Sunday, May 8, 2011

I thought my flyfishing camera was broken, and why 3 megapixels is enough

The Souhegan River on Friday

On Friday I took my first outing of the season. (Yes, I did catch trout: two rather blah looking stocked rainbows, about 9 and 12 inches.)

But before starting out I had to get my gear together, never an easy task when it's your first time fishing in 6 or 7 months. Fortunately I keep (nearly) all of my gear in one huge duffel bag. Nevertheless I dumped everything and spread it out on a bed.

Like many others I am sure, the next step in getting organized is to go through a mental checklist of everything needed for a day on the water. I always start with my feet and work my way up my body. Boot, yes. Socks, yes. Long underwear, yes. Neoprene waders, yes. Wading belt (with staff attached), yes.... etc. When I get the vest, I look in each pocket to be sure everything is there. These pockets are filled with the same stuff for each outing whether it be for smallmouth bass or trout, so I have a high likelihood of having everything I need. The only exception is my old 3.2 megapixel Pentax digital water resistant camera... it needs two fresh AA batteries from time to time.

Well, I took two AA's out of my desk drawer. I knew they were new, as I had just bought a 20-pack at Staples. But, when I plunked the batteries correctly into the camera and I turned it on, nothing happened. My heart sank. I opened the battery compartment and reinserted the batteries in exactly the same manner. Thankfully, this time it lit up and made a couple of "I'm ready" beeps.

I realized how old this camera is when I went into the menu to input the correct date and time, and saw the date choices starting with the year 2003! And of course a 1.5" screen and "only" 3.2 megapixels also suggests its old age (for a digital camera).

About megapixels: Almost always 3 MEGAPIXELS IS ENOUGH.

Let me explain. Ninety-nine percent of all point and shoot cameras have a sensor about 4.5mm x 6mm in size. The sensor is the digital equivalent of film. It collects the light that enters the camera body through the lens. The light is channeled onto a honeycomb of pixels (except pixels are generally square and not hexagonal) that cover the surface of the sensor, and from there software uses the information collected in each pixel to create the image. This camera has a grid of pixels that measure 2048x1536 pixels = 3,145,728 pixels = 3.2 million pixels = 3.2 megapixels.

So, how many pixels do you need? Well, the marketing departments of the camera companies seem to think that answer is about 12-16 megapixels. But that's too many. Here' why.

For viewing images on your high def television (1920 x 1080 pixels) or 24" computer monitor (mine has a resolution of 1800 x 1200), 2 megapixels is enough. Just multiply those numbers and you will find that the area is about 2 million pixels.  If your original image has more than that, it has to be downsized to fit. With a 12mp image, for example, software will squish 6 pixels into 1 pixel (in other words 12mp squeezed into 2).

Here's another example. The pictures on this blog must fit into a box that measures 650 x 650 pixels. That is approximately 4/10th of 1mp! Again, any image bigger than that has to be downsized.

But what about prints? Anywhere between 200 and 300 dots per inch looks great. At 200 dots per inch an image of 2048 x 1536 will make an excellent 10" x7.5" print. The image below was made into a 9" x 12" print and submitted into my photo club's monthly competition.  The print was sharp and full of color.  The judge liked especially the orange reflection in the water. The fact that it scored a reasonable but not great 26 out of a possible 30 points had nothing to do with the camera.

Many experts believe that optimal for these small sensors is 6mp. Why not more? Because as you cram in more pixels they each must get smaller. And this makes collecting light more difficult. Technological advances have helped, but the result of cramming in so many pixels is that taking pictures in low light conditions becomes difficult and the result is grainy looking images. The image quality on many older cameras with fewer megapixels is better than the image quality on many newer cameras with more megapixels. Unfortunately, the older cameras lack many of the cool features we find on the newest models; such as, image stabilization, 3" monitors, better handling, GPS, high def video, and speedy performance.

On the other hand, if you make prints bigger than 12"x9" then more pixels will help.

No comments: