Another good one for night sky is divide 600 by the focal length of the
lens to get the maximum exposure time that makes the stars still look
like dots.
From: Godfrey DiGiorgi
It's a neat trick, I like it.
One addition: I modify the low ISO setting to accommodate a maximum
exposure length of between 2 and 4 minutes. This seems to make the
best images for me, and fits within most of the SLR-class sensors'
maximum exposure length restrictions, for those cameras I own that
have them.
G
On Sun, Dec 9, 2012 at 9:58 AM, Bob W <[email protected]> wrote:
That seems to make sense - 100:6400 = 1:60 as near as dammit
B
-----Original Message-----
From: PDML [mailto:[email protected]] On Behalf Of George Sinos
Sent: 09 December 2012 17:35
To: Pentax-Discuss Mail List
Subject: Long Exposure "Rule of Thumb"
I was listening to one of the many photography podcasts recently and
heard someone mention this estimating technique.
He said he likes to make his night exposures at ISO 100 to minimize
noise, but zeroing in on the exposure time at that low ISO can take a
long time.
So, he makes his initial exposures at ISO 6400. It turns out that the
exposures length in seconds at 6400 is pretty close to the length in
minutes at ISO 100. For example, a 10 second exposure at ISO 6400
would work out to a 10 minute exposure at ISO 100.
Making the initial estimated exposure time at 6400 reduces the number
of test exposures he needs to make at ISO 100.
I had to make a little spreadsheet to convince myself. It's not exact,
but the error is relatively small. Probably less than is necessary to
give you a good starting point at the lower ISO.
I don't do a lot of night or long exposure stuff and maybe this is
common knowledge to those that do. I've been around a long time and
heard a lot of "rules," but this one was new to me.
gs
George Sinos
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