Glassmine Falls(?)

Posted on 08/05/2016 by Dave

The viewing area for Glassmine Falls is located at milepost 361.2 on the Blue Ridge Pkwy. in North Carolina. The falls themselves are located in the Asheville watershed area and thus cannot be approached. The distance to the falls is considerable, and the image to the left was taken using a 560 mm focal length lens set up. I visited this location on July 30,

Glassmine Falls

Glassmine Falls

shortly after noon. As can be seen, there is not a drop of water running across the cliff face. When the falls are running they enter from the upper left corner of the picture and run down across the center. They are said to be 800 feet tall, but apparently there is some dispute about this. Others claim the falls are only 200 feet tall. In any event, only a small for portion can be viewed. The moral of the story is, if you plan to visit, be sure to check rainfall amounts in the region to insure that water will be flowing.

 

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Greenville, SC – Falls Park

Posted on 07/22/2016 by Dave

Among the many things that drew me to Greenville, SC are the waterfalls in Falls Park on the Reedy River. They are said to be the largest in-town waterfall east of the Mississippi. They are easily viewed from the spectacular 344 foot Liberty Bridge that is suspended in the rear, providing an unobstructed view of the falls for its full-length.

Falls at Falls Park - Greenville, SC

If you would like to see more about Greenville, go here.  If you would like to see more waterfalls, go here.

 

 

 

 

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Optimum Aperture?

Posted on 07/22/2016 by Dave

For a long time now the conventional wisdom to help obtain maximum image sharpness has been to stop the lens down to its optimum aperture, usually two stops from maximum (wide open). However, this is not true in every case. After acquiring the recently released Canon 100-400 mm F4 .5-5.6 II lens, I ran some tests using Reikan FoCal Pro software to optimize the autofocus microadjustment in my Canon 5D III camera. While I was at it, I also ran their sharpness versus Aperture test. Here are some of the results:

Apeture Test

 

 

 

 

 

 

 

 

For comparison, I tested the much older Canon 300 mm F-4.0 autofocus lens. As can be seen, it follows the conventional rule.

Arpeture Tests

 

 

 

 

 

 

 

 

Several things are evident here. 1./some of the newer lenses are much sharper wide open than they used to be. 2./although the focus quality of the Canon 300 mm F-4.0 lens follows the  old rule perfectly, . The jerkiness of the trace suggests that the auto-focus repeat-ability of at least this older lens is not as good as shown by the smoothness of the 100-400 mm curve. It is indeed nice to see progress.

 

 

 

 

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Optimum Aperture Revisited

Posted on 07/18/2016 by Dave

Confirming our earlier observation that the old “close-down two stops for optimum aperture (sharpest image)” dictum didn’t necessarily hold for current lens designs, here are the results for the Canon 17 mm tilt shift lens. Not only is this lens sharpest wide-open, note that the image quality is substantially higher than that of the two lenses reviewed in the post, Optimum Aperture? .Canon TS-E17mm F4.0 Camera Lens

 

 

 

 

 

 

 

Unless there is subject matter  that is very close to the lens, depth of field is usually not a major concern – especially with a 17 mm lens.  Therefore, in most cases, setting the focus at one third of the distance into the subject field and  shooting  either wide open or a third stop down will yield both  maximum image depth of field for the selected aperture at the highest  possible image sharpness.

 

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