[LRflex] Re: Thunderstorm last night
- From: Richard Ward <ilovaussiesheps@xxxxxxxxx>
- To: leicareflex@xxxxxxxxxxxxx
- Date: Fri, 31 Jul 2009 23:37:13 -0700 (PDT)
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.
________________________________
________________________________
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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