So in addition to "excercising" the Hasselblad shutter every three months, one could re-calibrate their lightmeter to Sunny-16 every week or two.
But, to counterpoint that method...if I believed Sunny 16 to be a good rule of thumb, if I 'calibrated' my incident meter to f/16 within the past 2 weeks, it would be -0.2EV compared to pre-'calibration', and if I calibrated my incident meter to f/16 a few months ago, it would currently be -0.7EV compared to the same pre-'calibration' measurement. IOW the calibration brightness had CHANGED by 2/3EV just depending upon when I did that procedure shown in the video?! Yes, it is a WAG, but not close enough to be scientific.
So in addition to "excercising" the Hasselblad shutter every three months, one could re-calibrate their lightmeter to Sunny-16 every week or two.
So in addition to "excercising" the Hasselblad shutter every three months, one could re-calibrate their lightmeter to Sunny-16 every week or two.
Was that spelled correctly...did you really mean that you need to exorcise the devil from your Hasselblad shutter from time to time?
Which "Sunny 16"? - what latitude, what time of year, what elevation? How many clouds or flying buzzards are permissible in the sky?
Sunspots or no sunspots? Atmospheric pollution or not?
Don't forget the obligatory CLA every year. And when everything's done, re-establish your "personal zone system EI" for the materials used.
Calibrating a light meter is not trivial and often requires special equipment. However, testing a light meter against a known and stable light source, such as the sun, is easily done and useful. I do it once a year unless suspicious results demand a check.
Middle latitudes, between 10am and 4pm local time if I remember correctly, so this might not work for people in Scotland or Finland. Remember this is an approximate standard for those that want a quick sanity check before sending all the equipment to a calibration laboratory. As I noted I send my equipment out to calibration laboratories.
Just like the old adage to use the palm of your hand in lieu of a gray card, but one stop higher. ... as if gray cards themselves didn't vary enough!
No sun today! I did, just now, manage to get a break in the wind and rain long enough to rake up the downed branches all over the driveway.
Over many decades of involvement in photography, I have accumulated a variety of products that have '18% grey' areas for metering, I can count 6 different products that I still possess even today..., and just now metering all of these I find only one of them varied from the others by 0.1EV even though the vintage of origin varies across a span of half dozen decades.Just like the old adage to use the palm of your hand in lieu of a gray card, but one stop higher. ... as if gray cards themselves didn't vary enough!
I can't remember where but I think i once saw something about a 100(?) watt bulb having a standard EV at a specific distance, don't know if that sounds familiar to anyone( it may be from Adam's the camera )
Wilt - Even the pic you've posted shows how wacky the quality control is. I've already recited in numerous threads how I once took entire stacks of gray cards of various brands and measured them on a full-spectrum industrial densitometer. Not only were none of them actual neutral gray, but none were sufficiently close to 18% reflectance - sometimes as much as 15% off. Then there's problems of differing sheens and potential fading or discoloring over time.
That kind of unreliability is utterly unacceptable for any kind of accurate work, especially if chrome film is involved.
Same in principle goes with current collapsible gray discs, now popular with digital shooters. I have exactly one of them which is spot on, and way better than the average gray card. Just like checking light meters or darkroom thermometers, everyone potentially needs a reliable reference standard. I use the grayscale on the MacBeth Color Checker Chart. I've even cross-checked that many times with densitometry. The patches are precisely spaced between white and black, with a true 18% gray in the middle. Of course, these need to be kept clean and protected from fading. Even with all the problems of accurately representing hues over the web, the only example you show in the pic that actually looks gray is the MacBeth version.
The definition of a ballpark can be pretty big. When playing little league out in the country as the only white kid on the Indian Res team, I was always told to go to left field, meaning in my case, clear over the barbed wire fence and into the next pasture.
(I was bad at baseball).
100W bulbs have different Lumen ratings (and then are the ratings correct and also the ratings are for all directions) so they don't give out same amount of light. Some give out more light and some give out less light than others.
I can't remember where but I think i once saw something about a 100(?) watt bulb having a standard EV at a specific distance, don't know if that sounds familiar to anyone( it may be from Adam's the camera )
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