Understanding Exposure

[cyclohexane]

# If the image is underexposed details are quite sketchy and only the light/bright areas of the image are clearly seen.
# If the image is overexposed only the dark/shadowed areas are detailed.

Yes, but with negative film one can print highlight detail up to 3-4 stops overexposed, and the entire image will be visible.

* the more light, the smaller the opening needs to be (more light= higher f/stops) and the less light, the larger the f/stop (no light= small f/stops).

Actually, it's "more light = smaller f-stops". f/16 is a smaller number than f/11. Remember, these are fractions, focal length over a number.

[expensive_hobby]

Originally Posted by cyclohexane

Actually, it's "more light = smaller f-stops". f/16 is a smaller number than f/11. Remember, these are fractions, focal length over a number.

Oops... yes that would be a typo wouldn't it!

[kgphoto]

EH,

I have clipped only those areas that I am commenting on. Ready, Aim . . . lol

I think you have most of it down, but some of your wording is a little awkward and may lead some astray. As an example; "only's" are very hard to use. Underexposed may show "some" shadow detail, or still not show "some" highlight detail depending on how much under they are as well as how hot are some of the high lights.

RE: "Similar to the iris of the eye, the aperture allows in light. Think of it like this: the more light, the smaller the opening needs to be (more light= higher f/stops) and the less light, the larger the f/stop (no light= small f/stops). "

Here's the most problematic language. More light doesn't equal higher f:stops, but more light means you need the higher numbered f:stops, since they let in less light.

So it may be more clear to say, that the larger openings use the smaller numbers and the Larger the opening, the more light is let in for any given shutter speed.

I think your comments on shutter speed and meters is right on, with only the following clarification. Incident light meters measure the light falling on the subject and are held at the subject and pointed at each light source to measure relative ratios, but for an overall exposure are point at the camera from the subject position. When metering the surroundings, they are held at the surrounding, i.e. the background, and pointed at the camera. If you are talking about an accent i.e. rim light, you point it at the light source whether that is the sky from open shade or a studio strobe or flash.

As to your section on metering, you need to meter more than the highest and darkest and average. You need multiple points so you can predict how they will reproduce and then you can decide where to slide the range where it will do the most good, or how much light to add or remove to make the best image.

Finally each COMBINATION of f:stop and shutter speed count at one, unless you are only talking about flash then shutter speed contributes little. This is too complicated a relationship to be reduced to one sentence.

I hope that clears things up. Feel free to improve my descriptions as well. I see cyclohexane caught some of this too.

Originally Posted by expensive_hobby

Okay ladies and gentlemen... here's my summed up version of exposure. Please feel free to jump in to correct anything I've gone astray on

Exposure-- Hobby's Quick Summary
Exposure is definitely a multi-facted aspect of photography. It seems to be THE MOST multi-facted thing by far. (If not, just shoot me now!)

Film:

• If the image is underexposed details are quite sketchy and only the light/bright areas of the image are clearly seen.
• If the image is overexposed only the dark/shadowed areas are detailed.
• 
  

Aperture:

• Similar to the iris of the eye, the aperture allows in light. Think of it like this: the more light, the smaller the opening needs to be (more light= higher f/stops) and the less light, the larger the f/stop (no light= small f/stops).

Meters:

• Incident meters will read the light "falling" onto the subject; therefore, they should be pointed from the subject to the camera. They read an area ~180 degrees.

Metering for correct exposure:

• A reading from the lightest and darkest areas of the scene is needed.

*Each f/stop or shutter speed count as "one".

[cyclohexane]

Here's the most problematic language. more light doesn't equal higher f:stops, but More light means you need the higher numbered f:stops since they let in Less light.

So it may be more clear to say, that the larger openings use the smaller numbers and the Larger the opening, the more light is let in for any given shutter speed.

But they are not higher-numbered f-stops. f/16 is a smaller number than f/11, and f/11 is a smaller number than f/8, and so on. Larger openings use larger numbers.

Granted, some use "f8", "f11", and "f16", but in a mathematical sense they aren't the correct expressions for the diameter of the aperture.

[expensive_hobby]

Originally Posted by kgphoto

EH,

I have clipped only those areas that I am commenting on. Ready, Aim . . . lol

I think you have most of it down, but some of your wording is a little awkward and may lead some astray.

I absolutely agree! You're very correct... "only" should not have been used. Good catch!

Originally Posted by kgphoto

RE: "Similar to the iris of the eye, the aperture allows in light. Think of it like this: the more light, the smaller the opening needs to be (more light= higher f/stops) and the less light, the larger the f/stop (no light= small f/stops). "

Here's the most problematic language. More light doesn't equal higher f:stops, but more light means you need the higher numbered f:stops, since they let in less light.

So it may be more clear to say, that the larger openings use the smaller numbers and the Larger the opening, the more light is let in for any given shutter speed.

Again, you're absolutely right about my wording. Instead of equal signs I probably shouldn't found an alternative joining thing-- like maybe my favorite series of dots.

Originally Posted by kgphoto

Incident light meters measure the light falling on the subject and are held at the subject and pointed at each light source to measure relative ratios, but for an overall exposure are point at the camera from the subject position. When metering the surroundings, they are held at the surrounding, i.e. the background, and pointed at the camera. If you are talking about an accent i.e. rim light, you point it at the light source whether that is the sky from open shade or a studio strobe or flash.

I don't have meters, so thank you for clarifying this.

Originally Posted by kgphoto

As to your section on metering, you need to meter more than the highest and darkest and average. You need multiple points so you can predict how they will reproduce and then you can decide where to slide the range where it will do the most good, or how much light to add or remove to make the best image.

Interesting. I'll give that a try because I certainly wasn't doing that; at the very most I was doing three- light and dark, with an ocassional middle depending on the actual scene, but worried the third was overkill.

Originally Posted by kgphoto

Finally each COMBINATION of f:stop and shutter speed count at one, unless you are only talking about flash then shutter speed contributes little. This is too complicated a relationship to be reduced to one sentence.

Yes, I see where adding that one word better represents what I typed! Another good catch!

Originally Posted by kgphoto

I hope that clears things up. Feel free to improve my descriptions as well. I see cyclohexane caught some of this too.

I think you did a fantastic job!

[kgphoto]

Originally Posted by cyclohexane

But they are not higher-numbered f-stops. f/16 is a smaller number than f/11, and f/11 is a smaller number than f/8, and so on. Larger openings use larger numbers.

Granted, some use "f8", "f11", and "f16", but in a mathematical sense they aren't the correct expressions for the diameter of the aperture.

While you may be technically correct, you are arguing semantics now. "16" is not a smaller number than "11" even if the mathematic area it represents, is. The numbers are what are printed on the lens, so by convention that is what is commonly used. Anything else is just more confusing. Practicality must serve some purpose.

I liken it to most people don't have to know what goes on in a high combustion engine to be able to stick a key in a hole and make their car go. Let's use the KISS principle.

[cyclohexane]

Sorry, it may be semantics, but I feel that these semantics lead to misunderstandings. Why think "large aperture = small number" when you can think "large aperture = large number"? That is what you get when you leave the slash in place; I would think that is using KISS.

I guess we'll agree to disagree. What's up next? =)

[Rense]

What's up next? =)

how about the statement: "large aperture is less depth of field" ?

[jfrancho]

Let's use the KISS principle.

Now that's irony.

[kgphoto]

Originally Posted by jfrancho

Now that's irony.

Now see that's where you and I totally disagree.

I think of it like driving a stick shift car. Since you are always shifting(metering a few important points and then setting th exposure that captures them best) all the time, it becomes second nature.

If you are used to driving in "auto", then when you have to shift to 1 or 2 for a hill, you will have to think more about it and them may forget to put it back in drive. fod forbid you should accidentally shift into reverse while rolling forward.

Of course for much of your driving an auto transmission is fine and is particularly for freeway stop and go traffic(happy party snaps with auto flash). But if you want to be a pro driver on the circuit, you will have to get that formula 5D and use manual.

[jfrancho]

Now see that's where you and I totally disagree.

The only point where we diverge here is in our sense of humor. I never said anything about using auto. And yes, I have driven a formula ford which BTW has no sissy synchros.

[expensive_hobby]

Can we touch base on the Zone System real quick again? I know there's mixed feelings regarding it's use in the digital world, but I think there is some relevance to at least understanding it's concept.

I've been looking at it for a few days now. In the book I have it specifically refers to the different levels as roman numerals. Zone 0 (equivalant to N+5?) is black and Zone X (equivalant to N-5?)is white. Zone V (equivalant to N?)is middle gray- the one gray cards are made from.

Before I go further, am I correct when I conclude Zone V is what my in-camera meter "averages" a scene? Aaargghh... I'm not verbalizing this right. Is that what the exposure my camera's meter, meters for? Goodness is anyone following me on this question? (Maybe it's time for bed. lol)

[cyclohexane]

Before I go further, am I correct when I conclude Zone V is what my in-camera meter "averages" a scene?

I believe you are correct for partial (9%) and center-weighted average meter modes.

I haven't found an answer for what the meter is looking for in evaluative; the Canon white paper on the XT didn't turn up anything conclusive. Hopefully someone with more knowledge can chime in as to whether Canon's evaluative metering factors in color information or not.

[heartseye]

Virtually ALL camera meters seek to average the brightness range they "see" and then yield an exposure eqivalent to an 18% grey.
But that, really, is where any applicable resemblance to the Adams Zone System ENDS.

[KellyL]

I want to explain the shooting situation from my earlier post. This wedding was a very odd wedding situation. I was the "grooms" photographer...the bride had her own. It's a long story. ( See http://www.photocamel.com/forum/wedd...tml#post222604 .)Anyway, since I was the "second" photographer, I was not in charge of the posing, or where shots were being made. The "paid" photographer was in charge and calling the shots. (The groom made a deal with me...since he did not like the photos of the paid photographer and preferred mine, he asked if I would trade him wedding photos for a new patio, since he is in construction. I came out better, since the paid photographer was getting a whopping $400.00 on the deal.) Anyway, when the couple arrived at the VFW for their reception, the paid photographer began posing. I grabbed my camera...and suddenly realized that I was in the worst shooting conditions I could imagine. This did not stop the other gal who was shooting, but I was in a panic. Realizing that the dynamic range was outside my scope of expertise, I fired three shots...in a panic...knowing that I needed to get my camera set to auto...it was the only thing that was going to save me. Had I been in complete control of the situation, I would not have even attempted these shots in the blazing sun.

Regardless, I did get my camera set to auto and captured a few remaining shots. I learned some valuable lessons that day. So here is my example....

Auto, point, shoot...in full sun.

I was in control of the situation for the second shot taken at the church.

[Dean Johnson]

That second shot is wonderful Kelly!...it's a tad dark but that's easy to fix.

[expensive_hobby]

Originally Posted by cyclohexane

I believe you are correct for partial (9%) and center-weighted average meter modes.

I haven't found an answer for what the meter is looking for in evaluative; the Canon white paper on the XT didn't turn up anything conclusive. Hopefully someone with more knowledge can chime in as to whether Canon's evaluative metering factors in color information or not.

I never thought of googling it, but you inspired me to! Here's what I have found from Canon's site- Canon Technology:

Canon developed a 21-zone metering sensor to accommodate 45-point area AF. Using a newly developed algorithm, this metering system performs high-speed calculations of output from 21 zone sensors and AF information, and adjusts exposure instantly.
This configuration enables the camera to make compensations appropriate to shooting conditions and maintain exposure stability. The system also incorporates an average metering element that factors in periphery conditions, providing accurate exposure even when the composition changes slightly, or when the subject covers multiple metering points.

I'm thinking a couple of things here. Primarily even though there's a picture with the text, and I know it's using the AF points, I still don't know how it's deriving the settings as it takes in the "scene".

So evaluative metering is probably best for snapshots? And by using the partial and center-weighted metering, because the camera is aiming it's settings for middle gray I should have an easier time concluding how the exposure is effecting the image?

Edited: That description was for slr cameras, not digital. I'm assuming it's semi-safe to say it's almost parallel to how the digital cameras work.

[expensive_hobby]

Kelly that second shot is much nicer. The skin tones looks right, the groom has his hat off so you see "him", and the details missing from the first are in the second (primarily flowers but others areas too).

[expensive_hobby]

Originally Posted by heartseye

Virtually ALL camera meters seek to average the brightness range they "see" and then yield an exposure eqivalent to an 18% grey.
But that, really, is where any applicable resemblance to the Adams Zone System ENDS.

Heartseye logically I have no choice but to agree with you, and especially given there is no darkroom processing of the majority of my images.

Therotically however, I think there's some merit in the digital world regardless of how an individual weighs this Zone System-- be it heavily or lightly.

I could be horribly wrong, but if nothing else it provides *me* with a better visual/mental expectation of what changing the settings will produce.

[KellyL]

Thanks Dean. For the second shot I was using dragging the shutter in order to include as much ambient light as I could. The first shot I posted to help folks understand why I started this thread to begin with. Even in Auto, the camera is going to blow out highlights under some circumstances.

Pensive: Wow! You are asking great questions and showing great understanding.