[LRflex] Re: Thunderstorm last night
- From: "Aram Langhans" <leica_r8@xxxxxxxxxxx>
- To: <leicareflex@xxxxxxxxxxxxx>
- Date: Sat, 1 Aug 2009 06:42:48 -0700
Thanks Richard. I found the setting and have disabled it. I was in Zion a few
falls ago and was experimenting with moonlight and star trails and was waiting
15 minutes for the camera to "recover". I knew about the dark frame thing, but
it just never sunk in as to what it was doing. Same thing two nights ago. It
finally clicked. Waiting for another thunder storm....
Aram
From: Richard Ward
Sent: Friday, July 31, 2009 11:37 PM
To: leicareflex@xxxxxxxxxxxxx
Subject: [LRflex] Re: Thunderstorm last night
Hi Aram!
Great and Very Dangerous Photograph! Mega Kudo's. I would like to now point
you toward the topic of "Dark Frame Image Subtraction". This is what is almost
certainly what was slowing your image writes down so much. Canon offers what
they call "Long Exposure Noise Reduction" and it is (in my experience) easily
turned off in your cameras custom function settings. What the 'Noise Reduction"
is trying to do is prevent an occasional issue digital images sensors have when
the shutter speeds increase where pixels get stuck on or give a repeated false
signal and 'muck' up a photographer's image. What happens is, in your case, for
every 5 second of 'image' you shot, the camera took a 5 second image with the
shutter closed, and subtracts any pixels that aren't black from the 'real' 5
second image you shot. This computer processing takes a bit and add in the
'write' time to record the final image and Voila! your 5 second shot has become
a 10-15sec wait before you can shoot again.
I usually turn it Long Exposure Noise Reduction off in the custom functions
area of my 20D. I prefer the extra responsiveness it gives, but it does add to
my post production work. I was experimenting with multi minute star trails
landscapes and I;d be standing there freezing in the dark waiting forever for
the blinking to stop!
You might want to see if your version of Canon Software includes a way to
'automatically' do this during downloads or raw processing. I've heard current
Adobe Lightroom products can do this as well, but haven't ever encountered it
personally and can't comment on it's effectiveness (same for the canon
software).
Richard
________________________________
Life is hard...but I just take it one photograph at a time.
~•~
"You miss 100% of the shots you never take" Wayne Gretzky
~•~
In a world without walls and fences, who needs Windows or Gates?
~•~
It's okay to be stupid. Just don't be gung-ho about it.
________________________________
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From: Aram Langhans <leica_r8@xxxxxxxxxxx>
To: leicareflex@xxxxxxxxxxxxx
Sent: Friday, July 31, 2009 3:31:26 PM
Subject: [LRflex] Thunderstorm last night
We had a small thunderstorm roll through at dusk yesterday. I have never seen
lightning at this time of the day, where there was still some color in the sky
and clouds, so I thought I'd give it a try. I shot 50 frames and only caught
lightning on two of them. Had the camera (Rebel XTi) set on sequential
exposure, and the shutter at 5 or 8 seconds, and the cable release clicked on
so I did not have to stand there. It would fire one shot, then write it to
disk then fire the next shot. Last time I did this was with my R8 and motor
winder and it worked well. Problem with the digital Rebel is that after each 5
second exposure it took about 10 seconds to write the info to the card before
it took the next shot. So, I missed about 66% of the time. And, every time I
saw a great bolt, I looked over to the camera and it was still writing the
previous exposure. Drats. Maybe a 50 D would write faster? I think it has
something to do with the null exposure when using long shutter speeds. Maybe I
could turn that off if I looked at the manual.
did catch this one, however.
http://gallery.leica-users.org/v/Aram/misc/-7.jpg.html
comments and criticism welcome.
Aram
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