cap on. It will eliminate unwanted leaks and noise in your star exposure.

To correctly expose without star trails start with a base of ISO 1600, f2.8 and 30 second exposure. Anything beyond that you'll begin to have star streaks.

To expose beyond 30 seconds you'll need another equipment that will help track the earth's rotation such and the Vixen Polarie or an equatorial mount.

If you want to shoot star trails, I think Tuan's link explains it already.

Have fun and wishing you clear skies tonight. Hope this helps.






Feb 16, 2013 at 07:16 PM
 

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Lisa_Holloway
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p.1 #5 · Night/Star Photography - A Question


You guys are awesome, thank you SO much for taking the time to explain this to me. It makes a lot of sense and I'm excited to give it a try. We have a lot of really dark areas around and I'm good to camp out there for a while until it is really dark. This will be fun! Thank you again!! =)


Feb 16, 2013 at 07:25 PM
ramdisk
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p.1 #6 · Night/Star Photography - A Question


Thanks Jim for the brush up


Feb 17, 2013 at 01:59 PM
astro-ep
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p.1 #7 · Night/Star Photography - A Question


Great Overview Jim, Thanks. I learned a few things...

Lisa, Just to add a little more complexity with a nit-picky detail... The longer the exposures (and usually the higher the ISO), the more you'll end-up with "Hot Pixels". Depending on the sensor, and the outside air temperature, there can be a lot of them that will need manual removal. However, depending on how large you view, crop or print, they may not even be visible.

But if they are, and you don't want to manually remove them, you might also want to take a few "Darks". This is an astrophotography calibration process. Take the darks at as close to the same time as the regular shots (so the temperature matches). They should be the same length as the regular long exposure (ie. 20 second light frame, then shoot 20 second Dark frame), and at the same ISO. This is done simply by covering the lens (or entire camera) so that it sees no light and shooting the frame. To use them, place them a different layer in the stack, and subtract from the light frame(s). I've only done this a few times on a mixed landscape/star shot. But it helped quite a bit. You can add a layer mask to limit the areas, if it makes things worse on parts of the frame. Just remember that wherever there was a colored hot pixel, will now be black. So it works better in the darker areas of the frame. But can be a real time saver, if you happen to have a noisy sensor or longer exposures.

This is a technique that I use faithfully for each and every astrophoto that I shoot. Since a typical astro photo can take 20-30 hours of open shutter time, I spend a lot of time making sure that all the little details are cleaned-up. As we all know, its all the little details that come through in the final shot.

...my 2 cents-worth.

Eric




Feb 18, 2013 at 05:14 PM
dgdg
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p.1 #8 · Night/Star Photography - A Question


I found in lightroom, the hot pixels are removed automatically somehow. I literally see them disappear when I load the image. Since it just worked, I never bothered to figure out more about it.
For all the noise in the dark sky, the adding of "darks" is a huge plus. I don't do 20-30 hour photos, but have been out for a couple hours and find that even 4-6 "lights" with an equal amount of darks can dramatically improve an image compared to single night sky shot. If you are doing a landscape, you would need to add your land image over top of the stacked sky image. This adds complexity compared to a single shot, but is rewarding. I found the vixen polarie to be a lot of fun allowing those "lights" to be shot at 800 iso over several minutes even further reducing noise. This adds complexity again as you need accurate polar alignment. After I've done it once on a trip, on the other nights it only takes about 30 minutes to polar align (from opening my pack to verifying the test image). I wish I could get out more often even if I do just sky shots (no great landscapes present), but whenever my local astronomy group meets nearby it winds up being cloudy. These people with the big scopes are very nice and help me keep from being mugged.



Feb 19, 2013 at 02:16 PM





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