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Sensible M42 metered body to use today?

johnriley
Posted 16/04/2012 - 18:56 Link
The Praktica is not well engineered compared to Pentax, so I really think that the choice is clear. Also, the shutter releases are quite poor so again if you want something that is slick to operate then the Pentax Spotmatics seem the best option, by a long margin.
Best regards, John
Algernon
Posted 16/04/2012 - 20:23 Link
My first proper SLR was a Praktica, but I only kept it for about
3 months before buying a new Spotmatic. The release was awful

At least they had the engineering know how to make a finder that
could be adpated to the K-01

sportfinder_link

-
Half Man... Half Pentax ... Half Cucumber

Pentax K-1 + K-5 and some other stuff

Algi
Edited by Algernon: 16/04/2012 - 20:24
johnha
Posted 16/04/2012 - 21:12 Link
Algernon wrote:
I've wanted a Pentacon Super with the f/1.4 lens since 1970

http://www.praktica-collector.de/119_Pentacon_Super.htm

Sadly too expensive nowdays!

Wow, you wouldn't miss that very easily, looks like something out of Thunderbirds!

The SP1000 has arrived and seems to be working OK, the meter may be reading a tad low and there's a slight delay re-opening the aperture when I release the meter/stopdown switch. Obviously I won't know until I run some film through it, but it looks promising so far.

Thanks for the input.

John.
ChrisPlatt
Posted 16/04/2012 - 23:23 Link
ChrisR wrote:
I cannot comment on all the Spotmatic, models, but the meter in the Spotmatic II is certainly voltage dependant.

Like the rest of the Spotmatic line your SP II exposure meter incorporates a bridge circuit,
making it relatively immune to variations in supply voltage.
The same is true of the OP's SP1000.

There are numerous discussions of this topic on the Internet.
A majority of users report that a modern 1.5V battery provides readings
as accurate as the original 1.3V mercury cell.

In this Pentax Spotmatic series owners are far luckier than users of many older cameras.

Chris
Bring back the latent image!
Edited by ChrisPlatt: 16/04/2012 - 23:27
ChrisR
Posted 17/04/2012 - 09:05 Link
ChrisPlatt wrote:
ChrisR wrote:
I cannot comment on all the Spotmatic, models, but the meter in the Spotmatic II is certainly voltage dependant.

Like the rest of the Spotmatic line your SP II exposure meter incorporates a bridge circuit,
making it relatively immune to variations in supply voltage.
The same is true of the OP's SP1000.

There are numerous discussions of this topic on the Internet.
A majority of users report that a modern 1.5V battery provides readings
as accurate as the original 1.3V mercury cell.

In this Pentax Spotmatic series owners are far luckier than users of many older cameras.

Chris

Sorry you are incorrect regarding the Spotmatic II, my findings are not the result of being misguided by any web forum discusions,as I was not aware there were any, as I donít trawl the web.

My findings are the result of carrying out my own tests many years ago, long before web forums, when mercury cells were withdrawn from sale.

Just as a matter of interest I spent my whole working life as an industrial electrical engineer, I am no camera expert, but I am more than capable of carrying out a simple battery voltage compatibility test .


Take care.
Chris R.

I. El. (Eng). (Rtd).
Hardgravity
Posted 17/04/2012 - 19:42 Link
Agree to dis-agree ChrisR and ChrisPlatt.

I used a modern 'cheap' modern battery in my SPII and this is the result.

Comment Image


I'm happy that they work OK so..

As another M42 body, just for fun, why not try a Zenit?

Smaller than the Practicas and, I think, nicer to use. LINK
Cheers, HG

K110+DA40, K200+DA35, K3 and a bag of lenses, bodies and other bits.

Mustn't forget the Zenits, or folders, or...

PPG entries.
johnha
Posted 17/04/2012 - 21:50 Link
The battery that came with the camera is a Kodak KX400 inside a blue spacer and made in West Germany, so I guess this is a mercury battery (I can't see any voltage markings)?

After checking against my L408B in brighter light it looks like the meter is reading reasonably accurately.
Hardgravity
Posted 17/04/2012 - 22:10 Link
Go for it johnha, you can always use it until it dies then try a modern battery the same size using the spacer .

I look forward to seeing some shots taken with your new pride and joy, the next step is B&W and developing your own...

... oh the addiction...
Cheers, HG

K110+DA40, K200+DA35, K3 and a bag of lenses, bodies and other bits.

Mustn't forget the Zenits, or folders, or...

PPG entries.
ChrisPlatt
Posted 17/04/2012 - 23:39 Link
Hardgravity wrote:
I used a modern 'cheap' modern battery in my SPII and this is the result.

Indeed, and my SP1000 works as well with a modern battery too.

Perhaps our cameras are not aware of the results of simple battery voltage compatibility tests?

Chris
Bring back the latent image!
Edited by ChrisPlatt: 17/04/2012 - 23:43
ChrisR
Posted 18/04/2012 - 09:44 Link
ChrisPlatt wrote:
Hardgravity wrote:
I used a modern 'cheap' modern battery in my SPII and this is the result.

Indeed, and my SP1000 works as well with a modern battery too.

Perhaps our cameras are not aware of the results of simple battery voltage compatibility tests?

Chris

Below a brief description of various battery/cell types.

The Pentax Spotmatic II, along with other cameras of that era with similar light/exposure metering, did not have complicated circuits, number one electronics in miniature was not available, number two, they were not necessary.
This is why the mercury cell was ideal for any application which was voltage dependent for its accuracy, the open voltage for the single mercury cell was 1.35 v, but it was the discharge characteristics which was most important. The mercury cell throughout its service/discharge life, had an almost flat voltage decay curve, meaning that the voltage was almost constant at 1.35 volts, until the end of its life, when there was a sudden fall off voltage, and fail. This service life under light usage could be as much as, two to three years or more.

So cameras, such as the spotmatic II, would have the light/exposure meters calibrated to give a correct reading at 1.35 volts, as indicated above and would be accurate/stay in calibration throughout the mercury cellís life.

The alkaline cell when new has an open circuit voltage of, 1.5 to 1.65 v, the discharge characteristics of these cells has a steady voltage decay curve to end of live (total discharge). This higher start voltage will not damage the spotmatic II light/exposure meter circuit but it will give a high light/exposure indication, meaning that you will have an under exposure of film used, this high light reading will steadily reduce as the cell voltage drops through use, at the brief point when the discharge of the cell passes through 1.35 volts, the light/exposure reading will be correct/accurate, however as the cell voltage steadily drops through further discharge the light/exposure will get increasingly low, causing an over exposure of film used.

The zinc air cells have a start voltage of around 1.32v, therefore very close to the original mercury cell voltage, giving a correct light/exposure reading. The discharge characteristics of these cells are virtually the same as the mercury, an almost flat voltage decay curve. The main disadvantage of these cells, is the service life, before use, you remove the seal over a small hole in the cell, which allows air to enter the cell and activate it, the cells, life is then dependant on time, (ie) if the cell was not used after the seal was removed, total discharge will still occur in approx thirty to sixty days.

I hope the above clears up any misunderstanding of the different cells, and makes clear that the cell most suitable for purpose is the zinc air. Accepting the short service life, of these cells.


Take care.
Chris R.

I. El. (Eng). (Rtd).
Algernon
Posted 18/04/2012 - 09:44 Link
I'm surprised at the lack of interest by M42 users in the Yashica Electro-X In it's day (1968 ) one of the most advanced cameras you could buy. The first to use LEDs for metering and a very quiet electronically controlled Copal Square SE shutter with speeds 2 secs to 1/1000th. Even has a mirror lift lever.

A big plus is that some models use the readily available 6V Silver PX28 (or alkaline) battery. I suppose 4 x LR44 would work as well.

link

I've just dug out my old Elecro-X, which I haven't touched for 30 years. Borrowed a PX-28 out of my Pentax Spotmeter, put it in the camera and everything works and the meter is still accurate. Very heavy camera though... no use for the wimps who complain about the weight of digitals

Nice one on ebay (US) for £113 link

The same dealer has a Yashica Lynx Rangefinder in with a fixed 45mm f/1.4 ..... Yes f/1.4 lens link

Yashica lenses are of course made by their lens company Tomioka.... They even made a 55mm f/1.2 in M42
something Pentax never quite managed

-
Half Man... Half Pentax ... Half Cucumber

Pentax K-1 + K-5 and some other stuff

Algi
Edited by Algernon: 18/04/2012 - 10:01
ChrisPlatt
Posted 18/04/2012 - 21:38 Link
ChrisR wrote:
Below a brief description of various battery/cell types.

The Pentax Spotmatic II, along with other cameras of that era with similar light/exposure metering, did not have complicated circuits, number one electronics in miniature was not available, number two, they were not necessary.
This is why the mercury cell was ideal for any application which was voltage dependent for its accuracy, the open voltage for the single mercury cell was 1.35 v, but it was the discharge characteristics which was most important. The mercury cell throughout its service/discharge life, had an almost flat voltage decay curve, meaning that the voltage was almost constant at 1.35 volts, until the end of its life, when there was a sudden fall off voltage, and fail. This service life under light usage could be as much as, two to three years or more.

So cameras, such as the spotmatic II, would have the light/exposure meters calibrated to give a correct reading at 1.35 volts, as indicated above and would be accurate/stay in calibration throughout the mercury cellís life.

The alkaline cell when new has an open circuit voltage of, 1.5 to 1.65 v, the discharge characteristics of these cells has a steady voltage decay curve to end of live (total discharge). This higher start voltage will not damage the spotmatic II light/exposure meter circuit but it will give a high light/exposure indication, meaning that you will have an under exposure of film used, this high light reading will steadily reduce as the cell voltage drops through use, at the brief point when the discharge of the cell passes through 1.35 volts, the light/exposure reading will be correct/accurate, however as the cell voltage steadily drops through further discharge the light/exposure will get increasingly low, causing an over exposure of film used.

The zinc air cells have a start voltage of around 1.32v, therefore very close to the original mercury cell voltage, giving a correct light/exposure reading. The discharge characteristics of these cells are virtually the same as the mercury, an almost flat voltage decay curve. The main disadvantage of these cells, is the service life, before use, you remove the seal over a small hole in the cell, which allows air to enter the cell and activate it, the cells, life is then dependant on time, (ie) if the cell was not used after the seal was removed, total discharge will still occur in approx thirty to sixty days.

I hope the above clears up any misunderstanding of the different cells, and makes clear that the cell most suitable for purpose is the zinc air. Accepting the short service life, of these cells.


Take care.

Instead of just theorizing about the innacuracy the .2V difference will make, have you actually tried one in your SPII?

Conquer your fear of Google and you will find that there's a 1.5V silver battery to fit any Spotmatic model.
Any good electrical engineer knows that silver cells have a much more stable output than alkalines
and a service life several times greater than than those miserably short-lived zinc-air batteries.

Chris
Bring back the latent image!
Edited by ChrisPlatt: 18/04/2012 - 21:59
ChrisR
Posted 19/04/2012 - 10:15 Link
ChrisPlatt wrote:
ChrisR wrote:
Below a brief description of various battery/cell types.

The Pentax Spotmatic II, along with other cameras of that era with similar light/exposure metering, did not have complicated circuits, number one electronics in miniature was not available, number two, they were not necessary.
This is why the mercury cell was ideal for any application which was voltage dependent for its accuracy, the open voltage for the single mercury cell was 1.35 v, but it was the discharge characteristics which was most important. The mercury cell throughout its service/discharge life, had an almost flat voltage decay curve, meaning that the voltage was almost constant at 1.35 volts, until the end of its life, when there was a sudden fall off voltage, and fail. This service life under light usage could be as much as, two to three years or more.

So cameras, such as the spotmatic II, would have the light/exposure meters calibrated to give a correct reading at 1.35 volts, as indicated above and would be accurate/stay in calibration throughout the mercury cellís life.

The alkaline cell when new has an open circuit voltage of, 1.5 to 1.65 v, the discharge characteristics of these cells has a steady voltage decay curve to end of live (total discharge). This higher start voltage will not damage the spotmatic II light/exposure meter circuit but it will give a high light/exposure indication, meaning that you will have an under exposure of film used, this high light reading will steadily reduce as the cell voltage drops through use, at the brief point when the discharge of the cell passes through 1.35 volts, the light/exposure reading will be correct/accurate, however as the cell voltage steadily drops through further discharge the light/exposure will get increasingly low, causing an over exposure of film used.

The zinc air cells have a start voltage of around 1.32v, therefore very close to the original mercury cell voltage, giving a correct light/exposure reading. The discharge characteristics of these cells are virtually the same as the mercury, an almost flat voltage decay curve. The main disadvantage of these cells, is the service life, before use, you remove the seal over a small hole in the cell, which allows air to enter the cell and activate it, the cells, life is then dependant on time, (ie) if the cell was not used after the seal was removed, total discharge will still occur in approx thirty to sixty days.

I hope the above clears up any misunderstanding of the different cells, and makes clear that the cell most suitable for purpose is the zinc air. Accepting the short service life, of these cells.


Take care.

Instead of just theorizing about the innacuracy the .2V difference will make, have you actually tried one in your SPII?

Conquer your fear of Google and you will find that there's a 1.5V silver battery to fit any Spotmatic model.
Any good electrical engineer knows that silver cells have a much more stable output than alkalines
and a service life several times greater than than those miserably short-lived zinc-air batteries.

Chris

I am not theorizing, I am going on personal experience plus sound information, if you read my previous post carefully you would learn that actual start voltage of the cell is not the main problem, it is the decay voltage curve that is important.

I could have included all types of battery but that would have been irrelevant and made my post unacceptably long.

Ask yourself a simple question, why are miserable (your word) zinc air cells exclusively used in hearing aids, if other types of cells with a longer service life were suitable.

You carry on using whatever battery you like, that makes you happy but please try to refrain from misleading others.

Please donít start getting personal this forum is not for that,.
For the record, I am a British trained, industrial electrical engineer, you can not get better than that

Conquer my fear of google, I am afraid I donít understand that part of your post :.



Take care.
Chris R.

I. El. (Eng). (Rtd).
ChrisPlatt
Posted 20/04/2012 - 02:19 Link
ChrisR wrote:
You carry on using whatever battery you like, that makes you happy but please try to refrain from misleading others.

Please donít start getting personal this forum is not for that,.
For the record, I am a British trained, industrial electrical engineer, you can not get better than that.

It seems you are the one misleading others as empirical evidence has shown the following to be true:

A modern 1.5V cell will provide accurate exposure readings in any Spotmatic series camera.
The readily available silver oxide variety will provide stable output and long service life.


Armchair theorizing aside, I suggest you swallow your pride and actually try one in your SPII.

If it matters I am an experienced professional electronic technician, working in the field for more than 25 years.
After completing technical school my first employment was in the field of camera repair for a major manufacturer.

Chris
Bring back the latent image!
Edited by ChrisPlatt: 20/04/2012 - 02:46
womble
Posted 20/04/2012 - 02:40 Link
Algernon wrote:
I'm surprised at the lack of interest by M42 users in the Yashica Electro-X In it's day (1968 ) one of the most advanced cameras you could buy...

I try to limit my GAS to Pentax gear (and the odd Soviet thing or two). It looks a nice piece of kit, however. As an ex-typographer, I just love the Gothic Y on the viewfinder housing.

Thanks for bringing it to my attention. You should put some film in your example and go shoot a roll. How about on "roll in a day" day on Saturday?

K.
Kris Lockyear
It is an illusion that photos are made with the cameraÖ they are made with the eye, heart and head. Henri Cartier-Bresson
Lots of film bodies, a couple of digital ones, too many lenses (mainly older glass) and a Horseman LE 5x4.

My website

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