Archived posting to the Leica Users Group, 1998/06/27

[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]

Subject: RE: [Leica] Shutter Speed Inaccuracy
From: Tom Kumagai <kumagai@po.cnet-ma.ne.jp>
Date: Sun, 28 Jun 1998 08:28:45 +0900

The difference between between 1/250 and 1/236(which is 0.331038 ms off 4ms, thus 8.275934%). 
See the table below,(HTML). I don't think it's a big deal either. I used Excel on a WinChip 200 machine
to calculate. 

1/s (dial)	1/s actual	diff in ms	off by (%)
1000	952	-0.0504 	-5.04%
500	483	-0.0704 	-3.52%
250	236	-0.2373 	-5.93%
125	124	-0.0645 	-0.81%
60	65	1.2821 	7.69%
50	53	1.1321 	5.66%
30	32	2.0833 	6.25%
15	16	4.1667 	6.25%
8	8.7	10.0575 	8.05%
4	4.4	22.7273 	9.09%
2	2.3	65.2174 	13.04%
1	1.02	19.6078 	1.96%

Tom K.

- ----------
From:  Mark [SMTP:mark@steinberg.net]
Sent:  Sunday, June 28, 1998 0:50
To:  leica-users@mejac.palo-alto.ca.us
Subject:  [Leica] Shutter Speed Inaccuracy

TEAShea@aol.com wrote:
> 
> << M6 n$B!<(J 1666706, control of the shutter speed with a spectron:(J
>  nominal speed (measured speed) : 1000(952),500(483),250(236),
>  125(124),60(65),flash (53),30(32),15(16),8(8.7),4(4.4),2(2.3),1(1.02). >>
> 
> Dominique, this is quite an impressive performance.
> 

is it ?

actually it's overexposed, overexposed, overexposed, exposed, underexposed,
underexposed, underexposed, underexposed, underexposed, underexposed, 
underexposed, exposed. 

!!!

if we assume that they calibrated the light meter correctly, and it actually
reads the light correctly at whatever fstop, and indicates a correct exposure,
then the shutter will confound that correctness at all but two shutter speeds
(1/125 and 1/1). at 1/4 and 1/2 that confoundedness has become quite dramatic,
noticeably so ?

what's interesting is that for all the talk of incredible glass (and i have
seen the results for myself and am a believer) the notion of even accurate 
light metering is thrown out the window by inaccurate shutter speed.

i'd be interested to see the accuracy of the R8 shutter speed.

i guess the point i am trying to make, the question i am asking, regards
how critical accurate exposure is to a photograph, given the latitude one
has when printing the final result ?

i'm sure to a fuji or kodak emulsion scientist these errors are horrendous ?
or does the same "messiness" exist in the emulsion production process ? (i.e.
what kind of quality control is there in terms of ISO rating between
batches of film ? take three rolls of 3200 ASA film, how close are they
to that 3200 rating ?). (the scientists are horrified because they work
hard on consistency no doubt and here we ae throwing darts at their 
ISO ratings).

how about the paper scientist ? is that messiness reproduced there ?

chemicals ? temperature ?

i guess this message has become an exploration of all the various reasons
why shutter speed inaccuracy might be but a piss in the ocean of inaccuracy
in terms of creating final print.

current technology won't let us fix focus (no doubt someone is working
on the photoshop filter to fix it) but everything else is pretty elastic ?

m