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Since: Aug 17, 2006
Posts: 324
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(Msg. 16) Posted: Fri Feb 22, 2008 8:38 pm
Post subject: Re: Auto-focus on digital SLRs. [Login to view extended thread Info.]
Archived from groups: alt>photography, others (more info?)
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On Feb 22, 11:38 pm, "dullpain" <fac_....DeleteThis@hotmail.com> wrote:
> Modern SLR autofocus under most circumstances however is probably more
> accurate than manual focus overall under most conditions. Adding facial
> recognition algorithms may also be an advance, although I have not
> experimented much yet with my camera that has this feature.
That depends. I have a split prism screen in my D200 and find that
manually focusing is more accurate if I am not tired, provided I use a
lens with a reasonably long focus throw. For example, with a manual
focus 28mm lens I have I get good accuracy and repeatability, while
with a tamron 17-50mm which I also have it's practically impossible to
focus reliably because of the short throw of the focus ring (and the
fact that it has some play).
Of course autofocus doesn't get tired and works at lower light levels
than I can focus in. It's also much faster than me. So both systems
have advantages. And certainly autofocus is good enough for most
things, and the only way for some. |
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Since: Feb 17, 2008
Posts: 6
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(Msg. 17) Posted: Fri Feb 22, 2008 8:38 pm
Post subject: Re: Auto-focus on digital SLRs. [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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>
> Quite so. Unfortunately you don't tell us anything about what lenses you
> are using. There is quite a difference between a 20+ year old
> screw-driver type and a modern ultra-sonic AF.
> Or are you by any chance using auto-focus with a closed apperture? That
> would explain your problems, too.
>
Sorry didn't mean to skimp on the details.
I believe this is a kit lens, EF-S 18-55mm 3.5-5.6 II.
I was loaned another lens but for what I am doing (reading through a
magic lantern guide and testing all the features) I have not had cause to
use it; a 70-200 IS lens. It is a better lens but for indoor dog shots I
thought it was overkill.
--Steve |
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Since: Dec 18, 2007
Posts: 182
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(Msg. 18) Posted: Fri Feb 22, 2008 8:41 pm
Post subject: Re: Auto-focus on digital SLRs. [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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Since: Jul 02, 2007
Posts: 39
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(Msg. 19) Posted: Fri Feb 22, 2008 8:41 pm
Post subject: Re: Auto-focus on digital SLRs. [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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It's strange that the 'strobe thing' you experienced (which is AF assist)
didn't get a focus lock.
I would be interested to know what lens you were using and how far away you
were from the subject.
"Steven Green" <steven.green30.RemoveThis@verizon.net> wrote in message
news:qfGvj.259$Hd.114@trnddc02...
>> When it hunts (zooms in and out), what are you photographing at the
>> time? An image with very little contrast? A low light shot? Is the
>> subject moving?
>>
>> Also, what focusing mode are you using? AI Servo, AI Focus or One Shot?
> I was on One shot at the time.
>
> In this case it was a rather low light shot of my dog laying on a sofa.
> Indoors with lamp lighting. I don't think he was moving at the time. I
> think I tried the flash at the time and it did the strobe thing and
> couldn't make up its mind.
>
> He is a rather brown dog with a dark face. I think he has rather good
> contrast including the sofa. >> Stay informed about: Auto-focus on digital SLRs. |
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Since: Jan 22, 2008
Posts: 104
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(Msg. 20) Posted: Fri Feb 22, 2008 9:03 pm
Post subject: Re: Auto-focus on digital SLRs. [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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"Mr. Strat" <rag RemoveThis @nospam.techline.com> wrote in message
news:220220081344258949%rag@nospam.techline.com...
> In article <3bGvj.39860$w57.28071@edtnps90>, Dudley Hanks
> <hanks.dudley RemoveThis @gmail.com> wrote:
>
>> And, when you only have about 2% of "normal" vision, it becomes
>> indeispensible...
>
> My use of soft-focus lenses in a semi-darkened studio for many years
> may have something to do with it too.
Yes, eye-strain is definitely a hazard of the profession... >> Stay informed about: Auto-focus on digital SLRs. |
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Since: Feb 22, 2008
Posts: 2
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(Msg. 21) Posted: Fri Feb 22, 2008 9:03 pm
Post subject: Re: Auto-focus on digital SLRs. [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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"nospam" <nospam RemoveThis @nospam.invalid> wrote in message
news:220220081234494217%nospam@nospam.invalid...
> In article <47Gvj.2472$g81.875@newsfe3-gui.ntli.net>, Anon
> <abuse RemoveThis @yahoo.com> wrote:
>
>> Remember auto-focus is a contrast detection system,
>
> on a dslr, it's a phase detection system (unless in live view mode on
> some cameras). point&shoots use contrast detection.
True, but whichever system is used they all need to be able to detect some
difference in contrast.
Try getting a dslr to focus on a white card or a blank wall when there's
nothing else in view... >> Stay informed about: Auto-focus on digital SLRs. |
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Since: Jun 03, 2004
Posts: 917
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(Msg. 22) Posted: Fri Feb 22, 2008 9:03 pm
Post subject: Re: Auto-focus on digital SLRs. [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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In article <DIHvj.3343$St5.2888@newsfe1-gui.ntli.net>, Anon
<abuse RemoveThis @yahoo.com> wrote:
> Try getting a dslr to focus on a white card or a blank wall when there's
> nothing else in view...
kinda hard to manually focus on that. >> Stay informed about: Auto-focus on digital SLRs. |
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Since: Jan 22, 2008
Posts: 104
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(Msg. 23) Posted: Sat Feb 23, 2008 3:56 am
Post subject: Re: Auto-focus on digital SLRs. [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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"nospam" <nospam DeleteThis @nospam.invalid> wrote in message
news:220220081940165784%nospam@nospam.invalid...
> In article <DIHvj.3343$St5.2888@newsfe1-gui.ntli.net>, Anon
> <abuse DeleteThis @yahoo.com> wrote:
>
>> Try getting a dslr to focus on a white card or a blank wall when there's
>> nothing else in view...
>
> kinda hard to manually focus on that.
Not with an old manual focus, mechanical camera. You just set the focal
scale to the distance the wall is from the focal plane and, presto, it's in
focus. Takes less than a second. Well, maybe a second and a half if you're
clumsy.
Smile,
Dudley >> Stay informed about: Auto-focus on digital SLRs. |
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External
Since: Jan 08, 2008
Posts: 38
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(Msg. 24) Posted: Sat Feb 23, 2008 3:56 am
Post subject: Re: Auto-focus on digital SLRs. [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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"Dudley Hanks" <hanks.dudley RemoveThis @gmail.com> wrote in message
news:OPMvj.36818$FO1.28819@edtnps82...
>
> "nospam" <nospam RemoveThis @nospam.invalid> wrote in message
> news:220220081940165784%nospam@nospam.invalid...
>> In article <DIHvj.3343$St5.2888@newsfe1-gui.ntli.net>, Anon
>> <abuse RemoveThis @yahoo.com> wrote:
>>
>>> Try getting a dslr to focus on a white card or a blank wall when there's
>>> nothing else in view...
>>
>> kinda hard to manually focus on that.
>
> Not with an old manual focus, mechanical camera. You just set the focal
> scale to the distance the wall is from the focal plane and, presto, it's
> in focus. Takes less than a second. Well, maybe a second and a half if
> you're clumsy.
>
And for those who can't judge distances accurately, a US dollar bill is six
inches long. No, a five dollar bill is not two and a half feet!
Back in the days of sync cords and manual flashes and guide numbers, I had a
long sync cord (15'?) that I applied a piece of narrow tape around it every
foot. Made it easy to measure distance to the subject. >> Stay informed about: Auto-focus on digital SLRs. |
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Since: Dec 13, 2004
Posts: 840
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(Msg. 25) Posted: Sat Feb 23, 2008 5:35 am
Post subject: Re: Auto-focus on digital SLRs. [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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Jürgen Exner <jurgenex.TakeThisOut@hotmail.com> wrote:
> Quite so. Unfortunately you don't tell us anything about what lenses you are
> using. There is quite a difference between a 20+ year old screw-driver type
> and a modern ultra-sonic AF.
Canon EOS doesn't have screw-driver (AF motor in the body).
Nikon has such lenses.
> Or are you by any chance using auto-focus with a closed apperture? That
> would explain your problems, too.
Again, that would be ... somewhat hard with a Digital Rebel.
> Of course, you can always turn off AF easily enough with the flip of a
> switch.
Or move the AF from half-press-shuttor to another button and use
FTM lenses.
-Wolfgang >> Stay informed about: Auto-focus on digital SLRs. |
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Since: Apr 25, 2007
Posts: 51
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(Msg. 26) Posted: Sat Feb 23, 2008 6:23 am
Post subject: Re: Auto-focus on digital SLRs. [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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On Feb 22, 3:41 pm, "Ali" <m... RemoveThis @privacy.com> wrote:
> It's strange that the 'strobe thing' you experienced (which is AF assist)
> didn't get a focus lock.
>
> I would be interested to know what lens you were using and how far away you
> were from the subject.
Why? It happens all the time in low light situations. That's why the
lenses have a switch to shut off the AF. Tokina even makes lenses
that you pull the focus ring towards you and overide the AF (which is
nice). If you haven't experienced the joy of AF that can't find a
focus point, you haven't used your camera enough.
Sometimes you need to throw on a flash just for the IR focusing.
>
> "Steven Green" <steven.gree... RemoveThis @verizon.net> wrote in message
>
> news:qfGvj.259$Hd.114@trnddc02...
>
>
>
> >> When it hunts (zooms in and out), what are you photographing at the
> >> time? An image with very little contrast? A low light shot? Is the
> >> subject moving?
>
> >> Also, what focusing mode are you using? AI Servo, AI Focus or One Shot?
> > I was on One shot at the time.
>
> > In this case it was a rather low light shot of my dog laying on a sofa.
> > Indoors with lamp lighting. I don't think he was moving at the time. I
> > think I tried the flash at the time and it did the strobe thing and
> > couldn't make up its mind.
>
> > He is a rather brown dog with a dark face. I think he has rather good
> > contrast including the sofa.- Hide quoted text -
>
> - Show quoted text - >> Stay informed about: Auto-focus on digital SLRs. |
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Since: Mar 22, 2007
Posts: 365
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(Msg. 27) Posted: Sat Feb 23, 2008 8:03 am
Post subject: Re: Auto-focus on digital SLRs. [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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On Fri, 22 Feb 2008 15:42:07 -0500, ____ <internetphobic DeleteThis @deletedmail.com>
wrote:
: In article <220220081122278921%rag@nospam.techline.com>,
: "Mr. Strat" <rag DeleteThis @nospam.techline.com> wrote:
:
: > In article <EdFvj.249$Hd.83@trnddc02>, Steven Green
: > <steven.green30 DeleteThis @verizon.net> wrote:
: >
: > > I am new to the auto-focus world, both my film cameras are manual focus.
: > > I just got my hands on my sister's Digital Rebel XT (DRXT) to just learn
: > > some basics of the camera and see what features I really like.
: >
: > Being an old school old fart, I didn't think I'd like autofocus when I
: > switched to digital. But I love it. It takes a bit of getting used to
: > (and turning off all sensors except one), but it can focus a lot
: > quicker than these old eyeballs.
:
: In the old days- one knew how to pre-focus; yet oddly enough it works
: with AF cameras-if one knows what the hell one is doing.
You are so right. And your observation reminds me of one of my pet peeves: Why
don't modern automobiles have a place to insert a starting crank? Autos should
be crank-started. It's what Henry Ford intended, and our latter-day reliance
on electric starters is a stark reminder of how modern society has gone soft.
Bob >> Stay informed about: Auto-focus on digital SLRs. |
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Since: Sep 04, 2007
Posts: 220
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(Msg. 28) Posted: Sat Feb 23, 2008 9:14 am
Post subject: Re: Auto-focus on digital SLRs. [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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"Robert Coe" <bob RemoveThis @1776.COM> wrote in message
news:at50s3tmqbcmupvjj3cq2s3gmuhveitoiq@4ax.com...
> On Fri, 22 Feb 2008 15:42:07 -0500, ____
> <internetphobic RemoveThis @deletedmail.com>
> wrote:
> : In article <220220081122278921%rag@nospam.techline.com>,
> : "Mr. Strat" <rag RemoveThis @nospam.techline.com> wrote:
> :
> : > In article <EdFvj.249$Hd.83@trnddc02>, Steven Green
> : > <steven.green30 RemoveThis @verizon.net> wrote:
> : >
> : > > I am new to the auto-focus world, both my film cameras are
> manual focus.
> : > > I just got my hands on my sister's Digital Rebel XT (DRXT) to
> just learn
> : > > some basics of the camera and see what features I really like.
> : >
> : > Being an old school old fart, I didn't think I'd like autofocus
> when I
> : > switched to digital. But I love it. It takes a bit of getting
> used to
> : > (and turning off all sensors except one), but it can focus a lot
> : > quicker than these old eyeballs.
> :
> : In the old days- one knew how to pre-focus; yet oddly enough it
> works
> : with AF cameras-if one knows what the hell one is doing.
>
> You are so right. And your observation reminds me of one of my pet
> peeves: Why
> don't modern automobiles have a place to insert a starting crank?
> Autos should
> be crank-started. It's what Henry Ford intended, and our latter-day
> reliance
> on electric starters is a stark reminder of how modern society has
> gone soft.
>
> Bob
Sounds like a crank to me! >> Stay informed about: Auto-focus on digital SLRs. |
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Since: Jan 01, 2008
Posts: 30
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(Msg. 29) Posted: Sat Feb 23, 2008 12:25 pm
Post subject: Re: Auto-focus on digital SLRs. [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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On Sat, 23 Feb 2008 08:03:03 -0500, Robert Coe <bob RemoveThis @1776.COM> wrote:
>On Fri, 22 Feb 2008 15:42:07 -0500, ____ <internetphobic RemoveThis @deletedmail.com>
>wrote:
>: In article <220220081122278921%rag@nospam.techline.com>,
>: "Mr. Strat" <rag RemoveThis @nospam.techline.com> wrote:
>:
>: > In article <EdFvj.249$Hd.83@trnddc02>, Steven Green
>: > <steven.green30 RemoveThis @verizon.net> wrote:
>: >
>: > > I am new to the auto-focus world, both my film cameras are manual focus.
>: > > I just got my hands on my sister's Digital Rebel XT (DRXT) to just learn
>: > > some basics of the camera and see what features I really like.
>: >
>: > Being an old school old fart, I didn't think I'd like autofocus when I
>: > switched to digital. But I love it. It takes a bit of getting used to
>: > (and turning off all sensors except one), but it can focus a lot
>: > quicker than these old eyeballs.
>:
>: In the old days- one knew how to pre-focus; yet oddly enough it works
>: with AF cameras-if one knows what the hell one is doing.
>
>You are so right. And your observation reminds me of one of my pet peeves: Why
>don't modern automobiles have a place to insert a starting crank? Autos should
>be crank-started. It's what Henry Ford intended, and our latter-day reliance
>on electric starters is a stark reminder of how modern society has gone soft.
A crank starter sure would be nice if you accidentally leave your
lights on. And if the engine is too big to crank start, one of those
clockwork wind-up crank starters would work great. Just like manual
focus can work great if the autofocus isn't doing what you want.
Steve >> Stay informed about: Auto-focus on digital SLRs. |
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Since: Dec 31, 2007
Posts: 133
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(Msg. 30) Posted: Sat Feb 23, 2008 12:59 pm
Post subject: Re: Auto-focus on digital SLRs. [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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In article <kkd0s3h7vjcej95rfvbgjk5naq980trj1s DeleteThis @4ax.com>,
Steve <steve DeleteThis @example.com> wrote:
>
> A crank starter sure would be nice if you accidentally leave your
> lights on. And if the engine is too big to crank start, one of those
> clockwork wind-up crank starters would work great. Just like manual
> focus can work great if the autofocus isn't doing what you want.
>
> Steve
Good point, to place back in context any suggestions for speed focusing
rings for manual control?
--
Reality is a picture perfected and never looking back. >> Stay informed about: Auto-focus on digital SLRs. |
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