Basics of spot metered exposure?

Recently I left my basic incident/reflective meter some where at about 13,000 ft and a huge hike away . My cameras have only basic center weighted reflective metering or no built in meter (4X5). In the recesses of my closet I have a Pentax digital spot meter, thinking at the time of purchase that it would be the ultimate in exposure control. I have to confess that I've found it a little confusing and intimidating to use. The two or three books I have that talk about spot metering are not consistent. One talks about finding a nuetral color and metering from that. I don't know that my judgement is perfect enought to determine what is exactly nuetral. Another seems to use some sort of complex meter averaging. Any tips to get me a little further down the road and a basic start. I have a grey card, so suppose at the worst I can imitate the incent readings that I have come to depend on in even light.

The idea of finding something with neutral tonality that is in the same light as what you are photographing and then spot metering it is very accurate and one I would recommend in hyour situation. So then the problem becomes, what is 18% (neutral) tonality. The easiest is to meter a gray card like the Kodak card available from most photo stores in the same light as your subject with your spot meter.

A way to train your eye is to use a photo program and set the sum of the RGB channels to 384. 128, 128, 128 is a neutral grey but any other combination that adds up to 384 will give you the same exposure so based on that you can get a feel for approximately what darkness/lightness is a neutral tone for the various colors. While this may be crude, its a way to start you in seeing neutral tones. It also assumes your monitors brightness and contrast is calibrated.

Bracketing around your exposure in the meantime is a good safety measure.

Hey Roger

While I don't own a separate spot meter, I do use the spot meter in my camera .. almost exclusively. I rarely use any other method for meterinig, regardless of my subject. It's not always the best method, and I can certainly see times it would be more efficient and effective to have a better understanding of matrix metering, or incident metering. However, for now, I spot meter.

I highly recommend Charlie Campbell's book, "the backpacker's photography handbook" for its explanation and information on spot metering. He shows clearly what type of subects are neutral, and how to meter those that are not. The only thing he offers that I don't follow are his methods for metering white and black subjects. I find I use less compensation than he advises, but some quick trial and error will be your best guide.

As with everything else, it's just practice. Take your spot meter tomorrow, and go for a walk. Look for subjects you think are neutral, meter them, and check them against the grey card. You get better at it as you go.

Cheers

Carl
(nothing yet)

To followup on Carl's note, I purchased the Chromazone system http://www.photonaturalist.com/chromazone/index.asp that Charles Campbell has developed. It includes cards with recommended exposure compensations for many colors (five shades of green for instance!) and I rely on them quite extensively. It has yet to fail me.

Meg

Roger,

I personally like and use John Shaws measurement method.
Read John Shaws "Nature Photography Field Guide"

His recommendation using your (camera or external) spot meter and slide film in short:

A: measure the part of your subject you consider most important
B: determine how you want the measured part to appear in your shot
C: set exposure correction accordingly

+ 2 ½ stops open: Textureless white
+ 2 stops open: Extremely light
+ 1 ½ stops open: Light light
1 stop open: Light
+ ½ stop open: Dark light
Meter reading : Medium
- ½ stop down: Light dark
- 1 stop down: Dark
- 1 ½ stop down: Dark dark
- 2 stops down: Extremely dark
- 2 ½ stops down: Detail less black


EG:
Subject: Young Girl in light blue shirt
A: measure shirt
B: say you want this shirt to appear a bit darker than light blue (= Dark light)
C: correct measured exposure with 1/2 stop (open you diafragm 1/2 stop)

Subject: Young Girl in dark blue shirt
A: measure shirt
B: you want the shirt to appear dark blue
C: correct measured exposure with 1 stop down (close your diafragm 1 more stop over measured value)

Note for digital on my Nikon D100 I have approx 1 more stop available at the dark side before you arrive at textureless black and + 2 stops is nearly textureless white.

deBult's method is also the method I was originally taught. One caution for digital shooters, I would subtract 1/2 to 2/3 stop off of everything in the table above.

OriolesFan wrote:To followup on Carl's note, I purchased the Chromazone system http://www.photonaturalist.com/chromazone/index.asp that Charles Campbell has developed. It includes cards with recommended exposure compensations for many colors (five shades of green for instance!) and I rely on them quite extensively. It has yet to fail me.

Meg

I also use Charles Capbell's Chromazone system. It is very accurate. I simply find a card within the deck that matches a color within the scene that I am shooting. Then I spotmeter on the color in the scene and dail in the exposure compensation indicated. After a time, I can anticipate exposure values (which part of a blue sky is neutral or +1, or what green is neutral for example) and just occasionally need to confirm my intuition with the cards. I find that using this system, I need to bracket the exposure in only the trickiest of situations.

When I bought the system, it included a 4x6 18% Green plastic card. It works the same as a grey card, but you will find much more green in nature than grey.