I agree. Grey cards have 18% reflectivity and, when angled, as per user instructions, half-way between the light-source subject line and the subject-camera line, and when they are read from the camera position - i.e. not from a line perpendicular to the grey card - theoretically they would reflect a bit less light (you only measure the diffuse reflection, and not the "glare", the "specular" reflection, or not, it's the other way round, half-angled you actually take all the glare besides the diffuse reflection, let me think about it... it should give you a "closer" reading**) and the result would come near to the middle-grey for which light meters are calibrated. Notice that "half angle" is both on the vertical and on the horizontal plane. Basically you need an assistant (or the model) to hold a grey card and you have to meter to it with a tele lens.
Originally Posted by Leigh B
After having verified once in your life that if you keep the grey card angled in a certain complicated way, which is not easy if you are alone, and without projecting any shadow on it with your arm or your lens, it gives you a result that is consistent with an incident light meter, my advice is to totally forget the grey card (for light metering purposes that is) and just use the incident light meter in all those situations where the grey card would be used*.
The entire procedure of using a grey card with the correct angle and without projecting a shadow on it is so slow and clumsy that I don't see an use for it in an outdoor situation. Incident light meters are "cheap", work better, and are much faster.
* It's easier to verify that the grey-card method is equivalent to the incident meter method in the shade, the typical EV12 @ ISO 100 situation. In this situation, I see that grey card and reflective metering of all kind, and incident metering, normally agree quite exactly. As soon as I go in the sun for the test I suppose the "glare" of the direct sun rays weights more and the angling of the flat surface of the grey card becomes critical, besides the additional possibility of an unnoticed shadow projection on the card, and the meters don't agree any more because of a method error.
** Let's say reflected-light meters are calibrated for 14% grey. Whatever you give them, they reproduce - given a certain "standard" printing method - a print which is 14% grey. If you give them an 18% grey card (lighter) they would tend to give you a "closer" reading than with a 14% grey card. But if you angle the grey card in such a way that you maximise its "glare", it's even worse
Considering that light meters are calibrated for 14% or so, I would expect the grey card should be used in a way that minimises glare, not that maximises it! The instructions given for grey cards instead want us to maximise glare on the grey card. I'm confused
Doesn't matter. Just ignore the grey card. Grey cards suck. Incident meters work
Last edited by Diapositivo; 07-24-2011 at 08:10 AM. Click to view previous post history.
I am almost certain it is due to using a reflected meter to read a very bright subject. I am especially certain because you used the same meter for both readings, so there are definitely no mis-calibration issues going on. That is just what reflected meters do, and why I generally dislike them so much. I think they do more harm than good for anyone but the rankest of amateurs, who have no idea how to judge light yet.
Originally Posted by ntenny
Out of curiosity, what were the two exposures suggested by the two metering methods?
On a beach in bright light using negative film, I would probably just use sunny 16. Sand is bright. So I want it to have some healthy density on the neg. Using transparency film, I would probably close down half a stop, based on experience. Sand can blow out quite easily on transparency film. In bright snow that was covering the ground, I'd close down a whole stop with transparency film, and use sunny 16 with negative film.
"Truth and love are my law and worship. Form and conscience are my manifestation and guide. Nature and peace are my shelter and companions. Order is my attitude. Beauty and perfection are my attack."
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Originally Posted by Diapositivo
I honestly don't remember. It was a confusing situation---I'd been metering and shooting, and suddenly looked down and said "Why, the incident dome is in place!", then tried to figure out whether it had done any harm and concluded that it probably had.
Originally Posted by 2F/2F
I've just developed the roll and it looks good to the naked eye. You're probably right that incident mode was giving a more "correct" reading---in a more normal environment the fact that I was pointing it in the wrong direction would have messed that up, but the light was uniform enough on this occasion that I think I got away with it.
San Diego, CA, USA
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Incidental light metering is so simple to use and effective in producing a very large percentage of well exposed results in such a diverse range of lighting conditions that many people who are new to it and for a long time have used reflected light metering have difficulty in understanding that you can forget The Zone System and tone placement and that the only things you have to do to modify the incidental reading taken on negative film is if the subject is predominantly dark give half a stop more exposure, or if light overall half a stop less, and the reverse with transparency films because they are positive films. A very small amount of subjects are not suitable for incidental metering like trans- illuminated things like stained glass windows and distant landscapes where reflected metering is of more use