Re: too much light
- From: "Roger N. Clark (change username to rnclark)" <username@xxxxxxxxx>
- Date: Sat, 21 Jul 2007 10:55:59 -0600
ASAAR wrote:
On Sat, 21 Jul 2007 00:04:39 -0600, Roger N. Clark (change username
to rnclark) wrote:
All light can be "good lighting", but I rarely get out to whereDigital cameras (DSLRs with their large pixels) have far
it's dark enough so that the moon provides most of the nighttime
light, so I don't know whether it's good enough or not. Being
reflected sunlight it won't even require an extreme change to the
color balance, but it might be too dim for digital cameras. This is
one area where film cameras may have an advantage. Digital doesn't
suffer from film's 'reciprocity', but film doesn't suffer from the
'noise' that digital sensors produce with very long exposures (more
than several minutes long).
surpassed any film for low light photography. See:
http://www.clarkvision.com/photoinfo/night.and.low.light.photography
and note the 623 second exposure at ISO 1600 (pretty low
noise). Noise from long exposures (thermal dark current noise)
is simply beat by taking multiple shorter exposures and
adding them together. Thus with no reciprocity failure,
much higher quantum efficiency, and higher spatial resolution
than high speed (35mm) film, DSLRs are now the preferred
camera over film for amateur astrophotography (cooled CCDs
do better but at a cost of many times more).
Your web page notwithstanding, I'm still of the opinion that film
is better (in general) for very long, low light exposures. With the
right film, almost any camera will do a good job. Your web page
certainly shows what the best DSLRs can do with long, low light
exposures, but it doesn't compare film with digital, so it can't be
used as a source to "prove" your contention that DSLRs have "far
surpassed any film for low light photography". If they have, how
much does "by far" represent?
ASAAR,
That is a good question. I did add a new section just above
the conclusions called "Other Digital Cameras" to address some of
your questions. I included one new link (reference 10) that
shows a 20 minute comparison between an Nikon D200 and
Konica 400 film. Note the grain in the film versus the digital,
which has a smoother background, showing faint stars better.
I was also surprised how the bright stars were blown out
in the film. As exposure times increase, digital will do better
as the film reciprocity failure will become worse.
I was also talking about digital cameras in general, whereas you
narrowed it down to DSLRs. Most P&S cameras don't even allow
shutter speeds longer than 8 or 15 seconds. Your web page, although
titled "Night and Low Light Photography with Digital Cameras",
only demonstrated the low light performance of one camera, Canon's
1D Mark II and a 50mm f/1.8 lens. The lens is inexpensive, but the
camera certainly isn't, and is unlikely to be found in most
photographer's kits. I assume that the 1D Mark II was selected
because its long exposure, low light performance is extremely good.
But how representative is it of DSLRs in general? How well would a
D20 do, or Nikon's D70, or any of the DSLRs from Pentax, Fuji and
Sony? I'll omit the ones from Olympus, as I have a hunch I know how
they'd compare, at least for the older models. :)
The 1DII low light performance is similar to other DSLRs, and I
address that in the new section above.
If I have a quibble with anything on the web page, it's the first
sentence of the "Conclusions", which states :
Digital Cameras are capable of detecting small numbers of photons
and making credible detections of image detail.
This implies that it's true for all (or most) digital cameras.
There would be no problem wording it this way if you had also tested
some of the DSLRs that aren't as good as the 1D Mark II for long
exposures, and found that they also provide good image detail from
only a small number of photons. That not being the case, I'd have
changed "Digital Cameras are capable of" to "At least one digital
camera, Canon's 1D Mark II is capable of".
Again, I think the new section addresses this issue.
While it doesn't disprove anything you've said, or what is
contained on your web page, I viewed a number of web pages recently
when there was a discussion of photographing lightning. Techniques
were given for using both film and digital cameras. From what I
recall, DSLRs were recommended for use up to a point, and for longer
exposures, film cameras were chosen.
This may be, but it depends on the knowledge of the user,
and of course the camera. Small pixel cameras will not do as well
as those with large pixels. Once people learn a new processing
method, stacking multiple images, and changing their thinking,
multiple short exposures stacked, versus one long exposure,
then the limits of digital camera thermal noise are reduced
and one can surpass film.
Although your web page really had nothing to say about film, it
did show that if Desert Dweller wants to take pictures by moonlight,
any DSLR should be able to do so with only moderately long
exposures. Figure 7 (10 sec., ISO 1600, f/1.8) isn't too bad,
although the detail seems very low, even considering that it's only
from a 64k image file. Figure 8 (1 sec., ISO 1600, f/1.8) on the
other hand, has enough noise to wake the dead. :)
Yeah, the focus was off a little. I focused on the moon overhead,
but when I changed the view to the mountains the focus shifted.
The f/1.8 is pretty sensitive.
I reviewed some of my 4th of July shots, and found a couple taken
just after 10 p.m. that, while fairly dark, would make a reasonable
landscape shot, without too much noise. I'd want to limit it to
4"x6" and 5"x7" prints though. The exposure values were ISO 800,
f/3.8 and 15 seconds). I assume that most of the illumination away
from the shoreline was provided by the moon, but I don't know its
phase or sky location at that time and date, July 3, actually. At
least you demonstrated that shots illuminated by moonlight don't
require exposures of 1/2 hour or longer. But if it did, I'd like
to find out how digital images would compare with those from film,
at least where noise is concerned. Do you want to have a go at
another paper? :)
Yes, I'll add it to my (long) list of things to do ;-).
I googled astrophotography film versus digital and find most
of the web pages of 2004 and earlier vintage, and few using
cameras newer than a 10D. It seems the amateur astrophotographers
have moved to digital and largely forgotten about film.
I moved to digital (DSLRs) for astrophotography in 2002 when I
was convinced I could do better with a D60 than with film.
The nicest comparison I found was:
http://www.aoc.nrao.edu/~whwang/misc/D200_vs_film
I suggest picking up any and all photography books by
John Shaw. Then study the contents.
His books always seem to get good reviews. Do any deal with low
light photography rather than touching on it briefly?
I'm not sure of a good book on that subject.
Roger
.
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- From: Roger N. Clark (change username to rnclark)
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