Wednesday, May 25, 2011

Yes size IS important!!

This time I am not going to be posting any photos in my photo blog. But this is a very important topic to cover. What I am going to talk about is the size of photos. We are going to talk pixels today. Pixel is short for picture element. Don't ask me where the x came from, I have no idea. I suppose it is not that important either. What is important is that a photograph is made up of a whole bunch of little dots. Each of these dots is a pixel. You can measure a photograph by the dimension of the number of pixels across by the number of pixels down. Multiply those two numbers and you have the megapixels of the photograph (so that is what a megapixel is - wow thought it was more complicated than that).

If you talk about a computer screen resolution you are talking pixels. So a screen might be 640 x 480 (0.3 megapixels) or 1024 x 768 (0.7 megapixels). When you talk about an HD television you will see either 720P or 1080P when they talk about resolution. The 720 or 1080 is telling you how many pixels top to bottom there are (technically scan lines but it is the same concept - well LCD panels - oh forget it.. we still have 720 pixels.. trust me). The photograph out of your camera is going to have much larger dimensions. If you go into your camera you should be able to actually adjust the image size that the camera will take. That adjusts the megapixels of the photograph because it is reducing or increasing the number of pixels across and down. The camera will usually tell you what the dimensions are.

Time at this point in the blog to skewer a sacred cow. Megapixels is one of the worst measurements for quality of a camera. What most people will tell you is that you need a lot of megapixels to be able to print the photo, especially if you are going to make a large print. I use the website SmugMug for purchasing photos and hosting them too. They do an awesome job making fantastic professional photos. They have a web page in the help section that tells the minimum resolution for different size prints. The minimum size for a 36 by 36 print (which I would consider a very large print - wink) is 2160 x 2160. Well if we multiply those two numbers together we get 4.6 megapixel! And an 8 by 10 only needs 750 x 935 or 0.7 megapixel! So you can get an extremely small photo printed quite large.

There is a good reason to shoot very large photos though. When you crop a photo you are removing pixels. So if you are shooting with a very short lens, like a 50mm, and cannot get very close then if you have a lot of pixels in the photo your final product from a crop will still be large. But if you are shooting nice and tight then you can reduce your image size and get more photos on the memory card (and on your hard drive). Think about this, every pixel takes up some size in the photo. The more pixels the larger the file and the more space it will take.

Talking about size, what about photos for the web? Remember that we talked about a computer screen being measured in pixels. When you look at the screens the sizes, even on the largest of screens, are fairly small in megapixel terms. Most wide screens are somewhere between 1200 and 1900 pixels across. So any photo that is larger than that needs to be downsized to fit on the screen. If we have a lot of pixels in a photo we have a very large file. If you take a large file and in the html code (in the settings for the picture in the web page editor) simply say to display it at a particular size it does not change the actual size of the file. It is only telling the browser to zoom out on the photo. So that very large file still needs to download to the computer. Ever wonder why some web pages take so crazy long to open? If they have a lot of photos it is probably that the photos are very large.

So how do we fix that? You need to resize the image. Use your favorite photo editor and find the image resize feature (I use Photoshop Elements). Many web pages limit the area that the page is actually using to either 800 pixels across or 1024 across. So if you resize proportionally and set the width to like 800 pixels then you will get a good size file. You will find that the file size moves down from the original 4 or 6 or 8 MB file to something around maybe 80 KB or 120 KB or something. A file that is much smaller and will load way faster. It will be a bit on the small side to print so you will want to save it as a separate file than the original, but you now have an awesome file for the web. You can also email it much easier to friends and family too!

To summarize, you don't need a ton of megapixels to get a good print. Pretty much all the cameras out today will give you more than enough size in the image. You can reduce the image size in your camera if your shots are nice and tight and you won't need to crop later. If you are going to put the photo on the web then resize it down to something between 800 and 1024 pixels wide. Always keep the original photo intact so that you can go back to it if you need... well you should always keep the original of good photos. You never know when you might need it.

Good shooting!!

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