All Forum Comments
Comment by ChrisR posted on Another pointless thread at 19/04/2012 - 14:54
ChrisPlatt wrote:
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.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 cell’s 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? 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 cell’s 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.
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 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 don’t 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 don’t understand that part of your post :.
Take care.
Comment by ChrisR posted on Sensible M42 metered body to use today? at 19/04/2012 - 10:15
Algernon wrote:
Algi.mecrox wrote:
A post on another website alleges that the dealer margin in one Eurozone country on one Pentax lens, the 50mm f2.8 macro, is 69% with the DA 21mm coming in at a scarcely less tasty 61% - on a notional selling price before any dealer reductions. I've no idea whether similar margins apply to the UK. Even so, brush up those bargaining skills boys.
That's total nonsense. It must have been written by someone with less than half a brain and I find it hard to believe that yours is any bigger for repeating such tripe! . Most retailers margins nowadays on high price goods are around 10-20% and they have to give a cut out of that to the Credit Card companies.A post on another website alleges that the dealer margin in one Eurozone country on one Pentax lens, the 50mm f2.8 macro, is 69% with the DA 21mm coming in at a scarcely less tasty 61% - on a notional selling price before any dealer reductions. I've no idea whether similar margins apply to the UK. Even so, brush up those bargaining skills boys.
I completely agree, and I suspect most retailers are not even getting anything like the10-20%.
When we had retail price maintenance in Britain, every one was aware the retail mark up was thirty three and a third percent. Like it or lump it.
I worked in an industry with a mark up of between 200-250% on most equipment for capital work, but those days have long since gone, the same industry would now think Christmas had come if they had a mark up 5% on equipment for large capital work, most of the time its now 2-3%.
Take care.
Comment by ChrisR posted on Pentax/Ricoh putting prices up at 18/04/2012 - 20:52
ChrisA wrote:
Would second that.gartmore wrote:
To be fair to SRS the thread title has now been changed
Good move.To be fair to SRS the thread title has now been changed
Take care.
Comment by ChrisR posted on Pentax/Ricoh putting prices up at 18/04/2012 - 11:57
ChrisPlatt wrote:
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. 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.I used a modern 'cheap' modern battery in my SPII and this is the result.
Perhaps our cameras are not aware of the results of simple battery voltage compatibility tests?
Chris
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 cell’s 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.
Comment by ChrisR posted on Sensible M42 metered body to use today? at 18/04/2012 - 09:44
That is a very long list.
I will just go along with No8, I think many of us are guilty of this one. .
8. Go outside and shoot photos rather than spending hours a day on photography forums.
I will hold my hand up as guilty.
Take care.
I will just go along with No8, I think many of us are guilty of this one. .
8. Go outside and shoot photos rather than spending hours a day on photography forums.
I will hold my hand up as guilty.
Take care.
Comment by ChrisR posted on 100 things about photography at 17/04/2012 - 15:27
ChrisPlatt wrote:
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 don’t trawl the web. 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, I cannot comment on all the Spotmatic, models, but the meter in the Spotmatic II is certainly voltage dependant.
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
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.
Comment by ChrisR posted on Sensible M42 metered body to use today? at 17/04/2012 - 09:05
ChrisPlatt wrote:
Of all the Spotmatic series cameras I like the simple SP1000 best.
It lacks self-timer and hot shoe, features I never use.
All SP series camera exposure meters can work accurately
with a modern battery as they are not voltage dependent.
There is no need to purchase any special adapter.
The SP1000 works fine with a commonly available battery.
I recommend use of a silver-oxide cell as it will last
far longer than the zinc-air type.
Chris
I cannot comment on all the Spotmatic, models, but the meter in the Spotmatic II is certainly voltage dependant.Of all the Spotmatic series cameras I like the simple SP1000 best.
It lacks self-timer and hot shoe, features I never use.
All SP series camera exposure meters can work accurately
with a modern battery as they are not voltage dependent.
There is no need to purchase any special adapter.
The SP1000 works fine with a commonly available battery.
I recommend use of a silver-oxide cell as it will last
far longer than the zinc-air type.
Chris
Battery equivalent, to the discontinued mercury cell for the Spotmatic II is the zinc air battery as used in hearing aids, the only problem, as soon as the seal to the small hole is removed allowing air to enter the cell, it will discharge, if you use it or not.
Take care.
Comment by ChrisR posted on Sensible M42 metered body to use today? at 16/04/2012 - 09:30
Hi Nick.
As Vic said, best place for you to go, my wife and myself used to belong to a camera club, back in the 1970’s/80’s,the club sadly no longer in being.
Can remember the first meeting we nervously attended, but was made to feel most welcome, and soon felt part of the club.
My wife going on to win the south west photographer of the year, sponsored by Kodak, she has a much more of an artistic eye than me.
The morel of that in my case, don’t let your wife use the camera, she may just be better than you.
Take care.
As Vic said, best place for you to go, my wife and myself used to belong to a camera club, back in the 1970’s/80’s,the club sadly no longer in being.
Can remember the first meeting we nervously attended, but was made to feel most welcome, and soon felt part of the club.
My wife going on to win the south west photographer of the year, sponsored by Kodak, she has a much more of an artistic eye than me.
The morel of that in my case, don’t let your wife use the camera, she may just be better than you.
Take care.
Comment by ChrisR posted on Photographic Clubs at 14/04/2012 - 09:36
Simon.
Great set of images, but numbers 1,3 & 7, for me, good impression of speed/movement.
Take care.
Great set of images, but numbers 1,3 & 7, for me, good impression of speed/movement.
Take care.
Comment by ChrisR posted on Motorsport: Oulton Park, April 7 2012 at 14/04/2012 - 09:18
I`m going to Cornwall and then Jersey in August !! They`re welcome to their silly games - financial and sporting - as usual we are conned into believing it`s "good for the country" ??
Sorry JR - getting a bit political again !!
Tony ( bring back Much Wenlock and tug o` war )
Take care.