HDTenEightyP/NetNews huggingface dataset:
From: ka1gt@cbnewsm.cb.att.com (robert.m.atkins)
Subject: Re: Lens Focusing (was Re: lens tests..)
Organization: AT&T
Distribution: na
Date: Wed, 30 Sep 1992 16:02:55 GMT

In article <3830317@hpldsla.sid.hp.com>, tonya@hpldsla.sid.hp.com (Tony Arnerich) writes:
> ka1gt@cbnewsm.cb.att.com (robert.m.atkins) writes:
> 
> # In article <1992Sep24.232108.14002@odin.corp.sgi.com>, donl@glass.esd.sgi.com (donl mathis) writes:
> # > 
> # > |> In article <1992Sep22.201647.8945@truevision.com>,
> # > frank@truevision.com (Frank Loffel) writes:
> # > 
> # > |> > - How can you ensure perfect focus?
> # > 
> # > If you can arrange to put a point source right at the same position as
> # > your subject, you can use a knife edge at the film plane to ensure
> # > perfect focus.  Open the back of the camera, put a knife edge across
> # > the opening precisely at the plane the film will be in, and then move
> # > your head around until the edge cuts through the image of the point
> # > source.  The image of the point source is formed by rays coming through
> # > the whole aperture, all converging on a single point at the plane of
> # > focus, and then crossing over and diverging again behind the plane.  In
> # > other words, there are two cones, whose tips are joined at the plane of
> # > focus.  If your knife edge is on either side of focus, it will be
> # > cutting halfway into the cone, but you'll still be able to see the
> # > other half.  If you're precisely at focus, there is no diameter to cut,
> # > so the point should just wink in and out as it moves behind the knife
> # > edge.
> # ...
> # HOWEVER, these techniques are of little use when lens testing with a 35mm
> # camera, since you have no access to the image plane. 
> 
> I have yet to see a 35mm camera (besides auto-load P&S) where there is
> no access to the image plane. I have used the knife-edge technique on
> the film rails on many occasions in the last 20 years. As donl says,
> open the camera back.
> 

I guess I didn't explain myself clearly enough. My point is that you can
certainly get to the image plane OK, but you can't use that method for
each shot of a 36 exposure roll of 35mm film if you are trying to test
a variety of lenses, or one lens under a set of conditions (different
apertures or focusing distances). Unless you want to unload and reload
the film for each exposure, measuring in the image plane is not practical
for 35mm lens testing. The is no way to tell if the image is focused on the
image plane except by (a) trusting the AF, (b) trusting the viewfinder screen
or (c) making a number of exposure JUST inside and outside the position of
indicated best focus. The only time the image plane measurment is practical
is in astrophotography, where all your subjects are at infinity and once you
have found the correct focus position you never need to change it.

===============================================================
Bob Atkins  AT&T Bell Labs  email (direct)  att!clockwise!rma
===============================================================

Newsgroups: rec.photo
From: zrepachol@cc.curtin.edu.au (Paul Repacholi)
Subject: Re: USMs and post focal ...
Organization: Curtin University of Technology
Date: Sun, 27 Sep 1992 18:24:42 GMT

In article <27SEP199217152463@vms1.iscs.nus.sg>, nuscss1@vms1.iscs.nus.sg (Vax BULLET-IN-Board SysOps) writes:
...
> 	CF7 does not put the 630 into single or servo mode. It is
> 	*supposed* to allow manual focusing without having to flip
> 	the AF/M switch on the lens. Its one of the Custom Functions
> 	definable by the user. I don't know anyone else with another USM
> 	lens that I can try it out with.
> 
I was refering to the yellow button under the back cover that selects the AF
mode.

...
> 	hmmm... well, i've tried turning the focusing ring with about 
> 	as much pressure as it's possible without breaking something.
> 	it's still stuck as firmly as a clam. I fear using more strength to
> 	force the focusing ring may cause damage to the lens mechanism.

sounds like another design family... Prob the micro-USM type. This brings to
the number of EF focusing mechanisms to six... time for a new EF lens list RSN.

~Paul

Newsgroups: rec.photo
From: jamesp@cory.Berkeley.EDU (Jim Peroulas)
Subject: 430EZ battery pack
Organization: University of California, at Berkeley
Date: Sun, 27 Sep 1992 02:18:25 GMT



From: zrepachol@cc.curtin.edu.au (Paul Repacholi):
I had a quick check of my 430 when I got it. Just re-checked. The long center
pin is the common, the front pin is +6v. Note that this is after the sleep
circuit, so powering the flash from here will result in the flash not 'going to
sleep'. The back pin is the HV connection via an isolation diode. The 2 top
connectors in the battery compartment are the active ones. There is a direct
permanant connection from the -ve batt conector to the common pin of the bottom
connector. Anyone know the voltage for the back pin?


First of all thanks to all that have replied to my initial question. What I
was hoping to do was go through the connector on the side of the flash instead
of makeing something that would fit into the battery compartment.

From what I understand, I could just take a 6 volt battery pack and connect
the positive to the front pin and the ground to the middle.

My questions are:
1)	Would a battery pack composed of C or D size batteries be worth the
effort or do I really have to get some of the higher power packs that have
been mentioned?
2)	I'm assuming that HV connection stands for High Voltage connection.
Do I have to make some use of this pin? If not, why is it there?
AND most importantly:
3)	Where can I find a connector that will fit?

						-JP

Newsgroups: rec.photo
From: news@walter.bellcore.com
Subject: Re: Filters, Lots of Qs...Please help
Reply-To: jchen@wind.UUCP (Jason Chen)
Organization: Bellcore, Morristown, NJ
Distribution: usa
Date: Tue, 6 Oct 92 03:43:59 GMT

In article <1992Oct5.165459.29039@linus.mitre.org> rajiv@hilltop.mitre.org (Rajiv Kohli) writes:
>
>I just bought two filter, Polarizer and a tungsten Color Correction.
>I was just wondering if somebody could guide me the use of mixing two of
>them together. I don't like the idea of switching lenses in the first
>place and then followed by switching filters..OOOOOH!
>
>What I was wondering the results would be if I left the polarizer on and
>for night photography put the color correction on top of it. Is it a NOT!
>
>How about in the daytime if I left the Color correction filter on? Is
>this a NOT, too?
>
An ideal polarizer should be neutral density. It can be mixed with color 
correction filters, as long as you can stand the light loss. Purists will
also warn you of loss of optical quality. A third, and a very practical
concern is vignetting. You need to find whether your lens allows multiple
filters on it.

>Does the color correction work only for Tube lit room or for filament
>bulbs too?
>
You confused me. Didn't you just say the filter is for tungsten 
color correction? Then it is NOT for fluorescent correction.

>What make of filters are good? I was told that COKIN are plastic and not
>recommended. So I bought HOYO. Then somebody told me that I should have
>bought TIFFIN. The latter two are in glass.
>
Hoya and Tiffen are considered equal, if you don't get too picky.

>Last of all. When I use a 28mm setting on my 28-85 lens with wifee
>standing on the side and I try to cover a wide area (Also using a auto
>focus auto zoom flash), my wifee almost always comes out over exposed.
>Since she is always standing at a variant distance from the camera I am
>looking for a general to avoid over exposure of objects close to the
>camera when one is using a wide angle to cover a vast area. 

Your problem seems to involve an uneven lighting situation. But I can not
understand how that relates to the distance.... unless you are using a
flash. But then how it further relates to the wide angle lens? I pass. 


C. Jason Chen 
jchen@wind.bellcore.com
From: mas@mipl8.jpl.nasa.gov (Marc Sarrel)
Newsgroups: rec.photo
Subject: How does solarization work?
Date: 29 Sep 92 00:14:18 GMT
Distribution: rec
Organization: Jet Propulsion Laboratory

I've been following a few of the threads recently, and I've come up
with a question about solarization.

How does it work?

Basically, the technique goes something like this.  I'll have a better
idea once I actually get to do it in my photo class.

After cropping your image and doing some test strips with two series
of exposures running perpendicularly to eachother, expose your paper
for the first time, put it in the developer for a while, wipe off the
paper to remove excess developer, the expose the paper to light, no
neg involved.  The result is that some of the areas that would have
been dark in a normal image "wrap-around" and become light again.

There is an alternate method where you expose the paper once with a
neg in the enlarger.  Then, wipe the paper with a paper towel soaked
in developer.  Then expose the paper to the image a second time.  The
aparently gives a slightly different effect.

What, chemically, is going on here?

--marc
--
Marc Sarrel			"And they lived ever after, which is about
Jet Propulsion Laboratory	 all you can expect from a story like this."
mas@mipl8.jpl.nasa.gov		            --  Fractured Fairy Tales
Newsgroups: rec.photo
From: smustopo@nyx.cs.du.edu (sofjan mustopoh)
Subject: Re: Leica, why so high?
X-Disclaimer: Nyx is a public access Unix system run by the University
	of Denver for the Denver community.  The University has neither
	control over nor responsibility for the opinions of users.
Organization: Nyx, Public Access Unix at U. of Denver Math/CS dept.
Date: Mon, 28 Sep 92 23:15:19 GMT

In article <5129@daily-planet.concordia.ca> honna@cs.concordia.ca (SEGEL 
onna) writes:
>In article <1992Sep24.044302.176671@ns1.cc.lehigh.edu> gg00@ns1.cc.lehig
.edu (GULDEM GUVEN) writes:
>>I've been always wondering and never had a chance to hold a Leica. What
makes
>>them so expensive?
>
>I suggest you do everything you can to have the chance to hold one...
>and if you get that lucky, fiddle with the focus, remove and replace the
>lens, cock and release the shutter...your question will be answered or
>seem unnecessary.
>
>
>
>
>
>
>
>
>
>HS/ Michael
>   
>
>
>
>-- 
>***************************************************************
>honna segel
>department of computer science
>concordia university  *****************************************


  I have always dream about owning a Leica. My first contact with
  Leica is when a German tourist visiting Lake Toba ( Near Medan
  Indonesia ) let me hold his Leica M3 .  I was only 15 at the time
     Now here i am studying in USA saving enought money to start 
  my hobby again i bought Maxxum 800i and 50mm 1.7 and 5200i flash
  it cost me alot but not really that much.
     In my current student status a Leica will means starving my self
  with diet of one cauliflower a week to save that lump sum of money
  to buy it.

     I'm Still dreaming.  Z Z Z Z Z Z Z z

  p.s i don't mean that AF  jokes Leica
      i mean M6 leica

Muskie
Sofjan mustopoh
UK07802@mik.uky.edu

" Any body want to sel his or her Leica to a poor student on 
  instalment basis !!!!!!!"
From: andyc@hplsla.hp.com (Andy Cassino)
Newsgroups: rec.photo
Subject: Re: technical info (was Popular Photography, then Nikon magazine)
Date: 1 Oct 92 20:20:25 GMT
Article-I.D.: hplsla.5360810
Organization: HP Lake Stevens, WA

ehr@ecsvax.uncecs.edu (Ernest H. Robl) writes:
| 
| I have been using Nikon equipment for more than 25 years, and though
| I have been happy with the equipment itself -- or I would not have
| continued using it -- I have never been happy with the quality of the
| technical information available.
| 
| (stuff deleted) 
| 
| Even a good camera store isn't going to stock even a quarter of the
| items in the Nikon product line.  So, you either have to have them
| order it for you, or order the item from a mail-order house.
| 
| And, that means that -- unless you have seen someone else use this
| particular item -- you are ordering what may be a fairly costly
| item on only a very brief description.
| 
| In many cases, it's a case of just being able to find out that a
| particular accessory exists.

A friend once showed me a Nikon Technical manual from the early '70s. It was
a loose-leaf manual with information on everything in the Nikon system and
how to use it. It was truly wonderful, and still quite useful for those that
use "classic" Nikon gear. 

These days, while Nikon is not publishing any such information, there ARE
a number of Nikon "system" books that do a fair job of describing much of
the Nikon system. In fact, it's the same for Canon, Minolta, etc. Except
for Leitz and Hasselblad (that I am aware of) there are no 
manufacturer-produced books on how to use the various cameras and
accessories. It would appear that most manufacturers totally rely the
independent publishers to produce compilations of information about their 
systems (although they do provide some equipment and tech info to the
authors preparing the books).

Also... a good dealer really can help out, if one can be found. I'm fortunate 
to have a choice of several dealers that can advise quite knowledgeably 
on the use of almost any camera system. Unfortunately, it seems enough 
people shop their stores and then use the information to buy from a discount 
house that one must establish a purchase record before they'll start sharing 
the information very freely. Which is one reason I hardly ever use mail-order
any longer. A penny saved is goodwill squandered, in some cases.


    %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    % Andy Cassino                                       %
    % Hewlett-Packard - Lake Stevens Instrument Division %
    %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
From: zlsiida@fs1.mcc.ac.uk (dave budd)
Newsgroups: rec.photo
Subject: Re: How to calculate flash exp with extension tubes
Date: 2 Oct 92 12:24:04 GMT
Organization: Manchester Computing Centre

In article <1992Sep30.033612.25878@cello.hpl.hp.com> jacobson@cello.hpl.hp.com (David Jacobson) writes:

>In article <1992Sep29.174911.17757@u.washington.edu> watters@mendel.genetics.washington.edu (Mike Watters) writes:
>>Just a quick question (with hopefully some quick answers :)
>>
>>I'm going to be photographing some small artifacts and wanted to use
>>both flash (to get them well lit) and extension tubes (to get up close and
>>personal).
>>
>>I know how to figure things out normally (just set the lens to the f-stop
>>appropriate for the distance between flash and subject), but I suspect
>>the extension tube changes things a bit.

>Here are a few formulas that will solve your problem.  

>M = F/(S-F)

>S is lens (actually front nodal point) to subject distance
>M is magnification
>F is focal length

>effective_f_stop = geometric_f_stop * (1+M)^2

>When computing flash exposures from flash-to-subject distance and
>guide number, you want to use the effective f-stop.

>You can find the front nodal point by letting light from a distant
>object go thorough the lens backwards (ie go in the rear element and
>come out the front element).  Find the point where the image is
>formed, then measure 1 focal length toward the rear of the lens.
>(This doesn't work on some lenses, as the image is formed behind the
>front element.  This happens on my Sigma 24mm.)

>  -- David Jacobson

Does this require adjustment if the flash is a different distance from the 
subject than the camera is?


              Have another day    [Armageddon, the musical] 
  Dave Budd, MCC, Oxford Rd, Manchester, England   (44|0)61-275-6033  
Newsgroups: rec.photo
From: mvolo@ecsvax.uncecs.edu (Michael R. Volow)
Subject: Re: Lens Focusing (was Re: lens tests..)
Organization: UNC Educational Computing Service
Date: Thu, 1 Oct 1992 15:05:12 GMT

al@qiclab.scn.rain.com (Alan Peterman) writes:

>In article <3830317@hpldsla.sid.hp.com> tonya@hpldsla.sid.hp.com (Tony Arnerich) writes:
>>
>>I have yet to see a 35mm camera (besides auto-load P&S) where there is
>>no access to the image plane. I have used the knife-edge technique on
>>the film rails on many occasions in the last 20 years. As donl says,
>>open the camera back.

>Well there's Leica rangefinders....The bottom comes off, but access
>to the film plane is pretty poor.  

>-- 
>Alan L. Peterman                                 (503)-684-1984 hm & work
>                       al@qiclab.scn.rain.com
>It's odd how as I get older, the days are longer, but the years are shorter!
On the contrary, at least on my M2, the back cover can be not only
flipped up out of the film plane, but can easily be removed with
a little catch at the left side of the back of the cover.
-- 
Michael Volow, Psychiatry, Durham VA Med Center, Durham NC 27712
919 286 0411 Ext 6933               mvolo@uncecs.edu
Newsgroups: rec.photo
From: plak@phil.ruu.nl (Martijn Plak)
Subject: ilford delta
Summary: what's different?
Keywords: bw
Organization: Department of Philosophy, University of Utrecht, The Netherlands
Date: Sun, 27 Sep 1992 21:40:04 GMT

Hi all!

I have just used ilford delta b/w films for the first time, and have a question:

does anyone know what is so different about this films, compared to hp5?

have a good day!
From: zrepachol@cc.curtin.edu.au (Paul Repacholi)
Newsgroups: rec.photo
Subject: Re: 430EZ battery pack
Date: 27 Sep 92 18:14:44 GMT
Organization: Curtin University of Technology

In article <1992Sep27.021825.7288@pasteur.Berkeley.EDU>, jamesp@cory.Berkeley.EDU (Jim Peroulas) writes:
...
> From what I understand, I could just take a 6 volt battery pack and connect
> the positive to the front pin and the ground to the middle.
> 

Thats my initial plan too.

> My questions are:
> 1)	Would a battery pack composed of C or D size batteries be worth the
> effort or do I really have to get some of the higher power packs that have
> been mentioned?
> 2)	I'm assuming that HV connection stands for High Voltage connection.
> Do I have to make some use of this pin? If not, why is it there?

I believe not, unless of course you want the faster recycle time the exteral
converter can give you.

> AND most importantly:
> 3)	Where can I find a connector that will fit?
> 
Funny you should mention that... I am going up to the best conector etc agent
this week, but it is a long weekend in WA... Stay tunned. 

BTW, this will probably be a custom build job, so I may ask if any other are
intersted as well. Its not much more work to machine a bunch of them. Don't
ask yet please, Ill let you know...

~Paul
Newsgroups: rec.photo
From: lswab@x400gate.bnr.ca (Lyndon Swab)
Subject: Re: Pentax Auto 110 info wanted
Organization: Bell-Northern Research Ltd.,
Distribution: usa
Date: 30 Sep 92 20:22:42 GMT

>>>>> On Tue, 29 Sep 1992 16:12:48 GMT, bower@hfsi.uucp (Michael Bower Comm. ) said:

  Michael> Rec.photo netters:

  Michael> I have a chance to get a Pentax Auto 110 system here in my
  Michael> area.  This is a 110 camera that is basically a miniature
  Michael> SLR with several lenses.

  Michael> Can anybody shed any light on this setup.  Is it a good
  Michael> camera? bad camera? whatever?  I know the limitations of
  Michael> 110 film but aside from that, it looks like a nice camera
  Michael> for keeping in ones pocket.  (It is bulkier than the MINOX
  Michael> camera but the film is slightly larger and easier (and
  Michael> cheaper) to get.

  Michael> Any thoughts will be appreciated.
  Michael> Thanks in advance.

  Michael> Michael Bower
  Michael> bower@hfsi.com

My mother owned one of these for years.  It is a very "cute" camera,
but unfortunately, the picture quality is poor.  I have a minox (35mm) 
which, IMHO, is infinitely better.

The Pentax took thousands of pictures, but eventually, it flew apart.
It certainly isn't "Professional" quality.  The first thing to go was
the catch on the film door, so I would be very careful to check that
everything works fine before buying.

I wish my ma still had it...
--
Lyndon Swab     lswab@bnr.ca, (613) 763-7165, ESN 393-7165
From: simons@tuntu.think.com (Joshua Simons)
Newsgroups: rec.photo
Subject: Tom Thumb
Date: 5 Oct 92 10:44:51
Organization: Thinking Machines Corporation, Cambridge MA, USA
Distribution: rec
NNTP-Posting-Host: tuntu.think.com


Sorry if this is a silly question, but is it possible to take a picture
that would look as if it was taken by a small person (someone on the order
of a few inches tall) with an appropriately scaled 35mm camera? I'd like to 
end up with a standard sized print of the same quality as prints from 
standard 35mm film.

Any ideas? Thanks.

josh simons

--
simons@think.com
thinking machines corporation
245 first street					tel: 617.234.2844
cambridge, ma  02142-1214				fax: 617.234.4444
Newsgroups: rec.photo
From: stoppani@ninja.zso.dec.com (Pete Stoppani)
Subject: Re: Experience with Canon EF 100-300mm f/4.5-5.6 USM
Reply-To: stoppani@ninja.zso.dec.com (Pete Stoppani)
Organization: Digital Equipment Corporation - DECwest Engineering
Distribution: na
Date: Wed, 7 Oct 1992 02:42:35 GMT


|>In article <92279.203505IO92112@MAINE.MAINE.EDU>, IO92112@MAINE.MAINE.EDU writes:
|>>
|>>In article <19920ct5.201357.5558@cbnewsm.cb.att.com>, ka1gt@cbnewsm.cb.att.com
|>>(Robert. M. Atkins) writes:
|>>
|>>>unless my memory is fading (which it might be), I thought that the EF75-300
|>>>had a ROTATING zoom control, not a push-pull control (like the 100-300L)
|>>>Given this, it is hard to see how the zoom would slide in the vertical
|>>>position. The push-pull zooms (from most lens makers) are prone to this
|>>>"zoom creep" effect, but I've never seen it in lens which zooms via a
|>>>rotating ring. Maybe the "gearing" on these zooms is now so low that creep
|>>>is possible. If you say it is there, then I believe you.
|>>
|>>You are right. The Canon EF 75-300mm is the rotating ring zoom unlike
|>>EF 100-300mm USM with push/pullring. However, the zoom rings in both
|>>zoom so loose that whenever the lenses are in verticle position the
|>>zoom rings slide down. I own a EF 100-300 USM. Before I bought this
|>>lens, I went to photo shop to play both lenses. Both of them have the
|>>loose ring problem. I thought the lenses I played in the store were
|>>defect and wear down. But the saleperson picked up the lensfrom other
|>>packages, all of them were the same. Although I am really satified with
|>>the zoom ring, I got the EF 100-300mm USM through mail-orderfrom B&H
|>>because of its fast and quiet focus, and good optical quality.
|>>I personally don't own a EF 75-300mm zoom. From my limited experience
|>>in the photo store, the zoom ring DO slide down when the lens are in
|>>verticle position. Maybe other 75-300mm owner can share their experience.

I had the EF 75-300 and mine definitely had "zoom creep".

--
| Pete Stoppani          | stoppani@rust.zso.dec.com                 |
|  DECwest Engineering   | stoppani@decwet.enet.dec.com              |
|  Bellevue, WA          | decwrl!fungus.enet!stoppani               |
From: monta@image.mit.edu (Peter Monta)
Newsgroups: rec.photo
Subject: Continuous-tone with Kodalith?
Date: 4 Oct 92 22:35:59 GMT
Organization: MIT Advanced Television Research Program

I have some leftover Kodalith (in 35mm and 4x5), and I'm wondering if
it can be used for pictorial applications.  Are there low-contrast
developers, along the lines of those used for Tech Pan, that would
be suitable?

I'm also curious to see how natural scenes look:  Kodalith is
orthochromatic, and this makes pretty startling portraits, judging
by the old photos I've seen.

Peter Monta   monta@image.mit.edu
MIT Advanced Television Research Program
Newsgroups: rec.photo
From: andpph@ritvax.isc.rit.edu
Subject: George Eastman's musical descendant
Reply-To: andpph@ritvax.isc.rit.edu
Organization: Rochester Institute of Technology
Date: Sun, 4 Oct 1992 02:52:30 GMT

Does anyone know the name of a direct descendant of George Eastman who is a
MAJOR rock and roll star?

your assistance in this matter would be greatly appreciated. 
thanks,
andy