July 2008 /

The Archives

07.15.08 /
Professional “Product Photos” on the Cheap
Personal, Photography | Permalink | Comment?
Kristy mentioned over on her blog that we’re trying to purge ourselves of some of our excess stuff. Part of that means finding things that have been in boxes for a long time and getting rid of them, either by donating them, or, if they seem salable, by putting them up on eBay.

One thing that I do, when buying from eBay, is try to find an auction with a crappy cell-phone looking picture, or, better, no picture, and as little descriptive text as possible. These ones get missed by more searches and overlooked by more bidders, and as a result, I spend less money. So of course, to maximize our take from the items that we’re going to try to sell ourselves, we’re trying to do the opposite. And part of that means getting *nice* pictures of everything we want to sell.

What is a photographer with little equipment to do? Worse, what is a photographer who has pledged to forego discretionary spending to do? Why, construct a lightbox-alike for cheap, of course!

We had a white sheet that we’d purchased to project on (unfortunately, the day we wanted to project on our patio, it was quite windy, so the sheet was in pristine condition). Fortunately, among my equipment, I do include a few un-substitutable essentials: a tripod, a reasonably advanced digital camera (I am overqualified in this area). I also have a nice fast lens, which helps get rid of pesky backgrounds, and a totally-overpriced gray card. A word about gray cards–they cost so much because they’re supposed to last. But if you have a decent color printer and don’t mind reprinting one every month or so, you can use this handy one I threw together in Photoshop (more details about what it is, what it’s for, and how you use it later on).
1. Controlled lighting
2. White sheet
3. Tripod and camera
4. Gray card
Setup

Even with a tripod to help you out, you still want a reasonably bright light source; however, to save time, try to make sure that the light source isn’t going to change while you are shooting (light from a window is bad for this). To make it easy to reach your work surface, I recommend working up on a table. To give yourself enough room to work, the table needs to be relatively deep. Finally, you need to be able to attach a white sheet behind your work area, and the sheet needs to be long enough to drape down to your table surface and cover it. The sheet should be draped loosely, not forming a sharp angle where it meets your work surface–otherwise you’ll get strangely shaped shadows. Pictured at right (or above, depending on how this text lays out) is the arrangement I used. If you can arrange for your light to be coming in at a 45 degree angle, it will produce some nice shadows for you. I know that in a real lightbox, you try to completely eliminate shadows, but that isn’t going to happen for us.
1. Work table at comfortable height
2. Hang sheet behind, curved gently from vertical to horizontal
3. Light at 45 degree angle
Getting Started

Turn on your light source and walk away for at least five minutes. This is especially important if your light source is a CF bulb or (ugh) a fluorescent tube. The light will change as the source warms up, so just let it sit for a few minutes. Before we start shooting and every so often while we’re shooting, we’ll be metering to make sure we take the best pictures we can.

Before we start shooting, there are a couple of steps to get your camera ready. The first thing you should do, whatever camera you are using, is set the ISO value as low as your camera will permit. Higher sensitivity lets you shoot in lower light at faster speeds, but it adds a lot of noise to the picture; and we’ll have a tripod, so shutter speed is immaterial for our purposes. Once your light source has warmed up, take your camera off the tripod, bring it over to your work surface, and haul out your gray card. Almost all cameras have a feature that lets you adjust the “white balance”–this is how the camera compensates for the fact that most light sources are not pure white. The first thing you’re going to do with your gray card is set this white balance. The process varies from camera to camera. With my D70, I hold down the WB button and roll the primary selector until PRE is selected. While holding down the PRE button, I press the shutter release. On my SD400 point-and shoot, I press Func/Set, choose “CUSTOM” white balance, and then press the menu button. Check your manual for details. For this part of the process, you want to be pointing only at the gray portion of the card. Your camera may have a hard time focusing at close range; if manual focus is available, use it. If you have a viewscreen, you should see the colors of things around you abruptly change; if you have an SLR, snapping a few shots should show you quite a difference.

The next thing we’re going to use the gray card for is to figure out the best exposure for our photos. Sadly, many point-and-shoot cameras aren’t flexible enough to let you perform this adjustment on the camera. If you’re using one of them, instead place the gray card in the middle of your workspace and shoot a couple pictures of it. Try to make it take up about 1/4 of the frame in at least one of the shots and about 1/2 of the frame in another. We’ll use these later in Photoshop to correct your images. If you have an SLR, however, we can actually figure out the correct exposure settings using your card. Put your camera in aperture priority mode; after selecting the aperture you want to shoot at (I recommend f2.5 if you can), shoot a frame containing only the gray card, again probably using manual focus. Note the shutter speed the camera uses; then abandon aperture priority mode, and put the camera in full manual mode with the aperture and shutter speed from the previous step. The metering logic in SLRs will try to perfectly expose this “18% gray” value. A final note about exposure: when shooting photos in this style, I prefer to overexpose by about “one stop” of light, to help blow out any background details that may escape our shallow f2.5 depth of field. On my SD400, I do this by setting the “Exp” value to +1; on an SLR, you would do it by setting the shutter length to twice the value obtained from the previous step (so, for example, 1/40s -> 1/20s).

Please note that if you’re shooting on an SLR, I highly recommend that you use RAW mode. If you should overexpose an image too greatly, it can usually pull back at least half a stop of detail more than if you had been shooting JPG.

Place your camera back on your tripod and start shooting. If you are using a point-and-shoot that doesn’t let you manually adjust aperture and shutter, try to make the object you’re shooting fill as much of the frame as one of your test shots with the gray card; that will make color correction easier. In either case, remember to repeat the procedure above every hour or so to make sure that the light has not changed too much on you.
1. Let the light warm up
2. Use the lowest ISO setting available
3. Set the white balance on your camera using the gray card
4. SLR shooters, use aperture priority to figure out correct exposure with the gray card, then MAKE SURE to switch to manual
5. If you can’t adjust the aperture and shutter independently, take several test shots with the gray card to help with correction later
6. It might be a good idea to overexpose slightly, especially if you shoot RAW anyways. If you are unable to shoot in full-manual mode, you must overexpose
Shooting

Because we are working with (probably) an artificial light source from around the house, and because we’re actively trying to overexpose the image we produce, the shutter time is likely to be rather long; at anything longer than 1/60s, hand shake is likely to be visible in the image, and even if you are using a tripod, pressing the shutter release will likely cause some jitter. If you have a remote release, you should use that; and if not, you should use the self-timer feature. Set it to the minimum value (2s on my SD400), and use the 2s it provides after pressing the shutter release to gently let go of the camera.

Work as quickly as you can to prevent the light from changing too much on you. I recommend a brush to dust your work surface off if you are photographing items that have been in storage; if the bristles are soft enough, you can use them on the item itself. Keep in mind that if you attach any additional filters, such as a polarizer to cut reflections or a close-up lens to capture details, you should repeat the white-balance and metering steps; anything in the light path will change the light received at the sensor.

When you are done shooting, drink a beer.
1. Use a tripod
2. Use a remote / cable release if you have one
3. Use the self-timer feature if you don’t have any better option
4. Redo the metering and white balance whenever the light changes
5. I like a nice weiss beer
Post-Processing

If you are fortunate enough to be shooting with an SLR, you should have very little in the way of post-processing to do. Congratulations–the extra $374189 that you spent on your camera is paying off today The image at left came directly from my camera with no color correction whatsoever–just the RAW processing, but that’s a part of my workflow by now. What’s great is that if I’d followed my own directions (I didn’t–I left the camera in aperture priority mode, a big mistake) all I’d need to do at this point is crop. Because I left some of the exposure decision up to the camera, quite a few actually needed the kind of adjustments that the exposure section is meant to avoid.

If you’re shooting with a point-and-shoot or if your camera otherwise restricts your ability to control exposure, you still have some work cut out for you. The white balance should have removed any color casts, a particularly difficult problem to solve in image processing software, but there’s still the question of making sure your levels are where they should be. Because cameras try to expose “18% gray” correctly, photos that are mostly white tend to get underexposed–it thinks the white should be gray, see?–so you’re going to have to do what you can to correct that.

An important tool in post-processing is the histogram. You might remember histograms from that stats unit that sometimes happened toward the end of the year in math cla–WAKE UP BACK THERE–class. Histograms show the frequency of each of a discrete set of values. In image processing, the values are usually luminance values, and the histogram is to show you how much of your image has a particular brightness. At right is the luminance histogram of our sample gray card image, as I produced it on my computer. Notice the small spike at far left to show the region of the image that’s pure black, the small spike at right for pure white, and the large spike for “mid gray.”

The goal here is to, using the levels tool, find the adjustments that restore your photo of the gray card to the correct brightess. Once you’ve done that, write down the levels settings that you used, and apply them to subsequent images. This should resolve any brightness problems you may have.

07.07.08 /
Make Your Own Gray Card
Photography, Tech | Permalink | 3 Comments

I just bought gray cards. I had a gift certificate, I needed them, and it’s probably good to buy gray cards if you’re going to be using them a lot. They’re low-reflectivity, they’re sturdy, and they hold their color. But it hurts me to pay money for carefully colored cardboard, and I probably wouldn’t have purchased any without a gift certificate. But not white-balancing will hurt your photography. What to do? You could always hack your own… the results will almost certainly not be as good as a professional gray card, but they will be free. This is a photochop tutorial, so here goes.

Now, I know that gray cards are usually called 18% gray cards. And I know that they are 18% gray because, when you take a scene that is equal parts 0% black and 100% white, the 18% gray is the resulting color. I don’t know why that is–ask a physicist. And I don’t know enough about how printing works to do anything useful with that 18% number, so I’m going to cheat.

1. Make a new file, 2px by 2px. May as well set the background color to be white.

2. Zoom in to the maximum extent allowed (do this automatically by double-clicking the hand tool). You’re going to need to see what you’re doing.

3. Using the Rectangular Marquee tool, mask off the top left pixel and fill it with black. Repeat for the bottom right pixel.

4. Select the entire image (Edit > Select All) and turn your image into a pattern (Edit > Define Pattern). Name it whatever you’d like.

5. Create a new file, the actual dimensions you want to make your gray card. I find that it’s helpful to switch to “inches” here from pixels… for example, 4″ x 6″

6. Select your entire new image (Edit > Select All); we’re going to fill it (Edit > Fill…) with the pattern that you defined in step 4. Select “Pattern” from the “Use” drop-down list, and then choose your pattern from the “Custom Pattern” drop-down list. Note! If you are using an analog monitor, the resulting image may exhibit frightening moire effects.

7. We have cleverly constructed an image that consists of equal parts 0% black and 100% white. If only there were some way to average the two… (Filter > Blur > Gaussian Blur…) Oh look! 18% gray… see what I mean by cheating?

8. For added utility, I like to add strips of white and black at the ends of the card.

9. Our histogram shows we’re ready to go out and kick some butt! Just make sure to print this on a printer configured for ColorSync (if you can) and on the least glossy paper you can find (important!).

Some day soon I’ll have a tutorial about what to do with a gray card.

07.05.08 /
4th of July Redux
Chicago, Food, Personal, Photography | Permalink | Comment?

Well, like I said, I never let acute guilt about the role of the US in world politics keep me from a barbecue. We had our friends John and Lindz over for a really nice barbecue yesterday to celebrate the holiday in style. They brought their dog Chai, whom Sybil and Ruby were really glad to see, and we had a nice time; first hanging out inside and then moving out to the patio to grill and relax. Unlike our last cookout, it wasn’t too windy to talk; however, we almost missed the wind, since there were swarms of gnats instead. A light dusting of DEET-enabled bug spray and a citronella candle later, we were in business. Brats, burgers, corn, cheap beer–the All-American summer meal, amirite?

Afterwards we retired to our building’s sundeck, a really nice facility whose location had been a mystery to Kristy and I until last night. We got a nice late-afternoon / early-evening view of the city as the sun sank. We played a few rounds of Uno, but of the three hands we played, I was the only one not to win. Dick bastards.

As dusk gathered about us, we gathered our possessions and headed out to an “underground” fireworks show in Ukrainian Village, whose organizers/performers we are to varying degrees acquainted with. He’s a really cool guy, and in the image at left, he’s demonstrating why I describe the event as an underground show. Yes, that’s a real 6″ shell; it made a pretty impressive skyburst. There were literally hundreds of these, and it went on for at least 45 minutes. It was quite honestly better than I remember the 4th of July fireworks in my hometown being, and it was put on by a bunch of well-connected amateurs. The show has apparently been going for years now, and the whole neighborhood turned out to watch. The cop cruisers circled, but seemed to be looking for trouble at the fringes of the crowd, ignoring the pyrotechnics in the parking lot. Had we not eaten first, there were plenty of tasty-smelling kebabs making the rounds, and the smell of cooked brats mingled with the sulfuric tang of the display all night. Needless to say, I was there with my camera set up to try to capture the air show.

So, photography. I checked with the guy who had invited us all to make sure that photography was permitted. You know, “underground show” and all. It was enthusiastically encouraged, so I hauled out my tripod and set it up pointing at the sky. It’s amazing how unselfconscious I’m getting about it by now–at long last! Since it was going to be right over us, I swapped out the 50mm prime that I’d used to excellent effect on the 3rd for my 18-55mm zoom, so as to cover the greatest possible area of sky; I could use it wide-open without fear of vignetting, because a) I wanted to stop it down anyways so I could leave the lens open and b) I was taking pictures of a dark sky! Everything was looking great on the screen when I occasionally checked it for proper exposure. Not only were the histograms showing that I was “doing it right,” but the photos were good too. Of course, you might guess that I wouldn’t elaborate on this unless something were actually going wrong…

Fig. 1: Looking good on-camera…
Fig. 2: Oh fuck.

Heartbreak. This is what I forgot, when I switched lenses: the 18-55mm zoom is a piece of absolute shit when it comes to manual focus. First of all, distances are unmarked, making any manual focus dodgy. But that’s ok, right? because I’m shooting with a fairly deep aperture at stuff that’s far away–I can just set focus to infinity, and the depth of field will sweep in anything more than 50 feet away. Sadly, unlike any other lens I’ve used, turning the manual focus all the way to the end is not “infinity”; instead, it’s “nothing.” Perhaps that is why this lens had to be refurbed, perhaps it’s just a bad design, but you can actually place the manual focus adjuster so that literally nothing is in focus. Which is what I cleverly did, so that I could shoot more shots because I wouldn’t have to wait for autofocus on each one. About 2/3 of the way through the evening, I realized my horrible mistake, but by then we were on to the finale, and smoke obscured a lot of the effects, leaving a tantalizing glimpse of what might have been.

Fig. 3: Even looks better at this distance
Fig. 4: Aha, focused correctly

What I should have done: first, I shouldn’t have assumed infinity focus would work. I could have sacrificed a few of the effects, not taking pictures in order to use them for finding focus–this is what I ended up doing later. Alternatively, I could have let autofocus handle the first one, and then switched the camera to manual focus after I’d found the right distance. I could have bought a lens, like the Tokina 11-16mm that I’m lusting after right now, that actually has proper infinity focus. Finally, I could just relax, as Kristy suggests, and realize that although a lot of my pictures aren’t as focused as I’d like them, they still turned out really well. And there’s always next year, right?

Disappointment aside, I did add a few decent tricks to my arsenal. Using manual focus DID allow me to snap freely–with no focus time, the shutter opened immediately when I asked it to. I tried using my remote for a shutter release, so that my hand wouldn’t jitter the camera, but the mechanics of bulb mode with the remote (press to open, press to close) ended up being too difficult to be practical for high-speed use. I left the camera in bulb mode, but I used the shutter release button instead (press to open, release to close). This let me open the shutter right when I knew the shell was going to explode and release as soon as I thought it had made the effect I wanted. I figured out that there was a reason my tripod’s panning release has a variety of degrees of tension, too–by tightening it halfway, I could still pan the camera up, but it offered enough resistance that I could pan to where a firework was and snap a .5s – 1.5s exposure without my hand on the unlocked tripod causing any visible jitter. I worked most of the night that way, panning up to the shell, holding the shutter, releasing.

Between the new things that I picked up and the hard reminder that I got, I’m going to take some amazing pictures next time I’m near fireworks.

07.04.08 /
4th of July
Personal, Politics | Permalink | Comment?

I’m not much for celebrating the 4th of July. Far be it for me to turn down a chance to barbecue, or to see fireworks (I got some great pictures last night that I put in my flickr account here), but more and more these days the US seems like a blight on the world. Here’s hoping that by next July 4th, the Democrats will have solid majorities in the House and Senate, Obama will be in the White House beginning to repair our international reputation, troops will be on the way home from Iraq, and liberal nominees will be waiting to replace aging Justice John Paul Stephens. In the meantime, I can at least take solace in this news item.

NP: MC Hawking, Why Won’t Jesse Helms Just Hurry Up and Die?

Why no, I don’t believe in the ridiculous taboo about speaking ill of the dead. While I’m at it, fuck Tim Russert too.