I think there is a lot of misunderstanding of where that 18% comes from.
If you stood in the middle of a park tilting your meter down so it is not reading skylight you would get a perfect exposure. Why is that? Because the natural world around us just happens to reflect 18% of the light that hits it. When we take photos in which there is a lot of natural background we get pretty close to perfect exposure by assuming the scene reflects 18% of the light. That is because the 18% was arrived at by measuring a lot of stuff and finding out what the average scene reflected. It is not just some arbitrary number.
When we start taking fairly close up photos of more discrete objects such as white houses, black cats, etc. then we do not get that 18% reflection, and we have to compensate for that. Or we can actually measure the light falling on the objects (using either an 18% gray card or an incident meter) and set exposure for that.
Matrix metering is great for those really difficult photos like say a bride and groom. It sees that there is a very dark object and a very light object and its little computer brain says, "Ah ha, I will use an exposure in the middle. For the white house, or the black cat, it does not have a clue and will mis-expose along with any other reflected light meter since it figures what it is reading should average out to 18%. This is of course simplified, very advanced matrix systems have a bunch of different scene averages stored and compares the data to that. If it picks the correct one you get pretty good exposures, if it picks the wrong one you get poor exposures.
All any exposure system can do is compare the scene to 18% and adjust the exposure accordingly. Using a spotmeter allows measuring the different areas and doing that yourself with some degree of precision. Using an incident meter assumes you want the scene corrected to 18% (you may actually want it to be corrected to something else for a high or low key effect).
Any exposure system to approach 100% needs you to evaluate the scene and decide how you want it to appear in the finished image. That takes a certain amount of knowledge and experience.
graywolf http://www.graywolfphoto.com "Idiot Proof" <==> "Expert Proof" -----------------------------------
Jens Bladt wrote:
Paul wrote:
Even working in a strictly digital world, an understanding of exposure its finer points will separate truly good work from the merely adequate.
I second that. No camera or meter can yet figure out what you are in fact photgraphing. Cameras and meters still don't know if you are photgraphing a black dog or a white sheep. Until they do, the photographer must udnderstand that, the metering result is a suggestion, based on the assumption that all photgraphes should end up reflecting 18% of the light.
I know that matrix metering can add or subtract perhaps ?-1 f-stop to the average metering. This is very often far from sufficient. Especially for digital photography there's a danger of getting burned out highligts (IME) - which is in fact over exposure.
Jens Bladt mailto:[EMAIL PROTECTED] http://hjem.get2net.dk/bladt
-----Oprindelig meddelelse----- Fra: Paul Stenquist [mailto:[EMAIL PROTECTED] Sendt: 20. maj 2005 12:49 Til: [email protected] Emne: Re: Understanding exposure? Recommendations?
I think Shel's right in his contention that the "art" of exposure is disappearing, but it's no less important. Even working in a strictly digital world, an understanding of exposure its finer points will separate truly good work from the merely adequate. With studio situations involving backlight and fill or even trying to produce spot-on color on location, precise control of exposure variables can return big dividends. What's more, how can anyone judge the importance of these variables if they don't even understand them? As my Stuttgart engineer friend once said, "You can never know too much." Paul On May 20, 2005, at 6:37 AM, Shel Belinkoff wrote:
Jens, Bob ...
I've been reading the discussion between the both of you. You're both right, one or the other more so depending on just what and how one wants to learn about exposure, and how much involvement one wants in the process. I've made my views on other aspects of the debate known, so I won't rehash them here. I will say that it's good that this discussion comes up once a year or so as the "art" of exposure is disappearing, and we've entered the age of the "generic" exposure because of all the automation and fancy built-in metering that cameras contain these days.
Shel
[Original Message] From: Jens Bladt
You can subtract shades of grey - when printing - but realy not add them.
If
they are gone (in a too hard neg.), they are really gone.
BTW - one of the reasons I like Pentax *ist D. The images are soft and not over sharpened. This means I don't loose information before I even get to see my recordings. I will decide later, which shades I don't want. The competing camera brands (Rebel and D70) seem to me to have too much "on board sharpening" and "on board contrast". They loose information from the start. They are for amateurs - not for the enthusiast or pro. Regards Jens Bladt mailto:[EMAIL PROTECTED] http://hjem.get2net.dk/bladt
-----Oprindelig meddelelse----- Fra: Jens Bladt [mailto:[EMAIL PROTECTED] Sendt: 20. maj 2005 09:09 Til: [email protected] Emne: RE: Understanding exposure? Recommendations?
I don't agree. It has nothing to do with printing. We are talking about exposure here - not about how to resque faulty exposures.
First of all, to be a good printer (I belive, I used to be one - before
the
digital revolution) it's prefered to start out with the best possible negative (or digital image). That is properly exposed negatives, slides or image files. Where all shades between black and white are represented. When printing you can "subtract" to get what you want. Secondly, I was still talking about the negs, not the prints. You can't
get
out of a print what's not there in a neg. You can subtract shades of grey - when printing - but realy not add them.
If
they are gone (in a too hard neg.), they are really gone.
This is also one of the reasons that the "contrast/brightness" tool is a dangerous tool. You loose information. Using "levels" or
"shadow/highlight"
is better.
Jens Bladt mailto:[EMAIL PROTECTED] http://hjem.get2net.dk/bladt
-----Oprindelig meddelelse----- Fra: Bob W [mailto:[EMAIL PROTECTED] Sendt: 20. maj 2005 08:33 Til: [email protected] Emne: RE: Understanding exposure? Recommendations?
Yes - those things are important for people who want to go on to become
good
printers. But you have to be able to walk before you can run.
-- Cheers, Bob
That's true, Bob. But you are missing out good old techniques to increase contrast by underexsposure/overdevelopment and decreasing contrast by overexsposure/underdevelopment.
I recommend slide film lab as a better medium for early lessons in exposure. There are too many variables involved in b&w development that detract from the early important stuff about exposure.
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