exposure indicator - opposite behavior

[bob_fagioli]

<p>I read on this forum that I can use a Silver Oxide watch battery as a replacement for my PENTAX SPOTMATIC's PX400. So I bought a #392 (SR41W) battery from Walmart today. As another member mentioned the battery is a tad small but it can be centered easily. When I turn the meter on it tends to jump to the "+" (top). Then I adjust the aperture and shutter to center the needle. Ok, here comes what I'm calling "opposite behavior". Lets say the exposure needle is currently centered and the aperture is 4 and the shutter speed is 125. If I open up the lens by changing aperture to 2.8 or 1.4 needle moved down towards "-". This would indicate that the meter thinks I'm under exposing now. But how can that be? If anything it should be moving towards "+" since I'm letting in more light. Likewise, if instead I stop down to 5.6 or 8 the needle goes moved down towards "+". Again this is opposite of how I would expect the needle to move.<br>

What's going one here? Is the light meter broken? Is this the wrong battery?<br>

...<br>

If you read my other thread on this camera you know that I just got this PENTAX SPOTMATIC from my Aunt and I'm in the process of tiring to figure out what kind of shape its in. The camera has not been used for many many years and mercury battery that was in there was corroded. I cleaned the compartment out and just put this #392 (SR41W) battery tonight.<br>

Thanks<br>

-Bob</p>

[dan_daniel2]

<p>Well, it has to be asked: is the battery in backwards? Circuits like these will work fine regardless of polarity of the power, but can give reversed responses.</p>

<p>The other possibility is that this is exactly what Pentax wants- "You are overexposing, please REDUCE/MINUS the exposure"?? I can't say, but there are times my dyslexia and camera companies end up in a certain weird harmony of thought...</p>

[bob_fagioli]

<p>It was worth a try. I flipped the battery and tried it but the needle did not move at all with it like that so I must have have it in the right way to start with.<br>

I have the camera's operator manual. Here is what it says which is exactly opposite to the way it currently working:</p>

<blockquote>

<p><em>The needle moves up and down with the turn of the diaphragm ring. When the needle rests at the center, you will get correct exposure, If the needle does not come to the center no matter how far you turn the diaphragm ring, change the shutter speed. When the needle is off center and close to the (+) mark, you will get over-exposure: </em><br>

<em>change the shutter speed to a faster setting. If the needle is closer to the <strong>(-) </strong> mark, you will get under-exposure: change the shutter speed to a slower setting. </em></p>

</blockquote>

<div></div>

[personalphotos]

<p>Well it's one of 2 things IMO. Either the battery doesn't put out the correct voltage and current or 2) the meter has issues from either years of sitting around or the leaking battery.</p>

<p>I think the next thing to do is pick up a set of the matched replacement batteries that are commonly sold on Ebay. If with that battery you are getting the same results, then it's time to send the camera off to Eric. Or get a hand held meter.</p>

[bob_fagioli]

<p>Thanks Peter but I'm not sure what you mean by a "set of the <em>matched</em> " batteries. Can you provide a link or more details. <br>

Thanks<br>

-Bob</p>

 

[dan_daniel2]

<p>The other possibility with flipping the battery is that the smaller size means that the contacts aren't working properly. Button batteries often have a small insulator ring on one end only, so a holder designed for a larger button might not be making the proper connections. You might try balls of aluminum foil and tape to float the battery and avoid any possible shorts.</p>

<p>In any case, have you compared the meter readings with another camera? Do you have a digital camera or film camera that you can use to compare?</p>

[lance_blackburn1]

<p>If you have the manual, then it should show which way the positive terminal of the battery should be inserted. Looking at your Walmart battery, the positive terminal is on the back.</p>

[dan_daniel2]

<p>Manual- http://www.butkus.org/chinon/pentax/pentax_spotmatic/pentax_spotmatic-2.htm<br>

Says that the positive side of battery goes to top of the camera. I read this to mean that the positive side goes in first. If so, then your photo shows the positive side to the bottom of the camera, reversed? Try some aluminum foil balls/cubes to float the battery away from the body and keep it from shorting and see what happens to the meter travel?</p>

[bob_fagioli]

<p>I did have the battery upside down. I flipped it and the needle is goes in the proper direction. But that battery just doesn't fit right and if its not positioned perfectly the meter provides not reading. I wish I understood what several of you are talking about with "floating it with foil" but I simply can't picture it. I guess I should get a battery that fits property. Any suggestions?<br>

Thanks.<br>

-Bob</p>

 

[shaloot]

<p>Bob,<br>

My spotmatic's battery has a small rubber o-ring, that helps to keep the battery in place. Sounds like you corrected the problem of the needle due to the wrong placement, but now the inconsistencies are probably due to it not being held in place.<br>

sometimes hardware stores keep a wide variety of o-rings, you could take the camera there and try some...<br>

Keep us informed! We want to see/hear about you using that camera!</p>

[max_steinhardt]

<p>my SP1000 came with an O ring as well. Mine looks to have come from a company called Wein, which specializes in mercury battery replacements for old cameras. If you don't want to spend a lot of time finding the right sized O ring, it might be worth it to buy an (expensive) Wein battery once to get the O ring.</p>

[dan_daniel2]

<p>When I talk of 'floating with foil,' think of a globe of the world? You have this big fat ball, but it is 'floating' in its stand, held in place by two points only. Think of those two points holding the globe in the stand as the negative and positive terminals of the battery (and think of the globe as being sat on by Homer Simpson). By 'dots of foil,' I mean little balls- take a small piece of foil androll it into a low-density ball, and let the pressure of the battery compartment cover squich it into place.</p>

<p>I like Somanna's O-ring suggestion. Maybe there would be nylon or rubber washers to take up the thickness? You could put the aluminum 'dots' into the openings of the washers to make the connections.</p>

[bob_fagioli]

<p>When I search for"Wein" and "Pentax" I comes to this site that sells a "Weincell RM400R / PX400 - 1.35 Volt Battery" for $6. Is that the right replacement battery for the my Spotmatic?<br>

http://www.myoldcamera.com/Wein%20Cell%20Page%203.25.06.html<br>

PS: this is a cool forum. I'm glad I found you all :-)<br>

-Bob</p>

 

[max_steinhardt]

<p>yeah, that's the one. It's nice because after that battery dies, you can peel the O ring off and put in a silver oxide battery. The Energizer 392/384 is the battery I am using right now, and it fits perfectly.</p>

[bob_fagioli]

<p>Ok, I just ordered that battery. I'm eager to start snapping. Before I get the battery maybe I'll use my old Canon AE-1 camera as a light meter and match the Pentax to its settings and shoot a test role like that.</p>

[dan_daniel2]

<p>You might want to look into the 'Sunny 16' rule for working without a meter at all. Compare educated guesses to what a meter says and see what happens? For negative film, more than slides, it's pretty darn effective.<br>

http://www.fredparker.com/ultexp1.htm</p>