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I haven't read that, I will go and see if I can find it
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Underexposure and spot-metering
- Thread starter Christophe
- Start date
I haven't read that, I will go and see if I can find it
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Good point, which I have been trying to work out. Apart from the fact that I have not been in a darkroom since 1989, the only ones I am aware of are some in Central London and one in Rickmansworth off the M25 (easier to get to but closed since the start of the pandemic). I live in Ealing and know that the College has one, but doubt that they will let me in as a non-student (and I am chained to my desk 10-11 hours a day during the week).
Hmmm, someone was selling a basic Paterson set for about £200 in London... convince wife we don't need spare bathroom... pandemic so no one visits... better use of room... OK, maybe that is a mid-term plan.
I was reading this link about using a Stouffer wedge sandwiched into a film holder, but it still requires a contact print. My monitor is calibrated, but doubt that will be enough. Will search through the forum threads.
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@Alan9940 I agree entirely. It's a heuristic and not applicable for all film/dev combos. For the films and dev I use most 1/2 box speed has been experimentally confirmed with a densitometer in my own darkroom, the exception being Efke 100.
There are all manner of variables here that cannot easily be accounted for among which include, water content, thermometer variability, meter calibration, shutter accuracy, and so forth, which easily explain the differences among us all. For example, I have shutter speed tested dozens of leaf shutters, and they vary widely and in rough proportion to how long its been since they've been CLAed. Even new, some of the best lenses in the world - Hasselblad - have a hard time hitting 1/500. The point is that ASA and developer are but two of a very long list of variables that can affect final negative outcomes.
Interestingly, in no densiometric tests I've done over the past 25 years has ever shown film to be faster than box speed. I would attribute such results to most likely be a miscalibrated meter or a dragging shutter.
The single most common negative problem I see, particularly among those new to monochrome film, is underexposure. I therefore suggest the "shoot a 1/2 box speed" rule as a starting point. They are more likely to get high content negatives and film has plenty of latitude if that ends up being somewhat of an exposure. One they've established a pattern for workable negatives, they they can tinker with ASA and development to "tune" their negs to personal taste ... all without a densitometer.
In any case, I find none of this thread argumentative, but a fine exchange of ideas among quite experienced monochrome experts.
Happy Snaps,
There are all manner of variables here that cannot easily be accounted for among which include, water content, thermometer variability, meter calibration, shutter accuracy, and so forth, which easily explain the differences among us all. For example, I have shutter speed tested dozens of leaf shutters, and they vary widely and in rough proportion to how long its been since they've been CLAed. Even new, some of the best lenses in the world - Hasselblad - have a hard time hitting 1/500. The point is that ASA and developer are but two of a very long list of variables that can affect final negative outcomes.
Interestingly, in no densiometric tests I've done over the past 25 years has ever shown film to be faster than box speed. I would attribute such results to most likely be a miscalibrated meter or a dragging shutter.
The single most common negative problem I see, particularly among those new to monochrome film, is underexposure. I therefore suggest the "shoot a 1/2 box speed" rule as a starting point. They are more likely to get high content negatives and film has plenty of latitude if that ends up being somewhat of an exposure. One they've established a pattern for workable negatives, they they can tinker with ASA and development to "tune" their negs to personal taste ... all without a densitometer.
In any case, I find none of this thread argumentative, but a fine exchange of ideas among quite experienced monochrome experts.
Happy Snaps,
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- Sep 22, 2017
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- 300
did you check the shutter times of your camera, and is f 2.8 the same at all lenses you have?
Well, I lately checked shutter opening times of some of my mechanical lenses and cameras and the weren't very accurate at all.
The only times which are correct are if I use longer exposure time above 2 seconds controlled by hand.
It is important to know your gear. Having the best of all light meters does not help if the rest of the chain does not work proper.
I wanted to check this and therefore bought a middle grey towel, which wasn't very easy, but finally a found one at IKEA.
I also bought a white and a black one.
Made a test set up at a place where I often make close ups.
Metered all three values with Seconic L 758 DR at box speed using spot metering.
Without all special technicals I was able to get all the fine details in all towels which I also could reproduce in the darkroom printing it on paper.
Without spot metering I would have failed for this special scene.
But what would happen if I had metered 1 stop to bright or dark?
I'm quite sure I could control this in the darkroom.
Last week I was out with my Chamonix 5x4 and made several photographs of different locations.
8 sheets of film, all metered in the same way.
Developed all with the same procedure.
One was totally over exposed. After brainstorming I came to the end that I have forgotten to close the f stop from 5,6 to 32 making the exposure.
But I could correct this in the darkroom using a much longer exposing time with the enlarger an I got a quite lovely print.
Less depth of field of course but a special kind of the scene.
Will say there are many ways to get the best negatives but post processing is minimum half the the way to get photographs.
In the end I think film has a big range, much more than I ever had thought, especially large format.
Unfortunately this does not work in all light conditions, bright sun and very deep shadows are needing over exposing and under developing.
Dark scenes like the shoot with the bridge probably need some extra contrast which you could get with over developing.
John Blakemore said it's all about Previsualization and understanding of the materials.
Which is not always easy, of course.
Well, I lately checked shutter opening times of some of my mechanical lenses and cameras and the weren't very accurate at all.
The only times which are correct are if I use longer exposure time above 2 seconds controlled by hand.
It is important to know your gear. Having the best of all light meters does not help if the rest of the chain does not work proper.
I wanted to check this and therefore bought a middle grey towel, which wasn't very easy, but finally a found one at IKEA.
I also bought a white and a black one.
Made a test set up at a place where I often make close ups.
Metered all three values with Seconic L 758 DR at box speed using spot metering.
Without all special technicals I was able to get all the fine details in all towels which I also could reproduce in the darkroom printing it on paper.
Without spot metering I would have failed for this special scene.
But what would happen if I had metered 1 stop to bright or dark?
I'm quite sure I could control this in the darkroom.
Last week I was out with my Chamonix 5x4 and made several photographs of different locations.
8 sheets of film, all metered in the same way.
Developed all with the same procedure.
One was totally over exposed. After brainstorming I came to the end that I have forgotten to close the f stop from 5,6 to 32 making the exposure.
But I could correct this in the darkroom using a much longer exposing time with the enlarger an I got a quite lovely print.
Less depth of field of course but a special kind of the scene.
Will say there are many ways to get the best negatives but post processing is minimum half the the way to get photographs.
In the end I think film has a big range, much more than I ever had thought, especially large format.
Unfortunately this does not work in all light conditions, bright sun and very deep shadows are needing over exposing and under developing.
Dark scenes like the shoot with the bridge probably need some extra contrast which you could get with over developing.
John Blakemore said it's all about Previsualization and understanding of the materials.
Which is not always easy, of course.
There's a link to the Goldfinger Craftbook PDF on this forum already. See latest Resource Files.
One of the things that intimidates beginners is erudite (and fascinating for initiates) discussions on FB+F and densitometers. Few people begin in LF with the ambition of constructing graphs. What they want is to make pictures.
To this end, half box speed and twenty percent less development is very good advice. I suggest that "ordinary" film and developer are good starting points too. Refinement must be secondary to picture making. What is needed for a beginner is some triumphs of creation to nourish the soul.
In particular, it's counter-productive to advise beginners that certain negative densities correspond to certain print values. They don't, except for a specific exposure time, in a specific enlarger, at a specific height, on a specific paper, developed in a specific developer for a specific time at a specific temperature. This is all very fine, but it isn't picture-making.
I would like to suggest that many US photographers may be little bit in thrall to Saint Ansel and tend to emulate his later, heroic style of printing – glittering highlights and infinite blacks. The US has a great deal of magnificent scenery that responds well to this approach.
Ansel's most famous image is under-exposed. Everybody knows that, but it might be worth comparing the negative with the final print. The sky is actually lighter than the foreground and is full of wispy clouds. That gigantic, black, black, black sky isn't FB+F = Zero at all. Should it be? Despite the very unsatisfactory negative densities he went ahead and printed, anyway.
We are not in the business of transcribing reality. That's for passports.
John Blakemore uses the phrase "flexible negative" and on his workshops, he demonstrates how the same negative may be expressed in many different ways, all of them valid and satisfying.
Oops! I seem to be ranting from several of my hobby-horses at the same time. Best to stop before I start foaming at the mouth, all over my innocent keyboard. My apologies to any bruised toes.
I would be delighted to be proved wrong.
Keep yourselves safe, everybody.
One of the things that intimidates beginners is erudite (and fascinating for initiates) discussions on FB+F and densitometers. Few people begin in LF with the ambition of constructing graphs. What they want is to make pictures.
To this end, half box speed and twenty percent less development is very good advice. I suggest that "ordinary" film and developer are good starting points too. Refinement must be secondary to picture making. What is needed for a beginner is some triumphs of creation to nourish the soul.
In particular, it's counter-productive to advise beginners that certain negative densities correspond to certain print values. They don't, except for a specific exposure time, in a specific enlarger, at a specific height, on a specific paper, developed in a specific developer for a specific time at a specific temperature. This is all very fine, but it isn't picture-making.
I would like to suggest that many US photographers may be little bit in thrall to Saint Ansel and tend to emulate his later, heroic style of printing – glittering highlights and infinite blacks. The US has a great deal of magnificent scenery that responds well to this approach.
Ansel's most famous image is under-exposed. Everybody knows that, but it might be worth comparing the negative with the final print. The sky is actually lighter than the foreground and is full of wispy clouds. That gigantic, black, black, black sky isn't FB+F = Zero at all. Should it be? Despite the very unsatisfactory negative densities he went ahead and printed, anyway.
We are not in the business of transcribing reality. That's for passports.
John Blakemore uses the phrase "flexible negative" and on his workshops, he demonstrates how the same negative may be expressed in many different ways, all of them valid and satisfying.
Oops! I seem to be ranting from several of my hobby-horses at the same time. Best to stop before I start foaming at the mouth, all over my innocent keyboard. My apologies to any bruised toes.
I would be delighted to be proved wrong.
Keep yourselves safe, everybody.
- Joined
- Aug 29, 2020
- Messages
- 1,064
@David M Having done a ton of denisometric testing, I couldn't agree more - hence my general suggestion of 1/2 box ASA and 20% less development as a starting point.
I also agree that trying to map negative density to print reflective values is mostly a fool's errand. Let us keep in mind that Ansel Adams et al did most of their seminal work when papers were only available in graded forms. They were trying to develop technique that would best match the negative to a fixed paper grade. Hence, the emphasis on figuring out how negative density mapped to print values.
But, these days, with VC paper, the ability to split print means that the "right" density will vary locally and vary further by the soft/hard light ratio for any given area of the print. Split VC printing is an incredibly powerful tool, but it cannot print what is not there - hence my emphasis on avoiding underexposure.
There is, however, a value doing some densitometer tests - it will quickly expose a wildly out of calibration meter, thermometer, or other process outlier. But this is a "one and done" kind of thing. Having done the tests for all the film/dev combos I cared about, my densitometer sits as a nice paperweight on the shelf these days.
But to me, at least, the real value of learning to test in the early going is to create consistency of practice. We all want to just make pictures, but so many people become discouraged because they cannot consistently get onto their negatives (and thus their prints) that which they see in their heads. Testing and developing consistent technique help resolve this. I look at my very early work and then the work after I discovered testing, Zone System etc., and there is a marked improvement in my negatives' printability. Technique cannot be a substitute for vision, but vision without technique will never be fully realized.
The one area where I'd respectfully disagree is that the US "magnificent scenery" is most appropriate for these techniques while less so elsewhere. I've lived in three countries and photographed in many more. The landscape of Switzerland is every bit the equal of Montana - just different. The light in the English and Welsh countryside is astonishing and requires great facility to capture well. The flat northern illumination of Alaska can be found again in Finland. My point is that technique, well understood, brings value in all such circumstances.
Anyone who seriously studies a musical instrument knows the importance of playing your scales. They enable you to actually play music expressively later on. Densitometry, exposure control, and darkroom consistency are the "scales" of the photographer. You can make pictures without them, but you will make more- and better pictures having done so.
Happy Snaps ...
I also agree that trying to map negative density to print reflective values is mostly a fool's errand. Let us keep in mind that Ansel Adams et al did most of their seminal work when papers were only available in graded forms. They were trying to develop technique that would best match the negative to a fixed paper grade. Hence, the emphasis on figuring out how negative density mapped to print values.
But, these days, with VC paper, the ability to split print means that the "right" density will vary locally and vary further by the soft/hard light ratio for any given area of the print. Split VC printing is an incredibly powerful tool, but it cannot print what is not there - hence my emphasis on avoiding underexposure.
There is, however, a value doing some densitometer tests - it will quickly expose a wildly out of calibration meter, thermometer, or other process outlier. But this is a "one and done" kind of thing. Having done the tests for all the film/dev combos I cared about, my densitometer sits as a nice paperweight on the shelf these days.
But to me, at least, the real value of learning to test in the early going is to create consistency of practice. We all want to just make pictures, but so many people become discouraged because they cannot consistently get onto their negatives (and thus their prints) that which they see in their heads. Testing and developing consistent technique help resolve this. I look at my very early work and then the work after I discovered testing, Zone System etc., and there is a marked improvement in my negatives' printability. Technique cannot be a substitute for vision, but vision without technique will never be fully realized.
The one area where I'd respectfully disagree is that the US "magnificent scenery" is most appropriate for these techniques while less so elsewhere. I've lived in three countries and photographed in many more. The landscape of Switzerland is every bit the equal of Montana - just different. The light in the English and Welsh countryside is astonishing and requires great facility to capture well. The flat northern illumination of Alaska can be found again in Finland. My point is that technique, well understood, brings value in all such circumstances.
Anyone who seriously studies a musical instrument knows the importance of playing your scales. They enable you to actually play music expressively later on. Densitometry, exposure control, and darkroom consistency are the "scales" of the photographer. You can make pictures without them, but you will make more- and better pictures having done so.
Happy Snaps ...
Can't disagree with any of that.
Testing is vital, but not quite as vital as making images.
We have a far bigger toolbox than Ansel and we should use every spanner in it. As well as VC paper, we now have scanning as a resource and digital printing as an undreamed of luxury. Some things are different. What I notice most is a scanner's ability to extract information from parts of a neg that seem almost clear to the naked eye. This is balanced by a scanner's refusal to extract anything at all from over-dense negs. It's changed my own practice and I now have flatter negs.
[A parallel result of digital printing is that we now have a very much wider range of paper surfaces to print on. It's a pity that removing the silver hasn't made it any cheaper.]
My "magnificent scenery" comment was offered as a speculation in the context of printing styles, rather than a comprehensive list of the World's finest spectacles. You are quite right. Other spectacular views are available. Other printing styles are available too. We all know about the New Topographics and their desire to embrace a more matter-of-fact rendering. Paul Hill made a decision to record the vernacular Derbyshire landscape in "quiet" prints, too.
Other subject matter is available – for instance, there's what a friend of mine calls Gas Station Photography, but that seems to be done mostly in colour. Some of it I like very much.
One of my own Printing Heroes is WHF Talbot. No ready-made boxes of paper for him. No boxes of anything, so his carpenter had to make those little mousetraps. Many of his images would be admirable today, even from someone who didn't have to go the the trouble and expense of inventing the whole process first.
Ian, thank you. Very generous.
I seem to have ambled a fair old way from that attractive but underexposed arch. More exposure and then plus-something development, perhaps? I think it's worth going back.
Testing is vital, but not quite as vital as making images.
We have a far bigger toolbox than Ansel and we should use every spanner in it. As well as VC paper, we now have scanning as a resource and digital printing as an undreamed of luxury. Some things are different. What I notice most is a scanner's ability to extract information from parts of a neg that seem almost clear to the naked eye. This is balanced by a scanner's refusal to extract anything at all from over-dense negs. It's changed my own practice and I now have flatter negs.
[A parallel result of digital printing is that we now have a very much wider range of paper surfaces to print on. It's a pity that removing the silver hasn't made it any cheaper.]
My "magnificent scenery" comment was offered as a speculation in the context of printing styles, rather than a comprehensive list of the World's finest spectacles. You are quite right. Other spectacular views are available. Other printing styles are available too. We all know about the New Topographics and their desire to embrace a more matter-of-fact rendering. Paul Hill made a decision to record the vernacular Derbyshire landscape in "quiet" prints, too.
Other subject matter is available – for instance, there's what a friend of mine calls Gas Station Photography, but that seems to be done mostly in colour. Some of it I like very much.
One of my own Printing Heroes is WHF Talbot. No ready-made boxes of paper for him. No boxes of anything, so his carpenter had to make those little mousetraps. Many of his images would be admirable today, even from someone who didn't have to go the the trouble and expense of inventing the whole process first.
Ian, thank you. Very generous.
I seem to have ambled a fair old way from that attractive but underexposed arch. More exposure and then plus-something development, perhaps? I think it's worth going back.
- Joined
- Aug 29, 2020
- Messages
- 1,064
For reasons likely having to do with me, I am unable to find the aforementioned Craftbook here in the Resources area. A pointer from a kind stranger would be appreciated.
@David M one thing that really pops out at me in this conversation is that digital scanning of silver materials requires rather different negatives than does traditional silver printing. I do nothing "serious" with digital whatsoever yet, preferring for now to be in the darkroom so long as these old bones will let me. When the day comes that I have to buy a film scanner, I rather suspect a significant body of calibration time will ensue shortly.
As to the image the OP posted, my sense is that it is both underexposed and possibly underdeveloped as well.
Happy Snaps
@David M one thing that really pops out at me in this conversation is that digital scanning of silver materials requires rather different negatives than does traditional silver printing. I do nothing "serious" with digital whatsoever yet, preferring for now to be in the darkroom so long as these old bones will let me. When the day comes that I have to buy a film scanner, I rather suspect a significant body of calibration time will ensue shortly.
As to the image the OP posted, my sense is that it is both underexposed and possibly underdeveloped as well.
Happy Snaps
I made the changeover very hesitantly.
Digital printing offers all sorts of possibilities. The great thing that I discovered is the freedom to experiment. I remember staying up all night in the Red Chamber (those were the days!) to get a print right. I could get through a whole box of 20x16.
Almost all of that time was spent standing on alternate feet, just lifting up the corner of a tray, trying to keep track of the World Service.
On screen, you see the changes straight away. It means you can experiment more freely. If you want, you can make copies of your image or of individual layers and create a different interpretation on each. You only need to print when you're happy.
It's also much easier to remove those intrusive twigs at the edges without Ferri, scalpels, tiny, tiny brushes or profanity. And you only have to spot once. Oh, joy of all joys!
Most image-processing software will do very much more than you will ever need. You don't need to learn it all.
Here's a parallel example. London taxi drivers have to know every single one of all the streets and back alleys in central London and how to get between them in the shortest time at any time of day. You only need to know how to get between your station, your office, the pub, and back to your station again. Some people might want to know how to get to John Lewis or M&S, too.
So much for the benefits, but on the other hand, digital work is very much harder on the bum.
Digital printing offers all sorts of possibilities. The great thing that I discovered is the freedom to experiment. I remember staying up all night in the Red Chamber (those were the days!) to get a print right. I could get through a whole box of 20x16.
Almost all of that time was spent standing on alternate feet, just lifting up the corner of a tray, trying to keep track of the World Service.
On screen, you see the changes straight away. It means you can experiment more freely. If you want, you can make copies of your image or of individual layers and create a different interpretation on each. You only need to print when you're happy.
It's also much easier to remove those intrusive twigs at the edges without Ferri, scalpels, tiny, tiny brushes or profanity. And you only have to spot once. Oh, joy of all joys!
Most image-processing software will do very much more than you will ever need. You don't need to learn it all.
Here's a parallel example. London taxi drivers have to know every single one of all the streets and back alleys in central London and how to get between them in the shortest time at any time of day. You only need to know how to get between your station, your office, the pub, and back to your station again. Some people might want to know how to get to John Lewis or M&S, too.
So much for the benefits, but on the other hand, digital work is very much harder on the bum.
Thronobulax, try:
www.5x4.co.uk
You will see that some idiot can't spell PDF..
Goldfinger Craftbook
Here is a URL that will lead to a downloadable PDG of the book. https://www.digitaltruth.com/files/Goldfinger.pdf Or here: https://drive.google.com/file/d/0B6G6yz9RRO3ITUk4U0JrRXNvZlE/view I've attached a review too.
www.5x4.co.uk
You will see that some idiot can't spell PDF..
- Joined
- Nov 29, 2020
- Messages
- 14
I am still cautious with the number of variables I have to balance, but thanks to each and all your extremely helpful insights and advice, I am starting to put them into some sort of order. It has been a long time since I have had such under-exposed images, but as I am new to spot metering, I managed to get myself quite confused as to what I had done wrong (definitely operator error).
I do tend to overthink things such as this - which can be paralysing at times - but I will crack on (well, shuffle forward). The upside is that this exposing error has helped me to start to grasp, with a tangible reference point, certain aspects of the Zone System and how and why one might develop a negative with N+1 etc (not that it would have saved this negative). So I was slowing things down, dipping my toe into LF, but even that was too fast, I need to go slower and back to basics, but this can only be a good thing. It would be nice to make an image for it to come out the way I imagine it (although it does not mean it will be a good one of course...!).
I was fortunate to stumble across John Blakemore's Workshop book in a charity shop just after the first lockdown (as well as a hardcover, very large coffee table book of Michael Kenna's 'France' which is beautifully printed and a book on Eugene Atget, £40 for all three) and have been re-reading the Workshop with renewed attention.
I downloaded a shutter speed app, and it seems that my speeds are all over the shop, getting progressively worse the faster the shutter speed. Interestingly, both a TLR and the LF are most accurate at 1/30 and 1/25 respectively. Another variable!
I do tend to overthink things such as this - which can be paralysing at times - but I will crack on (well, shuffle forward). The upside is that this exposing error has helped me to start to grasp, with a tangible reference point, certain aspects of the Zone System and how and why one might develop a negative with N+1 etc (not that it would have saved this negative). So I was slowing things down, dipping my toe into LF, but even that was too fast, I need to go slower and back to basics, but this can only be a good thing. It would be nice to make an image for it to come out the way I imagine it (although it does not mean it will be a good one of course...!).
I was fortunate to stumble across John Blakemore's Workshop book in a charity shop just after the first lockdown (as well as a hardcover, very large coffee table book of Michael Kenna's 'France' which is beautifully printed and a book on Eugene Atget, £40 for all three) and have been re-reading the Workshop with renewed attention.
I downloaded a shutter speed app, and it seems that my speeds are all over the shop, getting progressively worse the faster the shutter speed. Interestingly, both a TLR and the LF are most accurate at 1/30 and 1/25 respectively. Another variable!
Keeping accurate notes of each of your exposures can go a long way to explain why images don't turn out the way you expected them to.
When tracking down errors in exposures, the one thing to remember is to change one and only one variable at a time.
Mike
When tracking down errors in exposures, the one thing to remember is to change one and only one variable at a time.
Mike
A
Anthony
Guest
I apologize if someone already mentioned this. The meter probably isn't linear. Most meters aren't. They give readings that are too high in dim light - a dark interior; and readings that are too low in very bright light - sun on white objects.
Anyway I suspect it's the meter. Do this: take a roll of film, and expose different toned surfaces in various brightnesses to Zone III, ja? For example, a dark object in dim light, and a dark object in bright light; mid-toned objects in bright and dim light; and a moderately light toned object (fleshtone or something akin to that) in bright and dim light. Develop the film and make a proof for minimum time for maximum black through the film edge. All the tones should match at Zone III. If not, the meter isn't linear. (Try to do this test in natural light, unless you use artificial light quite a bit. If so, make 2 tests.)
If all the tones don't match, it's not a big deal. Most meters behave this way. So now that you know, you can out-think the machine next time. You can do it easily - there are only so many brightnesses in the world.
Carry on.
Aside. That's why the old SEI was a great instrument, remarkable for its time. (Invented and manufactured by the genius Brits of course.) You zero a light source - a bulb within the meter, then compare that value to a subject value - when it matched, you read the exposure indications on the meter scales. It also had a c/ft2 scale - very handy for quick calculations.*
The SEI didn't read the actual subject. It read a light within the meter itelf that was calibrated - zeroed - each time you used it. Variables were eliminated. That internal brightness was compared to the actual subject brightness. When it matched, you had the proper luminance value, yeah? So the SEI could read a blinding bright cloud next to the sun at high altitude, or your Jack Russell terrier's rabbit hole. It was perfectly linear throughout the entire range. The range was enormous, I think 1 to 1,000,000. Ingenius. I wouldn't think of metering those extremes with any other meter; today I'd guess.
(This one doesn't work. SEIs used a selenium cell which eventually died, as did the welded in place incandescent bulb. Current technology make an efficient, cheaper SEI possible. C'mon you genius Brits, make a new one . . .)
I'm revealing my age - many years ago a pretty well known guy informed me about the SEI. (No it wasn't at RIT. Those clowns barely knew which end of a light meter to point at the subject.)
*You can also calculate quickly with an EV scale interpolated to c/ft2 - not difficult. I can post the method if someone is interested. I just don't want to be a Hero is all . . .
Anyway I suspect it's the meter. Do this: take a roll of film, and expose different toned surfaces in various brightnesses to Zone III, ja? For example, a dark object in dim light, and a dark object in bright light; mid-toned objects in bright and dim light; and a moderately light toned object (fleshtone or something akin to that) in bright and dim light. Develop the film and make a proof for minimum time for maximum black through the film edge. All the tones should match at Zone III. If not, the meter isn't linear. (Try to do this test in natural light, unless you use artificial light quite a bit. If so, make 2 tests.)
If all the tones don't match, it's not a big deal. Most meters behave this way. So now that you know, you can out-think the machine next time. You can do it easily - there are only so many brightnesses in the world.
Carry on.
Aside. That's why the old SEI was a great instrument, remarkable for its time. (Invented and manufactured by the genius Brits of course.) You zero a light source - a bulb within the meter, then compare that value to a subject value - when it matched, you read the exposure indications on the meter scales. It also had a c/ft2 scale - very handy for quick calculations.*
The SEI didn't read the actual subject. It read a light within the meter itelf that was calibrated - zeroed - each time you used it. Variables were eliminated. That internal brightness was compared to the actual subject brightness. When it matched, you had the proper luminance value, yeah? So the SEI could read a blinding bright cloud next to the sun at high altitude, or your Jack Russell terrier's rabbit hole. It was perfectly linear throughout the entire range. The range was enormous, I think 1 to 1,000,000. Ingenius. I wouldn't think of metering those extremes with any other meter; today I'd guess.
(This one doesn't work. SEIs used a selenium cell which eventually died, as did the welded in place incandescent bulb. Current technology make an efficient, cheaper SEI possible. C'mon you genius Brits, make a new one . . .)
I'm revealing my age - many years ago a pretty well known guy informed me about the SEI. (No it wasn't at RIT. Those clowns barely knew which end of a light meter to point at the subject.)
*You can also calculate quickly with an EV scale interpolated to c/ft2 - not difficult. I can post the method if someone is interested. I just don't want to be a Hero is all . . .
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Neither is the human ear. Have a look at the Fletcher-Munson curves to see how our hearing frequency response varies with volume.
Apparently, we're all nonlinear from tip to tail
A
Anthony
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Americans seem chronically non-linear . . .
Fortunate that we're next to Canada.
Fortunate that we're next to Canada.
I've bought and returned two SEI meters trying to find one that worked; neither would calibrate properly based on the top meter. Not surprising, I guess, given the age of these meters. I always wanted one of these because our 1 degree spot meters aren't...well...that precise. Try to meter a small(ish) sunlit part of a white cloud. At those distances, the 1 degree really covers too much area and doesn't provide an accurate measurement (I've blown out these areas on occasion because of this.) The SEI nicely zeroes in on small areas like that providing accurate readings; wouldn't think the difference between 1/2 degree and 1 degree would be that big a deal! However, I found trying to hold the patch steady on a small portion of cloud quite difficult. Is it the magnification of the viewing system? Kind of like trying to handhold a telescope on a single star in the sky!
However, I found trying to hold the patch steady on a small portion of cloud quite difficult. Is it the magnification of the viewing system? Kind of like trying to handhold a telescope on a single star in the sky! Easy! Just mount he SEI meter on a sturdy tripod, preferably with a geared head. That should make photography much easier.
With modern digital technology, it should be possible to devise a "tuneable" meter. In essence, the software would offer a histogram so you could adjust the output reading for each intensity of light and each wavelength. It might need a 3D histogram. Image stabilisation is a now very common technology so naturally it would be included to solve the half-degree problem.
Will anybody take up the challenge? I doubt it, but some mute inglorious App-writer might be reading this.
Half a degree is equivalent to a very long lens indeed. Here's a table of focal lengths vs angle of view. It stops at 800mm FL, – 2.6° on a 35mm camera.
With modern digital technology, it should be possible to devise a "tuneable" meter. In essence, the software would offer a histogram so you could adjust the output reading for each intensity of light and each wavelength. It might need a 3D histogram. Image stabilisation is a now very common technology so naturally it would be included to solve the half-degree problem.
Will anybody take up the challenge? I doubt it, but some mute inglorious App-writer might be reading this.
Half a degree is equivalent to a very long lens indeed. Here's a table of focal lengths vs angle of view. It stops at 800mm FL, – 2.6° on a 35mm camera.