Evaluating scene contrast
While much has been written and discussed about tailoring negatives to scene contrast through speed and +/- development tests much less seems to be written about how one actually goes about evaluating scene contrast. After all, if we misinterpret the scenes actual contrast much of our testing would seem to be wasted. Those using matrix metering and one average development time need not be concerned. But those adjusting E.I.'s and development time must make these judgments at the time of exposure. Exactly how do you go about evaluate scene contrast? Give me some ideas of how to get better at it.
The way i do it is to take spot-meter-readings of objects with different values in a scene. Then I decide what zone i want each to be, or rather, what zone i want my object (or area) of focus to be, and calculate where everything else falls. If the disparity between zones is too great, e.g., my subject is Zone V but the shadows fall on Zone I, there is too much contrast. In other words, I try to use the zone system. And I shoot a lot, as much as possible.
There are several ways to evaluate scene contrast. If using the Zone System one would normally meter the shadows and the highlights of the scene or subject with a spot meter which would measure the reflective values. For instance if the shadow meters at an EV 6 and the highlights EV 12 then one could place the EV 6 exposure on a zone III which would be two stops less exposure than the meter indicates for this luminance. That would indicate that the high values would fall on a Zone X and would require a N minus one or two development (depending on the high value subject matter and desired tonal rendition). Zone VIII would be the highest tonal value that would have texture apparent in the tone. Zone IX would have no texture present but would be marginally below Zone X tonality (which is typically considered to be paper base white). Alternatively one could place the low values on Zone II (three stops less exposure than the meter indicates) and the high values would then fall on Zone IX and may not require any reduced development. This may be true if the low values do not require the detail desired in the first example and if the highlights are specular in nature.
If one were using an incident meter and BTZS methodology, then one would meter the shadow values with the dome pointed toward the camera lens. Next a high value reading would be taken (again with the dome pointed toward the camera lens). The low reading EV would next be subtracted from the high value EV and the resulting difference would be added to 5 to arrive at a SBR for the subject or scene. For instance if you have a high reading of EV 12 and a low reading of EV 8 that would leave you a net difference of 4and when added to five would be a SBR 9. Since SBR 7 is considered to be a normal range that would indicate a reduced development to accomodate the extended contrast of the scene.
While it may initially appear that the Zone System provides for more creative latitude in shadow value placement, it should be noted that both systems allow for this creative latitude.
Last edited by Donald Miller; 02-16-2007 at 08:52 AM. Click to view previous post history.
Reason: Spelling error
I use the less detailed 'Expose for the shadows - develop for the highlights" method and to get an idea of how much to adjust I look at the shadows cast by the light. I adjust based on the strength of the shadows cast by objects in the scene, which admitedly requires a bit of experience to really fine tune, but works quite well for me without the need for a lot of gear I can't afford.
I put together a simple article explaining how I judge light conditions on my personal web site in the articles section. My method is not for those who like to have ultimate control over everything, so be warned ahead of time...
What the previous posters have said is correct, and this is an area where hard work is needed. There are no magic formulas - proper exposure (combined with development and printing) is simply something that comes only through lots of practice. I strongly recommend writing down your exposures as you make your negatives, and writing down your development. You learn from the knowledge you gain through trial, and particularly, error.
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Experience and knowing your film and developer combo.
Me, I simply use an incident meter for 90% of the time, with a spot meter when the light is really tough.
Friends don't let friends use 'Matrix' metering. Grin. Or as the wise old someone said "A meter in the hand is worth two in the camera."
Don't forget local contrast while considering the scenes over-all contrast. Sometimes you're better off dodging, burning and/or masking later, rather than squishing all the middle values together and sucking the life out of your main subject.
Note to self: Turn your negatives into positives.
I use pentax zone six modified, i spot meter the scene that include in my frame, first is the main object, I put it in the zone that I want, then I start to meter the others, if highlight more or less than zone VIII I will use N+ or -, but I'll measures the impact of N+- process to the zone of my main object, readjust, and then I start to check the shadow, if it's get adequate detail then done.
I think that I'm not capturing the scene but I want to make a photograph with tonality that I want (as my visualisations at that time, so far it's work for me
Last edited by haryanto; 02-16-2007 at 10:55 AM. Click to view previous post history.
I think that the high values in your example would fall on Z IX.
Originally Posted by Donald Miller
Here's what I did to learn metering:
Pick a scene close to home that you can go back to time and time again. It doesn't have to be anything special, the light just has to be extreme for minus development or flat for plus development. The scene I picked for minus development was a woodland with my white car parked in a sunny spot. Make one exposure based on your in camera reading (matrix metering) to give you a baseline and develop normally. Then look carefully at the shadows and decide how much detail you want to appear in the print. In my case it was a tree trunk. Meter that area and use it as your second exposure, marking development to make your highlights fall in the proper place. Then make two additional exposures, one reading a darker area of the shadows ( a tree trunk in shadow) and then one reading a lighter area of the scene. Mark each with the proper development to control the highlights. Keep notes.
Go to the darkroom and print each negative at your standard printing time and make straight prints. Compare the prints to 1) what your visualization was and 2) take the prints out to the scene and compare them to the actual scene in the same light.
The shadows will tell you which exposure works best for you. If your highlights are off, you can use the same exposure and adjust development on the later sheets.
The problem in metering shadows is that there are dark shadows and light shadows. Which one do you pick? The only way to decide is to try both and see which looks better in the final print. The same goes for highlights.