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Djamorpheus
Tinkerer
Username: Djamorpheus
Post Number: 39
Registered: 10-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, May 04, 2010 - 03:15 am: | 
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I'm wanting to recalibrate a gossen lunasix 3 (grey) to 1.55 silver oxide batteries. I have bat41 diodes, how should i solder them on? I'm guessing one will not do because it only drops 0.2 volts right? so i would need to do two in series? |
Sevo
Tinkerer
Username: Sevo
Post Number: 65
Registered: 09-2008
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, May 04, 2010 - 03:45 am: |
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One will do nicely - 1.55 to 1.35V is just what you want. The diode would belong in series to the battery. I haven't put one into a Lunasix so far, but on cameras it usually will fit between the connecting wire and one of the battery terminals or (if space right at the terminal is too tight) somewhere into the wire. Don't forget some heat shrink tube to protect it against short circuiting. |
Mareklew
Tinkerer
Username: Mareklew
Post Number: 69
Registered: 03-2010
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, May 04, 2010 - 04:56 am: |
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I have a Lunasix 3.
What I found out, that one diode is perfect about the voltage, but I needed to recalibrate the low-light range anyway - either my Gossen was out of whack due to age, or the voltage drop wasn't consistent enough over operating current range.
If I had to do it again I'd try to recalibrate without any diodes.
You can expect your meter to be accurate to better than 1/3 stop over the entire metering range, maybe with except of 1-3 (-4..-1EV). If it isn't, go on with calibration...
Marek |
Djamorpheus
Tinkerer
Username: Djamorpheus
Post Number: 41
Registered: 10-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, May 04, 2010 - 03:54 pm: |
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I have zinc batteries in it at the moment, i'm trying to calibrate it to a digital camera using reflected metering on an evenly lit wall. The sunny 16 rule as well. |
Mareklew
Tinkerer
Username: Mareklew
Post Number: 71
Registered: 03-2010
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, May 05, 2010 - 04:01 am: |
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I found dSLR camera metering to be aurate only down to about 3EV, below that it indicated something, but making a test exposure revealed error in the range of 1/2 stop. Lunasix goes down to -4EV, so seven stops below my dSLR stopped being accurate.
Test exposures with a dSLR are the way to go.
BTW: For Canon assume it has ASA125 on "ISO100" setting and use center-weighted metering (matrix will fool you here).
For older Nikon dSLR assume the opposite correction is necessary (ISO100 on camera is about ISO50-80 in reality), but I don't know about the current production.
Marek |
Djamorpheus
Tinkerer
Username: Djamorpheus
Post Number: 42
Registered: 10-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, May 08, 2010 - 05:39 am: |
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I'm trying to calibrate the meter but it wont stay calibrated, yesterday it was reading sunny 16 and now it reads a stop higher |
Mareklew
Tinkerer
Username: Mareklew
Post Number: 72
Registered: 03-2010
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, May 08, 2010 - 11:59 am: |
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1) clean the contacts. This meter draws only a few ľA, so contacts corroded so bad, that they only make an impression of being slightly metallic in origin will pass enough current for the meter to appear to be working. However, as the contact quality (or rather, lack thereof) varies from switch on to switch on, so will the reading.
2) The same about varipots. Before even attempting to adjust them make them go all the way there and back, apply few drops of contact cleaner, redo, let them dry.
3) After calibrating knock on the device from all sides (not too hard!) so varipots that are under tension, almost ready to move, do move. Check calibration again.
Marek |
Djamorpheus
Tinkerer
Username: Djamorpheus
Post Number: 43
Registered: 10-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, May 11, 2010 - 02:39 pm: |
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When you say apply a few drops on the varipots do you mean through the holes where you put the screwdriver in or from the underside?
the contact points near the battery compartment look pretty clean |
Mareklew
Tinkerer
Username: Mareklew
Post Number: 76
Registered: 03-2010
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, May 11, 2010 - 11:56 pm: |
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I cleaned them from below, the whole PCB is held only by 2 screws and there are no springy surprises underneath, but I wouldn't recommend removing the board without necessity either (it is somewhat hard to put back, not as hard as assembling a camera, but one nut is rather inaccessible without tweezers). I'd rather draw some contact cleaner into a syringe and apply it with a needle through the holes or around the board edge.
BTW: one more thing: check if the galvanometer is OK: put known fresh batteries in and activate alternately battery check and light measurement. The needle should each time show the same battery voltage and if you shake the unit while the needle is free to move it should still return to previous reading. Else you will hunt the calibration ad mortum defecatum.
Marek |
Mareklew
Tinkerer
Username: Mareklew
Post Number: 78
Registered: 03-2010
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, May 21, 2010 - 05:39 am: |
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Just to cross-link threads: I have posted a full procedure of Lunasix recalibration here:
http://lockaphoto.stufftoread.com/index.php/calibrating-gossen-lunasix-3-lunapro /
The corresponding thread on this site is here:
https://kyp.hauslendale.com/classics/forum/messages/2/18766.html?1274435956
Marek
PS: DJamorpheus: I can't tell, how did I know ;P |
