Photo of the Week - May 26, 2012

Garden Spider spiderlings on a Spider Sculpture
Araneus diadematus
Olympia, WA
May 26, 2012
On Memorial Day Weekend, I was lucky enough to see a group of newly hatched spiderlings in my yard.

When I originally saw them, dozens of baby spiders were clustered in a mass about 2 inches by one half inch. Alarmed by the closing of the gate, they quickly dispersed over an area of one foot or more - tiny yellow and black creatures scurrying for safety. They regrouped after about 5 minutes.

During the day Saturday, I took about 60 shots of the spiderlings from different angles and distances, trying to tell the story of their tiny size and large quantity. Without a frame of reference, it was pretty difficult to get a sense of scale and detail, too.

On Sunday morning, I went out in the yard to check on the spiders again. Imagine my surprise and great pleasure when I found that they had migrated several feet to a metal spider in spider web! I quickly grabbed my camera and shot multiple photos as they moved around. The body of the spider is about 1 and 1/2 inches tall.

Detail of the photo above
at full resolution
Spiderlings in a cluster
They will scatter as a defensive measure if scared.
A great explanation of spiderling balls from Bug Blog

Photo of the Week - May 21, 2012

Pathway of Tread Worn Roots
Kubota Garden
Seattle, WA
May 21, 2012

Photo of the Week - May 17, 2012

Spotted Towhee with mouth full of Bugs
Pipilo maculatus
Olympia, WA
May 17, 2012

Photo of the Week - May 15, 2012

Blue Camas
Camassia quamash
Mima Mounds, Thurston County, WA
May 15, 2012

South of Olympia lies some of the last remaining native prairie habitat in South Puget Sound. This landscape marks the southern end of the last glaciers to cover the region (about 15,000 years ago).

Two outstanding features make it worth a visit to this area - the Mima Mounds and the abundant wildflowers.

The Mima Mounds are dome-shaped mounds of rock and soil, covered with grasses. The mounds range from 8 to 12 feet in diameter and can be up to 7 feet tall. The mounds are close to one another, separated by wide swales. There are various theories for the origination of the mounds, from glacial melting and erosion to giant rodents. While no one knows the actual cause of the mounds, they are a wonder to behold. Washington State DNR runs the Mima Mounds Natural Area Preserve, a 637 acre site with walking trails and interpretive exhibits. It is open year round. Thurston County's Black River-Mima Prairie Glacial Heritage Preserve is open annually on Prairie Appreciation Day, which occurs in Early May.

In the early Spring, visit the Mima Mounds to see the native wildflowers. Blue Camas abound. One can also see White Camas, Shooting Stars, Violets, Balsamroot, and native Garry oak.

Washington State DNR Mima Mounds website

Photo of the Week - May 14, 2012

Skateboarder
Jefferson Park
Beacon Hill, Seattle, WA
May 14, 2012

Photo of the Week - May 7, 2012


Long-Tailed Weasel
Mustela frenata

Black Lake Meadows
Olympia, WA
May 7, 2012


Comparison of photos at different f-stops

All of the photos were taken with a
Canon 30D with Canon 100mm f/2.8 macro lens
on a tripod in bright sun.

The camera was about 1 foot from the subject
and 1.75 feet from the bleeding hearts in the background




Depth of Field and Sharpness

For many photographers, depth of field and sharpness are synonyms. Although they share many characteristics the two concepts are not the same.

Depth of Field describes the range of an image which appears to be in focus. Lenses can focus on one distance for each shot. A photo taken with a wide, low-numbered aperture, such as f/2.8, will have a narrow range in front and in back of the focus point which appears to be in focus. The same photo, taken with a small, high-numbered aperture, such as f/22, will appear to be in focus over a much greater range. Several factors, including sensor size and focal length will determine the actual depth of field.

An example: a photo taken from 10 feet with my Canon 30D and 100mm f/2.8 lens

  • at f/2.8 depth of field would be from 9.84 to 10.2 feet. Less than .5 feet would appear in focus.
  • at f/22 the apparent focus would be from 8.9 to 11.5 feet. The depth of field would be 5x greater - over 2.5 feet!
By experimenting with different f-stops at different distances, a photographer can make more or less of an image 'appear to be in focus'.

Photo with shallow Depth of Field
Photo with large Depth of Field

Sharpness is the crispness of an image at its focus point. Sharpness is best evaluated by zooming in on an image on your monitor or by examining a high quality print closely.

An image with shallow depth of field can be very sharp.

Shallow Depth of Field example
Zoomed to 100% actual pixels
An image with great depth of field isn't necessarily sharper than one with shallow depth of field.
Some factors contributing to lack of sharpness:
  • camera shake
  • subject movement
  • 'mirror slap'
  • digital noise
  • optics
Camera shake:
A wide, low-numbered aperture will take less time to make a photo than a small, high-numbered aperture will. As shutter speeds lengthen, the probability of the photographer movement increases. Compare your own steadiness at 1/250 sec. versus 1/30 sec. Traditionally, photographers are taught that the slowest shutter speed they can handhold is 1/focal length - 1/250 sec. for a 250mm lens, 1/60 sec. for a 50mm lens.

Subject Movement:
When photographing in breezy situations, longer shutter speeds will tend to make lightweight subjects move.

Mirror slap:
Mirror slap is the shaking caused by the mirror of an SLR camera popping out of the way to expose the sensor area. The vibrations caused by mirror slap are most evident at shutter speeds between 1/60 sec. and 1 sec. You can avoid these vibrations by using the mirror lock-up feature, which is called the exposure delay mode on many Nikon cameras. Note - this is not the same mirror lock-up feature used to clean your sensor. Refer to your instruction manual for specifics on this feature with your camera.

Digital Noise:
Higher ISO images are generally less sharp than lower ISO images. To counteract low shutter speeds, many photographers raise their ISO. In my own testing, I have found that most SLR cameras begin to show noise above ISO 400, especially in low light. While the noise at ISO 640 or ISO 800 is usually negligible, it can affect critical sharpness.

Optics:
Lenses do not perform equally at all apertures, nor do they perform equally throughout their zoom ranges. We should expect this, just as we expect that we won't get the same gas mileage at all speeds and road conditions. As with many mechanical things, lenses tend to work best in the middle part of their ranges, rather than at the extremes. In my years of photography, I have found that my SLR lenses are generally sharpest at apertures around f/8 or f/5.6. So, while they have better depth of field at f/22, they are generally not as sharp.

Prime lenses (non-zoom) lenses tend to be sharper than zoom lenses. Zoom lenses that cover either wide angle or telephoto, but not both, tend to be sharper than long range zoom lenses.

There are sharpness evaluations available online. DP Review has tested a variety of lenses. They have interactive charts which allow you to look at the sharpness of the tested lens at different zoom settings and apertures. Here is a link for the test for a Canon 50mm f/1.8 lens - a non-zoom lens of reasonable quality.

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