Simple Identification Test for the Best Aperture of my Sigma 10-20mm f/4-5.6


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Nov 16, 2004
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Looks like I am getting addicted to conducting homebrew simple test. Read about the sharpness evaluation of my Tamron.
After trying out a rented Sigma 10-20mm f/4-5.6 EX DC HSM ultra-wide angle lens earlier, I grew to love the distortions from it at the widest angle. I was certain that I need to get myself a piece of that lens. So I managed to trade with a CSer for this piece of lens.



SPECIFICATIONS AT A GLANCE
  • Lens Construction 14 Elements in 10 Groups
  • Angle of View 102.4 - 63.8 degrees
  • Number of Diaphragm Blades 6
  • Minimum Aperture F22
  • Minimum Focusing Distance 24cm/9.4 in.
  • Maximum Magnification 1:6.7
  • Filter Size Diameter 77mm
  • Dimensions Diameter 83.5mm X Length 81mm3.3 in. X 3.2 in.
  • Weight 465g/16.4 oz

I decided that I should perform a simple functionality check, identify potential front-back-focusing errors and determine the best aperture to give overall sharpness.

Identification of Best Aperture for Details
click on thumbnails to enlarge pictures


100% crops of images shot at 10mm with apertures f/8, 11, 13 and 22.
Left - Left of image, Center - Center of image, Right - Right of image
Sharpness are ranked from 1 (sharpest) and the highest (poor).
f/13 is the best aperture for capturing most details at 10mm and the worst being the most narrow aperture.
 

Nov 16, 2004
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100% crops of images shot at 20mm with apertures f/8, 11, 13 and 22.
Left - Left of image, Center - Center of image, Right - Right of image
Sharpness are ranked from 1 (sharpest) and the highest (poor).
f/11 followed by f/13 is the best aperture for capturing most details at 20mm and the worst being the most narrow aperture.



Sharpness at widest aperture at 10mm and 20mm
100% cropped images of the center (AF area=watch face) at 10mm and 20mm, wide open.
20mm gives a sharper image of the face compared to 10mm. However, at full resolution at 10mm, the face is very small and thus making it hard to distinguish the sharpness. It will only matter if I crop the image.

*The camera setup:
Aperture-Priority exposure mode, mounted on a tripod and 2sec-delay timer.
The lens had a Kenko PRO 1 Digital DMC UV Filter mounted on the front.
 

Nov 16, 2004
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The Trial Shots



Some trial shots with the Sigma 10-20mm f/4-5.6. The last shot is nonsensical, so can ignore it.
Simply love the distortions from this ultra-wide angle lens.
 

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