Jimmy T Loc: Virginia

Ouch, that made my head hurt!!!

Jimmy T Loc: Virginia

jerryc41 Loc: Catskill Mts of NY

Since you're talking about a triangle, you'll get lots of answers. I like to keep the ISO as low as possible. A darker scene will need a slower shutter, but you don't want blur, so open up the lens. As you say, there are three variables, so take your choice. Shooting on Auto would be a good start.

lamiaceae Loc: San Luis Obispo County, CA

EXPERIENCE! (And in my case reading a lot in the film days materials by Kodak and many Ansel Adams books.)

jcboy3

First, some words on the Sunny 16 rule. It says that for daylight, use an aperture of f/16 and shutter speed of 1/ISO (e.g. 1/100 sec for ISO 100). For other lighting conditions, you want to use other apertures. These are the conditions (from James Martin, Digital Photography Outdoors):

f/22 Snowy/Sandy (Dark shadows with sharp edges)
f/16 Clear & Sunny (Distinct shadows)
f/11 Slightly overcast (Soft shadows around edges)
f/8 Overcast (Barely visible shadows)
f/5.6 Heavy overcast (No shadows)
f/4 Open shade/Sunset (No shadows)

You can get a vinyl sticker (oval or rectangular) from Cafe Express; see http://www.cafepress.com/+sunny-16-rule+stickers

I have relied upon this rule in the past, when shooting film with a mechanical shutter camera, when my battery for my meter died. These days, it is still useful for checking your exposure compensation setting if shooting strongly backlit scenes.

The rule doesn't actually specify what shutter speed, aperture, and ISO to use, just that their relationship is fixed. More on picking these settings later.

Second, how to set exposure for dusk (or dawn). The best approach is to meter the sky for your exposure. If your scene includes city lights, then at some point the exposure will balance with the city lights and your shot will pop. I use the following exposure guidelines:

5 min before sunrise / after sunset, f/8 for 8 seconds (ISO 100)
10 min before sunrise / after sunset, f/8 for 15 seconds (ISO 100)
15 min before sunrise / after sunset, f/8 for 30 seconds (ISO 100)

City light balance is usually a couple of minutes around the 15 minute mark. This varies with conditions, so take a few shots each way.

Finally, we get to the exposure settings. These are shutter speed, aperture, ISO, and exposure compensation. Here's what they're for:

Shutter speed is used to control motion blur, subject or camera. The rule for hand holding is to use a minimum shutter speed that is 1/focal length in full frame (so 1/50 sec for 50mm FF, 1/75 sec for 50mm APS-C, 1/100 sec for 50mm micro four thirds). Basically, apply the crop factor to the lens focal length to get equivalent focal length and use it for the ratio. Image stabilization in the lens or camera can allow even slower shutter speeds. If the subject is moving, then you need faster shutter speeds regardless of whether you have image stabilization.

Walkers, 1/125
Runners, 1/500
Fliers, 1/2000

If panning, then use the minimum shutter speed for hand holding.

Aperture is used to control depth of field (DOF), which is how far in front and behind the point of focus should appear to be in focus for a normal print. This is also subject to adjustment for sensor size, using the crop factor. Aperture is a ratio, so smaller numbers mean larger apertures, which have shallower depth of field. But larger apertures also let in more light, so they can be used to compensate for faster shutter speeds. In fact, aperture and shutter speed can be thought of similarly; f/1.8 lets in more light than f/16, just as 1/50 sec lets in more light than 1/2000 sec.

Typical aperture settings for full frame:

Portrait with shallow depth of field, f/2.8 or larger (e.g. f/1.8)

Standard portrait, f/4-f/8

Landscape, f/11-f/22

Beyond f/16, an effect called diffraction begins to cause the image focus to soften, so such tiny apertures are generally not recommended.

Aperture is also adjusted for crop factor, so f/4 on full frame is f/5.6 on APS-C and f/8 on micro four thirds.

ISO is used to brighten the image when read from the sensor. High ISO settings produce noise in the image; how much depends on the camera sensor type and size. You want to know what ISO settings are good, acceptable, and crappy for your particular camera. Unless you need to increase ISO, it is usually best to use the base ISO of your camera (which will be 50, 100, or 200).

Finally, exposure compensation is used to adjust the exposure above or below what your meter says is a good exposure. This is done to compensate for scenes with high contrast, lights, shadows. Increase exposure compensation if you are trying to expose for the shadows, decrease exposure compensation if trying to expose for the highlights. With digital, try to not overexpose the highlights if they are part of your subject.

For example, shooting runners in the shadow of a building during bright daylight. ISO should be set to base value. Shutter speed should be high (1/500) unless panning for motion. Aperture should be moderate, because shallow DOF helps separate the subject from the background, but if the aperture is too large then your subject might move out of the in focus region between focus and exposure. Using continuous auto focus or pre-focus can help. Because the subject is in shadow, one to two stops exposure compensation are added.

If the result will be overexposed, then increasing shutter speed will have minimum effect. Using smaller apertures (larger f/number) will produce deeper DOF and reduce subject separation from the background.

If the result will be underexposed, then using using larger apertures will produce shallower DOF and risk the subject being out of focus. Using slower shutter speeds will risk motion blur from the subjects motion. Increasing ISO will have minimum effect until the ISO reaches unacceptable noise levels for your camera.

Adjusting Sunny 16 settings. The Sunny 16 rule says f/16, 1/100sec, ISO 100. But if I want a shallow DOF, then I may want f/4, which is 4 stops faster than f/16 (f/5.6, f/8, f/11, f/16). So the shutter speed and/or ISO must adjusted by 4 stops. Each stop is a doubling, so shutter speed should be 1/1600.

The exposure settings are a trade between motion blur, depth of focus, and noise. If your exposure is within the desired range of these settings, then you are good to go. If not, then you need to decide which of these features is more important for the shot. This process comes from experience; to get that experience you need to shoot a lot and assess your photos to see how they are affected by these settings.

NoSocks Loc: quonochontaug, rhode island

I don't know how, I just know. And the beauty of digital is that when I'm wrong, I can adjust and reshoot right away. Good chimping technique.

Bill_de Loc: US

That is probably the best answer the OP will get. To the point!

--

Psergel Loc: New Mexico

I'd start by knowing the slowest shutter speed you can safely hand hold with each particular lens. Then it's a choice between DOF and ISO noise. (assuming we're talking about a still subject)

burkphoto Loc: High Point, NC

Each scale — shutter speed, aperture, and ISO — works the same way. ISO is sensitivity. It controls how much light you need to make the exposure. If you double shutter *speed* (cut time in half), you must open the aperture by one stop. If you close the aperture by one stop, you must double the exposure *time.*

ISO 100 at 1/100 at f/16 is the same as ISO 200, 1/200, f/16, or ISO 100, 1/200, f/11, or ISO 100, 1/400, at f/8...

The point is to adjust shutter time and aperture to put the same "bucket of photons" on the sensor for a given ISO. ISO determines the "size of the required bucket." Enlarge that bucket with a higher ISO, and you can use a faster shutter speed (shorter time) or a smaller aperture, or some blend of the two. Improve the scene illumination, and you can do the same thing.

ISO WHOLE stops are 6, 12, 25, 50, 100, 200, 400, 800, 1600, 3200, 6400... The intermediate 1/3 stop intervals between each of those are 8, 10, 32, 40, 64, 80, 125, 160, 250, 320, 1000, 1250, 2000, 2400, 4000, 4800... (Not all cameras have an option to set intermediate thirds for ISO).

Shutter speed times in WHOLE stops are typically 8 sec, 4 sec, 2 sec, 1 sec, 1/2, 1/4, 1/8, 1/15, 1/30, 1/60, 1/125, 1/250, 1/500, 1/1000, 1/2000, 1/4000, and 1/8000. Some cameras extend either or both ends of this range. Most digital cameras can use the 1/3 stop intervals in between these, too. (...1/20, 1/25, 1/40, 1/50, 1/80, 1/100, 1/160, 1/200, 1/320, 1/400, 1/640, 1/800, etc.)

SOME digital cameras have menu settings to let you elect whole stop, 1/2 stop, or 1/3 stop intervals for one or more of these scales. I ALWAYS use 1/3 stop intervals, because I use BOTH JPEG and raw capture. You most certainly need 1/3 stop resolution if you are processing JPEGs in the camera.

You learn early on that there is a FIXED sensitivity constant for every ISO that determines correct exposure. You learn that meters are stupid — they are calibrated to read a scene that reflects 12% – 18% of the light falling on the subject, that if you meter white you get gray, and that if you meter black, you get gray. So you learn to use gray cards and/or incident meters, or the Zone System, or all three, depending upon the situation.

You also learn that increasing ISO increases noise, decreases color saturation and color depth, and for a given camera, you won't want to use higher than a particular ISO, even though it will let you.

You learn that fast shutter speeds stop action, and slow shutter speeds blur action. You learn that lens selection (magnification) affects how quick a speed you must use to avoid camera shake, and when you need a tripod, and when image stabilization works...

You learn that small apertures provide greater depth of field, but can also lead to diffraction LIMITING of sharpness. You learn not to confuse sharpness and focus. You learn that longer lenses have less apparent depth of field at a given aperture. You learn to control depth of field for OPTIMUM sharpness, and for creative effects of all sorts.

Much of this, you may read about online or in books, in more detail. However, to internalize it takes a lot of practice! There is no substitute for making those 10,000 images and learning from each of them what works for you and what does not.

IreneAC Loc: San Diego

This was very helpful, thanks, I learned a lot!
Bookmarked for future reference …

camerapapi Loc: Miami, Fl.

I can only give you my humble opinion based on what I do from experience. I guess we all struggled at one time or another in the beginning.
In the first place, I like to shoot with a tripod during the dusk hours. I try to go with the lower ISO that allows me to shoot under the conditions I encounter, usually 200-400 ISO.
As it gets progressively darker I know that at my favorite ISO settings the exposures will be longer but as I said, I shoot with a tripod, RAW file, noise reduction off and usually 1 stop underexposure with frequent use of the histogram just to make sure I am nailing the right exposure. At these long exposures moving subjects will be blurred which could or could not work for the shot.
How do I arrive at those conclusions? Experience.

Marionsho Loc: Kansas

You're right, no need to buy a book. Understanding Exposure is aval. at the library. If not they can get it.

RichardSM Loc: Back in Texas

I've not heard of a 13% gray card or do you mean 18% gray card.

jcboy3

18% gray cards are used for printing, 13% gray cards are used for white balance/exposure

burkphoto Loc: High Point, NC

If you use an 18% gray card, you get about a 1/3 stop underexposure. That is just about perfect for JPEG submission to most people labs, which DO NOT want customers to risk any chance of burning out highlights in white fabrics (threads should be visible). (They want to avoid the "blame the lab" phone calls to customer service.) A 1/3 stop tweak applied during print image rendering is not noticeable, especially given the lab software in common use (It converts 8-bit JPEGs to a higher bit depth for image adjustment, then renders them back to 8 bits for printing.)

Either card will work to the same end, given exposure compensation to taste.

My preference when using slide film and JPEG capture (or JPEG plus raw) has always been to use the 18% gray card with no exposure compensation. With slide film, I got better color saturation and avoided highlight burnout. With JPEGs, I avoid highlight burnout.

For raw capture only, I use the same card. I usually "overexpose" by 2/3 to 1+ 1/3 stop, depending on scene brightness and contrast range, then recover highlights in post-production. It's a bit of EBTR (exposing "beyond the right side of the histogram") based on experience with my camera in different situations.