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]

Is my picture too bright/dark?  This is where checking the back of the camera can get beginners into trouble.

It’s important to understand how to read a histogram. Looking at the LCD screen on the back of the camera might not render an accurate picture (your camera’s LCD screen might be set to maximum brightness, for example, which can give you the impression that your pictures are washed out or overexposed) and the LCD screen is also a very small representation of the big picture (pardon all puns.)

A histogram is a graph that displays brightness values. It’s divided into five equal sections moving from left to right: very dark | dark | 30 percent gray | light | very light. The center of the histogram, 30 percent gray, is the value most camera manufacturers use as the default tone for metering and calculating exposure.

Let’s say the building blocks of a histogram begin with a rectangle drawn on a piece of paper. Only instead of looking at it straight-on, you’re going to view it eye-level to the table so that the graph becomes a vertical axis (and shows nothing at this point.) Then you’re going to use a box of tiny little square tiles from Home Depot. Each individual tile represents one value of brightness in your image. You start placing tiles representing pixels into the graph, stacking them according to lightness or darkness. As you get more than one of the same value, you begin stacking them.  You will find that images have a LOT of one value, less of others, so some of those little tile stacks will rise pretty high, maybe even to the top of your graph, others will be short. After all the tiles are stacked from the image, you’re looking at a histogram (vertical axis graphic representation of light and dark values.)

Generally speaking, the goal in a properly exposed image is to find most of your tiles stacked heavily in the middle and tapering off into very dark (left) or very light (right) edges. (Of course, this rule was made to be broken; first learn the rules, then learn to break them.)

Take for example this image of David and Shelley’s thank-you cards.  I’ll consider this image “properly exposed” because it’s a straightforward exposure using the exact settings my camera’s light meter told me to use (I had it set to use center-weighted metering; more on that later.):

Nikon D700, 135mm lens, f4 @ 1/250 second, ISO 200

Here’s how all of the individual tiles stack up to represent this image in my histogram:

Notice that there’s a good representation of tiles stacked across the histogram, heaviest in the center and stretching out to either side? This particular image is slightly heavier toward the right as there are a lot of lighter tones in it. (I also blew out the front of the cream colored table the cards were resting on. I did this intentionally, I was metering for the cards, my main subject, not so much the table or wall behind them.)

Here’s an example of this same scene, image intentionally underexposed:

Nikon D700, 135mm lens, f4 @ 1/3200 second, ISO 200

Look at the histogram now and how all my little tiles are stacked heavily to the left; there’s no mistaking that no matter how the image appears on my LCD, it’s in fact very dark; also look at the cream table, which is closer to properly exposed then it was above (the !!! warning sign is still there, just disregard it for now. If you are working in Photoshop and come across it, it’s warning you that the histogram you’re seeing is cached from memory and you’ve since made adjustments to the image that might change its appearance. Just click it and Photoshop will generate a new histogram and the warning will go away.):

histogram of underexposed image

And the same scene intentionally overexposed:

Nikon D700, 135mm lens, f4 @ 1/30 second, ISO 200

And its resulting histogram:

overexposed histogram

Something interesting that I didn’t intend to find when shooting this example: I avoided most of these exposure issues in post processing by shooting in RAW. As I imported the underexposed and overexposed images into Lightroom, they appeared pretty similar to the correctly exposed image. I had to go back and manually un-do all of my regular workflow develop settings to get them to look like they did on my LCD as I was shooting.

[return to the PHOTO 101 Table of Contents]

Katz Eye is one of the leading brands of replacement focussing screen for digital single lens reflex cameras (dSLR). Today’s dSLRs ship with a stock focus screen that is optimized for auto-focus; Katz Eye lets camera owners replace this stock screen with one more suitable for manual focus. This is very helpful for photographers who are looking to move to manual focus Zeiss lenses, or photographers who work in low-light situations where their dSLR has a hard time keeping up on auto-focus.

The Katz Eye website is geared toward photographers who already know why they want one; the company is starting to realize, however, that there are a lot of photographers out there who don’t know about this split-prism focusing option, and they have plans to update their website with more information in the future.

I was nervous about installing the product myself, so before I ordered, I sent an email to customer service. I got a very detailed response almost immediately:

“The installation process isn’t too bad if you have a steady hand, good light, reasonable (or corrected) vision, and the patience to absorb all the available information in the installation guide,” emailed Rachael Katz.  “It’s a bit tricky, as the screen is easily scratched and the handling tab is quite small (about 1.5mm x 3mm), and keeping things clean during the process is always a concern.”

Rachael said many of her customers also choose to send the camera to Katz Eye or a local installer for professional assistance, and that ultimately, only I could know what is best for my unique situation. “Hopefully you will find your questions answered, but if not, please let me know and I will do my best to clarify for you,” she said. Totally comfortable that these people stand behind their product and are available to help customers, I placed my order.

Not to be outdone by the Katz Eye users on Flickr who complete the process themselves without difficulty, I set aside a quiet morning and mustered the nerve to operate on my camera. The only change I made from the installation instructions was to use a pair of flat-nose pliers with smooth jaws rather than tweezers to grip the tiny tab — but then again, if I hadn’t been drinking a grande Americano, maybe the tweezers would have worked just fine.

The whole operation took about 5 minutes start to finish; my first test shot with my new split prism screen, focus aimed at the star over the Starbucks siren’s head:

Nikon D700, Zeiss 35mm lens, f2 @ 1/400 second, ISO 400

Since I’m first and foremost a portrait photographer, I should practice on people. And speaking of those I practice on most, they need to be picked up from school right about now, so I’m off.

Bottom line: I’d absolutely recommend this company and product. Here’s a link to another user who gave it [an artful] whirl.

UPDATE: Kate, here’s a very low-tech look through the viewfinder via my iPhone (onOne software app works, but it doesn’t capture the viewfinder details.) The split prism is a tiny circle in the center of the viewfinder between the “S” and “T” rendered in both focus and texture. If my iPhone phone quality were better, you could see the texture.

very low-tech look through the viewfinder via iPhone

The test shots surprised me.

Nikon D700, 35mm Zeiss lens, f4 @ 1/250, ISO 200

Nikon D700, 28-70mm lens at 35mm, f4 @ 1/250, ISO 200

Both images straight-out-of-the-camera (SOOC), no color correction or sharpening or enhancements. (The first image of Christopher holding up his running shoes was color corrected and run through my general filters.) Both acceptable, workable images, pulled back. The surprise? I totally expected the Zeiss prime to yield sharper results than the Nikon zoom, but a close-up crop of the eyes (where I was aiming my focus) clearly points to Nikon.

It’s harder to see side-by-side when the images get smaller on screen, so look again at Christopher’s eyebrows, the reflection of me in his sunglasses, and the line where his sunglasses meets the bright studio strobe, first in the Zeiss (where you can see my left hand turning the focus ring) and then in the Nikon (where my left hand is mostly needed to support the behemoth 28-70mm):

Zeiss 35mm

Nikon 28-70mm at 35mm

Aside from the chromatic aberrations, which Zeiss wins hands-down, I’m pretty sure hopeful? pointing out the possibility that what we’re seeing is operator error. For the last four years, the auto-focus Nikon has been my go-to lens, especially since I work so much with small children. When I picked up the Nikon to test on Christopher, I shot it using auto-focus. Perhaps I should have switched it over to manual focus for a more fair comparison; but then, I still think there’s something to say about results getting skewed based on the total number of hours I’ve spent working with each lens.

And there’s one more point that bothers me: 20+ years ago when I was shooting with manual focus lenses on film SLRs, the camera body had a split focusing screen. Remember those? My D700 has only a plain screen. I’m interested in a 35mm f/2 manual focus Zeiss precisely for those times when a D700 starts tripping all over itself to autofocus in low light.

Hmmm. A split focusing screen test might be next up in this summer Zeiss experiment.

P.S. I didn’t have the heart to tell him that sunglasses are counterproductive in Eugene!

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]