LensTip.com

Articles

How do we test the lenses?

30 September 2007
Robert Olech

1. Testing methods



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The main part of a photography testing session is done by using the ISO 12233 test chart. This chart was designed by Stephen H. Westin from Cornell University and has been slightly modified to meet the needs of LensTip.com. The pictures on the test chart are taken in strictly controlled testing conditions. We strictly adhere to the following steps for each lens test:

  • Pictures are taken on a digital SLDR camera of a medium or high class with an 8-12 MPix APS-C/DX or 4/3 detector (Canon 20/40D, Nikon D200, Pentax K10D, Olympus E-3 or Sony A100) and with an 21-25 MPix full frame cameras such as Canon 1Ds MkIII, Nikon D3x or Sony A900.
  • The camera sits on a stable tripod.
  • Each snapshot is taken by an electronic remote control.
  • The pictures are taken with the mirror lock function on.
  • The pictures are saved in both RAW and JPG formats simultaneously at the highest resolution.
  • The camera sensitivity is set at ISO 100 (or ISO 200 when ISO 100 is not a native sensitiity).
  • The test chart is lit by two professional 500W bulb lamps producing light at a 5000K color temperature.
  • The whiteness balance is set to 5000 K.
  • The lenses are clear and free of scratches.
  • At each focal length we take about 5-15 exposures and then choose the best one. After each exposure the lens is again focalized. Additionally, we take several pictures with the manual sharpness adjustment for each diaphragm.
  • We use a total of four ISO test charts printed on special A0, A1, A2 and A3 foils in order to check the object performance at different distances from each photographed object. We then average the results.


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