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Re: [OM] Perseid meteor, IFO, light pollution, questions

Subject: Re: [OM] Perseid meteor, IFO, light pollution, questions
From: Chuck Norcutt <chucknorcutt@xxxxxxxxxxxxxxxx>
Date: Sat, 13 Aug 2016 07:16:03 -0400
I have nowhere near the Moose's Photoshop skills but was able to pretty much duplicate his "Different Levels" result in Photoshop by simply pushing the black slider all the way to the left and the highlights slider all the way to the right. Further variations can be accomplished with careful application of the clarity and whites sliders.

I only vaguely understand the use of levels as something other than a way to grossly screw up an image. I understand the use of a graduated mask in step 3 but don't know how to do it. In step 5 I don't understand the use of "select color" to select the dark stuff nor would I have thought of using the result of that as an inverted mask.

I'm traveling at the moment but am saving this little lesson to see if I can figure out how to duplicate it when I get home.

I know about dark noise reduction but have never used it and didn't think about it as the cause of the long post-exposure image processing. But I do know (now that I'm reminded) that a second exposure is required equal to the length of the first, ergo, another 20 seconds before you can use the camera.

Chuck Norcutt


On 8/12/2016 6:04 PM, Moose wrote:
On 8/12/2016 12:00 PM, Lawrence Woods wrote:
. . .  I was in my backyard 14 miles NW of Boston MA, a few hundred
feet from a well-lit main road.
I used a 12-40 f/2.8 m.Zuiko  set to 2.8 and 12mm on an E-M5, original
mark I model.  I had the camera on a tripod, used the 2-second
anti-shock shutter delay, manual exposure mode, and had image
stabilization turned off.  The light pollution was so severe that to
maintain any semblance of a dark sky over a 20 second exposure, I had
to crank the ISO down to 200.

This is an example of what I got:
http://zone-10.com/tope2/main.php?g2_itemId=20573
Lowering the ISO took its toll.  The meteor trail to my eye was
brighter than an ember in a fireworks display.

I also caught an IFO (identified flying object):
http://zone-10.com/tope2/main.php?g2_itemId=20576

These pictures have no post-processing.  I'm probably doing something
wrong, but when I tried to darken the sky, the stars and trails got
dimmer as well.

He did say that post-processing is necessary. Then he says he uses LR,
which is probably why he needs to get so far from urban light and still
has ambient light in his images. (He is not as expert as he might be.
Look at the big halos around the trees in his fisheye example.)

Getting what I think you want is fairly straightforward in PS.
<http://www.moosemystic.net/Gallery/Others/Woods/perseid_2016.htm>

The first three steps are to take care of the light pollution.

- Before doing any of this kind of stuff to a JPEG, convert to 16 bit.

1. Levels to kill the low level light. That also loses the meteorite,
but wait . . .
2. Different use of Levels to bring out the lights in the sky.
3. A graduated mask over 2. Shows the best of both. (See, I don't know
if this is advanced PS. It's darn simple.)
4. Raise Brightness to really bring up the Meteorite. Next step takes
care of background.
5. Use Select Color to select all the dark stuff, invert the selection
and apply as a mask.

Voila! Bright stars and meteorite in a velvet black sky. :-)

It's interesting how spending a lot of $ on hardware and a lot of
time/money on travel to an area with little light pollution all makes
sense, but spending much less on the right post tool and a little time
learning how to use it for the purpose seems like too many $ and too
much trouble. Can't have taken me ten minutes to eliminate the light
pollution and perk up the little lights. Longer to explain and
illustrate what I did, though.

I have a couple of questions about how the E-M5 functioned...

1) Can the Mark I E-M5 display progressive results on the LED screen
during a time exposure?  Page 89 of the manual is not at all clear on
what exactly Live Bulb and Live Time do, and trying Live Bulb didn't
seem to do anything.

No idea. I've never tried that stuff. Live Composite might be what you
are thinking about? That's not on the Mark I. Explained here.
<http://www.creativeislandphoto.com/blog/olympus-live-composites-star-trails>


2) After the shutter closed, it took about 40 blinks of the orange SD
card symbol (~15 seconds?) to write the picture to the card before I
could start the next exposure.  Why did it take so long after a time
exposure?

I imagine that's dark noise correction. After a long exposure, the
camera takes another one with the shutter closed. Noise from that second
exposure is subtracted from the first one. Not only Oly, everybody does
this. You can set it in Adv. Menu G, Noise Reduction.

The night-sky files were actually smaller than normal hand-held
daylight  pictures, running around 5.3 MB, versus 6.4 to 8.4 MB.

Many maker's Raw files are lossless compressed. A night sky shot with
noise subtracted has very little detail in large parts, so it compresses
more.

If you have PS, and would like a full size PSD file, showing exactly
what I did, and allowing you to tune it to your taste, or would like a
full size JPEG of the result, let me know.

Darth Himmel Moose

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