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Old Aug 21, 2003, 4:59 AM   #11
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Quote:
Originally Posted by Klaus DK
A fine explanation Shene in that first post of yours, but I have to correct you on that 15% grey mentioned in your first post. It is actually 18% reflectance and not 15%.

A greycard consist of 18% grey - which is an standard settled by the Industry many years ago!
Oh, thank you Klaus. That was a typo. On the other hand, many professionals, myself included, believe that that 18% is incorrect, and should be about 15% or in the proximity. I could not recall the reason. However, it could be due to a word-of-mouth from a well-known figure. Will post a quote if I could find the origin.

CK
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Old Aug 21, 2003, 7:54 AM   #12
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Thanks for all the answers. The fluorescent light tip put me on track. The setting was lighted by 1 halogene 12 v mini spot (15 cm away), 1 lightbulb 60 watt (40 cm away) and a monitor was close to the scene (40cm). The power network is at 220v @ 50 Hz power supply and the monitor is set at 70 Hz.

I tried to reinvoke this drastic light difference with same settings today, with and without monitor switched on. The light on scene today; natural light comes from outside, (for techno's: enough for 1/8 exposure without artificial light). Additional the same lightsources as yesterday were in place. Strangly even with monitor on I could not reinvoke this oddity while camera uses same settings (e 1/105, f8.0, iso 400, fluorescent type 2). I tried about 50 photos, while yesterday I saw the light difference repeatetly.

I will retry tonight, maybe outside light overshines the monitor flickering on the scene.
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Old Aug 21, 2003, 10:59 AM   #13
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Shene.

Well, you think it's 15%, but don't know why - as an proffesional. You know - that frase proffesional is just a word for at guy who earns money - not for knowledge.
:?
Hmm...Me - just an amateur yet - just quote KODAK, that makes these cards and has for many years. I can't see the reason, why they shouldn´t have corrected themselves ?

But maybe the meassuring of this 15 or 18% are different according to who makes them - or meassure the grey!!! :?

It could be interressting to hear from you, when you recall! (serious)!
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Old Aug 21, 2003, 1:35 PM   #14
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Klaus/Shene

My reading of his statment wasn't that 15% is what the cards are or what the meter is trying to match up, but that %15 works better.

By in my frazeled state, I could easily be reading way to much into his post.

Eric
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Old Aug 21, 2003, 6:42 PM   #15
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If the card is 15% and the meter is expecting 18%, won't the meter consistently underexpose the shot?

It's thinking "well, the target seems to be a little brighter than I expected, so I'll just cut back on the exposure a bit". This would then lead to darker, underexposed pictures, I would assume.

Of course, I've never seen a gray card, so I couldn't tell you the difference between 15 and 18%
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Old Aug 21, 2003, 8:49 PM   #16
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So far I have not be able to recreate this behaviour, not even when shooting a video (I did expect some faint flickering of the monitor). There must be something the user did, oops.
While testing I did notice something else, the lcd display has its own spotmetering, which stays effective even in all manual mode, ofcourse it does not influence the photo (besides making it some case impossible to see the subject).

The discussion about grey cards is very helpfull for further less manual exercises ;-)
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Old Aug 22, 2003, 1:59 AM   #17
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Quote:
Originally Posted by Mathilde uP
So far I have not be able to recreate this behaviour
If it *is* interaction between flicker and shutter speed, it's a random , stochastic, event, and you were just lucky (or not).

Have you bought any lottery tickets lately?
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Old Aug 22, 2003, 3:08 AM   #18
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If your camera has video or continuous shooting modes, point it at a TV set and then check through the saved file a frame at a time.

Sooner or later you'll find the black frame blanking black bar on your images.
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Old Aug 22, 2003, 11:03 AM   #19
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To Alan, I will certanly buy lottery tickets if a delicate machine makes the draw and I operate the machine ;-) Some people have a habit to discover bugs and find technical oddities. While it greatly adds value to knowledge it can also be at times tiresome and confusing.

Voxmagna, the movie edit program that came with the camera does not show frame by frame a complete movie. I would love to spread out my movies frame by frame, but sofar I have been to lazy to hunt for a freeware movie tool.
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Old Aug 22, 2003, 7:38 PM   #20
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Default 18% GREY CARDS

Kodac grey cards are in fact 18% reflective. This is a matter of color hues not proper exposure. True scene reflected light is aprox 15%. In the making of a standard Kodac used a color half way between white and black. This fifty percent grey card it turns out has a reflectivity of 18% of the light that strikes it. No one that I have ever met thinks that this is the hard and fast standard. It is rather accepted as a mean standard and is easier to control the 50% ratio of black and white to create a card. If you take a grey card and check it wit a good light meter you will be able to see the difference yourself. Then armed with this new information you can decide the proper midrange to set exposure or meter the palm of your hand, or flip a coin or have some magic runes to give you the answer.
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