[OM] Re: Weird problem on my OM1n

[tOM Trottier]

On 10 Dec 2005 at 6:26,
Chuck Norcutt <olympus@xxxxxxxxxx> wrote:

> I agree with Simon.  The all look very overexposed to me.  It's just
> that some are worse than others.  The problem could be that the
> meter is wrong, that the shutter speeds are not accurate or that the
> lens diaphragm is sticky and does not close down quickly enough...
> or some combination of all three.
> 
> To check the meter set the ISO dial at 125.  In bright sun (late
> morning to early afternoon) the meter should conform to the "sunny
> 16" rule. This is a "rule of thumb" that in bright sun with the lens
> set to f/16 the reciprocal of the shutter speed should be equal to
> the ISO.  So, at ISO 125 and f/16  the meter should be calling for a
> shutter speed of 1/125th second.  At ISO 250, 1/250th second, etc.

Unless the ground is covered with snow... 

Fill the frame with snow in midday sunshine and it should read, at 
125 ASA and F/16, between 1/500 and 1/1000. 

Or fill the frame with untanned caucasian skin in midday 
sunshine.  At 125 ASA and F/16, it should read 1/250.
 
> If it's cloudy with no shadows at ISO 125 and shutter at 1/125 the
> aperture should be f/5.6 or f/8.
> 
> To check the lens remove it from the body.  Set the aperture ring at
> f/16 or whatever its smallest aperture is.  The lens diaphragm
> should remain open regardless of the setting.  Then find the tab on
> the back of the lens that causes the aperture to close.  Snap the
> spring loaded tab with your finger several times as fast as you can.
>  The aperture should open and close just as fast.  If the blades are
> sluggish in closing down there may be oil on them.  If they don't
> close quickly the lens aperture 
>   may be wider than set at the time the shutter fires which will
>   cause 
> overexposure.
> 
> Sorry, I don't have any easy check for shutter speed except that if
> the meter and aperture are OK the shutter speed is all that's left. 
> If the meter or shutter are at fault you'll have to have the camera
> serviced. If the lens diaphragm is at fault and it's just the
> standard 50mm f/1.8 lens it would probably be cheaper to buy another
> lens than to have it serviced.

You can check the fast (1/125 & shorter) shutter speeds by 
taking closeup pics of your CRT TV screen. Focus so it's sharp. 
The screen is painted every 1/60 second by 262 or 263 lines, 
15,720 lines per second. Put a ruler at right angles to the lines on 
the negative (need a magnifying glass!) or print and you count 
them to determine the actual shutter speed using this table:
Lines
Shutter

                                                                15
                                                              1048
                                                                  
                                                                16
                                                               983
                                                                  
                                                                17
                                                               925
                                                                  
                                                                18
                                                               873
                                                                  
                                                                19
                                                               827
                                                                  
                                                                20
                                                               786
                                                                  
                                                                21
                                                               749
                                                                  
                                                                22
                                                               715
                                                                  
                                                                23
                                                               683
                                                                  
                                                                24
                                                               655
                                                                  
                                                                25
                                                               629
                                                                  
                                                                26
                                                               605
                                                                  
                                                                27
                                                               582
                                                                  
                                                                28
                                                               561
                                                                  
                                                                29
                                                               542
                                                                  
                                                                30
                                                               524
                                                                  
                                                                31
                                                               507
                                                                  
                                                                32
                                                               491
                                                                  
                                                                33
                                                               476
                                                                  
                                                                34
                                                               462
                                                                  
                                                                35
                                                               449
                                                                  
                                                                36
                                                               437
                                                                  
                                                                37
                                                               425
                                                                  
                                                                38
                                                               414
                                                                  
                                                                39
                                                               403
                                                                  
                                                                40
                                                               393
                                                                  
                                                                41
                                                               383
                                                                  
                                                                42
                                                               374
                                                                  
                                                                43
                                                               366
                                                                  
                                                                44
                                                               357
                                                                  
                                                                45
                                                               349
                                                                  
                                                                46
                                                               342
                                                                  
                                                                47
                                                               334
                                                                  
                                                                48
                                                               328
                                                                  
                                                                49
                                                               321
                                                                  
                                                                50
                                                               314
                                                                  
                                                                51
                                                               308
                                                                  
                                                                52
                                                               302
                                                                  
                                                                53
                                                               297
                                                                  
                                                                54
                                                               291
                                                                  
                                                                55
                                                               286
                                                                  
                                                                56
                                                               281
                                                                  
                                                                57
                                                               276
                                                                  
                                                                58
                                                               271
                                                                  
                                                                59
                                                               266
                                                                  
                                                                60
                                                               262
                                                                  
                                                                61
                                                               258
                                                                  
                                                                62
                                                               254
                                                                  
                                                                63
                                                               250
                                                                  
                                                                64
                                                               246
                                                                  
                                                                65
                                                               242
                                                                  
                                                                66
                                                               238
                                                                  
                                                                67
                                                               235
                                                                  
                                                                68
                                                               231
                                                                  
                                                                69
                                                               228
                                                                  
                                                                70
                                                               225
                                                                  
                                                                71
                                                               221
                                                                  
                                                                72
                                                               218
                                                                  
                                                                73
                                                               215
                                                                  
                                                                74
                                                               212
                                                                  
                                                                75
                                                               210
                                                                  
                                                                76
                                                               207
                                                                  
                                                                77
                                                               204
                                                                  
                                                                78
                                                               202
                                                                  
                                                                79
                                                               199
                                                                  
                                                                80
                                                               197
                                                                  
                                                                81
                                                               194
                                                                  
                                                                82
                                                               192
                                                                  
                                                                83
                                                               189
                                                                  
                                                                84
                                                               187
                                                                  
                                                                85
                                                               185
                                                                  
                                                                86
                                                               183
                                                                  
                                                                87
                                                               181
                                                                  
                                                                88
                                                               179
                                                                  
                                                                89
                                                               177
                                                                  
                                                                90
                                                               175
                                                                  
                                                                91
                                                               173
                                                                  
                                                                92
                                                               171
                                                                  
                                                                93
                                                               169
                                                                  
                                                                94
                                                               167
                                                                  
                                                                95
                                                               165
                                                                  
                                                                96
                                                               164
                                                                  
                                                                97
                                                               162
                                                                  
                                                                98
                                                               160
                                                                  
                                                                99
                                                               159
                                                                  
                                                               100
                                                               157
                                                                  
                                                               101
                                                               156
                                                                  
                                                               102
                                                               154
                                                                  
                                                               103
                                                               153
                                                                  
                                                               104
                                                               151
                                                                  
                                                               105
                                                               150
                                                                  
                                                               106
                                                               148
                                                                  
                                                               107
                                                               147
                                                                  
                                                               108
                                                               146
                                                                  
                                                               109
                                                               144
                                                                  
                                                               110
                                                               143
                                                                  
                                                               111
                                                               142
                                                                  
                                                               112
                                                               140
                                                                  
                                                               113
                                                               139
                                                                  
                                                               114
                                                               138
                                                                  
                                                               115
                                                               137
                                                                  
                                                               116
                                                               136
                                                                  
                                                               117
                                                               134
                                                                  
                                                               118
                                                               133
                                                                  
                                                               119
                                                               132
                                                                  
                                                               120
                                                               131
                                                                  
                                                               121
                                                               130
                                                                  
                                                               122
                                                               129
                                                                  
                                                               123
                                                               128
                                                                  
                                                               124
                                                               127
                                                                  
                                                               125
                                                               126
                                                                  
                                                               126
                                                               125
                                                                  
or just divide the number of lines you count into 15720.
 
You might test longer speeds by recording the sounds on your 
computer, eg with Studio Recorder from APH, and checking the 
time between the sound of the shutter opening and closing, 
(which would be between the mirror flipping up and down).

tOM

-- Quidquid latine dictum sit altum viditur --
   ,__@         tOM Trottier
 _-\_<,         758 Albert St., Ottawa ON Canada  K1R 7V8
(*)/'(*)        N45.412 W75.714         +1 613 860-6633
<a href="http://Abacurial.com";>Abacurial Information 
Architecture</a>
     Q,  Q,
    </  </      I would rather be exposed to the inconveniences
 (`-/---/-')    attending too much liberty than to those 
attending
~~@~~~~@~~~~~~  too small a degree of it.-Thomas 
Jefferson



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