More on Digital Directions
Digital camera talk, from Ask FR&R
- By: Buzz Bryson
Figuring Pixels on Pictures
Okay, so you’ve decided to enter the digital camera world. What about picture quality? Lots to think about here.
If you want to do the math on digital picture quality, figure an acceptable pixel density for Internet posting (screen viewing) is somewhere between 72 pixels per inch (PPI) to several hundred PPI for contemporary high-resolution screens. Typical LCD screens have a resolution of 1024 by 768 pixels, which is around 85 PPI. For a paper print, you’ll typically be looking at around 150 PPI. Thus an 8-by-10-inch print would require (8 x 150) x (10 x 150) = 1200 x 1500 = 1,800,000 pixels worth of image, only 1.8 megapixels from the camera. In theory, then, a 2mp camera, a size you can hardly find anymore, should be sufficient. Some would say you need to print at 300 PPI to get a high-quality image. In that case, you’d need (8 x 300) x (10 x 300) = 2400 x 3000 = 7.2mp. (Note that doubling the pixels quadruples the total needed.) A big increase, but still within the common image size of cameras available today.
Any tricks here? Not really. Except—well, you still can’t crop the fool out of an image and expect to produce a great print. Take a typical point-and-shoot (P&S) camera, and I’m just spec’ing out one of the first ones from a large dealer. It produces a 12-mp image, on a sensor that is 3,000 pixels x 4,000 pixels. Say you take a shot of your buddy holding up a big fish, showing him standing in the water. It’s a vertical composition, thus is 4,000 pixels tall by 3,000 pixels wide. Later, you decide you want a print from the waist up, just showing the fish and your friend’s head. You’re using half the image: it’s still 3,000 pixels wide, but now it’s 2,000 pixels high. You want an 8-by-10, and decide 150 PPI will work great. Again with the math: (10 x 150) tall x (8 x 150) wide, or 1500 pixels tall by 1,200 pixels wide. What you have will still work great.
This example worked; they don’t always. Your friend then asks for a shot of just the fish’s mouth, showing his favorite killer fly. Suddenly, you’re working with an image that’s perhaps 400 pixels by 400 pixels. Still printing at 150 PPI, you’re limited to a print that’s under 3-by-3. Blow it up more than that, and you’ll have a pixilated image. Whether that’s objectionable or not depends, somewhat, on how close you are to the image you’re viewing. Remember that rarely does anyone complain about having too many pixels. Frequently, they complain about having too few. Thud! Yes, that’s the other shoe dropping.
Most point-and-shoot cameras (or compact cameras, as they're sometimes called) have a zoom lens. Because the sensor sizes (and thus the captured image sizes) vary, virtually all of these express the zoom range in terms of “35mm equivalent”, providing a common point of comparison. Generally, you’ll want zoom lens that covers a range from a moderate wide angle to a moderate telephoto angle, say 35-125mm (in 35mm equivalent terms) or 28-105mm. More and more, there are “super zooms” that cover something like a 28-300mm range. Pick your poison, but consider that wide angle coverage is particularly handy if you fish from boats (you can only back up so far), and that extreme telephotos not only magnify the image, they magnify your shakiness.
And, as good as some lens are, the more you ask them to do, the more you’re straining optical limits (in other words, a 10-12x zoom range is a bunch). Finally, note the maximum aperture. The smaller the number (e.g., f/2.8), the larger the aperture or light-gathering opening—hey, you didn’t expect this to be logical did you? The better the light gathering, the better off you are in low light situations—think evening hatch conditions. The progression is logarithmic, so f/2.8 lets in twice the light of f/4, which lets in twice the light of f/5.6, etc.
You’ll be hard pressed to find a P&S that doesn’t have a built-in flash. And you’ll find your pictures are immensely better if you use flash, almost always. “Fill flash” is a common technique used by pro photographers to deal with the harsh shadows produced by overhead sunlight. Why do you wear a cap? To block that bright sunlight by shading your eyes. Who do so many photos have the angler’s face hidden? Because it’s in the shadow produced by his cap. Solution: use fill flash to add a bit of light under the cap. The point is, make sure the flash is easy to use, and is easy to change from “auto” (which will rarely fire during the day) to “fill” or “manual” (which will provide that fill flash you want).
As a long-time SLR user, I really prefer a visual viewfinder. It’s just second nature to me to put the camera up against my eye, and compose the picture. Holding the camera out, and looking through the LCD just doesn’t seem right. And in full sunlight, the “bold, bright LCD” just isn’t, well, bright. Alas, the number of P&S cameras with viewfinders continues to decline; the masses have voted, apparently. Still, some of us prefer them.
Do you need a waterproof camera for fishing? Well, you certainly shouldn’t limit yourself to land-based photography. If you are so nervous about dunking a camera that you won’t get into the water without a waterproof model, then by all means, yes, you “need” a waterproof camera. Do you “have” to have one? Certainly not. I carry non-waterproof cameras in the stream all the time. But . . . and this is common sense . . . I put them in something waterproof, and often, shockproof. This might range from a ziplock bag to a camera-specific waterproof bag to a small waterproof hard case that slips into a vest pocket. The point being, if the camera you like best isn’t waterproof, don’t let that stop you from getting it. You can keep it safe with other means. The waterproof camera does give you more peace of mind, and it does allow you to take underwater photos, which can be really cool.
Are there any that you really need? Yes. First is a spare battery. I consider that an essential. Ditto a spare memory card, or better yet, several. They are virtually non-problematic, but if you have but one, and it fails, you’re SOL. They’re too inexpensive not to have several. A lens cleaning cloth. Use the one you have for your expensive sunglasses. A case. It doesn’t have to be elaborate. All you want to do is keep from scratching the viewfinder or lens (if that is exposed), and to keep dust out of the body and particularly off the sensor. That’s about it for the camera itself. At home, if the camera doesn’t come with it, you’ll want some photo manipulation software. You don’t have to shell out hundreds of bucks for the latest version of Photoshop, but you do want a basic software package that allows you to crop the image, maybe adjust the exposure and resize the image for screen viewing and e-mailing.
Remember how you hate it when your buddies send you fishing photos that are each several mb in size? Don’t return the favor. Learn to downsize images for easy transmission and viewing. You probably ought to get a separate card reader, if one doesn’t come with the camera. It’s nothing more than an adapter that holds your digital media card, and plugs into your PC’s USB port for copying over to the hard drive. They are cheap, usually quicker than copying files directly from the camera, and don’t wear down the camera’s battery.
If the DSLRs are too large, expensive or complex for you, and the P&S models lacking, consider the 4/3 models. These typically have interchangeable lenses, like the DSLR, but have only LCDs (no viewfinder or prism) like the P&S models.
They are slightly larger than most P&S models, but notably smaller than DSLRs. The sensor is mid-sized as well, giving image files larger and generally better than in a P&S, and edging toward those in a DSLR. They are mid-priced as well. Examples include the Panasonic Lumix GF1 or the Olympus E-P1. If I had to pick a P&S camera, what would I consider an optimal feature set? I’d like a small one. Already having larger DSLR cameras and lenses, which are big and heavy, size and weight are important to me.
So I’d like a pocketable P&S. I’d like to have raw image capture, again like the DSLR, but that’s not a deal killer, as long as the camera captures large JPEG files. I’d like the camera to capture reasonably high quality images (low digital noise, equivalent to grain in film cameras) at ISOs (film speed) of 400 to 800, which will allow me to still get those late afternoon shots. I’d like a lens that zooms to at least 28mm (35mm equiv). I fish a lot from boats, and as said earlier, those only let you get so far away from the subject. On the long end, 200mm would be OK, if the maximum aperture (f/stop) isn’t compromised too much.
Otherwise, I can live with 100mm or so. I’d like that optical viewfinder, but can live with just the LCD screen. There are other “like to haves” but those are about the only necessities for me. Again, I didn’t mention waterproofing as a necessity. It’s not for me, but might be for you.
I’d check with dealers, web sites I trust, and friends for recommendations. And then I’d check for the price. I’d hope the camera performed as I expected. If it didn’t, by golly, I’d sell it and get another. The perfect P&S camera for me, and although it might be different, for you, is out there.