General exposure question - probably zone system related

[frank]

No worries, John. It's how I do it and it works for me, so I'm not so concerned about breaking some rule. I understand that I may be more lax about metering than others, and I'm okay with that.

 

[markbarendt]

why would I meter something else when I can meter the actual subject and place more or less exactly on the film curve where I want it. Just doesn't make sense to meter the wrong thing. Why would anyone do that and assume its the same reflectance as a grey card which isn't the middle of anything anyway. You might as well stick your finger in the air, see if the winds in the east and then pick a random number.

If you ain't going to use the Zone system as accurately as possible then you would be far better off using an incident meter which will give you more consistent results than badly applied zone system technique.

Yes, using a known reference point, like a gray card, along with a spot meter, is the theoretical equivalent of using an incident light meter, and it is every bit as accurate because a given subject, being illuminated by a given amount of incidental light, will reflect a certain amount of light. It doesn't matter if you're measuring the light falling on the scene or reflected from the subject, if "your/my" system is calibrated via film testing and experience, then either type of metering can provide exactly the same results.

The real difference between incident and reflective metering is mostly in how an individual photographer thinks about the task and prefers to do the math.

 

[Bill Burk]

If you were listening to me jnanian, you'd know the meter is the most accurate tool in our kit.

It's there to advise you, but you ultimately make the decision how to use that information.

It's like checking the speedometer of your car. On a mountain road you might drive 20 miles an hour faster than others could - because you know the road and there is no limit. But on an open highway you might drive exactly 4 miles an hour above the speed limit because a highway patrol officer is behind you and you figure at any other speed, the officer will be suspicious.

 

[markbarendt]

It works for me. But I'm not so much into film curves.

That it works is all that really matters.

 

[Hatchetman]

I use a grey card but can't afford a meter.

 

[alanrockwood]

I understand that for the zone system one generally places the "speed point" of the film (where absorbance is 0.1 above base plus fog) four stops away from the metering point. The exposure index is based on that four-stop gap.

Is that also the way factory speeds are determined, or do they use a different number of stops between the metering point and the speed point?

 

[markbarendt]

Yes, it is different Alan.

 

[removed account4]

If you were listening to me jnanian, you'd know the meter is the most accurate tool in our kit.

It's there to advise you, but you ultimately make the decision how to use that information.

It's like checking the speedometer of your car. On a mountain road you might drive 20 miles an hour faster than others could - because you know the road and there is no limit. But on an open highway you might drive exactly 4 miles an hour above the speed limit because a highway patrol officer is behind you and you figure at any other speed, the officer will be suspicious.

hi bill

yeah i know exactly what you mean. when i am working for others i use a meter ( look at the speedometer to make sure i dont' get arrested
for driving while being olive ) but as you know when i am exposing for myself i am a wreckless fool who relies only on my wits.

I use a grey card but can't afford a meter.

hatchetman, you can use your hand if you want .. i think it be 2stops over grey.

 

[Bill Burk]

Yes, it is different Alan.

That's right markbarendt,

I keep saying it's 2/3 stop (2/3 stop lower Exposure Index for Zone System) because I'm pretty sure that's about what it works out to be.

Correct me if I'm wrong.

 

[alanrockwood]

That's right markbarendt,

I keep saying it's 2/3 stop (2/3 stop lower Exposure Index for Zone System) because I'm pretty sure that's about what it works out to be.

Based on my densitometer measurements, I am getting an exposure index of ~50 for Fomapan 200. (I will spare the details of the development conditions.) This is for a four stop difference between the speed point and the metering point.

Based on the 2/3 stop idea mentioned above, my value of 50 would be equivalent to a conventional exposure index of ~80. Some say that Fomapan 200 is about half its rated speed of 200, which would be about 100, which is pretty close to 80, so maybe my results aren't too far from the expected result.

Comments?

 

[markbarendt]

2/3 stop from 200 is 125.

If you measure/test and find your EI is 50, then it's 50. No adjustment.

The EI includes all the variables in your system, including the failings of your shutters, aperture scales, film age and batch, technique, ....

 

[RobC]

I understand that for the zone system one generally places the "speed point" of the film (where absorbance is 0.1 above base plus fog) four stops away from the metering point. The exposure index is based on that four-stop gap.

Is that also the way factory speeds are determined, or do they use a different number of stops between the metering point and the speed point?

Agreed its different. Its based roughly on whats considered the average scene which is around 7.5 stops. So middle would be around 3.75 stops lower than 100%.

See following which is from the ISO standard for dermining film speed I think:

http://en.wikipedia.org/wiki/Film_speed#Determining_film_speed

As far as I'm aware Ilford use ID11 for all their ISO film speed tests and Kodak use D76. Use any other developer with their films and the ISO box speed goes out the window so as always the ISO speed is for guidance as a starting point only.

 

[markbarendt]

Here's a good illustration of what you're getting at Rob.

http://www.ilfordphoto.com/Webfiles/2010628953322222.pdf

See the bold numbers on page 3.

 

[Bill Burk]

...I will spare the details of the development conditions...

Actually, the details of "everything" is important when trying to figure out why you got different than 125 by Zone System testing. markbarendt started the list of all the camera factors that are incorporated in your tests. There are still many additional things that could differ between your "lab" and standard practice. The developer is important (if it's not a standard one). What angle the light hit the gray card, the angle you measured from, the kind of light... tungsten (and if so, with an 80b filter?), fluorescent, flash, daylight... Shutter speed you selected (Reciprocity law failure?)...

Somewhere in there you had something different than the manufacturer used for testing which caused your result to differ.

Based on the 2/3 stop idea mentioned above, my value of 50 would be equivalent to a conventional exposure index of ~80. Some say that Fomapan 200 is about half its rated speed of 200, which would be about 100, which is pretty close to 80, so maybe my results aren't too far from the expected result.

I agree that your "Zone System" finding of 50 corresponds to about a speed of 80 for "standard" metering. You can use those two speeds (50 when you Zone System meter, 80 if you just enter it in a camera to use on automatic) with confidence until you find a good reason to change.

Since you have a densitometer, you can feedback some actual work to verify that when you use an EI of 50 your shadows are slightly above 0.10

Flare will bring your shadows up too... That is always fun to try to factor in, because it is the wildest factor of the bunch.

 

[RobC]

Agreed its different. Its based roughly on whats considered the average scene which is around 7.5 stops. So middle would be around 3.75 stops lower than 100%.

See following which is from the ISO standard for dermining film speed I think:

http://en.wikipedia.org/wiki/Film_speed#Determining_film_speed

As far as I'm aware Ilford use ID11 for all their ISO film speed tests and Kodak use D76. Use any other developer with their films and the ISO box speed goes out the window so as always the ISO speed is for guidance as a starting point only.

Also for OP, you should note that the chart above is showing its the slope of the curve between two specified points which is really what determines the ISO speed of the film providing the 0.1 value is also achieved. And its only looking at a section of the straightline portion of the film.

From my own testing of some Ilford papers I find that a film density of 1.3 is my target for pure white. Anything higher will be blown out unless it's printed down. So I aim to contain my 10 stop SBR in a negative density range from 0 to 1.3 ( + (Fb+fog)). Result of that is that I nearly always get an EI of at least a stop less than box speed unless I'm using speed increasing developers such as Microphen.

A most extreme example of that is Delta 3200 which has an ISO speed of 1000 (using ID-11) but an EI of 3200 using Microphen.

 

[frank]

So it's pretty much just over exposing the meter reading (incident, or properly aimed reflected) by one stop.

 

[Bill Burk]

Try this to see how the meter method changes the Exposure Index that you need.

Set EI at half rated speed... Meter shadow and place on a shadow zone.

Then set EI at rated speed and take an average reading.

You might get the same f/stop and shutter speed if my theory is right, that it's the metering method that makes the speed difference.

 

[markbarendt]

So it's pretty much just over exposing the meter reading (incident, or properly aimed reflected) by one stop.

That is typically where it seems to land.

Using fixed density points makes talking about zones on a negative easier.

That doesn't mean it makes better prints though. Some people find considerably different EI's make their work better/easier.

 

[RobC]

if my theory is right, that it's the metering method that makes the speed difference.

The speed difference is created because in order to get 10 stops of SBR onto film which fits a nominal G2 print, you need to reduce development and/or developer dilution. The result of doing one or both of those is that you make the curve toe longer/shallower. To remedy that so that you get the required separation in the shadows, you need to reduce film speed. i.e. give extra exposure by approximately a stop if you're aiming for that 10 stop SBR on G2 paper.

However, Adams charts show Zone VIII on film density of 1.3. This for me doesn't match my testiing. I find I need Zone X on 1.3 film density.

So if you trying to emulate Adams numbers all sorts of anomalies occur. Whether thats because of differences in materials today or his enlarger or anyone of many possible other variations I don't know. All I know is that his numbers don't work for me and I have arrived at my own which make sense for me.

 

[Bill Burk]

The speed difference is created because in order to get 10 stops of SBR onto film which fits a nominal G2 print.

I just double-checked one of my charts. I assume for my own purposes that 7 stops SBR = Zone System Normal (not 8 stops I think I said in an earlier post).

When I do that everything seems to fall into place with just a 2/3 reduction in film speed (due to the difference in metered point to 0.10 by Standards vs Zone System stop down 4 stops to Zone I).

This is a thread where I started to explain how I operate...

(there was a url link here which no longer exists)

But to see what I really think...

(there was a url link here which no longer exists)

I'd be interested to hear about how you are putting together your own way of working because it sounds like you are kind of going down the same road.

 

[RobC]

my final proof of what I'm getting is done through a print test.

I have taken a piece of of A4 mountboard and cut out 12 squares with a mount cutter. I numbered each cut out square on edge with a corresponding number on same edge on A4 card.

I use this to reproduce the zone patch test photo in the Negative. I photograph a piece of hardboard from approx 6 feet focussed. I expose from metered -5 stops (zone 0) to metered plus 6 stops. I then take my zone 1 negative and print a step wedge until find the print time which just gives me very small difference between max black and the next step. When I have found that print time I print each of the negs in turn from zone 0 thru zone 11 using zero filtration, same time for all. I remove one patch square whilst I expose that sqaure and put it back and move onto next one etc. This proves or disproves whether my neg exactly fits the paper. If neg is spot on I get a hint of grey in zone 9 and zone 10 is pure white. It also shows whether you are getting full textural detail in zone 3 and zone 7 and whether its disappering in zone 2 and zone 8.
That will depend on your curve shape but it tells you a lot about your film, developer, paper combo. Only caveat is that you must use the newest paper possible.

Having used a densitometer to chart film curves I know what the range is that is required to achieve this. I also know that to get a noticeable difference between zone 0 and zone 1 you need at least 0.07 film density difference using this print test method. This usually means at least one full stop extra exposure to get zone 0 on the correct portion of the toe and that is usually above fb+fog. Sometimes more than one stop extra exposure. Again all depends on film, dev, paper combo.

I know adams says use zone 5 neg to determine print time but that doesn't make sense to me. And defintely don't use zone 0 neg because paper will go blacker than you can achieve in real world printing without toning. Zone 1 neg is the one to nail the print time with as far as I'm concerned.

Sounds like a lot of hassle and the first time it did it, it was. But now I know what I'm doing its real simple, especially since I don't print anything until I get my film curve where I want it which is usually close enough for the print test to be final proof.

Having done this you can be almost 100% sure that can meter anything and place it on any zone you like and get a correct exposure for it, certainly within a half stop at the worst. If you then do what I do which is meter for a highlight then printing is a breeze providing SBR is 10 stops or less.

 

[Bill Burk]

my final proof of what I'm getting is done through a print test..

Sounds like a very thorough test. I agree with your method and interpretation, it's inspiring.

I was getting ready to do some serious tests like that. I was setup for print sensitometry etc. I was going to aim for print reflection 0.04 and 97% of Dmax. Then it happened - a sort of short circuit. I had in my hands a negative I developed as long as my wife allowed that I would never want thinner... that I had a tough time holding on Grade 3 Galerie. I also had a negative so "hot" I would never want one with more contrast... I had a tough time holding it on Grade 2 going the other direction.

So I measured the two negatives' highlights and shadows and decided to aim for the middle between them. I think I wrote down 1.05 - difference from important shadow to important highlight. That means if my shadow measures 0.40, then my highlight should be 1.45. I do not concern myself with placing shadows precisely at 0.10, or even the beginning of the straight line. I only concern myself with the difference between the two important keys.

There's a lot of conversation regarding the precise placement of exposure to take advantage of the long toe of film. I won't argue against accurate exposure - it would make sense to me to occasionally read actual results from densitometer readings, against the planned exposure placement of specific spotmeter readings. I've done it a few times and have been a bit mystified that I hit 0.40 shadow when it was placed on Zone II. But I chalk it up to flare, and move on.

 

[markbarendt]

As you are starting to see Rob there are things in Adams' system that don't always make sense.

Adams' method is one of many possible practical implementations of photographic science, Adams' method is not the actual science.

That doesn't mean his system doesn't work, Adams has helped a lot of people make much better photos. By providing fixed numbers and standards he helped an incredible number of people measure their success and failure and see fixes and make good photos. He gave amateurs a way to talk about their work and compare notes. Good things!

In the end though Adams' standards are simply the equivalent of a business standard for a production line. His density targets, among other things, are based on his preferences; what he thought a photo should look like.

 

[markbarendt]

I'll also add (as I've said in other threads) that I think a lot of the questionable stuff (from misunderstandings to plain bad info) comes not from Adams, but from misreading Adams, along with the mischaracterizations, embellishments, errors, bastardizations etc. by other photographers/authors. It all went way over the top and ultimately became the misguided "zone system dogma" Stephen B. has referred to.

Yep it devolved into tribalism centered on prophets

 

[frank]

Yep it devolved into tribalism centered on prophets

A recurrent theme unfortunately!