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Please Help Me Understand Image Basics

by michael.cox / May 5, 2006 6:36 AM PDT

I'm struggling to understand how image size and image quality relate. I have a 7.1mb point and shoot. I want to produce the highest quality photos that will be less than 4 x 6".

Why are there sizes of resolution? Is a "Large" at 3072 x 2304 actually larger(in height and width) on a computer moniter than a "Small" at 640 x 480? Or are all the images all the same size(in height and width) raw from the camera and the different settings refer to how much data is stored in each file?

What does quality mean? Is it a way to further control file size within each resolution size mode?

If I want to create a high quality 2"x3" image, I would use the "Large" resolution at "Superfine" quality to benefit from all 7.1mb? If I want to create a high quality 8"x10", I would use the same, right?


The chart I'm referencing is a little more than half way down the following page...

http://www.dcresource.com/reviews/canon/powershot_a620-review/index.shtml

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Pixels
by snapshot2 Forum moderator / May 5, 2006 8:16 AM PDT

Image quality has more to do with;
How sharp is the lens,
How true are the colors,
How good is the exposure,
The talent of the photographer.

Megapixels relate to the amount of detail in the image.
A small photo does not need as much detail.

................................

The quality settings ("normal" "fine" "superfine") shown in the chart are about the amount of compression that is applied to a .jpg image.

For the best quality, set it to superfine and leave it there. The only reason to use one of the other settings is to crowd more photos onto a memory card.

Leave it set to superfine and buy more memory cards.

.........

I ran across a site that has a good write-up about the mathmatics of photography.

See if it helps:

http://www.shortcourses.com/pixels/index.htm

...
..
.

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Thanks
by michael.cox / May 6, 2006 11:08 PM PDT
In reply to: Pixels

Thank you

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There are sizes of resolution because...
by hfguide / May 7, 2006 12:34 AM PDT

...these *are* digital cameras, after all-- not just for print but for computer use. Wink So yes, a 640x480 picture will be 640x480 on your monitor. A 3072x2304 picture will be 3072x2304 on your monitor. And no, there's no difference in picture quality when it comes to merely viewing these pics onscreen just because of a difference in pixel size.

Quality only becomes an issue when you want to start printing these pictures. You see, each resolution on your camera *also* corresponds to an amount of megapixel, what people use to determine how large an image they want to capture in terms of print size. A 640X480 resolution is 1MP. The largest setting you have on your camera (''large'' --3072x2304), I assume is the largest MP setting your camera can take a picture at (7.1MP). The other rezzes on your camera correspond to various other MPs... For example, the 2048x1536 setting on your camera is 3MP.)

The higher the picture size in terms of MP, the more information it packs, and the larger size you can print it out to without losing quality. So it's all about maximum print sizes with MP's, not picture quality. A 7.1 MP image and a 4MP image will both yield you the same high quality print at 4x5; however, that would change if you tried to print larger than 5x7 . The 4MP would start looking pixely, but the 7.1 would still look good.

You can read more about this here--> http://www.microsoft.com/windowsxp/using/digitalphotography/learnmore/bestquality.mspx It contains a guideline about what MP you can take your pictures at according to print size. It seems that you can take your pictures at 2MP [according to the site], since all you want to print out to is 2x3. To shoot higher than 3MP is pointless and won't yield you better prints.

As for *fine* and *superfine*, I don't know much about your camera. However, I'm guessing that these settings have to do with image compression if you are taking pictures for the web or want to sacrifice a little quality to pack a few more pictures onto your memory card.

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