Guide Number
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 Holga 12MQ Electronic Quick Hot Shoe Flash Guide Number of 40 287120  US $13.99
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How Do GPS Units Guide Us?
GPS units may seem kind of on the pricey side at first glance, but if you take the time to understand how they work, it helps to make the cost more fair in your mind. These days it is quite common to find GPS systems as standard features in the newest model automobiles as well as personal items such as PDAs and cell phones. Even Amazon's new Kindle ebook viewer has a simple GPS application included. This article will explain in words that a regular person can understand how GPS systems operate. Complete technical details can be retrieved in other articles posted on the Internet.
Here We Go
Did you know that there are approximately 2500 satellites currently revolving around the globe? Quite a large percentage of them are global positioning satellites. Yet only 36 of them are actually still in operation with many others having been retired. These satellites transmit a consistent low-power signal which is picked up by GPS receivers such as the unit in your auto. By accurately measuring the distance from three of these satellites, the global positioning system can compute its exact position on earth.
When their solar power panels are completely unfolded, a GPS satellite can be about seventeen feet wide. Yep, they work on solar power and also have backup batteries installed for use when solar isn't available. They are constructed to last ten years (knock on wood). The longest working satellite is from 1978. That one goes around telling all the younger GPS satellites how hard it was in his day and how lucky the younger ones have it. Just kidding!
But Seriously
Earlier I talked a little about GPS receivers. So what are they exactly? Any electronic device that is able to receive signals transmitted by the GPS satellites is a GPS receiver. Today they can be seen everywhere: from the cruise ship to Alaska that your boss took recently to the new Navigon 7100 GPS in your neighbor's automobile. Portable GPS systems for public use are averaging out around $300, give or take a little. Considering you didn’t have to invest anything to design, build and launch the satellite into space, $300 is a very conservative price.
The US government is responsible for paying the costs involved in fabricating and launching satellites into orbit.|Our government here in the US has decided to take on the costs needed in creating this network of GPS satellites. All you have to do is turn on your GPS system in order to make use of the information that is freely transmitted by them. Hopefully now you have a better understanding of how your GPS system works the next time you power it on.
Higher Guide Number = Better Flash?
I'm looking to buy a decent flash and I currently own a Nikon D90.
What does the Guide Number indicate, and is a higher number better?
What flashes would you recommend, and why?
I'll consider third party flashes, such as Sigma.
Higher guide number only tells you that it's more powerful. Read up on flash guide number to learn more about it. It may or may not be "better", depends on whether you need more flash power.
I have a friend, who's using a Sony Alpha. He needed a flash but can't afford original Sony flash, so he came to me for advice (Real story, more than a year ago though).
Since I don't know anything about Sony Alpha system back then, I just check out flash speficiation on paper and say which one "probably" have the best value, so he ended up with a Sigma.
Problem is, we got it online, and there isn't a product shot from the back of the unit, so basically the flash only works in full auto and can't control it manually, maybe, not too sure. But problem is that it breaks down in 3 months, and the warranty claim took forever, until he gave it up and bought a Nissin brand flash, and it's working ever since.
Maybe that Sigma is a lemon, maybe not, but if it does, seems like Sigma's poor QC extends to even their flash unit...
You can try to get it, but then that's my (and my friend's) experience. Risk is always somewhat higher with Sigma.
A guide to whether you should fix or pitch your appliances and gadgets (Minneapolis Star Tribune)
A couple of things will keep your appliances and gadgets out of the (dwindling
number of) repair shops: Buy wisely and read the manual.
Advanced Macro Tutorial!
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