If you want to measure the light a subject receives then why not simply measure the incident light?Originally Posted by Vaughn
A gray card measured in a part of landscape doesn't make all colors middle gray, as you mistakenly stated. That kind of nonsense doesn't help the OP. Like suggestions that a gray card is for measuring the evenness of light received by a plain painting.
The topic is spot meters -- not incident light meters. Gray cards are very helpful (if not actually required) when doing copy work when one is using a spot meter, or any other type of reflective light meter.
Landscape...take the classic example of photographing a white horse and a black horse. Using a spot meter on the white horse, and using that reading will give you an under-exposed neg and a gray horse. Metering the black horse and using that reading will over-expose the neg and give you a gray horse. Using a gray card will give you a "proper" reading and give you a black horse and a white horse. But since neither horse is middle gray, the gray card is useless in determining how black and how white the horses actually are.
If the black horse is 4 stops darker than the gray card, that "proper" reading will turn the black horse into a sillouette -- no detail and no texture. If the white horse is 4 stops brighter than the gray card, the "proper" exposure could block up the values of the horse -- again no detail nor texture.
So forget the gray card, meter the black horse, determine how black one wants the horse and expose accordingly...for example, two stops less for full detail, 3 stops less if one just wants a little texture and a richer black. Meter the white horse, see where its light value falls relative to the black horse and the chosen exposure...then determine how much development to give the neg to keep the values of the white horse in a workable range on the negative.
Basically, if one is using a gray card to determine exposure, then a spot meter is not needed...any reflective light meter will do to give you an average reading for the scene off the gray card. But if one goes to the expense of buying a spot meter, one might as well use it to its full capability and determine the actual range of values in the scene...and a gray card will not do that.
I would think this info would be very useful info for the OP. There are many ways to approach metering...Mine works for me and it can work for others
Vaughn
"A gray card measured in a part of landscape doesn't make all colors middle gray, as you mistakenly stated."
Actually that is not what I stated, but I did not express myself very well, and can see where the assumption could be made that that was my meaning. Sorry about that. The second paragraph of this post does a better job of communicating what I meant.
Last edited by Vaughn; 21-Apr-2008 at 04:30. Reason: mellowing the post a bit.
The topic is spot meters -- not incident light meters.
WRONG - THE OP SPOKE ABOUT INCIDENT METERING TOO!
Gray cards are very helpful (if not actually required) when doing copy work when one is using a spot meter, or any other type of reflective light meter.
Landscape...take the classic example of photographing a white horse and a black horse.
A CLASSICAL EXAMPLE OF LANDSCAPE FOR YOU IS A WHITE HORSE AND A BLACK HORSE? ARE YOU KIDDING?
Using a spot meter on the white horse, and using that reading will give you an under-exposed neg and a gray horse. Metering the black horse and using that reading will over-expose the neg and give you a gray horse. Using a gray card will give you a "proper" reading and give you a black horse and a white horse. But since neither horse is middle gray, the gray card is useless in determining how black and how white the horses actually are.
If the black horse is 4 stops darker than the gray card, that "proper" reading will turn the black horse into a sillouette -- no detail and no texture.
AN USEFUL EXAMPLE FOR MEASURING A LANDSCAPE, INDEED.
If the white horse is 4 stops brighter than the gray card, the "proper" exposure could block up the values of the horse -- again no detail nor texture.
HOW ABOUT A HORSE 2 STOPS DARKER?
So forget the gray card, meter the black horse, determine how black one wants the horse and expose accordingly...for example, two stops less for full detail, 3 stops less if one just wants a little texture and a richer black. Meter the white horse, see where its light value falls relative to the black horse and the chosen exposure...then determine how much development to give the neg to keep the values of the white horse in a workable range on the negative.
Basically, if one is using a gray card to determine exposure, then a spot meter is not needed...
HOW ABOUT A SPOT METERING OF A MIDDLE GRAY TONE IN LANDSCAPE?
any reflective light meter will do to give you an average reading for the scene off the gray card. But if one goes to the expense of buying a spot meter, one might as well use it to its full capability and determine the actual range of values in the scene...and a gray card will not do that.
BASICALLY YOU WANT TO SAY MEASURING MIDDLE GRAY TONE IS NOT GOOD
I would think this info would be very useful info for the OP.
SURE, THE GUY WILL NOW WAIT FOR A WHITE AND BLACK HORSE TO INVADE THE CLASSICAL LANDSCAPE AND DO THE ARITMETIQUE...TO HELL WITH A GRAY CARD, GRAY TONES, THE SPOT METERING OF GRAY AREAS..ETC. ALL IS NOW CLEAR FOR THE OP.GOOD LORD!
There are many ways to approach metering... Mine works for me and it can work for others
Vaughn
"A gray card measured in a part of landscape doesn't make all colors middle gray, as you mistakenly stated."
Actually that is not what I stated, but I did not express myself very well, and can see where the assumption could be made that that was my meaning. Sorry about that. The second paragraph of this post does a better job of communicating what I meant.
then keep clear of those horses. The end is nigh.
Measuring a 'middle gray' in the landscape will not tell you about the contrast range of the scene, how much darker the important dark areas might be than the gray card or how much brighter the important high values might be than the 'middle gray'. None of the people suggesting the use of the gray card have said a word about calibrating your personal film speed, we don't know if the OP is shooting black and white or color, and if B&W none of the gray card people have mentioned calibrating one's developing time
IMHO the use of the gray card is more suited to the studio than outdoors. Outdoors I still believe one should use a spot meter and learn to read and meter the scene.
There is no reason for voices at all. This is really not very complicated.
steve simmons
Mostly just one end of the horse needs the wide berth.
Both horses are on a green grass hill - of the middle gray equivalent...
I'm starting to think there is a tendency amongst members of this forum to overly mystify a potentially simple subject!
Mark, take a good book and go accordingly. Better than taking the crumbs of unknown qualities of this forum. Just my 2 cents. Good luck!
First, there's absolutely no reason to allow any of this nonsense to get in the way of you enjoying LF. Life is short, just go take some photos and enjoy it, and screw the technical mumbo jumbo.
Having said that, let me add a discordant voice:
There are basically two kinds of light meters: Incident meters that sense the brightness falling on the subject, and reflective meters that sense the brightness reflective off of an object. The spot meter is a variety of the latter (measures reflective light but designed to have a very narrow field of view: 1 degree or so.) What all light meters share in common is that they're supposed to be calibrated based on 18% gray -- no matter how bright or dark the subject is, they will always give you a reading that will make the subject (on average) come out looking middle-gray.
Therefore, theoretically, if you're pointing the spotmeter at an 18% gray card, it should give you the same results as when taking an incident meter reading under the same lighting conditions. However, all sorts of complications may arise in reality -- slightly tilting the 18% gray card can for example result in a slightly different reading because of the reflective surface of the card itself. Also, different manufacturers of meters may have slightly different calibrations. etc etc. As a practical matter, if you're doing black and white work, one stop difference should not be a big deal considering the exposure latitute of bw film.
This is where I am confused about the discussion of this thread:
If you're only using a spot meter to measure exposure for middle gray, for example if you're pointing it at what you assume is a middle gray rock or tree trunk (or your gray card that you've taking along into the field) then there's really no point in using a spot meter, and you should leave it at home along with your gray card, and just carry an incident meter (or an incident meter that has a wide reflective reading option.) Why? Because in using a spot meter that way, all you're doing is measuring exposure for Zone V (middle gray) which is what the incident meter already does anyway. In both cases, you're taking an average reading.
Rather, a spot meter is really best used to measure readings for very specific parts of a scence -- as part of the Zone system, to measure exposure for the zone III, or the darkest area of the subject in which detail is required, for example.
Incidentally, I always make it a habit to simply halve my ISO setting on my meters (so if I am using 400 speed film, I always set the ISO to 200 on my meter) -- this is common practice. One stop "over-exposure" is a good thing.
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