3June2010

Manual Exposure

Posted by afkenner under: Photo.

I posted a basic explanation and tutorial today on using manual exposure for photography.

Definitions:
Light: Illumination of the scene you want to photograph.
Exposure: the amount of light captured by the camera’s sensor (or film).
Settings: things YOU can control on the camera.
Sensor: the device inside the camera that is sensitive to light and captures the image.

Task:
To produce a desired image given the available light, use the camera’s settings to control the exposure.

For now, we’ll assume you are NOT going to modify the light. Eventually you will want to learn to do this in a variety of ways (flash, reflectors, diffusers, etc.) but you should be comfortable with basic exposure control before adding light modifiers to the equation.

Settings:
You control exposure with THREE settings: ISO, Aperture and Shutter Speed. A change in ANY one of these will change the exposure, but they each play a different role and have different consequences beyond a change in the exposure. Manual exposure means setting each of these yourself instead of letting the camera choose a setting for you (no AUTO mode at all). A basic description of what each setting does:

ISO controls the sensor’s sensitivity to light. A large dial on top of the camera is marked with numbers from 80 (least sensitive to light) to 3200 (most sensitive to light).

Aperture (also called f-stop) controls how big the opening in the lens will be when the picture is taken. A bigger opening lets in more light than a smaller opening. To make things confusing, a smaller number ( 2.8 ) is the largest opening (more light gets in) and a larger number (8.0) is the smallest opening (less light gets in).

Shutter Speed controls the amount of time that light will be hitting the sensor. For most shooting, this is expressed in a fraction of a second, like 1/30 or 1/500. A thirtieth of a second is a longer amount of time than a five-hundredth of a second, so more light gets in at 1/30 than at 1/500.

How to USE the settings to control exposure:
NOTE: This is a GENERAL set of instructions. Creativity and artistic control will often break these rules on purpose to achieve a desired effect.

Go to a place with consistent, medium lighting. Outdoors in shade or inside in a well-lit location. Set everything on your camera manually as follows:

ISO: 200
Shutter Speed: 1/60 second
Aperture: f/4.5

Take a picture and look at the results.
• Too dark? There are THREE ways to lighten the image: higher ISO (400), slower shutter speed (1/50 sec.) or larger aperture (f/4.0)
• Too bright? There are three ways to darken the image: lower ISO (100), faster shutter speed (1/80 sec.), smaller aperture (f/5.0)

Change JUST ONE setting and take another picture. You should see a SLIGHT improvement in the exposure (lighter or darker). Keep changing the setting until you get a good image. NOW go back to the ORIGINAL settings, and try changing a different setting to get a correct exposure.

This method will yield properly exposed pictures, but so will any of the AUTO modes on the camera. Learning WHICH setting to change in a particular situation is where the mechanics end and the artistry begins. These are the reasons why you WANT to use manual exposure instead of letting the camera decide for you.

Earlier, I mentioned that there are different consequences to changing each element of the “exposure triangle.” Here are some consequences that are unrelated to the exposure but have an impact on the images you will capture:

Shutter Speed: Slower shutter speeds mean more sensitivity to camera shake and/or subject movement. It’s difficult to get a sharp picture at speeds below 1/30 second if your camera is handheld or if the subject is moving at all. Faster shutter speeds eliminate handheld camera shake, and very fast shutter speeds can freeze subject motion, even very fast motion.

Aperture: Changing the aperture also changes depth of field (DOF), which is a measure of how much of the scene from close up to far away is in sharp focus. A narrow aperture will result in greater DOF (more of the scene is in focus) and a wide aperture will lessen the DOF (only a small range of distance is in focus). This effect is more pronounced when the lens is zoomed toward the telephoto end of the range and less pronounced when at wide angle. Cameras like the G11 do not have a lot of aperture range, and their small sensors tend to increase the DOF in all shots, so this is less of an issue (and less creative opportunity) than it would be with a DSLR and a lens with a greater aperture range. Also, most lenses have a sharpness zone – a range of apertures where they perform best. This varies by lens, but you can assume that most lenses lose a little quality at the edges of the aperture range.

ISO: As you increase sensitivity to light, you also increase “noise” in the image. Noise is a term that refers to unwanted color elements in the image introduced by the image capture process. Noise looks like bits of color and is obvious when looking at the picture at 100% size on your computer screen, but a lot of noise can be visible at much smaller sizes and will detract from the appearance of your image. Therefore, ISO should be set as low as possible (80) for the least noise and cleanest image results. In many shooting situations (like indoors in normal room lighting) you need to set the ISO higher (400 or more) to get an acceptable image, but you will start to notice noise at ISO 400 and it will become really obvious at higher settings.

Conclusion:
If you have read this far, bravo and thank you. This is a long post with a lot of information. For other (better? clearer?) explanations, you can find all of this in other places online by searching for “exposure triangle” or any of the terms above.

As others have responded, there is no substitute for experience. Set your camera to “M” and start shooting. You will have some frustration in the beginning but soon you will find that the mechanics are happening automatically and you are making creative and artistic choices with your manual settings.

Share your results on POTN or another photography forum for lots of useful and helpful feedback.

Enjoy and happy shooting!

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24January2008

The Amazing Race

Posted by afkenner under: Travel.

SkiDubaiDinner in Apres at the Mall of the Emirates, sitting next to a wall of glass overlooking the bunny slopes of Ski Dubai. The race began after dinner, trying to organize a dozen people in a mall just a little smaller than Colorado. Once we got to the parking lot and packed all our bags into the back of the Jeep, Jonathan tossed out the bomb: why do we need to wait for everybody to finish dinner? We don’t need to caravan, we can get there on our own with a manual transmission, a hand-drawn map with barely legible landmark names and a handheld GPS unit. Maybe, just maybe, he might be right. Even if he was wrong, he was surely setting up the first real adventure of the trip – could we navigate the crippling Dubai traffic, the UAE’s deliberately obscure and misleading road signage and an uncertain set of directions to a point 125 miles away on the other side of the Arabian Peninsula? It had to be worth a try.

Now it was too late, we weren’t about to take no for an answer. We got organized in the red Jeep and pulled out of the parking spot. Challenge #1: find the right way out of the mall parking lot. Two exits were possible, only one of them matched our map. It took us three loops just to find our way off the roof, loops filled with speed humps and aggressive cross traffic. Good practice for Jonathan’s shifting skills. Sure enough, we made it down a level and started reading the hidden signs all over again. Only two loops this time before we found the ramp to ground level, and by now we understood what the signs meant so it was an easy single loop out to Sheikh Zayed Road, the major highway artery that bisects Dubai’s colossal skyline. With the self-proclaimed 7-star Burj al-Arab hotel on our left and the world’s tallest building lit from the ground up to the topping cranes and rising higher by the minute on our right, we tasted the freedom of the open road for about three minutes before a sea of immobile red taillights shattered our illusion and brought us to a dead stop.

Bursts of tantalizing speed alternated with frustrating stretches of traffic for quite a while, colored by the need to follow a map with no distance scale and points of reference that we had never seen before. Our destination was the National Paint roundabout, something that marked the end of the complicated navigation through Dubai and Sharjah and the beginning of a long straight run eastward across the peninsula to Masafi. Mary called once to check on us and reported that she didn’t get out of the mall the right way and she was taking the alternate route to National Paint. We agreed to touch base when one or the other of us reached that critical milestone.

Jonathan continued his stellar driving, avoiding caravans of fume-belching trucks and all manner of overly aggressive drivers in beat-up Toyotas and souped-up Benzes. The GPS froze up at some point, our little triangle-shaped car continuing to point straight into Dubai Creek, as though the Al Makhtoum bridge was just ahead of us even though we were almost into Sharjah several kilometers outside of Dubai. Trying to keep my eyes peeled for some important landmark noted haphazardly on the hastily-drawn map in my lap, I fumbled to remove and replace the half-dead batteries and managed to revive the activity on the tiny LCD screen. Surely we must have passed the important turnoff by now, on paper the notations for “bridge” and “mall” were so close together that there’s no way they could be twenty kilometers apart.

At some point, a sign appeared that seemed to share some sequential letters with a marginal note on the map, and I surmised that since every other car on the road seemed to want to jam into that exit and the traffic at the end of the ramp to the right was at a dead stop, it must be the right way for us to go. We took the exit, and then we sat and inched forward and sat some more. A hundred meters of forward progress in 10 minutes. Cars in front and behind, desperate either to leave our lane or enter it, usually both. No driver was satisfied with the lane he was presently in; every single car needed to squeeze its way into a space only a fraction of its length in a neighboring lane or even sometimes two or three lanes away. Remarkably, in five lanes of solidly packed traffic exhibiting almost zero forward motion, every single vehicle managed to change lanes at least a thousand times. As all traffic jams do, this one eventually vomited us forward onto a slightly more open stretch of road and we watched the Sahara Mall slide by on the right, full of the same retail megafranchises we imagined we would escape by leaving New York or even Capon Springs to travel nine time zones eastward to the Middle East. Certainly the US media portrayal of any Arab land does not include endless vistas of opulent malls with the very same megabrands we encounter in our own suburban shopping pilgrimages. As the muzzeins warble their compelling call to prayer several times a day from tinny public address speakers mounted in minarets only a few hundred meters apart, the shopping in this ultramodern Mecca never stops to take a breath.

Busy convincing myself that we’ve managed to find the right exit and start our eastward trek to Masafi, I barely notice the borrowed cell phone vibrating and chirping in my pocket. Mary’s calling to tell us that they’ve reached National Paint but the sign is turned off so we probably won’t see it. There are other landmarks, she tells me, like a long overpass and a large flashing blue sign. Oddly, it’s like she’s in the back seat describing what I’m seeing. I asked her about the sign hanging on the upcoming overpass and she read it aloud along with me. We were two cars behind her in the same lane. With a sense of relief and accomplishment, I imagined our work was done – with little more than the stars to guide us (plus a massively overbuilt and still completely undersized highway system, a personalized map and pinpoint satellite navigation) we had joined a twenty-first century caravan, crossing the desert to paradise. Or had we? Jonathan floored the accelerator and we sped by the caravan, cutting back in front and taking the lead. The race was on, even though we were the only ones who knew there was a race.

We had driven off the edge of our map. Only two verbal instructions remained: at Masafi, don’t follow the signs and turn right to Fujairah, instead turn left towards Dibba, then follow the signs for Le Meridien. Focused intently on the GPS which was now guiding us by road to a geocache hidden across the street from our hotel, I failed to notice Mary’s caravan passing us at a pair of roundabouts in Dhaid.

Believing that we were still Team Number One, we continued following the purple line on the tiny GPS screen. We passed through the Friday Market in Dibba, a primitive strip mall of enormous open stalls hawking carpets and produce. Overtaking some slower traffic on the right, we somehow found ourselves passing our own caravan once again. We realized that this was not going to be an easy victory for the red team. We pulled further away from the group and sped ahead to the next roundabout, remembering to head left as we’d been told. Our adrenaline soared as we entered seventy kilometers of hilly, twisty mountain roads that would lead around the northern tip of the small peninsula and down the coast of the Gulf of Oman to the Sandy Beach.

Mostly two-lane roads lay ahead of us, seriously limiting the opportunity for the others to pass us again. A short while later, Mary called to say she hadn’t seen us since we passed her at the Friday Market, and asked if we had made a mistake and turned right in Dibba. Knowing that we had a short time advantage, we also realized that we had confused the other teams into believing we were lost. This was exactly the edge that we needed to pull off a stunning victory in this hotly contested event. I wouldn’t give Mary a straight answer. “Roundabout? Left? I don’t know what you mean! Uh oh, losing my cell signal here, bad spot, talk to you later, don’t worry about us, we’ll eventually find our way there.” Nothing but open road and a few roundabouts lay between us and victory.

Signs for Le Meridien were plentiful and obvious at every roundabout, soon joined by less imposing and more timeworn signs directing the weekend traffic to the Sandy Beach. Passing through the final roundabout, we counted down the kilometers until the hotel appeared ahead on our left. Mary’s prophetic driving tip from our first car ride over a week ago came back to us now: “You can’t turn left here.” Just as I recalled this unfortunate truth, the phone rang. It was Mary: “You should be there, because we’re coming up on the hotel now.” If they know a back way in, we’re going to lose this race in the last crucial moments. The wide, grassy median came to an end and we swung around it in third gear, barely slowing down through the u-turn. The entrance to the hotel appeared on the right and the caravan appeared across the median on the left, just moments behind. We pulled into the gate and grabbed the closest parking spot, jumped out of the car and ran for the office door. Climbing the single step onto the welcome mat, we were indeed Team Number One in this leg of the race.

As the other vehicles pulled into the lot, we taunted them with our victory and as we expected they wilted with shame in the face of our awesome navigation and driving skills. “Team number one for what? There are teams? We were racing?” In our minds we had pulled off one of the greatest upsets in the history of competitive adventure racing. Everybody else just wanted to unpack and start enjoying a quiet weekend at the beach.

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23January2008

Photos!

Posted by afkenner under: Uncategorized.

Finally, a photo gallery.

Links to each date are on the top.

http://web.mac.com/akenner

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15January2008

Check-in

Posted by afkenner under: Travel.

breakfast.jpgA little early? Arrived at JFK at 6:20, bags checked in 10 minutes. Coffee, eggs, yogurt and Italian Wedding soup consumed by 7:15. Anybody got a deck of cards?

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4December2007

Thinking about going

Posted by afkenner under: Travel.

Scene: A discussion with Jonathan B. wherein we discover a mutual interest in travel writing.

Content: Musing about taking an adventure trip of our own someday.

Revelation: We each know someone currently living and working in the UAE.

Outcome: We can’t pass up this opportunity. All signs point to GO!

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