Exposure and contrast: the big confusion.
Hi out there,
sometimes my negatives turn out a bit flat, and i would like to get more contrast.
Now here comes the confusion:
Some people advise me to OVER-expose the film and then develop it regularly.
Other people say, more contrast is reached by UNDER-exposing the film and then push-processing it.
So where does the truth lie?! Or is both correct?
It all depends....
With your B&W film, if you are underexposed you will be in the low contrast toe of the Characteristic Curve; giving more exposure will move you to the higher contrast portion of the curve.
If you are already correctly exposed, you will need to underexpose slightly and push-process it.
there's rule in zone system, exposed for shadow develop for highlight, so you can control your overal contrast, u place shadow in zone III or IV then you give more time indevelop to rise the highlight
Originally Posted by daniele_vittorio
Neither is exactly correct. Remember the age-old adage: Expose for the shadows, develop for the highlights.
One could reformulate it like this: Expose for the shadow detail you want, develop for the contrast you want.
The problem is, it is often hard to tell the difference between an underexposed negative and an underdeveloped one; both will have less contrast than ideal to make a pleasing print.
Here are some guidelines:
If your negatives are flat, but you have adequate detail in the shadows, you need to develop longer. (underdeveloped neg.)
If you have bad shadow detail and less contrast than you want, you may get where you need by simply exposing more. (underexposed, but correctly developed neg.)
If you have less shadow detail than you want, but whites and blacks in the print, you should expose more and develop a bit less. (underexposed and overdeveloped neg. Note: this is what happens with traditional "push processing")
Also, keep in mind that different scenes require different contrast controls. If you print on paper, then much of your contrast control will come from changing paper grades. Unless you shoot sheet film and use the Zone System or one of the other methods that determines development for each negative individually, you will want to aim for your most common situation and middle ground, and use the contrast controls of paper grade change to deal with unusual situations.
Hope this helps some,
Exposure does not determine contrast but rather density. Development determines contrast. If your negatives are consistly flat then decrease your exposure and increase your development time. Try changing each by 15% to start.
Read a book like Ansel Adams' The Negative rather than asking people.
Last edited by Gerald C Koch; 07-16-2012 at 08:48 PM. Click to view previous post history.
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~Antoine de Saint-Exupery
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If you are using your film correctly and developing correctly, your images should not be flat. It should be about right. It should print OK with grade 2 or 3 filter. If this is not the case, something is wrong. Before using various techniques to enhance your contrast, you should investigate where and what is going wrong and correct it.
First place to check is, if you are exposing it correctly. You can kind of sort of tell this by looking at your negative. Is it overly thin or overly dense? Second place to check is, is it being developed correctly. Are you able to develop it at specified time at specified temperature? Are you agitating it correctly?
Can you tell us how you are judging contrast?
Can you tell us what your negative look like?
Develop, stop, fix.... wait.... where's my film?
A verbose restatement of some things previously shared:
A normal image with a fixed subject brightness range depicts a set of objects in print tones from black to white = normal contrast.
If you overexpose, the stuff that is supposed to be black on the print is now dark gray and the same objects in the shot now go from dark gray to white (where some of what should be light gray tones are now blocked up but may still be printed by burning in) = loss of contrast.
If you underexpose, the stuff that is supposed to be white on the print is now light gray and the same objects in the shot now go from light gray to black (where some of what should be darker gray tones are now gone forever beneath the exposure threshold) = loss of contrast. This is why you should expose properly for the shadows. If the shadow exposure falls below the threshold, you can't print what is no longer there.
If you underdevelop, the stuff that is supposed to be white on the print is now light gray (or darker) and all the other grays (except the black stuff) are darker than they should be and the same objects in the shot now go from black to light (or darker) gray = loss of contrast.
If you overdevelop, the stuff that is supposed to be black on the print becomes just slightly lighter and the lighter grays have become lighter or white because development affects the areas that have received more exposure on the negative to a greater degree that those areas receiving less exposure. That's why you develop for the highlights. Increased development doesn't change the shadow tones very much but has a great effect on the midtones and highlights. So, with overdevelopment the same objects in the shot can now go from almost black to white = loss of contrast, but not as much as with the other three variables.
You will get an increase in contrast from the set subject brightness range only with overdevelopment. If the subject tones only go from black to light gray, and there is nothing truly white, overdevelopment can increase the density of those areas in the negative to make them print as white = increase in contrast. The shadows will get a bit lighter, but not much. If you just very slightly decrease the exposure to compensate (by shooting at an ISO 1/3 stop lower for example) and then overdevelop, you'll end up with pretty much everything still recorded on the negative but with an increase in contrast.
The combination of intentionally underexposing slightly and then overdeveloping to raise the contrast is known as "pushing" (or "expansion" in Zone System lingo). "Pulling" or ("contraction") is the opposite condition. (OE + UD)
Pulling (contraction) and pushing (expansion) are intentional, and tools that can be used to tailor contrast and tonal range in the negative and print.
Underexposure, overexposure, underdevelopment, and overdevelopment when not intentional are simply mistakes and to be avoided.
Art of Photography
Go find a copy of the "Art of Photography." I am still learning and am already on my 3rd read through that book, particularly the exposure and developing chapters, but it has already helped my understanding immensely.
Originally Posted by Gerald C Koch
Mark Barendt, Beaverton, OR
"We do not see things the way they are. We see things the way we are." Anaïs Nin
If you're putting he shadows in Zone IV, wouldn't you need to give less development time to control the (now) overexposed highlights' density?
Originally Posted by haryanto