Image Size and Your Camera: What are the best settings for me?

The Megapixels Craze

One of the most known features of Digital Cameras today is the amount of Megapixels (MP) you have. Megapixels ultimately decide the maximum picture size you can take, but what is most commonly overlooked is exactly how many Megapixels is adequate for the what you are doing. If your main reason for having a digital camera is for conventional use it is important to note that for printing on a standard 4x6 sheet, a 1 MP camera can produce Photo Quality results. The following chart shows various Megapixel sizes and the corresponding print sizes and the quality of picture.

 

Fig. 1: http://www.bhphotovideo.com/bnh/controller/home?O=getpage.jsp&A=getpage&Q=Product_Resources/resolution_chart.jsp

But what if you aren't planning to print these pictures? The dental images that are being importing into ChairSide Imaging (CSI) don't need to be 3032x2008 pixels (6 MP). Take a look the resolution on your computer monitor. Typically computers have a resolution set or 800x600 or 1024x100% pixels. If we keep that in mind, anything bigger than 1 MP has to be compressed in order to fit properly on your computer screen. However, you still want to take a larger picture so you have more to work with. Shown in Fig 2 are a 3 MP and 6 MP photograph in CSI with a 5x magnify produces nearly identical results with an image that is half its size

3 Megapixels

6 Megapixels

 

As you can see, the pixilation that is evident in the 3 MP photo is minimal in comparison to the image being edited in the 6 MP picture. 

Image and Quality: RAW or JPEG?

In addition to image size, there are various settings on digital cameras for image quality. The varying factor between these types of files is essentially the amount of compression applied. Uncompressed formats such as BMP and TIFF keep all of the original images quality, but is accompanied by extremely large file sizes.  However JPG files (the more standard type) are what is known as "lossy" files. Meaning that with its compression it can create an image with file sizes that are significantly smaller than that of a BMP or TIFF, but, in turn, you may start to notice a change in quality between the JPG file and the original picture.

The way that a JPG works is that blocks of pixels are selected and reduced in quality; as you get higher in compression these blocks become more visible and loss of detail can be noticed. In spite of this, with the right image size and an adequate amount of compression the loss of detail is virtually unnoticeable unless you are blowing up the picture to incredibly large sizes.

Fine

Normal

Fig 3: Quality Comparison

*please note downloading the images can take a long time on slower connection speed

The above picture depicts two images taken by a 6 MP camera. For one picture the normal JPG compression rate was used and for the other the fine compression rate is used. If you click on these images to enlarge them you will notice that there is very little to no image quality loss, but yet the image size of the normal picture is less than half than that of the fine.

Performance: Speeding up the Transfer Process

We have compared the sizes and the quality of various photos, but how does this affect the way my software performs? It's simple. Taking oversized, large images takes longer to import and edit in CSI (and any other software). A large uncompressed image can take up to 5 seconds per picture as opposed to almost instantaneously loading its JPEG counter-part. As a test we took 12 of each of the slightly compressed images in Fig. 3 and compared how long it took to import the files into CSI.

6MP Fine Quality Image

10.5 Second Image Preview

18 Second Import

6MP Normal Quality Image

6.5 Second Image Preview

12 Second Import

3MP Fine Quality Image

5.5 Second Image Preview

10.5 Second Import

3MP Normal Quality Image

5 Second Image Preview

7 Second Import

Importing the 6MP Fine Quality Images by far takes longer to load and import into CSI, especially compared to the visually comparable 3MP Normal Quality Images. If you base this trial on the constant importing of images that is done throughout a given day in the office, this adds up to a lot of time that is being wasted on pictures that will never be used up to their full potential.

Conclusion

Based on the comparisons we can say that a general rule of thumb when taking Digital Images is to choose the image size and amount of compression to meet these needs and capture at the least possible compression. The whole point is that you want to be able to take a picture that you can work with without any quality loss, but at the same time keeping it minimal in load times.

 
   

Quality

   

Basic

Normal

Fine

Megapixels

 1.5

 3.3

 6.1

Fig 4: Quality x Size Comparison

The above example shows pictures taken with a Nikon D70S while changing its various settings and Megapixels size. From our testing we suggest that the 3MP picture in its 'Normal' setting is the picture will give you a great picture with limitless potential while keeping the file size down to a workable low of less than 1 MB. With this picture you can do major amounts of editing and magnifying in CSI with very little to no distortion in the picture itself.

For more information on buying a Digital Camera for your office, visit Digital Photography for our suggested choices as well as tips on what you should look for when shopping for your camera.

Although we have our recommendation of the size and quality picture to take, it is still important that you explore the settings that your camera has that will enable you to take brilliant pictures at more convenient and workable sizes. Remember, bigger is not always better!

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