18-200 Image Quality Diagram

Started Jan 24, 2007 | Discussions thread
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Mach Schnell
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18-200 Image Quality Diagram
Jan 24, 2007

Over the last few days I have assembled what I believe to be a useful diagram to describe the image quality attainable from the 18-200VR. Information was gleaned from sources such as slrgear.com, among others. Here is the diagram:

My intent here is to easily communicate the zones in which the 18-200 is able to create the best possible image. In this case, it is the areas of pink where the image quality is less than a value of 2. Note that the old photographer addage "f/8 and be there" seems to apply with this lens. The very sharpest overall is at 48mm and f/8.

I also included a hyperfocal table. If you are not familiar with this term, hyperfocal is a method for achieving sharp focus on everything within the frame. It is best illustrated with an example. Let's say you have a beautiful landscape in front of you and the best crop for your composition is at 26mm in focal length. You want as much in focus as possible without compromising image quality, so you set your f/stop to f/16. If you intersect 26mm with f/16 on the diagram you will see that the hyperfocal distance is 6 feet 0 inches. Focus your lens to exactly 6 feet and you are set. Most lenses don't include useful focus distances anymore so you might need to use a measuring tape to determine where 6 feet in front of you is precisely. Now everything from 3 feet to infinity will be in focus. Why 3 feet? Because the near focus limit is half the distance of the hyperfocal distance.

I hope you find this useful. Feedback is welcome. I'm thinking of doing this for a few other zooms as well. Let me know what you think.
--
Steve

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