Some people eat, sleep and chew gum, I do genealogy and write...

Monday, February 18, 2013

Buying a camera -- some additional thoughts

Resolution is a bugaboo. Camera manufacturers tout their megapixels as if the higher megapixel count really gave you automatically better image quality. It reminds me of the car manufacturers and horsepower. The newest Bentley Continental GT Speed is advertised at 616 horsepower and supposedly can go 205 mph. So you are going to drive this car on an Arizona freeway? Exactly where are you going to go 205 mph? In fact, I am not aware, outside of race tracks, anywhere in the U.S. you can drive over 100 mph without picking up a few friends with flashing lights. Unfortunately, except for the flashing lights, the analogy with extreme pixel count is valid.

Let's face it. Human eyes have a visual limit. In clear language that means that no matter how many pixels or megapixels a camera sensor has, once the camera exceeds human visual acuity, the additional resolution is wasted. What you do get is physically larger and larger images at the theoretical limit of visual acuity. I could get very technical here, but basically, there is a limit to the ability of the human eye, any human eye, to resolve detail. For practical purposes, that resolution, in computer terms, is about 300 dpi or so.

Once a camera system reaches the theoretical resolution of the human eye, any additional resolution will simply allow the image to be enlarged. There are tables online that compare the megapixel setting to the size of the photographic print. So how do you get more resolution from your camera? To a great extent, as I wrote in a recent post, the quality of the image depends primarily on the quality of the lens. If you want really high quality photos, you need really high quality lenses. In this case, read more expensive. For example, both Canon and Nikon have three levels of lenses for their DSLR (digital single lens reflex) cameras; a consumer level, a prosumer level and a professional level. Guess which ones are the most expensive.

When you buy an inexpensive camera, you will get an inexpensive lens system. End of story. But wait, that isn't the end of the story. What has happened is that less expensive cameras have evolved with higher and higher quality. Today's cheap cameras have high resolution sensors and adequate lenses.

So what else is important to image quality. It turns out that there is one more simple factor: the physical size of the sensor irrespective of the number of pixels. Professional cameras have "full frame" sensors that are considerably larger than point-and-shot varieties. A full-frame sensor is roughly equivalent to the resolution of 35mm film. There are cameras with even larger sensors but they cost more than consumers want to pay. Rather than make one huge sensor, manufacturers have resorted to using multiple sensors to achieve really high resolution images. In essence, you take a series of high resolution images and combine them with computer software into one huge image. These photos are called gigapixel images.

What does all this mean to a genealogist who doesn't want to become a professional photographer? Not a whole lot. In the end, you go to a store that sells cameras, you pick them up and get one that feels right and then do some looking online for reviews and make you decision based on how much you want to pay. If I went into any store selling cameras, say Walmart or Best Buy, and simply purchased the first camera that caught my eye, I would get a reasonably good camera. But if I do my homework, I might be able to get a really good camera for the same price.

But once you get out of the consumer area of cameras, the prices are not flexible. There are no discounts to speak of and the equipment starts to cost real money. I suggest that before you spend more than $1000 on a camera, you just might want to make sure you know what you are doing. It doesn't do you any good to buy and expensive camera is you don't know how to use it or understand what makes it expensive.

1 comment:

  1. Interesting article. I would like to add that it also depends greatly on what you intend to do. A good camera to make pictures of family houses and heirlooms sets different requirements than a camera for photographing manuscripts.

    For example, I specifically chose my camera (a Canon EOS 550D) because it has a relatively high resolution, large ISO range and remote-shooting capabilities. With this camera, I can set up a tripod and photograph an open manuscript (left + right page) in one shot and even double legal size pages are still very readable. I have my camera connected to my computer, so I can operate the shutter using my space bar. I operate the spacebar with one hand while turning the pages with the other hand. With this setup, I can easily take 5000 photos, or 10000 pages, per day.

    Because most archives do not allow you to use flash, you have to be aware of the light sensitivity of your lens and the ISO range of your camera. Higher ISO values means more sensitivity to light, but also a more grainy image. Ideally, you want a light sensitive lens so you don't need to crank up the ISO. But sometimes lighting conditions are so poor that you will not have another option than to turn up the ISO so that's something to look for because that's in the body of the camera and not in the lens (which you can always upgrade).