Film testing

Allen Friday · Feb 9, 2007

Donald Miller said:
Think about it this way if you will...why would someone arrive at a film exposure that evidences a .10 density above FB+fog and then effectively reduce that EI by two more stops (Zone III exposure)? If the film needs two stops more exposure (Zone III exposure again) than the first value wouild seem to be inadequate in practice. Perhaps you can come up with a reason for doing this...I can't come up with a good reason...the exposure at the determined EI at that EI is either adequate or it is not.

Donald,

Here you have demonstrated that you really do not understand the zone system. By making a zone III exposure, you do not "effectively reduce that EI by two more stops." You are not giving the film any extra exposure by doing this. Your analysis here would only apply if you metered a zone V area and then gave it zone three exposure. You give a zone three exposure because you are reading a shadow area of the scene, that area recieves less light than the mid tone, so you compensate for this by giving more exposure. Think of it this way, if you meter a zone V area in the scene you should get exposue X. If you meter a zone III and adjust by two stops, you should still get exposure X.

timbo10ca · Feb 10, 2007

Donald Miller said:
Tim, I can't speak for anyone else and what they recommend. I observe a fair amount of parroting taking place in the area of recommended procedures. I understand what you are saying about complexity of the process...it can be a bit much at times.

Looking at this logically, since we are engaged in making prints rather than negatives as the final product, doesn't it make sense that we would be starting with determining the characteristics of the print material and then tailoring the camera negative to fit the paper rather than assessing some arbitrary value sofar as density or exposure point to the negative.

This is a very good point. I still need to start somewhere though, and you need a good negative to have a shot at a great print. I will continue to wade through the mass of knowledge until I "figure out what's right for me". I've heard great things about BTZS, and how exacting/accurate it can be. I'm not going to give up on it until I fully understand it enough to say whether it is or isn't right for me. I hope to get to the point where I can judge the light and the scene and know intuitively what to use for film, exposure, development, paper, etc etc. Until then, I need training wheels- big ones

Tim

timbo10ca · Feb 10, 2007

Donald Miller said:
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.

My problem with the use of this type of metering for B&W is that you are only measuring incoming light with an incident meter, not what the camera is seeing regarding shades/tones of the subject. Regardless of whether there's alot of light, or very little, if something is white, you want to expose so that it's white. Your incident meter doesn't know it's white, just the amount of light falling on it. For some reason it makes sense to me to use incident light for color though........ Maybe I just answered my own question..... I'm tired.
:confused:

Donald Miller · Feb 10, 2007

Allen Friday said:
Donald,

Here you have demonstrated that you really do not understand the zone system. By making a zone III exposure, you do not "effectively reduce that EI by two more stops." You are not giving the film any extra exposure by doing this. Your analysis here would only apply if you metered a zone V area and then gave it zone three exposure. You give a zone three exposure because you are reading a shadow area of the scene, that area recieves less light than the mid tone, so you compensate for this by giving more exposure. Think of it this way, if you meter a zone V area in the scene you should get exposue X. If you meter a zone III and adjust by two stops, you should still get exposure X.

Allen,
Here we go again. Let's look at it this way. If we were to test a film using Zone System methodology, we would assign an EI based on a negative density at a given exposure of .10 above FB + fog. Let's say that we find that the film exposes at an EI of 50 to give us this desired density, This EI is determined to represent a Zone I value in Zone System parlance.

Everything is fine until we then expose the film under actual use conditions. I find that Zone System practitioners will typically assign a Zone III or IV placement for their shadow values. This means that the EI of 50 is not a valid number based upon field use. How invalid is the EI when the shadow placement is at Zone III or IV? In the case of the film that we determined to have an EI of 50 the actual placement will be EI 12 1/2 at a Zone III placement or slightly above EI 6 for a Zone IV shadow placement. Now I don't know how you figure your math, but that is the way I figure mine...and yes I do understand the Zone System. Now I don't know any Zone System practitioners that pay much attention to a Zone V placement...in fact, I think that everyone that I ever encountered paid attention to shadow placement for the exposure...as I said before, they seem to universally place at either a III or IV for their shadows. That still is two or three stops more exposure than the film tests indicated. More exposure translates to a lower effective EI in my book.

Roger Hicks · Feb 10, 2007

"If this is difficult to comprehend, you might avail yourself of Phil Davis latest book on the subject."

Dear Don,

Please do not attempt to patronize me until you know more about the subject and have thought it through.
Go through the thought experiment I described in my last post, and tell me how the incident light meter can tell whether it is in front of the black velvet on white snow, the white snow alone, the black velvet alone, or a normal scene.

Then tell me how you are measuring the subject brightness range with an incident light meter.

To turn your own words back on yourself, you find this difficult to comprehend, you might try thinking instead of parroting. Oh -- and if you try measuring black velvet on snow, you'll find that depending on the angle of the plush, the type of snow and the angle of the sun, it can exceed five stops; I've tried it. I'm not sure it can reach six stops, but this doesn't affect the argument.

I hate to appear rude, but really, I do have some idea of what I am talking about, and even if I didn't, as I say, the thought experiment will demonstrate clearly that you are wrong.

Cheers,

R.

Roger Hicks · Feb 10, 2007

timbo10ca said:
My problem with the use of this type of metering for B&W is that you are only measuring incoming light with an incident meter, not what the camera is seeing regarding shades/tones of the subject. Regardless of whether there's alot of light, or very little, if something is white, you want to expose so that it's white. Your incident meter doesn't know it's white, just the amount of light falling on it. For some reason it makes sense to me to use incident light for color though........ Maybe I just answered my own question..... I'm tired.
:confused:

The basic problem here is that you are thinking clearly and Don isn't, as demonstrated by the thought-experiment described in my previous post (the incident meter in front of velvet and snow).

Exposures for colour slide are determined by the need not to 'blow' the highlights, i.e. they are keyed to the highlights. Exposures for negatives are determined by the need to get adequate detail in the shadows, i.e. they are keyed to the shadows.

If the highlights and shadows are exactly 5 stops apart -- the subject brightness range of an 'average' scene -- then both incident readings (of the highlights) and spot readings (of the shadows) will be identical. If the SBR is greater or less than 5 stops, the readings will disagree.

His technique -- one incident reading in the highlights, one in the shadows -- assumes a constant, average brightness range, with the shadows 5 stops down from the highlights under any given lighting.

An incident light reading in the shadowed area will give you detail under most circumstances (the obvious exceptions being black velvet or similar very dark subjects) in the darkest shadows in the shadowed area. The easy way to get around the black velvet problem is to deliberately over-expose the film, i.e. under-rating it: EI 200 or even 100 for an ISO 400 film.

Spot meter the shadows properly and you'll find that you don't need the absurdly low EIs beloved of so many Zonies. Use any other metering technique than spot metering and you'll need a 'fudge factor' based on rote, experiment or experience to get adequate shadow detail.

With a spot meter, I normally rate films effectively at 1/3 to 2/3 stops slower than the true ISO, because I prefer the tonality that way. With any other style of metering (though-lens, incident for mono) I set the meter according to the light: typically ISO on an overcast day, half ISO (or even a little slower) on a brilliantly sunny day.

If there are no deep shadows in the shadowed area, his technique means that you will be overexposing unnecessarily, resulting in reduced sharpness and increased grain. You might be giving as much as two or three stops more than you need, even after allowing (as I do) for a little extra exposure in the interests of tonality. As I recall, he shoots LF, where grain and sharpness don't matter. With smaller formats, they do.

Likewise, an incident light reading in the most brightly lit area gives you a good idea of the brightest possible highlight, but again, there may be no pure white in your picture. If you are shooting a nude on a fur, for example, the brightest area might be a skin tone some 2 stops down from a pure white.

In other words, his technique will give you a very good idea of the maximum possible subject brightness range under given lighting, and no idea whatsoever of the actual subject brightness range.

Although he thinks he is working very precisely, he is, in fact, being saved by the inherent flexibility of the process, and by the fact that the bigger the format, the less precise you need to be: as long as you expose generously rather than too sparingly, you'll be all right.

What really annoys me is that he is downright rude to, and dismissive of, those who work from first principles and demonstrate the absurdity of what he maintains. The Zone System is a perfectly fine way to determine exposures, if your tastes lie that way, but it is a small subset of sensitometry, not the foundation thereof.

Cheers,

R.

Roger Hicks · Feb 10, 2007

Donald Miller said:
Furthermore, taking Efke PL 100 as an example. The EI of the film at SBR 7 (normal luminance scale) is 50. While at SBR 6the EI is 80 and at SBR 5 it is 100. This is based upon my tests using Pyrocat HD as the developer (1-1-100 dilution). Thus the film that I use can vary one stop in EI by altering development for SBR 2 variance. Tri X and Tmax 100 both exhibit similar characteristics.

Dear Don,

With all due respect, with your metering system, these figures are next to meaningless, as you are not keying your exposures to the actual shadows, but only to a theoretical minimum shadow detail (see my post to Tim). For neg films, ISO speeds are keyed to shadow density, and so are any meaningful EIs.

Cheers,

R.

David A. Goldfarb · Feb 10, 2007

I share Roger's skepticism about incident metering for field and landscape work, but I can also see why it works much of the time for those who use it.

This is, after all, very much the way many people work with portraits and still life in the studio. It works in the studio, because we can control the light and don't usually have objects of widely varying reflectance or light sources themselves in the scene. When there are objects of widely varying reflectance (e.g., bride and groom), experienced photographers know how to compensate for that by reducing the contrast ratio and possibly using softer light, and when there are light sources in the scene (e.g., candle flames, lamps, computer screens), anyone with common sense knows that a combination of incident readings doesn't provide enough information, and it's not a bad idea to make a few Polaroids just to be sure.

And in the field, how often do we really need--using the Zone System, BTZS, or development by inspection--to depart from our normal development times? Well, it depends on the kind of light you like, but I find that using the Zone System more than half of my landscape negs fall into the "N" pile, and I suspect that if I used incident metering and BTZS, most of my negs would fall into the same piles, and with some common sense I would know what kinds of scenes are likely not to be rendered accurately with incident metering, and just as in the studio, I'd use reflective readings for those scenes, and maybe even make a Polaroid to be sure.

When does the Zone System not work for me?--usually when I've failed to previsualize accurately, or in more concrete terms, when I've put Zone III in the wrong place and don't realize it until I'm trying to print. BTZS would eliminate the potential for that error in judgment and introduce the potential for other errors in judgment. So whatever system you use, I think the main thing is to recognize when you've got a difficult scene, and when you might have to exercise some judgment to be sure you're getting on film what you think you're getting, and not being blinded by the system itself.

BBarlow690 · Feb 10, 2007

Wow. So many posts.

I do what I describe in my Film Test Kit. It's based on an update of Fred Picker's system. It works with any format, any film, any paper. It calibrates equipment and materials to each other. It's simple, reliable, and repeatable. I never miss having dead-on exposure unless I'm sloppy. The calibration tests take about a half day, and much of that is waiting for negs to dry (I don't watch them dry, I go outside and watch the grass instead).

It seems like we're making it much harder, and much more confusing, than it ought to be.

Roger Hicks · Feb 10, 2007

BBarlow690 said:
It seems like we're making it much harder, and much more confusing, than it ought to be.

Hear! Hear!

In fact, I'd argue that even half a day ain't worth the effort unless you are going to do things properly and use a densitometer. Otherwise:

1 Shoot real pics, of a range of your favourite subjects, bracketing +/- 1 stop

2 Print the ones that print best. This gives you a good idea of what EI will work best for you. By all means repeat the experiment. Let's say you can't decide between ISO and ISO minus 1 (200 for an ISO 400 film). Fine: next time, shoot at ISO minus 1/2=EI 300 (or minus 2/3=EI 250 or minus 1/3=EI 320 if that's more convenient). On this roll, bracket +/- 1/2 or 2/3 stop. Or if ISO minus 1 works best for you, then shoot at that, but consider bracketing this roll at +/- 1/2 or 2/3 stop.

3 If the majority print on grade 2 or 3, your development is about right. If you need 1-2-3 or 0-1-2, you're overdeveloping. Knock off 10% until it comes out right. If you need 2-3-4 or 3-4-5, you're under-developing. Add on 20% until it comes out right.

Over half a dozen rolls of shooting real pictures, you'll zero in on the optimum dev time and EI without ANY testing with grey cards or the like. Then

4 For subjects with an unusually short tonal range, increase development by 50 per cent; for those with an unusually long tonal range, cut it 15 per cent. There's nothing sacred about 15/50: you can use 20/100 or 10/30 or anything else that you find suits you better. Again, it's a simple question of zeroing in.

The point is that the reason that many people make poor prints is not that they don't understand the Zone System: it's because they lack experience. An experienced photographer/printer will get better prints with or without the Zone System or formal testing than an inexperienced one will get with all the testing in the world.

There are those who will tell you that the Zone System or other testing methods will make it quicker and easier to learn. Maybe -- for them. But there are others who will find testing slow, tedious and ultimately of little or indeed negative value: it puts them off photography. People like this will do better taking real pictures.

One more piece of heresy. If you don't like the results with the film you're using, CHANGE IT. The belief that it's best to choose one film, whether on someone else's advice or at random, before you've tried a reasonable range of films, is bordering on the feeble-minded. Sure, as soon as you find one you like, stick with it. The same goes for developers. But don't choose too early. Personal preference is too important a factor. For example, at ISO 400 I shoot mainly HP5 Plus and my wife shoots mainly Tri-X (both developed together in Ilford DD-X for the same time). Both she and I prefer her shots on Tri-X and mine on HP5 Plus.

(When I say 'you' I mean, of course, 'everyone', not 'BBarlow690' -- this isn't aimed at you)

Cheers,

R.

Steve Smith · Feb 10, 2007

BBarlow690 said:
It seems like we're making it much harder, and much more confusing, than it ought to be.

And here too!

The reason I joined in on this thread is that I consistently need to print on grade 4 paper to get good contrast without the image looking muddy. In theory, I should be able to do this on grade 2 or 2.5

If you think of paper grading (multigrade or fixed) as a way of matching the response of the paper to the tonal range of the image on the film, then I am not getting enough contrast on the negative to start with.

As a quick experiment, I went out last Sunday with my Olympus XA loaded with HP5 and took a series of pictures. In each case I took one picture normally with the film speed set to 400 and I took a second identical picture with the XA's + 1.5 stop lever engaged so effectively EI 160 (or thereabout).

I processed the film and, obviously, the images with more exposure are darker. Looking closely, the light areas of the film (which are the shadows on the print) show more detail. Again, no surprises there. What I can't tell by looking at the negatives is how the dark areas of film (the highlights on the print) are going to turn out. I will try to print some in the next few days to see the differences but my feeling is that the images from the darker negatives will print fine on a lower grade of filtration than I normally use with no real loss of highlight detail.

This may seem like a lot of messing about but I just want to gain a bit more understanding in order to simplify things in the long term.

Steve.

jstraw · Feb 10, 2007

Donald Miller said:
Allen,
Here we go again. Let's look at it this way. If we were to test a film using Zone System methodology, we would assign an EI based on a negative density at a given exposure of .10 above FB + fog. Let's say that we find that the film exposes at an EI of 50 to give us this desired density, This EI is determined to represent a Zone I value in Zone System parlance.

Everything is fine until we then expose the film under actual use conditions. I find that Zone System practitioners will typically assign a Zone III or IV placement for their shadow values. This means that the EI of 50 is not a valid number based upon field use. How invalid is the EI when the shadow placement is at Zone III or IV? In the case of the film that we determined to have an EI of 50 the actual placement will be EI 12 1/2 at a Zone III placement or slightly above EI 6 for a Zone IV shadow placement. Now I don't know how you figure your math, but that is the way I figure mine...and yes I do understand the Zone System. Now I don't know any Zone System practitioners that pay much attention to a Zone V placement...in fact, I think that everyone that I ever encountered paid attention to shadow placement for the exposure...as I said before, they seem to universally place at either a III or IV for their shadows. That still is two or three stops more exposure than the film tests indicated. More exposure translates to a lower effective EI in my book.

Don, the flaw in your description is that you are equating a tested-for Zone I value with "shadows." There is a reason that one would place shadows on Zone III when the film speed test told you that a Zone I placement is required for maximum black..."shadows" are not necesserily, or even typically maximum black. Zone III is considered the lowest value for which *detail* will be apparent. The photographer placing his shadows on Zone III is knowingly, intenionally placing shadows two zones above max black.

jstraw · Feb 10, 2007

BBarlow690 said:
Wow. So many posts.

I do what I describe in my Film Test Kit. It's based on an update of Fred Picker's system. It works with any format, any film, any paper. It calibrates equipment and materials to each other. It's simple, reliable, and repeatable. I never miss having dead-on exposure unless I'm sloppy. The calibration tests take about a half day, and much of that is waiting for negs to dry (I don't watch them dry, I go outside and watch the grass instead).

It seems like we're making it much harder, and much more confusing, than it ought to be.

Where can I learn more about your kit?

Roger Hicks · Feb 10, 2007

Steve Smith said:
This may seem like a lot of messing about but I just want to gain a bit more understanding in order to simplify things in the long term.
Steve.

Dear Steve,

Always a good idea when you have the time and the money.

Repeat the experiment, giving your negs 20 per cent more development. That will bring you a LOT closer to grades 2 and 3.

There is a fashion for underdeveloping negatives, God knows why. As Mike Gristwood said when he was at Ilford, "We don't understand why people accuse us of deliberately giving out wrong developing times. Why would we do it? Spite? Or because we really want to stop people getting the best results from our materials?"

Of course dev times have to be adjusted to suit your camera, metering technique, developer, dev technique, enlarger and so forth. But the manufacturers' dev times are the best possible STARTING point -- certainly far better than the maunderings of those who would have you believe that you should always develop for 10-20 per cent less than all published times.

Cheers,

R.

Steve Smith · Feb 10, 2007

Roger Hicks said:
Repeat the experiment, giving your negs 20 per cent more development. That will bring you a LOT closer to grades 2 and 3.

I will try this. Up to now, I have always metered at the film's ISO and used Ilford's developing time for normal negatives taken in fairly bright conditions but added about 20 - 25% developing time for overcast conditions. This is based on some advice I read somewhere which seemed to make sense to me in as much as: if the tonal range of the scene is reduced and the black will always be in the same place, then the highlights will not be black enough on the film so some extra developing will give it some extra density.

i.e. If the film can record from 0% to 100% and the scene is only 0% to 80%, 0% will always be in the same place but the brightest part of the scene will only ever get to 80% (Does that make sense or does it confuse it more?!!).

Perhaps I'm thinking too much and I should get out and take more pictures instead!

Steve.

Roger Hicks · Feb 10, 2007

jstraw said:
Don, the flaw in your description is that you are equating a tested-for Zone I value with "shadows." There is a reason that one would place shadows on Zone III when the film speed test told you that a Zone I placement is required for maximum black..."shadows" are not necesserily, or even typically maximum black. Zone III is considered the lowest value for which *detail* will be apparent. The photographer placing his shadows on Zone III is knowingly, intenionally placing shadows two zones above max black.

Dear Mike,

Not only that: Zone I (using the classical 9-Zone system) is a residual category, which may or may not (but almost certainly won't be) a full stop below Zone II. You know this; others may not. As you correctly say, if you take a reading of the darkest shadows in which you want texture and detail (the textbook definition of Zone III in the 9-Zone system), this will give you that texture and detail.

I find that if I use the I.R.E. 1 index on a Pentax meter (2-2/3 stop down from a mid-tone) I can get texture and detail in the area read if I set the true ISO on the meter, though I generally prefer half a stop more than that in the interests of better tonality. This is true of both of the Pentax spot meters I own, one analogue, one digital. With my Gossen spot-meter, I normally use 2 stops down from the mid-tone.

To reinforce another point you made elsewhere -- at least, I think it was you who made it -- there's a certain amount if interpretation in all exposure determination anyway. A neg density of 0.03 is just about printable. How much more neg density you want after that, in order to get the tonality you want, is a matter of art, not science.

Cheers,

R.

MVNelson · Feb 10, 2007

My advice is, do as you proport that you will do, take your time and learn a way to get what you want out of your work. As far as BTZS vs ZS the concepts are not as mutually exclusive as their proponents would make them be. Unfornutately it is fairly easy to criticise on way of doing things vs another way on theory alone. One really has to learn and practice both ways before a practical accurate comparison can be made and that takes time and efford. In the BTZS exposure techniques include both the incident and spot metering methods. I use BTZs methods because it works for me. I have exposed film using the incident metering system in the worst contrasty scernarios like what you have decribed and because the materials (paper grade(es), film(ds),dev/sbr and efs/ei) are all taken in consideration during the exposure calulation the resultant negatives are well exposed but more important the printed image matches my previsualization. I use the spot metering method when it is practical to do so(can't get the light dome in the scene where the incident light is...out of my reach). This being said I don't believe in the "my way is better than your way" rhetoric and espacially when that ultimately causes the destruction of helpful comment and civility. Photography is an almost unlimited art form that is limited only by our imagination. Exposure methods are only tools used to make a go of trying to express our imagination. From what I have seen of your post you seem to be doing a good job! So.... Lastly , keep the frustration vs fun ratio leaned heavily towards the fun side of the equation .

Chuck_P · Feb 10, 2007

MattKing said:
I am not sure whether I understand this correctly.

I take from these discussions about BTZS that the exposure and development recommendation that results from use of the BTZS system does vary with the light hitting the subject, but does not vary with the reflectance of the subject.

If my understanding of the Zone System is correct, the exposure and development recommendation that results from use of the Zone system does vary with the light hitting the subject, but also varies with the reflectance of the subject.

Am I totally confused?:confused:

Matt

I am not familiar with BTZS so I will not speak to it.

In the ZS, your development of the film is strongly dependant upon your initial "placement" if the important low shadow value on the scale of zones i.e., at Zone I, II, III, IV, or even V. Keep in mind that high shadow placements can push your important highlight area clean off the scale, and it is not always necessary to do this; it only becomes necessary when you, the photographer, desire extra luminosity in your important shadow area. Then, you will have to resort to compensation development methods to hold those high value surfaces with the printable density range of the paper you are using.

This notion of always placing the important low value on III or IV or always IV as it has often been mentioned, IMO, short changes the versatility of the ZS. The low value placement is imortant because, it is that placement that absolutely determines where the important high value will "fall" at the upper end of the scale of zones. Anyone with "The Negative"can find examples of where low values were placed as low as Zone I or II. I have found and I do mean found (not just by blindly following AA's writings) that using the, quote "minimum exposure consistent with securing desired shadow detail" absolutely does afford me the best and most easily printable negative.

In the ZS, the light that is "incident" upon the reflective surfaces within the scene is not a deciding factor to anything; it is the light that is reflected from those surfaces that is imortant. Because, the intensity of the light falling on a surface determines how strongly it is reflected back to the film plane and therefore determines the range of luminances you see within your viewfinder. An incident meter is not the tool to use to get the most out of the ZS. A one degree spot meter will tell you, from the cameras position, that light from surface "A" is four times more intense, or two ev numbers higher, than light reflecting from surface "B". Therefore, for example, it will tell you that surface "A" that is falling on zone VII of the scale should print two zones higher than surface "B" that is falling on zone V of the scale.

None of this, IMO, can be predicted or visualized with uniformity if one is constantly changing ISO speeds due to changing conditions of light. These are thoughts that have come to mind as I progress in following this thread.

Chuck

Roger Hicks · Feb 10, 2007

Steve Smith said:
..i.e. If the film can record from 0% to 100% and the scene is only 0% to 80%, 0% will always be in the same place but the brightest part of the scene will only ever get to 80% (Does that make sense or does it confuse it more?!!).
.

Dear Steve,

It makes good sense but it's not as important as it might seem.

First of all, most films can record a far greater brightness range than can be represented linearly on paper: maybe 500% or more. That's with normal development.

But let's begin with the maximum brightness range of most papers, which is about 128:1 or 7 stops, a log density range of 2.1 (to convert stops to log density range, multiply by 0.3). A few are higher but it doesn't affect the argument.

Now consider a subject brightness range with that same 7 stops or 128:1 (log range 2.1).

Assume that the projected image at the film plane has a brightness range of 6 stops or 64:1 (log range 1.8) because of flare, i.e. the flare factor is 2. That's a realistic flare factor for many 35mm cameras.

(The best LF cameras can approach unity, i.e. no flare, while box cameras and toy cameras may have a flare factor of 4 or more. For these, the projected image will have a brightness range of 7 stops/128:1/log range 2.1 for the view camera or 5 stops/32:1/log 1.5 for the toy camera)

If you develop the film to a gamma of 1, then 1 stop of image brightness will correspond to 1 stop of negative density and the overall neg density range will be 1.8. If you develop it to a gamma of 0.5 then 1 stop of image brightness will correspond to 0.5 stop of negative density and the overall neg density range will be 1.8 x 0.5 = 0.9 (3 stops, 8:1).

Now let's work backwards from the paper. Typically, you might be looking at an ISO(R) for grade 2 of 90. This means that if the image projected onto it has a brightness range in excess of 3 stops (log 0.9, 8:1) it will expose the paper across its full range of tones, from the maximum black on the paper (density 0 on the neg) to pure paper-base white (anything above density 0.9 on the neg).

Remember to allow for enlarger flare (just like camera flare) and again assume a flare factor of 2. To get your 0.9 log density range (8:1 or 3 stops) on the baseboard, you need 1.2 (16:1 or 4 stops) neg density range.

Using the same figures as before, this means you need a gamma of 1.2/1.8 = 0.67 when developing the film.

In the course of all this, the brightness/density range has been expanded and contracted mercilessly: 128:1 (subject) > 64:1 (image) > 16:1 (neg density) > 8:1 (projected image in the enlarger) > 128:1 (developed image on paper)

Now, all of these numbers can and do vary. Subjects vary. Camera flare varies. Enlarger flare varies. And the ISO(R) of grade 2 paper varies, from maker to maker in the same developer. and for the same paper if you change developers. While all the numbers I have used are entirely credible, they are examples deliberately chosen to make the sums easier. Once again, does not affect the underlying argument.

You can attempt to control everything via film contrast, i.e. gamma, i.e. development time, or you can use both dev times and paper grades to effect your controls. Most printers do both, though a few choose to limit themselves to graded paper or even to a single grade of paper.

This has been a long and complicated post, and it's why I've written several of the books I have, plus working on the Photo School at www.rogerandfrances.com. If you want to understand what you're doing, you have to read a lot of books and (as you are doing) try things for yourself, your way. It's no use trying to parrot stuff, or to do half-hearted testing according to a modus operandi you don't find congenial.

As compared with this post, which may contain errors, my books have the advantage that the last few have been read at draft or proof stage by knowledgeable photographers, while of course the web-site has to withstand queries from everyone who reads it. If errors are pointed out to me, I change them. But there are plenty of people who point out 'errors' that are no more and no less than results of their own imperfect understanding or unclear thinking.

The length and complication of this post also explains why I generally recommend doing things the easy way, as in my four-step post earlier. In your case, I'd be inclined to check the blacking everywhere in the enlarger, especially the underside of the neg holder, the bellows and the back of the lens panel. I'd also look closely at the enlarger lens to make sure it's sparkling clean, and check my safelights; you should be getting enough contrast from your dev times, especially those in overcast weather.

Cheers,

R.

Allen Friday · Feb 10, 2007

Donald Miller said:
Allen,

Everything is fine until we then expose the film under actual use conditions. I find that Zone System practitioners will typically assign a Zone III or IV placement for their shadow values. This means that the EI of 50 is not a valid number based upon field use. How invalid is the EI when the shadow placement is at Zone III or IV? In the case of the film that we determined to have an EI of 50 the actual placement will be EI 12 1/2 at a Zone III placement or slightly above EI 6 for a Zone IV shadow placement. Now I don't know how you figure your math, but that is the way I figure mine...and yes I do understand the Zone System. Now I don't know any Zone System practitioners that pay much attention to a Zone V placement...in fact, I think that everyone that I ever encountered paid attention to shadow placement for the exposure...as I said before, they seem to universally place at either a III or IV for their shadows. That still is two or three stops more exposure than the film tests indicated. More exposure translates to a lower effective EI in my book.

Congratulations Donald,

You have now conclusively proven, once and for all, that when it comes to the zone system, you are totally incompetent. You do not understand it, and what is worse, your lack of understanding is so great that you cant even consider the possibility that you dont get it.

Donald, if I take a zone I reading and place it at zone I on my meter I will get exposure X. If I take a zone II reading and place it at zone II on my meter I will get exposure X. If I take a zone III reading and place it on zone III I will get exposure X. If I take a zone IV reading and place it on zone IV on my meter I will get exposure X. If I take a zone V reading and place it on zone V of my meter, I will get exposure X.If I take a zone IX reading and place it on zone IX, I will get an exposure X.

Basing exposure on any zone does not change the EI of the film. I am not doubling or giving 2 ½ stops change to the film speed like you said in your first post. The EI stays the same. The only time EI is changed is if + or - development is called for, and then the EI is adjusted to compensate.

From now on, whenever you jump in with your attacks on the zone system, I am going to refer readers to this thread. Anyone who has even a cursory knowledge of the ZS will be able to judge the weight to give your writings.

timbo10ca · Feb 10, 2007

MVNelson said:
My advice is, do as you proport that you will do, take your time and learn a way to get what you want out of your work. As far as BTZS vs ZS the concepts are not as mutually exclusive as their proponents would make them be. Unfornutately it is fairly easy to criticise on way of doing things vs another way on theory alone. One really has to learn and practice both ways before a practical accurate comparison can be made and that takes time and efford. In the BTZS exposure techniques include both the incident and spot metering methods. I use BTZs methods because it works for me. I have exposed film using the incident metering system in the worst contrasty scernarios like what you have decribed and because the materials (paper grade(es), film(ds),dev/sbr and efs/ei) are all taken in consideration during the exposure calulation the resultant negatives are well exposed but more important the printed image matches my previsualization. I use the spot metering method when it is practical to do so(can't get the light dome in the scene where the incident light is...out of my reach). This being said I don't believe in the "my way is better than your way" rhetoric and espacially when that ultimately causes the destruction of helpful comment and civility. Photography is an almost unlimited art form that is limited only by our imagination. Exposure methods are only tools used to make a go of trying to express our imagination. From what I have seen of your post you seem to be doing a good job! So.... Lastly , keep the frustration vs fun ratio leaned heavily towards the fun side of the equation .

This is exactly what I plan to do. Thanks.

Tim

Chuck_P · Feb 10, 2007

Allen Friday said:
Congratulations Donald,

Basing exposure on any zone does not change the EI of the film. I am not doubling or giving 2 ½ stops change to the film speed like you said in your first post. The EI stays the same. The only time EI is changed is if + or - development is called for, and then the EI is adjusted to compensate.

QUOTE]

I agree that EI does not change with a choice of exposure i.e., shutter vs. aperture for a given EV (if I followed correctly the reason for your very pointed response to Donald).

But, if we agree that a personal EI that we have successfully tested for (such as 64 for Plus-X 125 in my case) is based off of arriving at the speed that gives a .1 density above fb+f for a zone I exposure, then why would one change from that tested speed because n+1 or n-1 development is planned? Changing the speed due to + or - development would negate the whole testing for the personal EI, IMO.

I'll state, for purposes of making my point, the following: The "normal" development time is found (when following the ZS method) by taking the personal EI and then exposing for a zone VIII desnity of 1.25 to 1.35. The development time that returns that density is then your "normal" time. Once found, there is now something by which to systematically depart from to get expansion and contraction of the upper zones.

The "n+1" development time is found by making a zone VII exposure (at the personal EI) and then the developing time is increased until a zone VIII density is reached for that zone VII exposure. The "n-1" development time is found by making a zone IX exposure and then reducing development until a zone VIII density is reached for that zone IX exposure.

I would argue that changing the EI when + or - development is planned is incorrect if the ZS is being applied.

All in the interest and love of the "wet process".

Regards
Chuck

timbo10ca · Feb 10, 2007

Chuck1 said:
Allen Friday said:

Congratulations Donald,

Basing exposure on any zone does not change the EI of the film. I am not doubling or giving 2 ½ stops change to the film speed like you said in your first post. The EI stays the same. The only time EI is changed is if + or - development is called for, and then the EI is adjusted to compensate.

QUOTE]

I agree that EI does not change with a choice of exposure i.e., shutter vs. aperture for a given EV (if I followed correctly the reason for your very pointed response to Donald).

But, if we agree that a personal EI that we have successfully tested for (such as 64 for Plus-X 125 in my case) is based off of arriving at the speed that gives a .1 density above fb+f for a zone I exposure, then why would one change from that tested speed because n+1 or n-1 development is planned? Changing the speed due to + or - development would negate the whole testing for the personal EI, IMO.

I'll state, for purposes of making my point, the following: The "normal" development time is found (when following the ZS method) by taking the personal EI and then exposing for a zone VIII desnity of 1.25 to 1.35. The development time that returns that density is then your "normal" time. Once found, there is now something by which to systematically depart from to get expansion and contraction of the upper zones.

The "n+1" development time is found by making a zone VII exposure (at the personal EI) and then the developing time is increased until a zone VIII density is reached for that zone VII exposure. The "n-1" development time is found by making a zone IX exposure and then reducing development until a zone VIII density is reached for that zone IX exposure.

I would argue that changing the EI when + or - development is planned is incorrect if the ZS is being applied.

All in the interest and love of the "wet process".

Regards
Chuck

Click to expand...

This sums up my original confusion. But I think what is being termed as a different ISO when you are changing development is Ansel's adding a bit of exposure if you're reducing development because inherently the lows will lose out on a smidge of detail (my words- you can quote me on that if you like ).

timbo10ca · Feb 10, 2007

BBarlow690 said:
Wow. So many posts.

I do what I describe in my Film Test Kit. It's based on an update of Fred Picker's system. It works with any format, any film, any paper. It calibrates equipment and materials to each other. It's simple, reliable, and repeatable. I never miss having dead-on exposure unless I'm sloppy. The calibration tests take about a half day, and much of that is waiting for negs to dry (I don't watch them dry, I go outside and watch the grass instead).

It seems like we're making it much harder, and much more confusing, than it ought to be.

I'd also like to hear more about this kit.

Thanks,
Tim

oops- just found it- and ordered two!

jstraw · Feb 10, 2007

timbo10ca said:
I'd also like to hear more about this kit.

Thanks,
Tim

oops- just found it- and ordered two!

Where?

Film testing

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