Rule of thumb: By 2 of the largest cards you can afford. You wont go wrong and it will almost always be more then you think you would need, but you will always want a spare because you will always need it.
Now, I am going to tackle memory cards another day, so I don't want to really get into that - other then to make the point... again.. size matters.
So we left off yesterday talking about size of sensor chips. I told you it would pay off to figure out what you have, because today we are going to talk about how they effect your prints, and that digital Zoom.
Lets take the easiest first.
Turn it off. You don't want it. You don't need it. Manufacturers are not doing you any favors by giving you this option.
Well... you own a computer right? If you have prints made you do them online or take them someplace with a printer like a One Hour or Pro Photo lab right?
Any cropping you want is done, better, cleaner and more effectively with ANY basic computer or digital printer then with your CAMERA. Yep. It's true... digital zoom is making your sensor do the cropping for you and without good software, it really isn't designed to do that. Besides, if you want to zoom in on something that you can't physically get to with your optical (thats your real camera lens) zoom, chances are you will need to do other editing to the image as well! You should do it where you have the most control... like a photoshop program and save yourself the digital zoom headaches.
Optical zoom, is your physical lens on your camera. Digital Zoom is your camera "brain" cutting the captured image. Yep... your cutting away your prized megapixels as well... reducing the image size you can print... simply by not knowing better. Just turn it off (check your menu options) and make the commitment to only using your optical zoom! You will be happy you did!
Next. Sensor size and Printing
Sensor Size can effect your print images in 2 ways. The first is a direct reflection of larger size + more information = better quality, sharper images, and being able to print larger. (Or crop in closer to any one area without losing quality!)
This is no different then the thoery behind why 110 film sucked and large/meduim format cameras were the cream of the crop for professionals... 110 film was super small and didn't have the room to store a lot of information being roughly the size of my pinky nail where Meduim and Large format negatives are roughly the size of the palm of your hand. They could store a lot more information and capture light and details better. They also could be blown up larger, and without "graininess" or what you would call a pixel in digital - because they were simply larger to start with. Same thing in the digital world as far as bigger being better.... and for the some of the same reasons... now there are more having to do with how they are made differently.. but for our purposes... were going to leave it at that.
The other way different sensors effect your prints has to do with the SHAPE of your sensor. Take a look at the shapes below on our sensor chart.
Your standard iphone, and point and shoot cameras are more square then rectangle - right?
Now here is a chart for your print sizes...
Notice that your common prints 4x6 and 5x7s are more rectangle then they are square? So what does this mean... basically.... if you have a point and shoot camera.... with a square sensor and you print 4x6 your going to crop your image from the top and bottom... Good to know ahead of time right? You want to know why many places started offering 4.5X6 prints - because they are FULL FRAME from point and shoot cameras (more square then rectangle) Nothing like shooting uncle Bob only to cut off his head every time... this means you want to take the time to check the cropping before you order prints - most places online or in store kiosks will do this - you just have to know about it - if it doesn't prompt you... ASK for help! It's a lot less time consuming then doing it via photoshop or something like that if your end result is just to print.
Note: You can compromise and always leave extra room at the top (when shooting horizontally) or on the sides when shooting vertically.
On the flip side, a 4x6 is considered Full Frame for most DSLR's, showing you everything edge to edge.
However, that also means you have to keep in mind that as you print larger and the print sizes get more square your now cropping side to side. So if you are shooting a group, you have to give yourself extra room shoulder to shoulder (or past the shoulders really) in order not to crop off a person....
I hope you can see why understanding your megapixels and knowing about the differences in sensor sizes is super important to you! You have to be aware what your camera's limitations are!
You always want your end print to be the result you want!!! Keeping in mind your sensor size, and quality will plays a big role in composition!