Roger Hicks
Allowing Ads
Dear Steve,Then I am going to remove the negative and replace it with a blank piece of film from the same roll and do a test strip to find minimum time for maximum black.
I will then replace the negative and expose for this time. If the negative was exposed and processed correctly, I should have a good print (assuming grade 2 to 3 filtration).
Dear Steve,
I'm not convinced by this, as it assumes zero density (above fb+f) somewhere in the 'real' negative, which can by no means be taken for granted. Even if it could, how much use is it?
But when it comes to the darkroom it is a bit more hit and miss. I think there could be a more logical method. I suppose that's what those enlarger lightmeters I can't afford are for!
Steve.
With that in mind, an extra stop of exposure is probably a fairly good rule of thumb whether you have done your personal tests or not.
Tim, the first thing to understand about film testing is that nothing is linear. Development effects densities unequally. You're always doubling or halving the quantity of light. There is a discrete step between unexposed film and minimal exposure, not a continuous one, etc.
If you increase exposure and reduce development, that's not doing the same thing as reducing exposure and increasing development. The reason lies in the fact that development impacts highlights in a different way than it impacts the shadows.
The nature of the reaction of photosensitive emulsions (film and paper) to light is the single most fundamental thing to grasp. It's because of its characteristics that what seems to be equivalent operations are not. You should probably get some graphics of a characteristic curve to help you.
At this point, I guess if you want to know the WHY rather than the HOW, you need to get a textbook like Ansel Adam's The Negative (the last editions are way more readable than the earlier ones).
The reason why the EI is different between the N, N+ and N- is twofold: first, because development also effects slightly film speed, as I've said in an earlier post. But that's just a minor correction, sometimes half to a third of a stop. The real reason is because that's how you control the contrast.
Let's say you have a scene. A portrait in the sun, light diffused from a lightly overcast sky. The light comes from the left side of your subject. Her left side is brighter than her right side because of this. You meter her left side and her right side. There's a difference of one stop. If you expose and develop your film normally, there will be a difference of one stop on the final print. You have exposed and processed for N, and thus you did not alter the contrast of the scene.
Let's say you expose it less than in the previous case. What it does is that overall, the photo will be darker, right? You have slightly underexposed. Both sides will be darker, but will bear the same relationship to each other: one stop of difference.
But let's say that on top of that you develop more. THAT's where the magic begins. The darker side will stay dark, but the brighter side will be three stops brighter than the darker side on the negative, and on the print you will also see this difference. You will have a portrait with more contrast. You have exposed and developed for N+, and you have augmented the contrast of the scene.
It never mentions anything about choosing an ISO for different lighting conditions, and then developing accordingly, which I think is subjective (Light cloudy, medium cloudy.... what the hell is that anyway?!). The way I understood the Zone System is by measuring the exposure range, and keeping the shadows on Zone 3 (using your single pre-determined ISO), you then expand or contract the scene if necessary using your development.
There is alot of great info in this discussion. Michel, I guess what I was trying to get at (and I have read all 3 of AA's books, and have a relatively good understanding of film curves), is that in The Negative, all the talk of film testing is directed at getting a single EI, or personal ISO for your camera/film/developer system, and sticking with it regardless of lighting condition, then applying the tenets of the Zone System to it. It never mentions anything about choosing an ISO for different lighting conditions, and then developing accordingly, which I think is subjective (Light cloudy, medium cloudy.... what the hell is that anyway?!). The way I understood the Zone System is by measuring the exposure range, and keeping the shadows on Zone 3 (using your single pre-determined ISO), you then expand or contract the scene if necessary using your development. Is this just the same as using box speed for cloudy/dark, NOT metering and placing shadows on Zone 3 (just knowing through experience that they'll be there using that film speed), then increasing the development to get a full range in tones? My confusion is laying in that I've been thinking that you use these different film speed ratings depending on lighting, and still placing shadows on Zone 3, as there are an infinite number of film speeds you could choose depending on the lighting in the scene, and the Zone System is supposed to be a standardization to remove this. (Am I daft and just carrying on a circular discussion?)
Tim
The only non-subjective way to assess the contrast of a scene is to use a spot meter and measure shadows ans highlights. Otherwise, one can make an educated guess, but only based on experience. It's an acquired skill, in a seat-of-the-pants way, but it can be good enough for 35mm.
I don't know that I agree that the only non subjective way is to use a spot meter...incident metering (determining the SBR of the scene) seems to be highly accurate in an objective way.
I do agree that EI is a movable (indefinite) factor dependant on the development of the negative.
I don't know that I agree that the only non subjective way is to use a spot meter...incident metering (determining the SBR of the scene) seems to be highly accurate in an objective way.
I do agree that EI is a movable (indefinite) factor dependant on the development of the negative.
There is alot of great info in this discussion. Michel, I guess what I was trying to get at (and I have read all 3 of AA's books, and have a relatively good understanding of film curves), is that in The Negative, all the talk of film testing is directed at getting a single EI, or personal ISO for your camera/film/developer system, and sticking with it regardless of lighting condition, then applying the tenets of the Zone System to it. It never mentions anything about choosing an ISO for different lighting conditions, and then developing accordingly, which I think is subjective (Light cloudy, medium cloudy.... what the hell is that anyway?!).
Tim
So, Adams does address changing the exposure of the film when you are giving it increased and decreased development. He, however, does it as an adjustment to the indicated exposure on the meter, rather than putting a different film speed into the meter and then using the meter reading. But, as he states, "The effect is the same in either case."
Roger,
An incident meter is very capable of measuring the brightness range of a subject or scene because it measures the light falling or registering on the dome and this corresponds to what you are metering. In fact an incident meter can be equally as effective as a spot meter. If one measures the EV of a shadow region and of the highlight region and subtracts the low reading from the high reading then adding this to five you will have the SBR of the scene. By what you wrote, I wonder if you understand the principle of incident metering. I have used the Pentax digital spotmeter
for years. I discarded it after I found that incident metering gave me greater accuracy and now use a Sekonic 558 exclusively.
I checked back in my AA book, and indeed he sticks to one EI for all development times. The reason why my EI shifts between dev times is because film speed varies a bit with development time. So I was a bit overboard in the way I explained it, and yes, you can use a fixed EI for all your dev times, but while the effect of development is mostly felt in the highlights, it can effect the shadows as well, although only to a lesser extent. You may or may not need to compensate for EI, and I think that is also dependent on the type of film developer you use. If it's simpler for you to stick with one EI, go for it.
If you go with the fixed-EI procedure, you would have, say an EI of 200, N=6; N- = 4; N+ = 8. If you do further testing, you might find that you need to change your EI for N- to 160, one-third of a stop more exposure, and to 250 (one third less) for N+ to keep the exact same density in the shadows. But as I said, that should be a minor correction, and my previous example was a bit exaggerated.
The only non-subjective way to assess the contrast of a scene is to use a spot meter and measure shadows ans highlights. Otherwise, one can make an educated guess, but only based on experience. It's an acquired skill, in a seat-of-the-pants way, but it can be good enough for 35mm.
In sum, for the EI-correction method: for a high-contrast scene, you set you meter to 160, measure shadows and place them on Zone III, and develop for 4 mins. For a low-contrast scene, you set your meter to 250, measure the shadows and place them on Zone III, and develop for 8 mins. Nearly all of the expansion/contraction appears in the highlights, and a slight EI compensation is taking care of the slight increased or reduced film speed due to development.
People who use BTZS always calculate precisely the EI compensation, but for many practical purposes it can be ignored.
Tim, It appears that you are trying to reconcile the irreconcilable.
The Zone System as it is presented in the books that you mention has several areas that are difficult if not impossible to reconcile with reality especially when it comes to tonal representation in the print.
The light falling on you is the same as is falling on the barn. You take a meter reading in the sun and then a second in your own shadow. Compare the two and then add in the BTZS factor and you have your SBR.
I still don't understand how you position your meter in relationship to your subject. Let's say you are sixty yards from a barn, looking at it from one of its corner. The sun is setting, at your right. The right hand side of the barn is light. The left hand side is dark. There's a river with piranhas between you and it. You have to meter the contrast range of the scene, between the light and the dark side of the barn. How do you do that?
Clever. But what if the shadow area is under foliage, so that "through the checkerwork of leaves the sun flung spangles, dancing coins" ?
Then why does everybody harp on reading these 3 books and doing film testing? I have to take advice and what I read at face value- I don't know any better. I have John P Schafer's books as well, but haven't gotten to them yet. Maybe they will help. I'm reading BTZS now- maybe that will help (although I almost threw it in the trash when trying to wade through the terrible explanations of logs, etc- they made much more sense in highschool). I'll get Fred Picker's book- maybe that will help. See the problem here? Too much reading and no "doing". I just want to get this figured out so that I'm not weighed down when I start using my view camera. LF photography has enough of its own difficulties- I don't want to be guessing about my film and developer as well.
I appreciate all the advice I am getting- you have no idea how much, as I have nobody to teach me. But sometimes the advice is difficult to put into practice, because it is beyond current skills and understanding. When somebody has alot of knowledge and experience in a field, what may seem a simple flippant suggestion can be tough to put into practice by the novice, because they have not reached that stage yet. I have really benefitted from this discourse though. It has clarified many things for me, and solidified them in my mind a bit stronger.
Thanks,
Tim
Or what if a cow took a dump in the trees and the meter did not capture the crap as it fell?
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?