Digital BW, The Print

Fred was a great man that introduced the Zone system to a legion of 
photographers. I taught his method for many years and found it most 
satisfying. I also gave strict orders to my students that they were 
not allowed to shoot barns, flowers, bees on flowers, babies, kids 
with ice cream, puppies, bums, etc. That was MY idea, not his ;-).

Steve Roberts

--- In DigitalBlackandWhiteThePrint@y..., "millerhillsteve" 
<steverob@s...> wrote:
> Fred was a great man that introduced the Zone system to a legion of 
> photographers.

My feelings about Fred were very complicated. For example, I bought 
his cold light stabilizer (the one circa 1983, not the later ones) in 
which the copy in the catalog bragged that Paul Horowitz had designed 
the contacts on the (what? power transistor I think?) sockets to be 
gold plated, so as to give better connection. This being my field 
(electrical connectors) at which I worked for real $$ at the time, I 
knew this to be pure nonsense. In this application, tin or even nickel 
would have worked maybe even better. Yet the black box still worked, 
though it's Achilles heel was that it cut down the light level a lot 
to acheive stability. He charged a lot for it for that gold plated 
black box.  Sales copy, blowing smoke and I knew it...

On the other hand, I found it maddening that no other manufacter built 
a print washer that could hold 15 prints in different slots. 12 slots 
wasn't enough for me, to make a long darkroom session work for me I 
needed to get about 14 copies of a print(s) and an extra for residual 
silver testing. Just a weird personal preference, but no one else made 
a print washer that could hold as much. I called him up  
half-heartedly because the inserts for film reel washing were a little 
too long and bowed EVER so slightly when inserted in the washer. I 
told him it was a minor problem, I could easily sand it down myself in 
five minutes so I really didn't care about a replacement. He said 
"Well I CARE!!!! Send it in!!!" His sudden vehemence was ,um, 
interesting.<g> btw, when many years later the washer DID develop a 
problem, a serious crack in the housing, it was replaced right away.
Jim H.

Hi Jim,

> the contacts on the (what? power transistor I think?) sockets to be
> gold plated, so as to give better connection. This being my field
> (electrical connectors) at which I worked for real $$ at the time, I
> knew this to be pure nonsense. In this application, tin or even nickel
> would have worked maybe even better.

I thought tin oxidized over time, and gold didn't...therefore, for
longevity, gold (or now paladium is it?) were preferred?  That is my
understanding as to why edge connectors use gold plated fingers, isn't it?

Regards,

Austin

Hi Austin:

No, tin doesn't oxidize.  That's why it's used to make pewter--and line "tin" cans.  But it's very soft (malleable), which may be why it won't be used for electrical connectors.  Also, it may not be very conductive, like gold and silver.

Len

  ----- Original Message ----- 
  From: Austin Franklin 
  To: DigitalBlackandWhiteThePrint@yahoogroups.com 
  Sent: Saturday, April 06, 2002 12:20 PM
  Subject: RE: [Digital BW] Re: Picker


  Hi Jim,

  > the contacts on the (what? power transistor I think?) sockets to be
  > gold plated, so as to give better connection. This being my field
  > (electrical connectors) at which I worked for real $$ at the time, I
  > knew this to be pure nonsense. In this application, tin or even nickel
  > would have worked maybe even better.

  I thought tin oxidized over time, and gold didn't...therefore, for
  longevity, gold (or now paladium is it?) were preferred?  That is my
  understanding as to why edge connectors use gold plated fingers, isn't it?

  Regards,

  Austin


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[Non-text portions of this message have been removed]

--- In DigitalBlackandWhiteThePrint@y..., "Austin Franklin" 
<darkroom@i...> wrote:
> Hi Jim,
> 
> > the contacts on the (what? power transistor I think?) sockets to 
be
> > gold plated, so as to give better connection. This being my field
> > (electrical connectors) at which I worked for real $$ at the time, 
I
> > knew this to be pure nonsense. In this application, tin or even 
nickel
> > would have worked maybe even better.
> 
> I thought tin oxidized over time, and gold didn't...therefore, for
> longevity, gold (or now paladium is it?) were preferred?  That is my
> understanding as to why edge connectors use gold plated fingers, 
isn't it?
> 
> Regards,
>

No, because, given enough contact force, after insertion, an airtight 
connection is usually acheived. Tin, being soft, can look oxidized, 
but wipe a contact across it that digs in, and that layer is broken. 
Nickel is a little tougher.

More than this, if voltages signifigant enough for power transistors 
are coursing through a point of contact, I don't care what is 
seperating them- oxidation,  minor rust, etc...it will arc through.

Paladium is many times a wise alternative for gold when low signals 
are being passed. It still can form an oxidation layer, so it must be 
used with discretion to replace a gold connector.

Gold is used when: low level signals are being transmitted; the mating 
connectors have ultra-low insertion forces because of say, you're 
plugging in a pc board connector with hundreds of fingers (imagine a 
sort of super super long ISA/ PCI  or DIMM slot- lots of force to get 
it in, so each contact must have lower insertion force); there just 
isn't a lot of wiping travel going on from start of contact to end. SO 
gold is still what should be used on a 'puter finger edge connector.

And yes, in high humidity or excessive environmental specs gold IS 
considered when high reliability is needed as in the military. But so 
is Paladium. If I remember the copy from all those years ago, a power 
transistor socket, if that is what it was in Fred's box, just really 
doesn't need it. 

Gold is many times a detriment because it is VERY soft and after some 
number of insertions, wears through to the base below it. Instead, 
using tin, one can plate a much heavier thickness and it isn't as 
soft. And as such, tin is less sensitive to variations in contact 
force which can occur due to manufacturing tolerances.

Yada yada yada.<g>. My heads starting to hurt...
Jim H. 

> Austin

--- In DigitalBlackandWhiteThePrint@y..., "Len" <len@m...> wrote:
> Hi Austin:
> 
> No, tin doesn't oxidize.  That's why it's used to make pewter--and 
line "tin" cans.  But it's very soft (malleable), which may be why it 
won't be used for electrical connectors.  Also, it may not be very 
conductive, like gold and silver.
> 
> Len

HHmmm...well, not being a metalurgist just a contact tester, tin may 
not oxidize. But it puzzles me because I was able to get all kinds of 
white growth when torture testing tin plated connectors. Strange thing 
is, you can just plug and unplug a tin connector a few times after 
this and contact reestablishes through the tin-IF the contact force is 
high. You rely on it's softness to re-establish connection. And on 
it's thickness of plating, since it's so cheap you can make it thick.

I always found gold to be softer than tin, but it is true that there 
are different hardnesses of gold connector, as called out by the 
military, unless they dropped the spec since I've been away. There is 
'soft gold' and 'hard gold', and I believe their was even a 'medium 
hard gold'. This is really scraping my memory but I believe that 
Nickel was added to the gold to make it "harder". Most applications 
ten years ago called out for hard gold, at the risk of some minor 
oxidation seeping through the porosity of the gold mixed in with the 
small amount of nickel (not an alloy of course- a mixture). Hard gold 
worked best on pc board fingers, since repeated insertions were 
expected, but soft gold made the best contact under low contact 
forces/wiping travel.

So if you have inserted a gold plated finger too many times and the 
gold has worn, it is more unreliable than a tin connector. But tin is 
impractical for other reasons that I have already stated in my last 
post (low insertion force, travel, low level signal transmisssion).

So yes gold has better conductivity, but not always, for pragmatic 
reasons.

Ugh! I retired years ago. Ask me about Fred Picker or 
something...<GGG>
JIm H.

----- Original Message -----
From: "jimhayes361" <jimhayes@...>
To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
Sent: Saturday, April 06, 2002 7:37 AM
Subject: [Digital BW] Re: Picker


Jim,

I had a similar experience. I had bought one of his print flatteners which
at the time was made of plywood. After a few uses, one side came lose a bit.
When I called they were adament that I return it right away and in a very
short time I received a hefty replacement beautiful crafted from 3/8" Lexan.

Fred really stood behind his stuff.

Martin
>
(snip)
>
> On the other hand, I found it maddening that no other manufacter built
> a print washer that could hold 15 prints in different slots. 12 slots
> wasn't enough for me, to make a long darkroom session work for me I
> needed to get about 14 copies of a print(s) and an extra for residual
> silver testing. Just a weird personal preference, but no one else made
> a print washer that could hold as much. I called him up
> half-heartedly because the inserts for film reel washing were a little
> too long and bowed EVER so slightly when inserted in the washer. I
> told him it was a minor problem, I could easily sand it down myself in
> five minutes so I really didn't care about a replacement. He said
> "Well I CARE!!!! Send it in!!!" His sudden vehemence was ,um,
> interesting.<g> btw, when many years later the washer DID develop a
> problem, a serious crack in the housing, it was replaced right away.
> Jim H.
>
>
>
> Please visit the Group Homepage to check the Files, Bookmarks, Polls and
other resources as they are often being updated. The page is at:
>
> http://groups.yahoo.com/group/DigitalBlackandWhiteThePrint
>
> Please follow these basic guidelines:
> - Include your full name with your message.
> - Include the address of your website, if you have one.
> - As threads develop, trim off excess portions of earlier messages to keep
them short.
> - As the topic of a thread changes remember to change the subject header.
> - Good manners are required at all time. No personal attacks or "flames."
> - Complete your Yahoo profile.
> - Before posting a question, search the message archives and the various
resources on the homepage.

>
>
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>
>