OT - Delay in focus on Digital Cameras

Interesting. I've got some AG1B's. They any good to anyone? (8 of them).

Coop

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It's not me - it's GB you need to thank for the link - check the attribs!
:-)

On Thu, 29 Apr 2004 17:21:21 +1000, "RT" <notr.tho @cqu.edu.au>
wrote:



I seem to recall a technique of bathing the film in hydrogen to up
it's sensitivity used in astronomy.

..............................­........
Careful explanation snipped - ta.


Hmm - shoulda charged you for 'em :-)


I thort you ran into grain size problems if you pushed it too far - and I've
never heard of anything like 51k ASA!

(My only processing experience was with B&W Panasonic X and Tri-X followed
by conventional papers.
Did jag a couple of nice ones, which made it worth it - have now given the
gear to a niece who has jagged some very nice ones :-)

(snip)

(snip rest)

This WAS the point in an earlier thread, but it was subsumed by discussion on
autofocus. And this remains the issue with any "budget" digital cameras i.e.
<$A1K

Google

Actually it is  PF  (FPs are different)

See http://www.dhios.co.uk/archive s/flashbulbs/Bulbs1.htm

which gives data for every imaginable type of flashbulb.

Mmm - well not quite.  They list the PF25 but not the PF25B, but do list
both PF5 and PF5B
Perhaps I misremember - maybe there was no 25B, just the 25/97.   (The /97
indicated blue)
*Was* a while ago :-)

On Thu, 29 Apr 2004 10:43:42 +1000, "RT" <notr.tho @cqu.edu.au>
wrote:

That chart has explained a lot, cheers :)

On Thu, 29 Apr 2004 10:40:24 +1000, "RT" <notr.tho @cqu.edu.au>
wrote:



Actually it is an FP25, and the FP lamps had relatively long duration,
and constant output during the burn so they would  provide more or
less even illumination as the Focal Plane shutter moved across the
film plane, which typically took something on the order of 30
milliseconds. The FP synchronization on the camera would close the
contact something on the order of 10 milliseconds before the shutter
began going across the film. That was to allow them to light and reach
full brightness. Total burn time was typically about 40 milliseconds.

Higher voltage doesn't do a thing for them. It is the current that
counts, you need to get them to light, and is ohmic heating, anything
over 3 volts could usually light them in a millisecond or so...

plan B of course is to fire off a few kilojoules in Xenon flash tubes
in a few milliseconds. That provided enough light for arerial
photography at night.

 Burn the print off the paper.

Starve ther lizards!   See what you mean.   Have bookmarked it for later :-)

(It's a depth of field calculator)

My Finepix S5000 allows me to "pre-capture" the focus by half depressing the
shutter button (In fact it also allows full manual mode where I focus it
myself)
With prefocus you simply aim it at something about the same distance away as
the item you want to capture. This also works to compensate for someone up
against a bright window or the like. Prefocussing on something with better
lighting adjusts the settings according to THOSE lighting conditions,
meaning you can get a better result for the photo you want to take.

The problem I have with this particular digital is not the delay in focus,
but the delay in CAPTURING the image.
Even manually, or pre-focussed, there is a huge delay from when you finish
pressing the button, to when it decides to capture the image, so you don't
get the shot you wanted.
For example, I had a father holding his toddler daughter. She was eating an
iceblock, and regularly holding it up for him to take a bite - SO CUTE.
But try as I might, the delay was so long, that taking the shot as she held
it out to him, he had already taken a bite, and she'd returned the iceblock
to herself by the time the photo would capture. To get the shot I'd wanted,
I'd have had to predict when she was going to hold it out - but it was
random - and press the button a moment before she began to hold it out for
him. Not being good at forseeing the future, or reading minds, this doesn't
work well.

This REALLY frustrates me. And basically destroys what is otherwise a
fantastic camera. Brilliant if you want fixed images like landscapes etc.
Totally USELESS for those fantastic candid-moment type shots - unless you
"pose" the candid moment - which I ended up doing with that father and
daughter, by getting her to hold the iceblock there, but it just isn't the
same thing sometimes, the facial expressions etc are rarely the same when
posed.

The resolution of 6 megapixel, which is really 3 megapixel but using a
"Super-CCD"  to get more dpi than the normal 3 megapixel gets, is way ample
for my needs. It produces fantastic A4, and still exceptional A3 shots. I
just wish they'd do something with the delay in capture.

On Thu, 29 Apr 2004 10:43:42 +1000, "RT" <notr.tho @cqu.edu.au>
wrote:

Thanks for that link... :) i played with focal lengths...god....
how the hell do ya focus on a subjet 4.5 kms away with the hyperfocal.
:)

Argh.    I've tried to stay out of this but.....

Would either of you  care to comment on the depth of field  as a function of
lens focal length vis a vis aperture??

ie - depth of field of a 70 mm lens at f3.5 is greater/less than the depth
of field of a 70 mm lens at f16?

depth of field of a 70 mm lens at f3.5 is greater/less than the depth of
field of a 700 mm lens at f3.5?

(OT - Stealth, I got some $s and am back on m'ship)
(OT - Paul - you firing those PF25Bs at  10KV to get 51,000 ASA or what?)

Sorry ... spaced out ...

threeweeks@f8

Hey Paul old trout .
Reading your stuff again  and observing your burning film again
I have a T90 cannon here with 200 mil lens
you can borrow  if we cross paths  in the scrub.

talung1 at hotmail dot com
put Paul sacacs in subject line to beat
spam filters  also my bullet proof TLB  lovely tough old gear
T90 only shot about ten rolls in its whole life

Here's a new email address for you, Saccers:

three weeks@f8

<GRIN>

Stop yer whinging :-)    I put it in brackets AND warned it was off topic...
And for you young kids, PF25B (later called PF5B) are blue flash bulbs of a
particular size (bigger than PF1s) - in this particular case some I had and
sent to Paul S.   And if you don't know what a flash bulb is, refer Google
:-)

Now, how many here do you think know what a PF25B is?

P'raps we can rename him O Winston Sarkers :)

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On Wed, 28 Apr 2004 17:11:05 +0800, Paul Saccani



so when long exposures mean more chopping off of desirable bits they
have less depth of field.

saccas where do you get the exotic camera gear you use? ...the CIA?

Stealth Pilot

Thanks Richard - will do

John

Hi John,
Feel free to post your question in aus.photo - you'll get (hopefully)
a good range of answers/suggestions from us regulars there...

Cheers,
Richard

Yes, you are correct but such fiddles are a bit of a pain.  Looking for a
simple fix or alternative.



Thanks for the info GB - much appreciated.
Must say I am very happy with my camera apart fom the focussing issue.  Use
it regularly for work - damn convenient for taking shots of parts that are
difficult to describe to suppliers.  Even used it on macro to get details
off printed circuits boards that my eyes have trouble reading.

Cheers,
John

On Wed, 28 Apr 2004 00:52:39 +0930, Michael



the problem you have is depth of field ...or the lack of it.

I last studied this stuff 30 years ago but long focal length lenses
have very shallow depth of field as I recall.

Stealth Pilot

I have had a similar problem with focusing.
last airshow I was at I was using an eos 1000f (gasp)
with a tamron 70-300 (LD572) I tried the trick of
focusing on the horizon then tapeing up the lens
and turning of the auto focus. no problem except I
have found that all auto-focus lenses focus past infinity
when pointed at the horizon. when taking a shot of a plane
200ft away its not in focus. focus on the plane and the
horizon its out. not that long ago I got and EOS630 tried it
at the airport, and put on the vivitar 100-300 same thing.

I grab my AE-1 and put a 200mm lens on infinity, problem gone
no focusing past infintity and everything beyond 40ft is in focus.

So I have been wondering for quite a while why auto lenses go past
infinity, any thoughts?..Do digi SLR's focus past infinity?

TIA.

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