New Orleans photography » A Big Easy photo blog

You know you have sensor dust when:

annoying little gray spots show up on your digital files.  They are especially troublesome/noticeable when they overlay on skin tones, or in places that make them more tedious to Photoshop:

Sensor dust is nothing new (Google it.) When I bought my first digital SLR in 2005, I also bought a brush from Visible Dust to clean the sensor. Back then, I used it all the time. Last year, when I moved to the D700, I set my menu options to “clean sensor at shutdown.” I’m careful with my gear. I take proper precautions when changing lenses. All of those things combined bought me some time, and I got out of the habit of paying attention to dust.

Even still, sensor dust is inevitable, and when it starts to regularly cost me time spent Photoshopping, I get annoyed, and I want it fixed — quickly. So I dug out my old Visible Dust brush.

If I had read more than I did before I started, I would have learned that sensor cleaning has changed in the last few years. What happened to xrdbear is exactly what happened to me:

And I got very, very scared. So scared, in fact, that I set everything down and walked away for a full day rather than face what I imagined to be a nearly catastrophic error resulting in a very costly repair bill.

The next morning, I went back to reading. I started with bythom, and then moved on to this photo.net thread. I looked at Ken Rockwell, but I quickly clicked away because he was telling me what I already knew, that I shouldn’t be messing with my sensor.

I used a brush cleaning solution to clean my sensor brushes, and then I swept them over the trouble spots (in some cases, several passes, in others, probably a dozen or so) to rid my sensor of the oil streaks.

WHEW! I got my images zeroed back to a no-visible-dust default:

I’ve since returned to Ken Rockwell’s page advising me to never do as I did, probably to avoid the exact dilemma I found myself in (or worse); he cleans his cameras with a vacuum and sends them back to Nikon when they get really bad.

[return to the PHOTO 101 Table of Contents]

We’ve learned that aperture controls the amount of light coming in through the lens, shutter speed controls the amount of time in which light is allowed to reach the sensor. ISO lets you control how sensitive your sensor is in reacting to that light.

50 100 200 400 800 1600 3200 6400

Just like the aperture and shutter speed scales, ISO moves from left to right, 32 being the lowest and 3200 being quite high, each stop along the way doubling or halving (depending on which direction you’re going) the amount of light sensitivity the sensor needs to properly record an image.

ISO is always the first setting I choose when trying to determine exposure. When I pick up my camera, I verify the ISO setting and, if necessary, change it. I do this first, religiously and without fail.

Q: First, religiously and without fail? Why?

A: Okay, okay. Since you asked, I’ll tell you. But it’s a painful story and not one of my brightest moments.

Once, many years ago while I was still shooting film, I took my camera to an LSU game at Tiger Stadium. I shot the entire night game on ISO 3200.

LSU won and life was good.

And then I returned to my newborn photo business (officially about a month old) and shot a maternity session (Monica had the baby the very next day), a family Christmas card (Miette’s husband left the very next day for a four-month deployment) another family for Christmas cards (Jenny has three young boys and a husband — a family dynamic that tends to scream “We’re only here because Mommy is making us, hurry up and get this over with!”) And then my parents flew out from Oregon for a visit and I was very excited to get a portrait of the two of them. I can still see that image of them, standing together backlit in evening light, cooperating with my instructions with the courtesy amused parents afford children learning.

Fast forward one week. 12 rolls of film return from the lab with not one — NOT ONE — usable image among them. I shot four sessions with my shutter speed and aperture set as if I were shooting on ISO 100, when in fact my ISO was still dialed to 3200 from the game.

…Wherever you go, you will top all the rest.

Except when you don’t.
Because, sometimes, you won’t.

I’m sorry to say so
but, sadly, it’s true
that Bang-ups
and Hang-ups
can happen to you.

You can get all hung up
in a prickle-ly perch.
And your gang will fly on.
you’ll be left in a Lurch.

You’ll come down from the Lurch
with an unpleasant bump.
And the chances are, then,
that you’ll be in a Slump.

And when you’re in a Slump,
you’re not in for much fun.
Un-slumping yourself
is not easily done.

— Dr. Seuss, Oh, the Places You’ll Go!

Not easily done no kidding. Especially after the kind of complete and utter failure that produces honest quitters, made infinitely more painful by such an elementary mistake and the involvement of people I genuinely care about. I spent that day making the most humbling and difficult phone calls of my photographic career, three of the four sessions impossible to re-shoot.

I will never forget Jenny’s response to me I sat in the pit of my Slump and waited for her anguish to crush what little spirit I had left:

“Christine, if that’s the worst thing to happen to me today, then I’m in pretty good shape!”

And while she went on to talk of other things, I sat thinking of the very powerful and generous lesson in forgiveness she had just given me, a gift I’ve never forgotten.

Along with some other lessons I won’t soon forget, not the least of which: Check, double check and triple check your settings before you start shooting. Now that the world has pretty much gone digital, this step is infinitely more reassuring. Even after checking my settings, I always take a test shot to verify my camera is seeing the settings I envision it to see. And then I can put the technical details aside and just shoot.

For me, ISO is the easiest place to begin; then I choose my aperture (because I tend to shoot wide open or in the critical aperture range) and then I choose whatever shutter speed I need to make all of that happen. (And then I double check image quality, white balance, metering and exposure compensation, because I consider it painful to spend time correcting in Lightroom or Photoshop what it takes .02 seconds to fix in-camera. But that’s a post title all its own!)

Here is my very simple formula for choosing ISO: choose the lesser of all evils. Back in the film days, I could buy film with ISO 32. Today, the digital SLR I’m shooting has a lowest ISO setting of 200. So I always start out hopeful that ISO 200 will do the job and I bump that up only as and if necessary because I still need more light after my aperture settings are in place and I can’t make any more adjustments to shutter speed (for reasons we’ve already learned, such as the relationship between focal length and shutter speed or showing the intended effects of freezing/blurring action, etc.)

If, after I’ve set my aperture and shutter speed, I find I still don’t have enough light, then I have to stop and think about the photo. Is it a portrait that the client might want a 20-inch-by-30-inch printed for over the mantle? If so, then I’m probably going to whip out my strobes and dial them to produce enough light to keep me at ISO 200 which in turn will keep me in business.

But generally speaking for the rest of the time, if there is no client involved and I still don’t have enough light, then I simply bump up my ISO and have fun shooting rather than drag out more gear and spend more time fiddling with photography (which tends to frustrate my family very quickly these days).

Q: Why wouldn’t you just use ISO 3200 all the time?

A: You could.

I don’t, because the image quality isn’t creamy and crisp; but sometimes, if the difference is ISO 3200 or no picture at all, I’ll dial 3200 and keep shooting. Which is what I did on this evening when MeDannyP came to visit (original post here):

Nikon D300, 18-200mm f/3.5-5.6 lens at 18mm, f3.5 @ 1/125 second, ISO 800

Nikon D300, 18-200mm f/3.5-5.6 lens at 18mm, f3.5 @ 1/15 second, ISO 3200

Granted, grown men at the end of the evening under harsh sodium vapor lights are going to photograph grittier than young children under properly balanced studio strobes firing from behind a large softbox, but compare anyhow the ISO 800 and ISO 3200 above with this next photo, taken with the same camera body set at ISO 200 (original post here):

Nikon D300, 28-70mm f/2.8 lens at 70mm, f5.6 @ 1/125 second, ISO 200, strobes

Homeschool Moms who bring me their children don’t want sodium vapor 5-o’clock shadows in a quick snapshot to tack up on the fridge; they want creamy enlargements fit for frames. They want ISO 200.

Technology is moving ever closer to the photographer’s side, first with digital and now, more recently, by making great strides in digital ISO. Nikon and Canon (and perhaps others, but Nikon and Canon are the two companies I’m familiar with) are producing camera bodies that yield extremely usable images on high ISO settings. Next time MeDannyP is in town visiting, I’ll reshoot inside Union Station with the D700 at ISO 3200 and post the two images side by side; but I can already tell you the visible result is that with the D700, Nikon took shooting at higher ISOs two steps forward. If you’re looking to buy a camera, compare images shot at high ISOs to take advantage of the newest technology you can afford to get your hands on. The higher usable ISO, the more light you have to work with (the key word being “usable.”)

Exposure = ISO + Aperture + Shutter Speed

Q: If the answer to the equation begins with ISO, and even you admit it’s the first setting you choose, why did you teach me aperture and shutter speed first?

A: Because ISO is so easy. It’s either smooth and creamy at one extreme or harsh and gritty on the other, and everything else in the middle.

Nuances of shutter speed and aperture are more difficult to wrap your brain around, so I figured let’s get those out of the way. Congratulations! Not only have you already made it through the hardest part, you’ve just finished exposure!

[return to the PHOTO 101 Table of Contents]

Exposure = ISO + Aperture + Shutter Speed.

We’ve learned that aperture controls the amount of light coming in through the lens. Shutter speed controls the amount of time in which light is allowed to reach the sensor. (Coming tomorrow: ISO lets you control how sensitive your sensor is in reacting to that light.)

We’ve also learned that shutter speeds should generally be equal to or faster than the focal length of your lens if you are handholding your camera. So keeping that in mind, take a look at your lens, make note of your focal length, and then look at this shutter speed chart, paying particular attention to the sweet spot setting that corresponds with your focal length.

Whereas aperture is determined by the lens, shutter speed (and ISO) is determined by the camera body. Shutter speed is literally the speed in which your camera body’s shutter opens and closes during exposure.

Shutter speeds are measured in fractions of seconds. 1/2 is one-half second, which is pretty fast in general terms but actually pretty slow for a shutter speed. 1/8000 of a second is pretty fast in general terms and in photography.

Shutter speeds are important when you’re trying to show action, either by using blur to show movement or by freezing action.

For example, look at the difference I made in these two photographs of my son simply by paying attention to my shutter speed (and then adjusting my aperture accordingly until my meter said I had enough light):

Nikon D700, 28-70mm lens at 28mm, f2.8 @ 1/1000 second, ISO 200

Nikon D700, 28-70mm lens at 28mm, f16 @ 1/15 second, ISO 200

In the top photo, I froze the action with a 1/1000 of a second shutter speed; it sort of looks like we were just sitting around on some playground equipment because the shutter was much faster than the action. Technically, it’s correct — any camera on program (or auto) mode could have taken this shot.

But a camera on program mode doesn’t always capture the truth or the flavor of an image. That’s the photographer’s job. In this case, changing the shutter speed to 1/15 of a second made the image unmistakably, dizzyingly merry-go-round.

Then for sport I shot two frames at the exact same settings, simply to illustrate the relationship between shutter speed and action. If there’s action you wish to freeze, a fast shutter speed is a requirement. But if there’s no action, the fast shutter speed is hardly noticeable.

Nikon D700, 28-70mm lens at 56mm, f2.8 @ 1/2000 second, ISO 200

Nikon D700, 28-70mm lens at 56mm, f2.8 @ 1/2000 second, ISO 200

In the first image, it’s the frozen action that the image is all about. A fast shutter speed is required for this. The second image, shot with the exact same settings as the first, is all about depth of field, and depth of field is controlled by…

Bueller? Bueller? Anyone? Anyone?

Aperture!

[return to the PHOTO 101 Table of Contents]

Exposure = ISO + Aperture + Shutter Speed. Learn it, know it, live it.

Let me start by saying I don’t buy the top of the line camera body Nikon makes, especially since I’ve gone digital. Digital camera bodies are like computers; in a couple of years, newer, better technology will render today’s bodies almost useless. (Almost. But that’s a discussion for another day.) Lenses, on the other hand, hold their use and value. Lenses contribute more toward making a great photo than a camera body does.

I’d rather have a $1500 lens on a $500 body than a $5000 body with a $500 lens (well; ideally, I’d have a $1500 lens on a $5000 body.)

One of the most important considerations in buying and/or using a lens is aperture.

This is how I think of aperture: imagine a sheet of glass between you and your subject. That sheet of glass represents aperture when shooting wide open. There’s only that tiny stretch of depth across your frame that will be in sharp focus. This is known as shallow depth of field. I did my best to photograph an example of shallow depth of field using critical aperture (keep reading) where you can literally see the plane of focus:

Nikon D700, 70-200mm f/2.8 lens at 200mm, f5.6 (critical aperture) @ 1/1600 second, ISO 400

Aperture, by definition, is the variable opening by which light enters a camera through a lens. Aperture is the lens opening or f/stop in a photographic equation. Aperture is the amount of light made available to the sensor to record an image.

So let’s review focal length just for a moment and return to the numbers printed on a lens: for example, my Nikon 105mm 1:2.8 lens. We know that the 105mm means focal length, but what does the ratio-looking 1:2.8 mean?

This number designates the widest aperture available for that lens and it’s written as a ratio because aperture is in fact a fraction (stay with me.) For example, my 105mm 1:2.8 lens can be shot wide open at f/2.8. Some zoom lenses will have numbers that look like this: 1:4-5.6 This number means that f/4 is the largest aperture available at the widest (wide angle) end but only f/5.6 at the longest (telephoto) end (say, for example, it’s a 70-200mm zoom, f/4 at 70mm and f/5.6 at 200mm is the widest aperture available for that lens.) My 70-200mm telephoto zoom lens has a 1:2.8 ratio; I can shoot wide open at f/2.8 no matter what focal length I’m at with this lens.  That’s a more in-depth explanation as to why, in an earlier lesson, I explained I can keep shooting wide or nearly wide-open with that lens as a toddler runs toward me without having to change my exposure settings.

This number is the crux of the issue of lens choice. All of my lenses are f/2.8 or f/1.2 — all of them. Lenses slower than f/2.8 are deal-breakers for me. It’s just the way I shoot. Perhaps you shoot differently; say you shoot landscapes at mostly f/22 and don’t have much use for a lens wide open. Perhaps you never shoot pictures indoors, so a lens that can perform in low-light situations isn’t of much use to you. That’s exactly my point, why I’m going to all of this effort to show you how to use your camera; it’s why I can’t tell you one way or another what camera-lens combo would be the best gear for you to buy. Remember Rilke?

Look at this aperture scale to help you visualize aperture as the amount of light splashing in through your lens toward your sensor:

f/1.2 f/2.8 f/4 f/5.6 f/8 f/11 f/16 f/22 f/32

Each stop on the aperture scale = one full stop of light.

Take our exposure equation that we learned last post:

Exposure = ISO (sensitivity to light) + Aperture (amount of light made available to record an image) + Shutter Speed (the length of time the light is made available to record an image)

How sensitive you’re making your camera to light + how much light you’re letting in and for how long. That’s it! That’s your exposure equation. How much light you’re letting in is controlled by aperture. Think of aperture as pouring light onto your sensor through your lens; at f/2.8, you’re just dumping it in wide open but by the time you stop down to f/22, you’re pouring it quite detailed through a small funnel.

Photography is, by definition, painting with light. Not enough light and you might as well take your ball and go home. Light gives a photographer options and options are the paint in a photographer’s hands.

Moving from f/2.8 to f/5.6 on the aperture scale is two full stops of light. In ISO terms, which you might be a little more familiar with if you’re using a point-and-shoot and ISO is really the only adjustment you make, that’s the equivalent of moving from ISO 400 to ISO 1600. Think of the difference in the quality of your images when you shoot on ISO 1600 as compared to ISO 400. (If you don’t already know this offhand, don’t worry; we’ll cover it.) If you’re starting at f/5.6, you’re going to have to make up that loss of light somewhere. Looking back at our exposure equation, there are only two other options: ISO or shutter speed. If you’re working with a long telephoto lens, you might not have as much wiggle-room to slow your shutter speed. That leaves you bumping up your ISO which might give you noisy or not so crisp and clear images.

There’s also the issue of performance. A “critical aperture” is the aperture at which a lens can be expected to best perform, and is generally two stops from the maximum (or largest) lens aperture. So if your largest aperture is f/1.2, then you can expect very good, clean, sharp images from shooting that lens at f/4; but if f/5.6 is your maximum aperture, you’ll have to stop that lens down to f/11 to achieve “critical aperture.” Scroll back up to the aperture chart and look at the circles, particularly at f/11 — visually compare the amount of light available at f/11 with the amount of light available at f/4 or even f/1.2. See my concern?

Generally speaking, the larger the f/stop (think of the size of the circle, not the number!) the better the lens. The larger the f/stop, the “faster” the lens.

Q: Why is f/22 smaller than f/2.8 when 2.8 is a smaller number than 22? It’s very confusing!

A: It is confusing. It’s math. “f/stop” is literally (speaking in mathematical terms) a fraction that indicates the diameter of the aperture (or lens opening). “f” stands for the “focal length” of the lens, “/” is “divided by” and the number indicates the stop. So a 28mm lens set at f/2.8 would be [focal length] 28 divided by 2.8 = 10. The diameter of that lens opening would be 10. A 28mm lens set at f/22 would yield a diameter of 1.27. So in this case, a circle with a diameter of 10 would be larger than a circle with a diameter of 1.27 — whew!

Or, you can simply commit to memory the size of the circles in the chart I drew, f/2.8 being much larger than f/22, each numbered stop along the way halving the light reaching the sensor. That’s what I did.

Q: Why does it go f/1.2 and then f/2.8? Shouldn’t it be f/1.4?

A: That’s a good question. Sometimes it does, some lenses are f/1.4. The numbers don’t quite line up perfectly with halving and doubling. Sometimes cameras factor in half-stops or thirds, producing far more numbers than I included on the scale above. You’ll see the same things happen next post when we get to shutter speed, moving from 1/60 to 1/125. Don’t get too hung up on it.

The numbers on the charts I’m giving you are considered the “whole stops.” It’s a good frame of reference for a beginner. Once you memorize those numbers, you’ll find it becomes second nature to move from whole to whole in calculating exposure. This is useful because if you are shooting f/5.6 at [shutter speed] 1/250 but you’d like to be shooting at f/2.8 to blur your background more, all you have to do is adjust your shutter speed two stops to the right to make up for shifting your aperture two stops to the left. So the exposure of f/2.8 at 1/1000 is equal to the exposure of f/5.6 at 1/250 for this particular photo. Both photos will look the same as far as brightness and contrast, but the image shot at f/2.8 will have less depth of field.

Here’s an example of changing shutter speed and aperture combinations to produce basically the same exposure. In this case, I wanted to illustrate the difference in depth of field (notice the backgrounds) with different apertures. I moved my aperture roughly 5 steps to the right on the scale above, so I had to move my shutter speed roughly 5 steps to the left to compensate for the loss of light in order to achieve the same basic exposure. I was using my 28-70mm lens and probably should have shot 4 photos, two at 28mm and two at 70mm but my model was in a hurry to get to her meet so I shot two frames at roughly “normal” focal length, the first to illustrate shallow depth of field and the second to illustrate great depth of field:

Nikon D700, 28-70mm lens at 48mm, f2.8 @ 1/800 second, ISO 400

See those pretty little circles in the background above? That’s bokeh. Wide open apertures produce blurry backgrounds and beautiful bokeh and shallow depth of field (blurry background.)

Nikon D700, 28-70mm lens at 48mm, f18 @ 1/20 second, ISO 400

F/18 renders great depth of field (focus plane extends much farther throughout the background.) However, depth of field does not always insure sharp focus. A corresponding shutter speed of 1/20 to make up for the loss of light when I moved to f/18 was clearly against the rules we learned in focal length — it’s not a “first learn the rules, then learn to break them” example, it’s an example to illustrate why paying attention to focal length and its relationship to shutter speed is important. Remember, I was handholding my lens (the body-lens combo weighs about 10 pounds) at 48mm with a shutter speed of 1/20 and result is screaming camera shake or blur. Look at these close-up crops of the same images from above:

Nikon D700, 28-70mm lens at 48mm, f2.8 @ 1/800 second, ISO 400

Nikon D700, 28-70mm lens at 48mm, f18 @ 1/20 second, ISO 400

Extra Credit: Let’s say that second image was shot at (I’ll put it into whole stops to make it easier for you) [aperture] f/16 and [shutter speed] 1/30. iTunes treat goes to the first person who can tell me (before I post the answer in the next topic) what my exposure on that second image SHOULD have been, assuming a shutter speed of 1/60.

Bueller? Bueller? Anyone? Anyone?

[return to the PHOTO 101 Table of Contents]

So we’ve agreed that you’re looking to create technically correct images that are in-focus and not too bright (overexposed) or too dark (underexposed.) You’ve chosen a lens that gives you roughly the focal length you’re looking for depending on what you’re shooting.

Q: I chose a 105mm lens, but how do I get the flowers to go all blurry in the background when shooting portraits? I’ve got a 200mm lens so I can get close enough to him without getting wet, but how do I freeze the water that my son is splashing in the pool? My daughter is jumping on her bed; I have a 28mm lens. What do I use to make the other settings work so that I can freeze her in the air mid-jump?

A: Here’s the magic equation:

Exposure = ISO + Aperture + Shutter Speed

Here’s a flowchart to help get you thinking about what kind of images you want to make:

Learn it, know it, live it.

Next up: breaking down the details. Picking your own iso, aperture and shutter speed numbers is how a photographer differs from a camera. Knowing this, and what to look for in a camera and lens to help you, separates the men from machines.

[return to the PHOTO 101 Table of Contents]