I guess it’s more important sitting next to your friend who owns a lousy 8.2 MP camera that one can now brag that my camera is 23% bigger, better, etc. This, however, completely ignores the fact that the resolution of the camera is not 23% better. There are only 23% more pixels. The resolution, which accounts for sharpness and acuity of an image, is determined by the number of pixels in a row or column of the sensor while mega pixels are calculated by multiplying these two numbers. This makes the difference because if you want to double the sharpness of an image based on the pixels used you need 4 times the pixels.

Let’s do some math here to explain this fact. Both cameras contain a 3:2 format sensor.

EOS 30D: 3,504 x 2,336 = 8,185,344 px

EOS XTi: 3,888 x 2,592 = 10,077,696 px

Dividing the total pixel numbers leads to

10,077,696 / 8,185,344 = 1.2312

which shows the 23% increase in pixels I mentioned above.

To get the increase in resolution we need to either divide the number of pixels in a row or in a column, which leads to 1.1096. That’s only an 11% increase in resolution. Why is that so? Because we are working in a two dimensional space which leads to the square root. Take the square root out of 1.2312 and you get 1.1096.

Let’s consider one is buying this camera because the desire is to create prints larger than 8 x 10. With the pixel difference you can now go and print a 8.9 x 11 at the same resolution. I doubt that this is explained to customers when they buy such a camera. And if you print 4 x 6 this increase in pixels does not make a difference at all. Well, at least they can go home and say: mine has more than yours and thus must be better.

Often there is an argument that more pixels are good because this allows for cropping without loosing resolution. Applying the math from above only 10% cropping is possible without loosing resolution. I don’t know if that improvement really helps anyone.

Another issue often overlooked when talking about more pixels is the noise or grain. More pixels on the same size sensor mean smaller pixels. Smaller pixels are equivalent to more noise or grain. The noise goes up by 23% because statistically you have 23% more pixels which in turn reduces the likelyhood of a pixel being hit by a photon by 23%. That brings up the noise. From my point of view noise is much worse to deal with in an image than cropping and resolution problems. It’s really hard to reduce noise without reducing the acuity or sharpness of an image.

In terms of printing the 8.2 MP camera allows for a 11 x 17 print at a resolution of 206 dpi while the 10 MP camera brings this to 228 dpi. I doubt that anyone would notice the difference.

Removing the trays, they say, reduces food waste, conserves water and energy used in cleaning and reduces the need for polluting detergents. Looking further at the pictures in the article I noticed that the food is served on plastic plates. Without having evidence in the pictures I assume that drinks are served in plastic cups and there are plastic forks and knifes.

Lets analyze this situation a little further and have a look at the reduction of food waste. Food waste is probably the least problematic waste there is because it’s bio degradable. Our digestive system proves this fact on a daily basis. So what’s the real problem with food waste? The real problem is that food waste costs money in the cafeteria and that’s not good for business. First and foremost reducing food waste increases cafeteria profit. That’s not a bad thing in itself but it has nothing to do with going green. It’s good business practice. Using the trays as a vehicle to achieve this goal is not the smartest way but putting it down as going green makes a good case.

Conserving water and energy is not bad either. Isn’t that what we all want. But again I’m suspicious that this is driven by simple business calculation and not by going green. As I mentioned above, food is served on plastic which makes cleaning the trays the only part which requires a commercial dishwasher and manual labor. That’s money right there. But there are many studies showing that it is more beneficial to the environment to use real plates and silverware and wash them than to create tons of waste of plastic dining utensils. Thus, keeping the trays and removing the plastic dinnerware would have been the right choice of going green. But this decision would have required an investment without an immediate gratification.

Last but not least there are the polluting detergents. Again, studies show that a full [emphasis on full] dishwasher uses less energy and water than handwashing dishes. There are biodegradable detergents that are environmentally safe. But again that’s not a simple change. It’s easier to remove the trays being the last piece that requires a dishwasher, get rid of the dishwasher and put it all in a green perspective.

While I do believe that the Toyota Prius and other hybrids are an excellent idea, I do have my concerns about those new developments where companies try to market hybrids that hook up to an electrical outlet. Lets get the frame of reference clear. The underlying idea of a hybrid car is to preserve fossil energy by using less of it while driving the car.

The technology of hybrid cars allows the potential energy stored in the moving car to recharge batteries while breaking. Usually when we slow down a car using its brakes, the energy silently disappears as heat created by the break pads and shoes rubbing on a metal disk or drum. Instead of dissipating this energy into the environment we use an electrical generator coupled to the drive train charging the batteries which slows down the vehicle and in addition saves us the wear and tear on the break pads. That’s almost perfect recycling. It’s important to understand the whole concept about where the energy goes while driving a car.

Traveling on a level road with no head wind etc. needs the least energy possible. The other energy consuming items to consider are: roll resistance of tires, friction in the gearbox and the drive train, the overall efficiency of the engine, wind resistance, and most important – acceleration and deceleration.

This is all very technical but a necessary evil to get it all straight. In stop and go traffic e.g. during a daily commute there is a lot of acceleration and deceleration, or to put it different, breaking. Since there is not much we can do about friction and roll resistance of our tires we can work on speeding up and slowing down the car. Now we have a little bit of a chicken – egg problem because the batteries need to be charged in the first place to run the electro motor but they only get charged when we slow down the car using its potential energy.

Well let’s assume we have charged the batteries somehow and now we start the car. During acceleration both the gas engine and the electro motor provide torque to accelerate. That saves energy on the gasoline side. The faster we accelerate a car the more gas it takes because the energy needed to get a mass from 0 to 60 mph in 5 sec is much higher than the energy needed to arrive at the same velocity in 10 sec. Traveling at constant 60 mph would cost no energy if we wouldn’t have to deal with wind resistance, roll resistance, friction, etc. Since these factors are small compared to the energy it takes to accelerate, you can see your mpg gage go down once we are traveling at a constant speed. Arriving at a read traffic light we need to stop the car. Now we use the electric motor as a generator to convert the potential energy stored in the moving vehicle into electricity. While the generator is charging the batteries it creates a negative torque that in turn slows down the car. The torque itself depends on how much energy you try to pump back into the batteries. This allows to control the break force. In theory all the energy we put into the car while accelerating is now put back into the batteries while decelerating. That’s how it works. We loose some energy due to inefficiencies but we gain a lot by using the energy stored in a moving car. So much about how a hybrid car works.

We see that the trick is to reuse the energy we put into the car at the beginning instead of dissipating it as heat into the environment.

Now let’s have a look at the overall energy equation of a rechargeable car. Here we use power coming from an outlet to charge the batteries. But where does that power come from? It comes from a power plant that is either fired by coal, gas, or nuclear fuel. All three are non renewable energy sources. That means we just use a different energy source than gas which is not any better in terms of preserving our resources. Looking at the overall energy conversion efficiency from coal to heat to electricity it’s probably worse than a combustion engine. Don’t get me wrong, the conversion from electricity to mechanical energy using an electro motor is pretty good. Somewhere around 90%. But the conversion from coal to steam and then to electricity is only about 40% efficient. The point is that using rechargeable hybrids only moves the problem from one end to the other.

Considering millions of these cars on our roads the electrical power consumption would go up dramatically. Since the power companies suggest to charge your car over night this is a good deal for them because that’s when the load on the grid is low meaning they can improve there economy of generating power. But this also increases the use of fossil energy sources. We reduce the demand for gasoline but we increase the demand for coal and gas. The way this is sold is that at current electricity rates a full charge of the car costs somewhere between 50 cents and a dollar. The car runs 100 to 150 miles and the math shows that’s cheaper than buying gas. However, it’s only cheaper because the power companies buy their energy such as coal at a much lower rate because they buy in such large quantities. Looking only at dollars rechargeable cars are better. Looking at the overall energy balance sheet, there is nothing gained, at least not for our children.

]]> http://www.notion360.com/?feed=rss2&p=4 0