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peter
Guest
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 Posted: Sat May 19, 2007 7:27 am Post subject: canon 20D flash sync at 1/320? |
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When I attach a canon speedlite 550ex (high speed sync off) on a 20D, the
shutter speed automatically reduced to 1/250s if I had it faster.
Is there a way to override this?
I found by experiment, I can flash sync at 1/320s (the experiment is done
with a 3rd party flash that does not change the shutter speed). So I would
like to use this speed with the canon speedlite, but it won't let me.
Any ideas? I checked all the custom functions and none of them look like it
would help. |
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Annika1980
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| Posted: Sat May 19, 2007 7:27 am Post subject: Re: canon 20D flash sync at 1/320? |
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On May 19, 1:14 am, "peter" <nos...@nospam.com> wrote:
| Quote: | When I attach a canon speedlite 550ex (high speed sync off) on a 20D, the
shutter speed automatically reduced to 1/250s if I had it faster.
Is there a way to override this?
I found by experiment, I can flash sync at 1/320s (the experiment is done
with a 3rd party flash that does not change the shutter speed). So I would
like to use this speed with the canon speedlite, but it won't let me.
Any ideas? I checked all the custom functions and none of them look like it
would help.
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Turn high speed sync on. That's why they call it high speed sync. |
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John McWilliams
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| Posted: Sat May 19, 2007 2:57 pm Post subject: Re: canon 20D flash sync at 1/320? |
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peter wrote:
| Quote: | When I attach a canon speedlite 550ex (high speed sync off) on a 20D, the
shutter speed automatically reduced to 1/250s if I had it faster.
Is there a way to override this?
I found by experiment, I can flash sync at 1/320s (the experiment is done
with a 3rd party flash that does not change the shutter speed). So I would
like to use this speed with the canon speedlite, but it won't let me.
Any ideas? I checked all the custom functions and none of them look like it
would help.
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High speed synch should be turned on.
--
john mcwilliams |
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ASAAR
Guest
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| Posted: Sun May 20, 2007 3:18 pm Post subject: Re: canon 20D flash sync at 1/320? |
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On Sun, 20 May 2007 05:10:08 -0700, Roger N. Clark (change username
to rnclark) wrote:
| Quote: | Of course I know how an ND might be used too change
DOF. I posted a simple question to see how the OP
was using an ND with a flash. It is not a simple
problem, and the ND does not itself change DOF.
From his response, it might open other dialog,
but with your attack, he is probably scared off.
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And of course you saw my reply as an "attack", just as I predicted
you would.
| Quote: | To the OP: some people in this newsgroup seem only
out to attack other people, and waste a lot of
space and often destroy discussions. The
attack by ASAAR is yet another example.
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And as usual, your knee-jerk reaction is not to open the dialog
that you profess to prefer, but to turn an imaginary attack into a
real one. |
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Roger N. Clark (change us
Guest
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| Posted: Tue May 22, 2007 2:39 am Post subject: Re: canon 20D flash sync at 1/320? |
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ASAAR wrote:
| Quote: | On 21 May 2007 15:23:00 -0700, acl wrote:
OP (::
::: If I can cheat the sync speed, I could effectively reduce the sunlight's
::: intensity and enable fill-in flash at greater shooting distance, or save
::: flash power at the same distance (battery pack last longer), and less
::: blinding flash into the subjects' eyes.
I think this is how it goes with the ND:
the flash has a maximum duration, which along with the
intensity dictates the guide number. When you add the
ND effectively the guide number drops, so even though
you expose longer for a general scene, if you were at the
limit of the flash without the ND, then with the ND
you are over its limit and your image is underexposed.
If you are still within range of the flash after
putting on the ND, then you are OK and can effectively
use the longer exposure/wider aperture. However,
if you put on the ND without changing exposure
and only increase aperture then there should be no change in
the guide number, if the aperture change exactly
compensated for the ND reduction. A lot of things
to balance, including do you have enough aperture
that you can open up to compensate for the ND.
If you can't open up enough to compensate for the ND
loss, then again you risk underexposure.
Well I don't disagree with anything you say, but if I think of adding
an n-stop ND filter as reducing the ISO by n stops, then I don't see
much complication. Maybe I am missing something, I don't use ND
filters or flashes.
You didn't miss anything and the OP gave every indication that he
fully understands the tradeoffs of using an ND filter. Proving my
contention that if Roger had any useful, helpful, unobvious
information to provide, he should have simply posted it, and it
would have been to everyone's benefit. He later claimed that his
reply was simply an "honest question", but his final, 'obvious'
explanation shows otherwise, the condescending "How does an ND
filter reduce depth of field?" was more likely asked for the reason
I gave than Roger's face saving after-the-fact explanation.
I showed how the ND filter could reduce DOF, said that Roger
should also know the answer "quite well" and I'd be amazed if the OP
hasn't also known that for many years, as well as most people that
have purchased ND filters. As you've shown, owning and using an ND
filter (or flash) is no great obstacle to understanding such a
simple concept.
What is your problem? It was an honest question, |
and I had not thought through the implications because like acl,
I have never used an ND filter with a flash.
Stop trying to find a problems to pounce on people.
You spend too much time doing just that to many here.
Roger |
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Roger N. Clark (change us
Guest
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| Posted: Tue May 22, 2007 12:46 pm Post subject: Re: canon 20D flash sync at 1/320? |
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ASAAR wrote:
| Quote: | The problem is that you find it extremely difficult to admit the
obvious. If a complete newbie asked "How does an ND filter reduce
depth of field?" I'd have no problem believing that it was a simple,
honest question. That you'd ask such a question and feign ignorance
given your history of knowing and writing papers delving into the
most minute, esoteric camera and photography details, such as
(remember this?) trying to prove or demonstrate that DSLRs have as
much DOF as point & shoot cameras, and then expect us to believe
that you're asking someone to explain to you how a ND filter can
reduce DOF? Give us a break! Whether we get along or rub each
other the wrong way is of no matter in this instance. I readily
admit that you know more about photographic minutia than most people
here, and most ng regulars that have read your messages probably
agree. But that doesn't mean that you can get away with pretending
to not understand such a basic concept as to how an ND filter can be
used to reduce the DOF. That's so simple one might almost expect it
to be rejected from a "Dummies" manual. And all this to avoid
having to admit the real motive for your question. Sheesh.
You are wrong again. |
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BaumBadier
Guest
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| Posted: Tue May 22, 2007 12:46 pm Post subject: Re: canon 20D flash sync at 1/320? |
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On Tue, 22 May 2007 03:51:56 -0700, "Roger N. Clark (change username to
rnclark)" <username@qwest.net> wrote:
| Quote: | But that doesn't mean that you can get away with pretending
to not understand such a basic concept as to how an ND filter can be
used to reduce the DOF. That's so simple one might almost expect it
to be rejected from a "Dummies" manual. And all this to avoid
having to admit the real motive for your question. Sheesh.
You are wrong again.
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Perhaps this is an error in semantics. Some people assume or think that DOF
refers always to a shallow DOF (depth of field) because that's when the term DOF
is most often used. DOF does not automatically refer to a shallow (narrow) or
deep (long) DOF, it's just Depth-Of-Field. It has to be further qualified on if
you are intending to discuss a shallow or deep DOF. "Reduce the DOF" can be
taken both ways. Are you reducing a shallow DOF (making it deeper) or reducing a
deep DOF (making it shallower, more narrow)?
I blame most of this on the english language and camera conventions. (Are you
going UPtown or DOWNtown? In english they mean the same thing.) For a newbie,
when you say "increase the aperture", they sometimes think that means to
increase the f/stop number. This, of course, is backward. Because the greater
the f/stop number the smaller/lesser the aperture. Or to use a greater shutter
speed. Does that mean use a longer (greater) shutter time? Or shorter shutter
time? The number 1000 is much higher than 1/4th after-all, and those are the
numbers presented to them on their camera settings.
All of these things can be taken in 100% reverse if some universal conventions
or precise language isn't agreed upon first, leading to vast misunderstandings.
Anytime you are reducing the available light entering the lens (as in using an
ND filter) you are going to have to compensate for it in 1 of 4 ways, 1)
Increase the length of the exposure (lower shutter speeds), 2) enlarge the lens
aperture (decrease the f/number), 3) raise the available ISO number (by the
film used or digital camera setting), or 4) add in more light, as in the use of
a flash.
Option #2 would indeed reduce (narrow, make more shallow) a deep DOF. But it
would also increase the shallowness of the DOF (make it even more shallow).
See, it can be written both ways but you have to define what kind of DOF you are
referring to first when you are saying you are going to increase it or reduce
it. |
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Alan Browne
Guest
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| Posted: Tue May 22, 2007 3:41 pm Post subject: Re: canon 20D flash sync at 1/320? |
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Roger N. Clark (change username to rnclark) wrote:
| Quote: | ASAAR wrote:
attack deleted
Technically, and rather obviously, an ND filter by itself has no
effect on the DOF.
Of course I know how an ND might be used too change
DOF. I posted a simple question to see how the OP
was using an ND with a flash. It is not a simple
problem, and the ND does not itself change DOF.
From his response, it might open other dialog,
but with your attack, he is probably scared off.
|
I simply never came back to this NG since that posting, but the use of
an ND to reduce DOF (by forcing a larger aperture) should be quite
evident to most, whether or not flash is used. Yes, more flash power
will be required, but it's still less than wasteful HSS.
Cheers,
Alan
--
-- r.p.e.35mm user resource: http://www.aliasimages.com/rpe35mmur.htm
-- r.p.d.slr-systems: http://www.aliasimages.com/rpdslrsysur.htm
-- [SI] gallery & rulz: http://www.pbase.com/shootin
-- e-meil: Remove FreeLunch. |
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