Underexposure with incident metering

[Spanik]

Does your meter give you more consistent results?

Can't tell before thursday when they are develloped.

 

[Sparrow]

Dear Stewart,

Highlight 1: How and when is a direct reading of shadows, using the shadow index, going to fail to give adequate shadow detail?

Highlight 2: You know, I've never bothered to write down my meter readings. Why would I? In any case, pointing an Invercone at a clear sunny sky seems an eccentric way to take a reading: it doesn't match any advice I've ever seen on using incident light meters. My incident-light readings are influenced by the time of day; the latitude; whether the subject is front-lit or back-lit; and whether I'm using an Invercone (a particularly brilliant design), an incident light dome, or a flat receptor.

If your idea of an incident light reading is pointing an Invercone at a clear sunny sky, then indeed you must indeed need to do a great deal of fudging/interpreting of the readings.

Cheers,

R.

... 'adequate shadow detail' I could be facetious and ask if there is a formula for finding that, but leaving that aside ... no I don't keep records either, but I do have a little sticker on my meter at Sunny f16 as I sometimes take a reading off the sky to get an idea as to how bright the day is, sort of a Sunny f5.6 for use in Manchester. (As you will know the human eye is extraordinary as a comparator of tone but near to useless at assessing quantum) I do understand I'm subverting its proper usage in doing that 🙂

 

[Roger Hicks]

... 'adequate shadow detail' I could be facetious and ask if there is a formula for finding that, but leaving that aside ... no I don't keep records either, but I do have a little sticker on my meter at Sunny f16 as I sometimes take a reading off the sky to get an idea as to how bright the day is, sort of a Sunny f5.6 for use in Manchester. (As you will know the human eye is extraordinary as a comparator of tone but near to useless at assessing quantum) I do understand I'm subverting its proper usage in doing that 🙂

Dear Stewart,

Highlight: Yes. Being able to see it, i.e. not having blank film in the darkest areas where you want texture and detail. The ISO standard merely formalizes the point at which exposure starts to be useful.

Sorry, you've lost me with "I sometimes take a reading off the sky to get an idea as to how bright the day is, sort of a Sunny f5.6 for use in Manchester."

Cheers,

R.

 

[kanzlr]

I find the solution quite simple. Use your brain to determine exposure considering the reading from your light meter to be no more than one of the factors you take into consideration. You also take subject luminance and other factors such as what you want the photo to convey into consideration. It is actually quite simple. People easily determined the best exposure many years ago before light meters were commonplace.

Remember, no meter will tell you the best exposure no matter how you use it. It will only measure the light intensity.

that, basically.

the meter tells you how "much" light there is, not how your subject will be exposed.

 

[shortstop]

Close, but step 2 is backwards. If you're using the mid-tone meter index, close down 2-3 stops or you'll get hopeless over-exposure. Spot metering of the shadows (Zone 2) is the only way to guarantee texture in Zone 2 without fudging, guesswork or willful over-exposure, but most decent spot meters have a "shadow" index. Use this instead of the mid-tone index (substantially useless on a spot meter) and then, as you say, for Step 3, use the highlight index. If you can get close enough, you can also do this with a non-spot meter: see http://www.rogerandfrances.com/subscription/over-under-indices.html To be honest, it's all pretty flexible and you can get away with a lot, but at least if you do it in the way I describe you'll be closer to theoretical and practical standards and will need to rely far less on flexibility aka sloppiness. Cheers, R.

I have a Profisix with Spot attachment.
Tell me if this is correct. I point the cell toward a part of the scene that I want to be in zone II. Read the LV; then close three stops and take the photo.
If the scene has a high contrast, measure the highlights and underdevelop N-1 or N-2 (if I'm using a single sheet).

 

[Sparrow]

Dear Stewart,

Highlight: Yes. Being able to see it, i.e. not having blank film in the darkest areas where you want texture and detail. The ISO standard merely formalizes the point at which exposure starts to be useful.

Sorry, you've lost me with "I sometimes take a reading off the sky to get an idea as to how bright the day is, sort of a Sunny f5.6 for use in Manchester."

Cheers,

R.

... examples:

Full midday sunlight ... I wanted to see the chap in the bar so I would have opened up 2 or 3 stops from sunny f16 (negative film obviously)

... similar conditions in overcast north of England may have a sky that reads f5.6 so to get the same detail in the shadow I would still need to open up 2 to 3 stops from that.

It's a simple way of finding the ambient lighting value

 

[Roger Hicks]

I have a Profisix with Spot attachment.
Tell me if this is correct. I point the cell toward a part of the scene that I want to be in zone II. Read the LV; then close three stops and take the photo.
If the scene has a high contrast, measure the highlights and underdevelop N-1 or N-2 (if I'm using a single sheet).

That'll do it! I can't remember if the Profisix spot is true spot (1 degree) or larger (there are Gossen attachments for 7.5/15 degrees as well). Obviously you need to go closer with the wider-angle ones, or pick larger areas of tone.

You may find that 3 stops is too much, in which case try 2-1/2 or even 2.

Cheers,

R.

 

[Roger Hicks]

... similar conditions in overcast north of England may have a sky that reads f5.6 so to get the same detail in the shadow I would still need to open up 2 to 3 stops from that.

It's a simple way of finding the ambient lighting value

Dear Stewart,

Ah, I see... Thanks. Though (a) the shadows probably aren't as deep and harsh so probably 2 stops would work as well as 3 and (b) a spot meter reading of the shadows would tell someone without your experience what exposure they needed to give without a 2-3 stop fudge factor.

There is absolutely nothing wrong with your metering technique. But then, any metering technique can be made to work, with enough experience. Most of the time, if I bother to use more than one kind of metering, beginning with the one requiring the biggest fudge factor first (i.e. incident, for negatives), I get exactly the same readings; or within 1/3 stop. But spot reading shadows doesn't require fudging...

Cheers,

R.

 

[shortstop]

That'll do it! I can't remember if the Profisix spot is true spot (1 degree) or larger (there are Gossen attachments for 7.5/15 degrees as well). Obviously you need to go closer with the wider-angle ones, or pick larger areas of tone. You may find that 3 stops is too much, in which case try 2-1/2 or even 2. Cheers, R.

Thanks,
It has a 1-5-10 degrees spot attachment.
Ehere can I buy your books? I've seen on amazon.co.uk your book on perfect exposure.

 

[Gumby]

Dear Ed,

(1) No, I mean precision. Of exposure. The meter reading (which is often accurate) is in many cases only tangentially linked to the precision you require in your exposure.

(2) Try The Focal Encyclopedia of Photography, fully revised ed. 1965, vol 2, p 558, several years before I started writing about photography. There are numerous other references but this one, I think, suggests that the term was by then widely accepted.

Cheers,

R.

Ahh... you were talking about precision of exposure but I mis-read that as you talking about precision of the statement being made. I should have known that you would not make such a basic grammar error. 🙂

Thanks for the reference. I like learning new things.

 

[Sparrow]

Dear Stewart,

Ah, I see... Thanks. Though (a) the shadows probably aren't as deep and harsh so probably 2 stops would work as well as 3 and (b) a spot meter reading of the shadows would tell someone without your experience what exposure they needed to give without a 2-3 stop fudge factor.

There is absolutely nothing wrong with your metering technique. But then, any metering technique can be made to work, with enough experience. Most of the time, if I bother to use more than one kind of metering, beginning with the one requiring the biggest fudge factor first (i.e. incident, for negatives), I get exactly the same readings; or within 1/3 stop. But spot reading shadows doesn't require fudging...

Cheers,

R.

Sorry Roger I'm not making myself clear this is just one of my methods, it's good for snapshots and consistent lighting ... one doesn't need to stand about in 30 degree heat messing about with a spot meter and fretting about K values, one just takes photos

I choose an appropriate method for each case, whereas you seem to be advocating taking the same hammer to every nut here .... and anyway even with a spot meter there are shadows that are dark enough to blow the rest of the photographs' highlights which would require a reasoned compromise (or fudge as you would have it) from the photographer

 

[David Hughes]

Hi,

Nice to see you two back together...

Ever since the opening post I've been wondering why incident light readings for landscapes but no one else has said a thing.

Regards, David

 

[Roger Hicks]

Sorry Roger I'm not making myself clear this is just one of my methods, it's good for snapshots and consistent lighting ... one doesn't need to stand about in 30 degree heat messing about with a spot meter and fretting about K values, one just takes photos

I choose an appropriate method for each case, whereas you seem to be advocating taking the same hammer to every nut here .... and anyway even with a spot meter there are shadows that are dark enough to blow the rest of the photographs' highlights which would require a reasoned compromise (or fudge as you would have it) from the photographer

Dear Stewart,

Hardly. That's your interpretation of what I said, not what I actually said. All I'm saying is that the only way to be sure of adequate shadow detail is competent spot metering. Well, that or deliberate overexposure. I rarely use spot metering except in tricky situations with very large brightness ranges.

Essentially, either use a spot meter properly, or (with a spot meter or anything else) fudge it. As I've said, ANY means of exposure determination can be successful with enough experience/fudge. I quite often guess.

Cheers,

R.

 

[Juan Valdenebro]

Hi Roger,
Metering the shadows, the light reflected by them, to place them in the lowest textured grays, is good for nothing, really, but to get, just what was metered, in that place... But it doesn't guarantee at all that the whole scene is being correctly exposed. That's what I meant when I said spot metering the light reflected by a gray card can be a better way of metering than incident or in camera common metering: again, the scene, as I said in a previous post, is well recorded because medium grays are placed in the middle of the film's latitude, and then there's enough film latitude in both ways -on film- to cover darker and lighter surfaces, and then it's development what we use to decide the final contrast on film, and what becomes white or close to white...
As the OP wrote, incident light readings can give underexposure... I heven't seen them give overexposure, though... I don't know what's your experience in using slide film... I know you have used it, but how deeply and with what precission and for what kind of job? I ask it because I had to curse, before working with it, two years of my career using slide film only, and incident light metering, ant the same when I specialized one year in architecture photography and another year in product photography, both with large format on slide film, and we set all we have to set and meter all we have to meter, and then the usual thing is clicking just once, not even twice. And then to the lab. For example, if you have enough experience, you must know that if you meter with an incident meter the light falling on a white building on direct sun, and if you do the same scene with the same meter on a cloudy day, there will be one of those slides showing gross underexposure...
But, if you do both spot metering a grey card, both slides will be fine.
Maybe you knew that, or maybe you can ask someone about it, or maybe you can try it...
I know how to meter the three common ways (in camera average-reflected light, incident, and spot-reflected light) and how to compensate for different situations depending on light and the system used, but in my opinion spot metering is the most precise and reliable way to do it... It's also the opinion of many photographers doing serious work and worrying about exposure and zone system a lot more than I do.
About being all three systems the same, you have the right to your opinion.
Cheers,
Juan

 

[Roger Hicks]

Hi Roger,
Metering the shadows, the light reflected by them, to place them in the lowest textured grays, is good for nothing, really, but to get, just what was metered, in that place... But it doesn't guarantee at all that the whole scene is being correctly exposed. That's what I meant when I said spot metering the light reflected by a gray card can be a better way of metering than incident or in camera common metering: again, the scene, as I said in a previous post, is well recorded because medium grays are placed in the middle of the film's latitude, and then there's enough film latitude in both ways -on film- to cover darker and lighter surfaces, and then it's development what we use to decide the final contrast on film, and what becomes white or close to white...
As the OP wrote, incident light readings can give underexposure... I heven't seen them give overexposure, though... I don't know what's your experience in using slide film... I know you have used it, but how deeply and with what precission and for what kind of job? I ask it because I had to curse, before working with it, two years of my career using slide film only, and incident light metering, ant the same when I specialized one year in architecture photography and another year in product photography, both with large format on slide film, and we set all we have to set and meter all we have to meter, and then the usual thing is clicking just once, not even twice. And then to the lab. For example, if you have enough experience, you must know that if you meter with an incident meter the light falling on a white building on direct sun, and if you do the same scene with the same meter on a cloudy day, there will be one of those slides showing gross underexposure...
But, if you do both spot metering a grey card, both slides will be fine.
Maybe you knew that, or maybe you can ask someone about it, or maybe you can try it...
I know how to meter the three common ways (in camera average-reflected light, incident, and spot-reflected light) and how to compensate for different situations depending on light and the system used, but in my opinion spot metering is the most precise and reliable way to do it... It's also the opinion of many photographers doing serious work and worrying about exposure and zone system a lot more than I do.
About being all three systems the same, you have the right to your opinion.
Cheers,
Juan

Dear Juan,

Highlight 1: No. That's the point. You never know how much darker the shadows will be. One stop? Five stops? If it's five, well, bad luck.

Highlight 2: Studio advertising; travel; products; food; step by step; all professionally. Across maybe 30 years. In other words, enough to have a fair idea of what I am talking about.

Highlight 3: It's not an opinion. It's a statement of fact. You have yet to explain the difference between reading the light falling on one defined surface (a grey card) and another (a translucent "artificial highlight"). Please do not confuse facts and opinions.

Incident readings -- including your willfully complicated version with grey cards -- work fine for slides. But not for negatives.

Reflect, perhaps, that someone who has written a well-regarded book on exposure theory and practice has probably studied the subject quite deeply and carefully. More deeply and carefully, on present evidence, than you have.

Cheers,

R.

 

[Ranchu]

The problem Roger, is that you're applying BW film methods to color film. Development is fixed with color so the shadows aren't as important as the midtones and the highlights. Why meter for them?

 

[Rob-F]

Using the meter as Rob F reports, (and as I previously mentioned) - you are using a foot-powered spot meter to take the shadow readings.

Foot-powered spot meter! Ha, that's a good one! It's not really a spot reading, though. It's still an incident reading, because it's still reading the light falling on the subject, not reflected from it. Of course, you could argue that it's an incident reading taken "on the spot." 😛

 

[Richard G]

The problem Roger, is that you're applying BW film methods to color film. Development is fixed with color so the shadows aren't as important as the midtones and the highlights. Why meter for them?

Because colour negative film can take a whole lot of overexposure, so exposing for shadow detail works brilliantly, still allowing retention of detail in the highlights.


Fuji Superior 400(?): Exposed with an M6 reflective reading from the back of a very dark cafe late on an overcast afternoon.


Le Petit Croix by Richard GM2, on Flickr

 

[Rob-F]

2 Metering a piece of white paper and giving 2-1/2 stops less exposure (because the white card reflects 2-1/2 stops more than the grey card)

Cheers,

R.

OOps! The meter will respond to the white paper as if it were an 18% gray card, thus giving a reading 2 and 1/2 stops more stopped down than it should be. Thus we must open up 2 and 1/2 stops, not stop down that much!

OK, with that said, I want to say I have never really been able to mathematically show that 18% is a true midpoint. My reasoning goes, one stop brighter than 18% would be 36%. So two stops would be 72%. We can only get to 100%, so there's no room for another doubling. But intuitively, the jump from 72% to 100% seems like another half-stop or so. OK, that accounts for our belief that there's 2 and 1/2 stops from 18% gray to full white. And that seems fine. Now let's go in the other direction: one stop darker, 9%. Two stops darker, 4 and 1/2%. Three stops darker, 2 and 1/4%. Four stops darker, 1 and 1/8%.

Question: How far should this sequence be carried on? We are already four stops below our chosen 18% midpoint, whereas there are only 2 and 1/2 stops the other way. What kind of a midpoint is that? I don't know; I am raising a question here, I don't know why 18% is a magic middle tone.

One other thing (Roger): (Psychologist here) "Psychophysics" refers to a method of quantifying the response of the nervous system to various stimuli. For instance, if there are 100 candles lit, how many candles must we blow out before an observer can notice the change in light level? A: one. The Just Noticeable Difference (JND) for illumination level is one part in 100. Or: the ear's response to sound levels is logarithmic. Three deciBels equates to a perceived doubling or halving of sound intensity. And the JND is one deciBel. Another example: ever notice how the eye doctor finds your prescription? She starts with a power weaker than you need, and ascends through the correct one, noticing when you say, "no, the last one was better." Then she starts higher than your true prescription, and descends, until you say, "no, the one before this one." That's called the 'Method of Ascending and Descending Series," developed by experimental psychologists. That's another application of psychophysics. It's not about "what looks right!" It's about quantifying subjective inner experience.

 

[Rob-F]

Why would we not designate 1% and 99% as the end-points of the gray scale? Then if we designate 12 and 1/2% as the mid-point, now we have three stops to full white, and three stops the other way to 1 and 1/2% (which is pretty close to our arbitrary 1%). Then the midpoint will be an equal number of stops between white and black. Why wouldn't that make more sense?