Sunday, September 1, 2013

Spot Metering (Cont'd)

Canon Elan-7, EF 40mm STM Lens, 
Partial Metering (on the light grey gravel at the right), Kodak Ultramax-400

Yesterday,  I did an introduction to Spot Metering, following my own long-coming revelation of what this seemingly elusive-to-grasp subject is all about. In order for me to "get it", I had to re-build a far simpler model of Spot / Zone-System Metering in my own mind than that of the concept's co-originator, Ansel Adams (no less!).

Although I got no Comments here on the Blog, I got plenty of activity on my Facebook page, as I post this Blog on several Photography sites there. After reading the comments, all of which were very constructive and helpful, I decided a follow-up Post was required, and I got permission to use the words of a Vermont based Photography instructor, https://www.facebook.com/stephen.m.schaub, as he provided much more detail on the topic. Stephen corrected me gracefully on certain points, mainly that I ought to stick with the language of Ansel Adams as originally proposed, especially now that I understand the concept. He also correctly pointed out that with using these techniques, it is best to do it in the context of your entire process, from your initial measuring of the light readings, through to the considerations of what film you're using (it's characteristics) as you develop it in the darkroom.  This part was more helpful to others who participated in the exchange than it was to me, as I'm a "Figital" photographer, using film scans, not a darkroom.

I'm simply going to quote some of what Stephen said here:

"... it is helpful to keep the information within the outline of traditional zone system terminology as not to confuse people. All camera meters are dumb and read for the sake of argument measure Zone 5 or middle grey. For negative material you need to expose for the shadows and process for the highlights (so meter with a spot meter on a shadow area that needs full textural detail, Zone 3, take that reading and under expose by two stops, so from 5 to 3... you place the exposure on zone 3 and see where the other values fall.... to do this you need a real spot meter.... in camera is ok but really not user friendly. For example you would like your highlights to fall around a Zone 7 if they need full textural detail but many films can handle way beyond Zone 7 with detail and of course a good scanner also is a must.

The main point not to be lost here is that "all camera meters are dumb", and this means that the METER ELEMENT ITSELF is able to read the light, and convert it into an electrical signal, for one and only one value, which is calibrated to "Zone 5" on Ansel's system. This was ALWAYS the point at which I got lost, because I wasn't thinking about just the meter element itself, but as an Electronics guy, I was also thinking of the circuitry it is attached to, which the camera can automatically "fiddle with" to make a human - interpretable light meter. So you see, what I just said there is already over-complicating things. But let me at least add this point, and I think then you'll understand: the newer cameras (both film and digital) with Matrix (Evaluative) Metering do their magic by using a "Matrix" of a whole bunch of these tiny, "dumb" meter elements whose electrical outputs are all wired to the camera's internal computer, which is programmed to "evaluate" the light coming from all the meters in the matrix, and then set a correct overall exposure value (EV) that is actually based on Ansel Adam's Zone System, so I've been told. This EV is then used by the computer to automatically set the camera's Aperture and Shutter Speed for a correctly exposed overall scene. At least that's how it works in theory, but there are some little problems under some circumstances, and that's why the camera makers also offer the option of built-in spot metering - which is only good if you really... I mean REALLY know how to use it, as Stephen teaches his students (edited to maintain simplicity):

"...ok here is a zone system in 2 quick steps I teach to my students....1. Using a hand held spot meter meter for the area you need full textural detail.... under a shaded tree, dark hair etc..... then take that reading and place it at Zone 3 by underexposing by Two stops. 2. Just shoot and and have fun... if you are pushing a film keep your shadow placement at Zone 4 so nothing will be lost on the toe so meter for the shadows and underexpose by one stop. Thats it.... this of course in an in camera situation would be easy.... meter using the in camera spot meter the shadow region that has to have full textural detail and then using the exposure comp button under expose by two stops (so a -2).... thats it.."

At this point I was getting confused again, so I had to add this to the discussion:

"OK - I think - I understand. It was always this "place it at Zone-X" stuff that confused me... how do you "place it"? You answered that question - "by underexposing by two stops". But getting back to my write-up, I'm suggesting that "place it" means "point your meter at it, lock your exposure there, re-compose if necessary and shoot". If the camera has an ideal spot-meter in it, wouldn't that amount to the same thing - if I point my camera spot-meter at a girl's nice dark hair, instead of the mid-grey of her cheek, wouldn't the camera just set itself with the right shutter / aperture that would bring out the detail in her hair, although it might over-expose her skin a little?"

Stephen replied:

"if you meter for a persons hair that is dark it will meter it for Zone 5 or 18% grey as the meter has no idea what it is looking at... so instead you would meter the girls hair and the camera would suggest a Zone 5 meter reading, you would then just underexpose by two stops and the hair would now be a zone 3 with full textural detail and most Caucasian skin would then fall around Zone 5.5 to 6.5.... you can only place one exposure and the rest of the metering fall where they will so with negative material you meter for the shadows and let the highlights fall where they will....with transparency material it is the opposite, you meter for the highlights and let the shadows fall"

NOW I finally got what he was saying. In my article, I had said that as long as you find the middle grey in your frame and meter on that, you don't need to do anything else - you don't need to adjust your exposure up or down, you simply lock on your middle grey, recompose and shoot. That is technically correct - I wasn't wrong in saying that, because you have to match a spot meter to the only value that it knows - middle grey. But Stephen's instruction to his students is more comprehensive - what if you don't have a middle grey to meter on? The other day, I was contemplating the back end of a nice Triumph TR-6 that was white with black bumpers - thinking, what if I wanted to take a close up of that, using the zone system - what would I do? I was looking for a middle grey, but not really seeing one. Now, knowing Stephen's teaching above, I know that I'd meter on the black bumper and underexpose by 3 stops - black is black after all, and on Ansel's scale, black is Zone 1, but the meter wants to make it Zone 5. However, it was under strong sunlight making it not quite black, so I'd rather "place it" at Zone 2, which is underexposing by 3 stops. Now I understood what is meant by making the decision of "placing it at Zone-x".

With the approach I suggested in yesterday's post, looking for a middle grey and locking on it is correct, but it misses an important point. A good photographer should be able to "see in black and white", and therein lies the value of the Zone System - the idea is to learn every tone of a black and white scale, even though we're really seeing it in colour. From this, you learn the language of photography in the same way as by learning the notes of various musical scales you learn the language of music. Practising photography with a spot meter and thinking of a scene in terms of the 11 shades of grey from black to white will help you to "see in black and white". Getting the right exposures is merely a side-benefit of learning this language.

Finally, Stephen made a very important observation concerning my feeling that so much modern photography looks dull and lifeless:

"... another point.... one of the reasons digital looks dull and lifeless in many cases is that the capture is linear and not and "S" curve like most films... this curve provides much of the POP and contrast you see in a film scan.... but digital raw is a linear capture and requires a bit of work by the shooter to add the "S" curve to bring out the life and micro contrast of the file... the metering mode does not matter as long as it is correctly exposed but rather what you do with the sensor data in post production (is what counts). ... there are a select few companies like Ergosoft ($$$$ software) who make and give you the power to make  linear icc profiles.... I use this software, have since 2004. In the end what really kills online images is a lack of understanding of how much compression is happing with web projection.. .. I cringe every time I post and artwork online as 70% of the image quality is gone and that does not even touch on the issue of monitors, calibration and viewing conditions... "

(Stephen - I heavily edited your above statement, I hope it captures the gist of what you're saying).

So, what have we learned about spot metering? Let's summarize:


  1. Don't use it unless you learn the Zone System that goes with it. If you don't know what you're doing with your camera in Spot Mode, your results will be unpredictable at best.
  2. If You don't want to learn the Zone System, you might as well use your Matrix Metering, because it has a computer behind it that already knows the Zone System very well.
  3. But if you've used Matrix Metering and your picture looks dull and lifeless, just like half the pictures do on Flickr, do not publish your picture yet - you still have some work to do on it in Post Processing. If you don't want to learn the Zone System, that's OK, but DO learn how to use PP software tools to benefit your photography - and this can be done whether you shot digital or film. The beautiful thing about the times we live in is that we can now afford ourselves the advantages of both!
  4. The Zone System is the best way to learn to see things in Black and White - even if you don't shoot in B&W, it will still make you a better photographer, and this, I gather, is why Stephen teaches it to his students.


One more point I forgot to deal with yesterday - I mentioned that there is a difference between Spot Metering and Partial Metering, but then I forgot to explain it. The difference is only in the size of the area being metered. A Spot Meter measures light in a 1 degree to 6 degree cone, and a partial Meter picks up where the Spot left off - from 7 degrees through about 15 degrees. So the concept is exactly the same, but a Spot Meter provides more than double the accuracy of a Partial Meter.

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