Multi-spot metering in b&w landscape

[renes]

Great thanks to all of you for this clear explanation!

But now I have a few question more:

Aim the one degree spot at the darkest area in the scene where you still want to see some detail. Close down two stops.

"expose for the desired shadow values and develop for the desired highlight values"; it is extremely relevent in B&W negative photography.

Is there any dark area you would not like to have it detailed?
In other words: when it need not to be detailed?

The same question refers to the the brightest area.

Search this forum on how to do a film speed test using your spot meter and how to determine development times. The zone system is calibrating your meter to your film development time at an optimum film speed. Keep in mind every hand held light meter reads an 18% gray card. This is usually referred to as Zone 5. The meter reads every value as if it were zone 5 or the 18% gray card regardless of how light or dark the tone is. Your shadows will be two stops less than the meter reading.

I use mainly TRI-X 320 and Fuji Acros 100 and develop in Kodak D-76. I am going to buy Sekonic L-558 spot lightmeter, and it reads 13% gray card. Should it be calibrated to 18%? Could it be made by service or I can do it on my own? I should test a film speed using spot meter not till then, right? I wiil try to find how to make it.

[percepts]

Not a simple to question to answer.
The manufacturers development times usually give contrast on film which retains approx 7 or 8 stops from black to white if printed onto grade 2 paper with no filtration. This works well for some subjects and not so well for other subjects. All depends on the brightness range of the subject.
For landscapes it is often the case that with some bright sky and some deep shadows, the subject brightness range (SBR) is possibly 10 stops and in extreme cases can be a lot more. On an overcast day it may only be 7 stops or less.

So you have to work out a standard development time which gives you a known amount of stops in your subject brightness range on grade 2 paper. Typically for landscape work that is 9 or 10 stops but is a personal and subjective choice.

Then when you meter the subject you pick your shadow area which you want full detail in, meter it and reduce exposure by 2 stops.

At the other end of the scale a highlight value wich just retains a little detail is the metered value which is opened up by 3 stops. So from the shadow value to the highlight value (retaining a little detail) is 5 stops. Assuming your standard development is for a 10 stop range, then having metered the shadow area you meter the highlight area in which you want a little detail and check that the difference is 5 stops. If it is then perfect. But if the difference is 7 stops then you have some choices to make. You can either reduce development time to reduce the contrast on film so that everything is printable or you can decide which is more important in the subject and adjust exposure to capture the highlights and let the shadows start to block up. Or you expose for the shadows and let the highlights block up.

The usual method is to still expose for the shadows because the highlights will still be captured on film but will be difficult to print.
If you expose for the highlights and let the shadows block up, you will lose the shadow information completely as it won't be captured on film.

So yes you can place the exposure where you want knowing that you are favouring either shadows or highlights and that if you favour one over the other then the other will either lose detail or be difficult to print.

But using the zone system you can work out development modifications for SBR which are above or below normal and bring everything within easy printing range. This will cover the vast majority of subjects and only with extreme SBR will you have to lose something at either end of the scale.

You also have to learn by experience how dark a shadow area is but since most subject brightness range will fit on film, the usual method is to expose for a shadow which ensures the complete subject range is captured on film and worry about getting the correct tone when printing.

Finally black and white prints usually benefit from having a full range of tones in the print from black to white but this is subjective and a personal choice. It is not mandatory to have a maximum black in a print. There are beautiful prints which have no tones close to black. Basically large areas of pure black usually don't look good in a print but it depends on the subject composition as to what looks good or doesn't. So you can let things go completely black if you want or not.

[Flauvius]

An Example of all this theory:

If your shadow reading is: "5"; - Then imagine your shadow reading to be: "3".

Then, if your meter's highlight reading is: "7", - (and if you count on your fingers) - you will have a (5) zone light spread.

Wha La, you have perfect lighting!

[percepts]

I am going to buy Sekonic L-558 spot lightmeter, and it reads 13% gray card. Should it be calibrated to 18%? Could it be made by service or I can do it on my own? I should test a film speed using spot meter not till then, right? I wiil try to find how to make it.

DO NOT try to adjust your light meter.

It is myth that light meters should be adjusted to 18%. Yes there is a lot of bad information on the web and in books. Most of it because people have just copied what someone before them said.

A big part of doing film speed tests is that it takes care of any inaccuracies in your lightmeter. So if your light meter is consistently out by 1/8 th of a stop that will be reflected in the fact that the personal EI/film speed you arrive at will be altered by 1/8th of a stop as well.
So providing nothing major is wrong with your light meter it will work fine out of the box. If there was an error in your light meter which was not consistent, then adjusting the meter would not resolve the problem anyway. So until you have proved there is a serious error with light meter don't touch it.

Is 18% middle grey? NO.

Z0 = 1/2
Z1 = 1
Z2 = 2
Z3 = 4
Z4 = 8
Z5 = 16
Z6 = 32
Z7 = 64
Z8 = 128
Z9 = 256
Z10 = 512

Z0 thru Z10 is a continous grayscale from black to white. Z0 is black and Z10 is white
Assume Z0 thru Z10 are 1 stop differences. Each stop is twice as bright as the previous stop. Z5 is 5 stops brighter than Z0 and 10 is 5 stops brighter than Z5.
Z5 is the middle of the scale.

So we shine 512 units of light at the greyscale and meter the Z5 area. It reflects 16 units of light. 16 units of light is 3.125% of 512. It is not 18%. Somebody has been lying or talking bollocks. Or have they?

Suppose our greyscale only goes upto Z5 and we shine 16 units of light at it. The mid point is halfway between Z0 and Z5 which is Z2.5. The reflectance value for Z2.5 is 2.828 units of light. 2.828 is 17.67% of 16 which is pretty damn close to 18%.

So 18% is the mid point of a 5 stop range which is good to know if you are using slide film such as velvia. But its pretty useless for black and white film which has 7, 8 and more stops of range.

However, 18% is always 2.5 stops less than 100% reflectance. (at least very close to 2.5 stops). So on a 10 stop range 18% would be Z7.5. On a 12 stop range it would be Z9.5 etc...

That means a kodak grey card is always 2.5 stops less than the brightest part of the subject assuming it is in the same lighting. And that is the problem because shadows are not in the same lighting as areas in direct sunlight. So if you place the grey card in sun it is useless for working out shadows. And if you place it in the shadows it is useless for working out areas in sunlight. But using the zone system you don't need to use a grey card because with a spot meter you can be more accurate by metering shadows, working out difference for highlights and adjusting development to suit SBR.

[renes]

Thanks for next advice and so clear explanations. I can not wait to use it in practice with my 6x9 and 9x12 Voigtlander Bergheil cameras.

I wonder how to use (if possible) the Zone system when taking b&w landscape on 120 roll-film back - there is only one possible development, not so much flexibility in processing as with sheet film. Did you face with similar problem?

To help a bit I bought a second roll-film back, one to use with 100iso neg (sunlight & contrasty sceneries), second one for 320iso (cloudy, overcast & low contrast views).

Is it any solution which can help in accounting development time when you took (and have on film) 3-4 shots with different range stops between the darkest and brightest area in the scene. Average?

[ki6mf]

The only thing you can do for 120 roll film is develop the whole roll for the calculated exposure. If you keep separate backs for different development times you are OK on doing the entire roll and would vary the development for the entire roll as needed. When the sun is shinning I have found that you are almost always in a n -2 or n-3 situation and shorter development times are important.

[percepts]

some zone system users have development times for N, N+1 stop, N+2, N-1, N-2 and some have even more.

But in reality using 120 film you can buy one or two extra backs and / or know that one stop extra range should be easily coped with when printing on VC paper. 2 stops extra range can be coped with using VC paper. Zone system was designed before VC paper existed. So only if you are printing on graded paper is development modification really necessary for vast majority of subjects.

Also light levels tend to stay fairly constant whilst photographing one particular subject so you can easily fire off 10 or 12 frames which will all require the same development. A roll of 120 film is cheap. Use it. And keep a spare back for the occasional extreme case but even then you can just change film and shoot a whole roll for one particular subject.

[Brian Ellis]

"Is there any dark area you would not like to have it detailed?
In other words: when it need not to be detailed?

The same question refers to the the brightest area."

Sure. There will often be small areas in a landscape photograph that contain nothing you care about in the scene. And if you try to exposure for them you'll end up blowing out the highlights. Same with highlights the other way. It's really all an aesthetic decision - what kind of print do you want to make? Maybe you want a dark, moody print, maybe you want a bright, high-key print. So you expose and develop accordingly.

[Mike1234]

I agree with what others have said here. Have at least three RFH's so you can expose/develop to best suit the requirements of a given group of images. That said, I'm no longer shooting 120 B&W and, if I was, I'd use one back and use a whole roll for every shot. But I'm shooting 6x12cm so this allows six exposures per image... not at all bad as one can bracket and have have backup negs in case one is mucked up in processing or post processing.

[Richard M. Coda]

Aim the one degree spot at the darkest area in the scene where you still want to see some detail. Close down two stops.

You have just placed the shadow area in Zone III.

That's usually the proper exposure for the scene.

Now, aim the spot at the brightest area in the scene.

If it's a five stop range between the darkest and brightest reading, use normal development.

Less than five, increase development.

More than five, decrease development.

No need to take a whole series of meter readings and average them. That's defeating the purpose.

Just make certain that you have given enough exposure to get some detail in the shadows. Then, develop for the highlights.

That's the Zone System in a nut shell.

I tried to understand this in college (1982) when I learned of it... couldn't do it. Tried to think too much into it, like it was quantum physics or something. Then one day a few months out of college I was playing around and I had an epiphany... it just hit me like a ton of bricks. I couldn't believe how easy it was!