HDTenEightyP/NetNews huggingface dataset:
From: mikec@spider.co.uk (Mike Coren)
Newsgroups: rec.photo
Subject: Lithium vs. Alkaline test results
Date: 14 Dec 92 09:47:17 GMT
Organization: Spider Systems Limited, Edinburgh, UK.


Hello again folks.  A couple of days ago, I posted up my own opinions as to
the lithium vs. alkaline battery debate.  This past weekend, I dug out a
review (preview?) of the Lith-EON 1.5V lithium AA's, which I had saved from
the November issue of Popular Photography.  They subjected the batteries to
their "flash test", where they repeatedly fire a flash gun powered by the
batteries and time the recharges.  Here are the results for both the Lith-EON
and conventional alkaline AA's:

The alkalines had a fairly linear recharge time vs. number of flashes graph.
By about 20 flashes, recharge time was over 10 seconds.  By 50 flashes, it
was at 15 seconds, by 100 flashes, it was near 20 sec, and by 150 flashes it
required 30 seconds to recharge.

The Lith-EON recharge times were fairly constant until the batteries were
nearly spent.  Recharge times remained under 10 seconds until 150 flashes,
then rose gradually to 15 seconds by 250 flashes.  The curve rose quite
sharply after that, being at 25 seconds by 270 flashes.

This test demonstrates the extra current capability of lithiums over alkalines.
Unlike alkalines, however, lithiums die fast and give little warning.  Also,
the lithiums did not regain very much by sitting unused for a couple of days.
At the time of the test, the Lith-EON batteries were unavailable in the US,
but they did say that in Japan they cost about 2-1/2 times as much as alkaline
AA's.  As in the UK, that's about the same price per volt as "normal" 2CR5
lithium batteries.

The review also mentioned that there will soon be rechargable nickel metal
hydride batteries available (Harding was mentioned as a source).  These, they
project, will provide for lithium-type recharges (under 10 seconds) for up to
about 100 flashes on a single battery charge.

Enjoy!
Mike Coren

-- 
Michael D. Coren, Electrical Engineer             mikec@spider.co.uk
Telecommunications Techniques Corporation, Germantown, Maryland, USA.
Temporarily at Spider Systems Limited, Edinburgh, Scotland, UK.
From: atomas@geloser.login.qc.ca (J-F Bissonnette)
Newsgroups: rec.photo
Subject: Re: Kodachrome 64
Date: 18 Dec 92 22:14:57 GMT
Organization: Gentleman Loser System, Montreal/Qc/Cdn

> One is very green compared to the other.  The most significant
> difference?  The green roll had about a year to go before expiring, the
> magenta roll was near the expiration date.
> 
> This is a fairly reproducable phenomena which I and some other
> Kodachrome photographers I know have observed: "Fresh"  K25/64 tends to
> produce greenish colors while K near or past it's expiration date is
> more magenta.  As I understand it, the only difference between
> "standard" K and Professional K is that the Pro stuff is aged by Kodak
> to its peak color reproduction and then frozen to hold it at that point.
> 
Not exactly, but you got it quite right for the difference between
the two.  The pro stuff is not aged but is just like it sould be.
But the standard stuff is modified by Kodak before it goes in the
stores.  Kodak as assumed that the average amateur photographer
will take quite some time before getting his film to processing,
thus it will get some changes in colors toward blue-magenta if
I'm not making any mistake.  So Kodak will produce an amateur film
that will go in the opposite color i.e. yellow-green.  

I know for sure that they do it for negative film, I think that
they would do the same for chrome film.

Ref:  Kodak technical information book

J.F.



--
atomas@geloser.login.qc.ca
Gentleman Loser System -- Montreal, Qc, Canada
Newsgroups: rec.photo
From: jacobson@cello.hpl.hp.com (David Jacobson)
Subject: Re: Depth of Field
Date: Tue, 15 Dec 1992 18:21:30 GMT
Organization: Hewlett-Packard Laboratories

In article <aj882694.724420720@tasman> aj882694@tasman.cc.utas.edu.au (Andre George Jenkins) writes:
>Sorry,
>
>I know I've recently asked for the DoF formulae, but a tidy-up of my hard drive
>'tidied up' some things that shouldn't have been: I threw ot the folder they
>were in, accidently.
>
>If some kind soul could post them here or mail them too me, I'd be very
>grateful.
>
>Thanks again
>
>Andre
>aj882694@tasman.cc.utas.edu.au
>
>

The distance from the point of perfect focus to the nearest point in
focus is given by

              c f s (s-F)
doffront = -------------------
             F^2 + c f (s-F)

And the depth to the farthest point is given by 

              c f s (s-F)
dofrear = -------------------
             F^2 - c f (s-F)

except that if the denomintor is zero or negative then all points
beyond the subject, clear out to infinity, are in focus.

        f       geometrical f number of lens 

        c       allowable circle of confusion, say .000030 meters
        
        s       distance beyond front nodal point of lens (approx. center)

        F       focal length of lens


You can simplify this a lot if the distance is fairly far.  For
example, s*(s-F) can be replaced by just s^2, and s-F in the
denominator by s.  

If s is infinity, then the closest point that is in focus is at
distance F^2/(c f).  This is the hyperfocal distance.

Someone else wrote:

> I also heard that one third of this depth is before the object and the
> rest behind the object. Is this true? Can anybody send me any
> information about this?

Well, under exactly the right circumstances yes, but in general no.
The easy rule that works right is to find the point on your focusing
scale corresponding to the nearest point you want in focus and
similarly for the farthest point.  Then focus half way between *by
physical distance on the focusing scale*.  

  -- David Jacobson

Newsgroups: rec.photo
From: micki@netcom.com (Michelle Stone)
Subject: Re: Vivitar Ring Flash Question
Organization: Netcom - Online Communication Services  (408 241-9760 guest) 
Date: Wed, 16 Dec 1992 08:53:51 GMT

GE.DWS@forsythe.stanford.edu (Drew W. Saunders) writes:

>Does it have more than one light?  (For side-flash)

I looked at this some time back and decided to get 
the Nikon flash instead.  But this question I can 
answer.  The light is a ring.  There is one bulb 
in it and it goes all the way around.

The flash that I liked the best was the Minolta
macro flash.  It had four lamps in it and you 
could turn any of them on or off.

The Nikon has two lamps and you can decide which
ones are used.  When I need vertical or horizontal
lighting, I move the flash around its mount.

Michelle

-- 
micki@netcom.com

By the way.  I find myself to be a recent addition to the 
unemployment statistic.  I am a software manager.  If  you know
of an opportunity, please let me know!
From: sog@craycos.com (Steve Gombosi)
Newsgroups: rec.photo
Subject: Re: Need help getting dark B&W sky
Date: 13 Dec 92 19:12:05 GMT
Organization: Cray Computer Corporation

In article <180600010@hpcndaw.CND.HP.COM> antonsen@hpcndaw.CND.HP.COM (Tim Antonsen) writes:
>The sky in the Sierras is a remarkably deep blue. The sky in Texas is, I'm
>sorry to say, not the same. This probably explains your problem. Filters are
>unlikely to solve it. You could try infrared film (properly filtered) for
>*reeeeealy* black sky, but you probably don't want its other characteristics.

In addition, skies everywhere are less blue than they were in Adam's day -
especially the last year or so (thanks to aerosols and particulates from
Mt. Pinatubo). Try again in a year or two - I think you'll have better results.

Steve
Newsgroups: rec.photo
From: ka1gt@cbnewsm.cb.att.com (robert.m.atkins)
Subject: Re: Choice of Teleconverter
Organization: AT&T
Distribution: na
Date: Wed, 16 Dec 1992 18:36:09 GMT

In article <1992Dec16.152312.26162@spider.co.uk>, mikec@spider.co.uk (Mike Coren) writes:
> In article <zawada-141292175621@ottawa.eid.anl.gov> zawada@athens.eid.anl.gov (Dave Zawada) writes:
> >Hi,
> >
> >I am thinking of buying a 2x teleconverter for my Eos 10s.
> >I would use it with my 100-300 USM lens.
> >
> >The salesman at my local camera shop has told me that
> >I would be better off going with a Tamron converter, as
> >opposed to one from Canon.  He claims that the Tamron is
> >100% compatible, has the same quality optics, and is
> >around $100 cheaper.  Is there any truth in his statement?
> >
> >Any comments/suggestions would be greatly appreciated.
> >
> >Thanks in advance,
> >
> >Dave
> 
> Tamron is a good name, which I would trust.  Canon only recommends their own
> converters for use with one or two of their larger and more expensive lenses,
> like the 400mm L.  I'm not sure why, though.
> 

Most manufacturers (Canon, Nikon etc.) recommend only the use of their own
teleconverters - for reasons of quality mainly. What I think you mean is
that Canon only recommend the use of their teleconverters with a restricted
subset of their lenses. This is because of mechanical, not just optical,
compatibility. The front element of the EF converters stick out in front of
the mount, so the prime lens it is attached to must have room for it to fit.
The lenses that the Canon EF converters are compatible with are basically the
fixed focal length "L" series telephotos (200/2.8L through 600/4L). They
might fit one or two others (?) but Canon specify compatibility only with
the L series telephotos.

===============================================================
Bob Atkins  AT&T Bell Labs  email (direct)  att!clockwise!rma
===============================================================
From: chorley@vms.ocom.okstate.edu
Newsgroups: rec.photo
Subject: Re: Nikon 105 f2.8 wanted
Date: 14 Dec 92 21:18:14 GMT
Organization: OSU College of Osteopathic Medicine

In article <168BD81AF.ADMSRUBN@VM.UWP.EDU>, ADMSRUBN@VM.UWP.EDU writes:
>  
> A friend of mine is looking to buy a used Nikkor 105 f2.8.  If
> anyone has one for sale, please call me at 414-595-2576 or email me with
> details so I can pass along info to him for follow-up.

Do you mean the Micro-Nikkor?
>  
> Thanks.
>
From: chuq@Apple.COM (Eeyore's Evil Twin)
Newsgroups: rec.photo
Subject: Re: Maxxum 5xi LCD display
Date: 21 Dec 92 05:30:03 GMT
Organization: Pooh Corner Country Club -- A Planned Community

mssmith@afterlife.ncsc.mil (M. Scott Smith) writes:

>   Basically, this number is shown all of the time, regardless of whether the
>camera is on or off.

>   My question is: is this normal?  Is there a way to turn it off?  Is it
>draining the battery?

Yes, it's normal. No, there's no way to turn it off. If it drains the
battery, it's really minimal, and if you leave the camera off for a while,
it'll shut itself off completely.

-- 
            Chuq "IMHO" Von Rospach, ESD Support & Training (DAL/AUX)
                      Member, SFWA =+= Editor, OtherRealms
                chuq@apple.com | GEnie: MAC.BIGOT | ALink:CHUQ 

                       Sterling Holloway: We'll miss you.
Newsgroups: rec.photo
From: markm@wri.com
Subject: Ektachrome Flavors ??
Reply-To: markm@wri.com
Organization: Wolfram Research, Inc.
Date: Tue, 15 Dec 1992 15:21:51 GMT



Greetings!

Some time over the summer, someone posted an excellent comparison of all the  
different Ektachrome flavors (HC, X, etc.).  I didn't really have a need for it  
at the time since I was using Kodachrome almost exclusively.  Well, budget  
constraints now force me to consider switching to E6.

Does anyone still have this summary?

Or how 'bout starting a new thread on favorite Ektachrome flavors?

--Mark
Newsgroups: rec.photo
From: briang@atlastele.com (Brian Godfrey)
Subject: Re: Idea for Photo Publicaton
Organization: Atlas Telecom Inc.
Date: Thu, 17 Dec 1992 23:54:42 GMT

In article <1gjkuvINN44k@cheech.cs.ubc.ca> samuel@cs.ubc.ca (Stephen Samuel) writes:
>There used to be (a few years ago) somebody who organized collecting
>and mailing groups of photographs around the country to people who then
>commented on those photos.  Is this still being done? (I've not seen any
>signs of it so far (I've only started reading this group, again, today).
>
>If it's not being done, does anybody have a copy of the rules that were 
>used for the original groups?  I'd like to start something like this up
>again.

   I was the administrator of the Theme Portfolios, two or three years ago.
I lost my job over a year ago and only recently got access to rec.photo
again.  It appears that they have died while I was gone.  I cannot start
them up, because my current position involves frequent travel outside of
the country for extended periods of time (2-6 weeks at a time.)  I would
not be able to do a proper job of administering the program with such an
unpredictable life and that would be very unfair to participants, but I am
willing to help start it and support you if you can commit to the time it
takes to make it work well.  

   The way it worked was that rec.photo readers nominated and voted on 
themes, then had a month or so to prepare submissions for the portfolio 
following that theme.  There was a new theme each month, and everyone had 
the opportunity to participate.  Discussion of the photos in rec.photo was 
encouraged.

   If anyone else thinks we should restart the Theme Portfolios, and thinks 
you might actually submit photos to them, please let us know, so we can 
decide if it is worthwhile.  

-- 
--Brian M. Godfrey
  atlastele.com
Newsgroups: rec.photo
From: sysrick@starbase.spd.louisville.edu (Rick McTeague)
Subject: Need help with Canon AE-1 problem...
Date: Mon, 14 Dec 1992 06:54:52 GMT
Organization: University of Louisville

I just picked up a broken Canon AE-1 at a local pawn shop for $50. The
problem was described to me as a "short somewhere". Hmmmm... That's
the kind of thing I like hearing, because it generally means nothing too
serious...

Well, I've been looking at it, and here's what I know: The camera is
mechanically functional; after fixing one small electrical problem 
(an open - not a short - where someone tried to fix it before and tore a
flexible circuit board in the camera's bottom), I can hit the shutter
release and it'll "snap".

Here's where I run into a problem, and I assume this is what someone
must have been trying to fix before: The shutter (curtain? whatever it's
called) never actually opens, because the "hold right side of the shutter open"
solenoid doesn't seem to get the proper signal. The "seam" of the
shutter _does_ move, so the cameras is attempting to fire the shutter.

There's also the possibility that the previous owner miswired it; I
tried switching the wiring around (in a logical way), but it causes 
the shutter to stay open continuously once the shutter release is hit.

The meter never moves, unless I press the (I assume) battery test 
button on the top of the camera. Also, if I turn the lens aperture ring
off the "A" (automatic?) setting, an "M" indicator in the viewfinder flashes.
I guess this means "Manual", but it never stops - even when I lock
the shutter release off - unless I turn the aperture ring back to "A"
(or my battery goes dead).

Is there anyone out there who's familiar with the insides of an AE-1? 
My current best theory is that a leaky battery may have caused some
corrosion in the area just behind/under the battery connector. It looks
like a pretty major disassembly job, and I really don't want to do it
unless it's the only choice. And yes, I'm reasonably mechanically and
electrically skilled...

While I'm at it, would anyone consider exlaining the two buttons on the
left of the lens mount? I guess I could go to a camera shop and ask, but
I'm hoping someone will tell me.

Any help you can give would be appreciated... I'd really like to replace
an aging SRT-101-with-coke-spilled-in-the-lens with this camera.

Rick
-- 

Rick McTeague
Electrical Engineering Department, Speed Scientific School
University of Louisville, Louisville, KY 40292
(502) 588-7020

Internet: sysrick@starbase.spd.louisville.edu

Disclaimer: I'm a stand-up comedian; if anyone takes me seriously, I'm
            doing something wrong!
Newsgroups: rec.photo
From: briang@atlastele.com (Brian Godfrey)
Subject: Re: Attaching filter swatch sample to SB-24
Organization: Atlas Telecom Inc.
Date: Fri, 18 Dec 1992 00:03:04 GMT

In article <16DEC92.17515926@sklib.usask.ca> supplies@sklib.usask.ca writes:
>Does anyone know a good safe way of attaching a filter from a swatch
>book to the flash head?

   Tape.

>The Lee filter swatches are exactly the width of the SB-24  and just a little
>longer.

   In case anyone didn't know it, Rosco filter swatches are also the right
   size to tape over most flash units.  You can get a book of them for free
   by calling B&H or some of the other mail-order camera shops.  Probably
   also by calling Rosco.  (No, I don't know the number.)

>Can I just tape them on? What about the heat generated by the flash?
>I don't want melted gel/tape stuck to my flash.

   Don't like that battle-scarred pro look, eh?  :-)

   The tape will leave some glue behind which will accumulate unless you
   remove it periodically with alcohol or something, but nothing should
   actually melt onto your flash unless it's a lot hotter than my 283 or
   285.  The gels are certainly made to take the heat.  If your tapes 
   does melt, try a different tape.

-- 
--Brian M. Godfrey
  atlastele.com
Newsgroups: rec.photo
From: jacobson@cello.hpl.hp.com (David Jacobson)
Subject: Re: Filter/Optics Question...
Date: Wed, 16 Dec 1992 18:25:46 GMT
Organization: Hewlett-Packard Laboratories

In article <1992Dec16.000542.7497@adobe.com> wtyler@adobe.com (William Tyler) writes:
>In article <1992Dec15.040116.19838@cello.hpl.hp.com> jacobson@cello.hpl.hp.com (David Jacobson) writes:
>>In article <2024@intermec.UUCP> jay@intermec.com () writes:
>>>   Question:  Is is possible to use a filter somewhat smaller than
>>>	      the front element of the lens it's put on and avoid
>>>	      vignetting by stopping down.
>>>		 
>>>	      Put another way, does stopping down result in a smaller
>>>	      area of the front element being used to create the image.
>>
>>You can probably do this.  To find out, open the back of the camera
>>and open the shutter using bulb or the slowest shutter speed and the
>>desired f-stop.  (With many whizzo electronic cameras you have to
>>defeat an interlock.)  Now look through the corner of the frame.  If
>>you see just the shape defined by the diaphragm you are ok.  If you
>>see a football (American usage) shaped area defined by two circles you
>>have vignetting.  but if you can't see the filter ring you are no
>>worse off than the lens was by itself.  It might be hard to tell, and
>>you will have to compare filter off vs. filter on.
>
>Stopping down is the wrong thing to do to avoid vignetting. One way of
>thinking of the optical situation is that you have put a small
>circular object in front of and very close to your lens. You don't
>want to be able to see the object. But stopping down will help to
>BETTER FOCUS it, thus making its dark image appear on your film (i.e.
>vignetting). 

Note that the result of my procedure was to verify that the filter
ring did not add any vignetting.  If the ring isn't visible, then
it can't possibly be having any effect.

Bill says that stopping down is the wrong thing to do.  His argument
is based on defocusing the offending obstruction.  However, it appears
that he has missed an important point, namely that two factors
contribute to the needed diameter of a filter ring.  First is the
angle of acceptance times the distance from the front nodal point to
the filter ring.  Thus a wider angle lens needs a bigger filter ring.
The second is the diameter of the aperture.  With a smaller aperture,
you use less of the peripherey of the lens.  

  -- David Jacobson
Newsgroups: rec.photo
Subject: Re: Does Minolta X-700 allow shutter priority auto mode
From: fred-mckenzie@ksc.nasa.gov (Fred McKenzie)
Date: 15 Dec 92 13:02:57 EST
Followup-To: rec.photo
Distribution: world
Organization: NASA/Kennedy Space Center, Florida

In article <fourie.27@odie.ee.wits.ac.za>, fourie@odie.ee.wits.ac.za (Andre
Fourie) wrote:
> I have purchased a 2nd hand Minolta X-700 camera. The camera seems to 
> support only aperture priority "A" and program "P" modes as well as a manual 
> mode. Somebody told me that the camera can be used in shutter priority mode 
> as well.

Andre-

I'm not familiar with the Minolta X-700.  However, I have the Pentax Super
Program, which has similar capabilities.

With the Pentax, full program mode requires that both the body and lens be
set for program.  If the body is set for program, but the lens is set for a
specific aperture, then it becomes aperture priority.  If the body is set
for manual, but the lens is set for program, then it becomes shutter
priority.

If the Minolta lens has an "A" or a "P" setting, it may behave as suggested
above.  I'm not sure how to verify or disprove this, if the manual doesn't
cover the program lens/manual body combination.  You might try it, and see
if there is an indication in the viewfinder to let you know what is
happening.

fred-mckenzie@ksc.nasa.gov
From: pharris@ucscm.ucsc.edu (Peter Harris)
Newsgroups: rec.photo
Subject: Re: Mirror lock-up, Has anybody really tested?
Date: 16 Dec 92 21:12:13 GMT
Organization: University of California Santa Cruz
NNTP-Posting-Host: twilight-mac07.ucsc.edu
X-UserAgent: Nuntius v1.1.1d13
X-XXMessage-ID: <A754DCD868060257@twilight-mac07.ucsc.edu>
X-XXDate: Wed, 16 Dec 92 22:17:12 GMT

Yeah, well, it sure helps w/long tele stuff and
my Nikon F (and F2) aint no doubt about it. Put
it on de tripod and hook up de ole cable
release. There  IS a clear difference.
>Newsgroups: rec.photo
Peter Harris
University of California Santa Cruz
Organization: University of Illinois at Chicago
Date: Friday, 18 Dec 1992 23:27:52 CST
From: Rich Chong <U41602@uicvm.uic.edu>
Newsgroups: rec.photo
Subject: Re: color change w/o exposure change: Why?
 <1992Dec14.163600.28639@athena.cs.uga.edu>
 <1992Dec14.174747.16726@walter.bellcore.com>


>Even when the exposure/lighting conditions are exactly the same between
>consecutive frames, with slight shift in panorama view, the colors of
>the sea, sky and sand always show up slightly different between prints.
>
>Is this caused by the processing or different angles with respect to the sun?
>
>Jason Chen

Probably yes and yes. When you say "exposure conditions are exactly the same
between frames", do you mean that you turn off any automation on your camera,
like auto-aperture and auto-speed? You should, because you don't want any
metering in the camera changing when you shift the camera to another angle.
Even if the lighting looks the same to your eyes, it can be quite different.
As you pan around, the sky may get darker or lighter. The addition of a diff
building in the scene may reflect differently also fooling your metering.
and then when you try to join two pictures of a sky, they will've been
exposed differently. Don't be fooled by a digital auto speed or auto aperture
display, 1/60th of a second on the display could mean anything between
1/45th to 1/90th in reality. Beter to meter it, and lock it on.
The same goes for processing. If each print is metered or color-balanced
separately, the same thing will happen. And that will depend on where you
get your prints processed. If you took it with auto-mode and then also
processed it with an auto-processor, then there a chance you were hit by
a double whammy. Lotsa luck!

Rich Chong  -  RC Tech Enterprises, Inc.
Newsgroups: rec.photo