on 21/05/2004 16:53, Carlos J. Santisteban Salinas at cjss@xxxxxxxxxxxxx
wrote:
> The 'plain' 2 max. exposure time depends on the ASA setting. I've tested
> 33s @ 1600, a bit more than a minute @ 400 and well over 5 min @ 100, IIRC
> -- I don't want to burn a nice pair of 357s ;-)
My red diode 1981 test showed these results:
ASA 1600 @ f11
6.1 s.
6.1 s.
6.0 s.
6.2 s.
5.9 s.
6.1 s.
ASA 800 @ f8
7.8 s.
7.7 s.
7.4 s.
7.9 s.
7.9 s.
7.7 s.
ASA 400 f5.6
9.4 s.
9.2 s.
9.3 s.
9.9 s.
9.8 s.
9.9 s.
ASA 200 @ f4
10.9 s.
10.9 s.
11.1 s.
11.3 s.
11.2 s.
11.3 s.
ASA 100 @ f2.8
12.7 s.
12.7 s.
12.5 s.
12.7 s.
12.6 s.
12.7 s.
ASA 50 @ f2
13.6 s.
13.5 s.
13.4 s.
13.7 s.
13.7 s.
13.8 s.
>> For a moment I thought a red diode woud be less readable by the SBCs due to
>> the green coating of the MCs. A green one might be seen better. Of course
>> this would be assuming that an MC lens works like a green filter, nonsense.
>
> I don't think the coating would act like a filter. And, even if it would,
> don't forget that the typical green MC reflections come from the *rejected*
> light *over* the lens surface (not from the light *thru* the glass), thus
> in extreme cases it would act like a pinkish filter.
This is the correct reasoning, you're right Carlos, of course.
>> I have posted a Provia 100F w/o compensation of abot 4 minutes exposure at
>> TOPE Landmarks. Some opinions about color shift were posted there.
>
> I don't think a single scanned pic is a valid reference to evaluate
> reciprocity failure.
Neither do I. I mentioned it just as an isolated example for Dado to see,
and because I learned quite a bit from what people gently commented.
>> W/ Ektachrome 100, star trails come up very colorful on a black sky @ +2, f
>> 5.6.
>
> Star images should be less affected by reciprocity failure, and *accurate*
> exposure calculation is quite difficult: the actual focal length *does*
> matter here, not just f/stop, exposure time and film speed.
I bet they are. This topic started a little thread w/another listee who made
beautiful 8+ hours exposures using an OM1n and fisheye or w/Tamron 17mm,
about a year ago. I wanted to know how did he calculate exposure, but he
didn't tell...
Mine were w/21mmf3.5 @ 5.6 +2comp E100. Then, with the help of this list, I
measured how long exposure had been. Posted the result, must be somewhere
here in my HD.
> From: Andrew L Wendelborn <andrew@xxxxxxxxxxxxxxxxxx>
>>
>> Out of curiosity, I just tested a 2n. Body cap on, black bag over viewfinder.
>> Shutter closed at 3m20s. Will try the other 2n when its film is finished.
>
> Mine did about 3 min. I've got another OM-2n (which badly needs a CLA) that
> closes at 3m23s.
Well when I finish the loaded Velvia 50, I will test again my OM2_without
LEDs_ until I have to install new pair of Renata/Varta ;))
Regards,
Fernando.
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